STAIR-BUILDING
=Introductory.= In the following instructions in the art of
Stair-building, it is the intention to adhere closely to the practical
phases of the subject, and to present only such matter as will directly
aid the student in acquiring a practical mastery of the art.
Stair-building, though one of the most important subjects connected
with the art of building, is probably the subject least understood by
designers and by workmen generally. In but few of the plans that leave
the offices of Architects, are the stairs properly laid down; and
many of the books that have been sent out for the purpose of giving
instruction in the art of building, have this common defect—that the
body of the stairs is laid down imperfectly, and therefore presents
great difficulties in the construction of the rail.
The stairs are an important feature of a building. On entering a
house they are usually the first object to meet the eye and claim
the attention. If one sees an ugly staircase, it will, in a measure,
condemn the whole house, for the first impression produced will seldom
be totally eradicated by commendable features that may be noted
elsewhere. It is extremely important, therefore, that both designer and
workman shall see that staircases are properly laid out.
Stairways should be commodious to ascend—inviting people, as it were,
to go up. When winders are used, they should extend past the spring
line of the cylinder, so as to give proper width at the narrow end (see
Fig. 72) and bring the rail there as nearly as possible to the same
pitch or slant as the rail over the square steps. When the hall is of
sufficient width, the stairway should not be less than four feet wide,
so that two people can conveniently pass each other thereon. The height
of riser and width of tread are governed by the staircase, which is
the space allowed for the stairway; but, as a general rule, the tread
should not be less than nine inches wide, and the riser should not be
over eight inches high. Seven-inch riser and eleven-inch tread will
make an easy stepping stairway. If you increase the width of the tread,
you must reduce the height of the riser. The tread and riser together
should not be over eighteen inches, and not less than seventeen inches.
These dimensions, however, cannot always be adhered to, as conditions
will often compel a deviation from the rule; for instance, in large
buildings, such as hotels, railway depots, or other public buildings,
treads are often made 18 inches wide, having risers of from 2½ inches
to 5 inches depth.
=Definitions.= Before proceeding further with the subject, it is
essential that the student make himself familiar with a few of the
terms used in stair-building.
[Illustration: Fig. 1. Illustrating Rise, Run, and Pitch.]
The term _rise and run_ is often used, and indicates certain dimensions
of the stairway. Fig. 1 will illustrate exactly what is meant; the line
_A B_ shows the _run_, or the length over the floor the stairs will
occupy. From _B_ to _C_ is the rise, or the total height from _top_ of
lower floor to _top_ of upper floor.[A] The line _D_ is the _pitch_ or
_line of nosings_, showing the angle of inclination of the stairs. On
the three lines shown—the _run_, the _rise_, and the _pitch_—depends
the whole system of stair-building.
The _body_ or _staircase_ is the room or space in which the stairway
is contained. This may be a space including the width and length of
the stairway only, in which case it is called a _close stairway_, no
rail or baluster being necessary. Or the stairway may be in a large
apartment, such as a passage or hall, or even in a large room, openings
being left in the upper floors so as to allow road room for persons
on the stairway, and to furnish communication between the stairways
and the different stories of the building. In such cases we have what
are known as _open stairways_, from the fact that they are not closed
on both sides, the steps showing their ends at one side, while on the
other side they are generally placed against the wall.
Sometimes stairways are left open on both sides, a practice not
uncommon in hotels, public halls, and steamships. When such stairs are
employed, the openings in the upper floor should be well _trimmed_ with
joists or beams somewhat stronger than the ordinary joists used in the
same floor, as will be explained further on.
_Tread._ This is the horizontal, upper surface of the step, upon which
the foot is placed. In other words, it is the piece of material that
forms the step, and is generally from 1¼ to 3 inches thick, and made of
a width and length to suit the position for which it is intended. In
small houses, the treads are usually made of ⅞-inch stuff.
_Riser._ This is the vertical height of the step. The riser is
generally made of thinner stuff than the tread, and, as a rule, is not
so heavy. Its duty is to connect the treads together, and to give the
stairs strength and solidity.
_Rise and Run._ This term, as already explained, is used to indicate
the horizontal and vertical dimensions of the stairway, the _rise_
meaning the height from the top of the lower floor to the top of the
second floor; and the _run_ meaning the horizontal distance from the
face of the first riser to the face of the last or top riser, or, in
other words, the distance between the face of the first riser and the
point where a plumb line from the face of the top riser would strike
the floor. It is, in fact, simply the distance that the treads would
make if put side by side and measured together—without, of course,
taking in the nosings.
Suppose there are fifteen treads, each being 11 inches wide; this
would make a run of 15 × 11 = 165 inches = 13 feet 9 inches. Sometimes
this distance is called the _going_ of the stair; this, however, is
an English term, seldom used in America, and when used, refers as
frequently to the length of the single tread as it does to the _run_ of
the stairway.
_String-Board._ This is the board forming the side of the stairway,
connecting with, and supporting the ends of the steps. Where the steps
are _housed_, or grooved into the board, it is known by the term
_housed string_; and when it is cut through for the tread to rest upon,
and is mitered to the riser, it is known by the term _cut and mitered
string_. The dimensions of the lumber generally used for the purpose
in practical work, are 9½ inches width and ⅞-inch thickness. In the
first-class stairways the thickness is usually 1⅛ inches, for both
front and wall strings.
[Illustration: Fig. 2. Common Method of Joining Risers and Treads.]
Fig. 2 shows the manner in which most stair-builders put their risers
and treads together. _T_ and _T_ show the treads; _R_ and _R_, the
risers; _S_ and _S_, the string; _O_ and _O_, the cove mouldings under
the nosings _X_ and _X_. _B_ and _B_ show the blocks that hold the
treads and risers together; these blocks should be from 4 to 6 inches
long, and made of very dry wood; their section may be from 1 to 2
inches square. On a tread 3 feet long, three of these blocks should be
used at about equal distances apart, putting the two outside ones about
6 inches from the strings. They are glued up tight into the angle.
First warm the blocks; next coat two adjoining sides with good, strong
glue; then put them in position, and nail them firmly to both tread
and riser. It will be noticed that the riser has a lip on the upper
edge, which enters into a groove in the tread. This lip is generally
about ⅜-inch long, and may be ⅜-inch or ½-inch in thickness. Care must
be taken in getting out the risers, that they shall not be made too
narrow, as allowance must be made for the lip.
[Illustration: Fig. 3. Vertical Section of Stair Steps.]
[Illustration: Fig. 4. End Section of Riser.]
[Illustration: Fig. 5. End Section of Tread.]
If the riser is a little too wide, this will do no harm, as the
over-width may hang down below the tread; but it must be cut the exact
width where it rests on the string. The treads must be made the exact
width required, before they are grooved or have the nosing worked on
the outer edge. The lip or tongue on the riser should fit snugly in the
groove, and should _bottom_. By following these last instructions and
seeing that the _blocks_ are well glued in, a good solid job will be
the result.
Fig. 3 is a vertical section of stair steps in which the risers are
shown tongued into the under side of the tread, as in Fig. 2, and also
the tread tongued into the face of the riser. This last method is in
general use throughout the country. The stair-builder, when he has
steps of this kind to construct, needs to be very careful to secure
the exact width for tread and riser, including the tongue on each.
The usual method, in getting the parts prepared, is to make a pattern
showing the end section of each. The millman, with these patterns to
guide him, will be able to run the material through the machine without
any danger of leaving it either too wide or too narrow; while, if he is
left to himself without patterns, he is liable to make mistakes. These
patterns are illustrated in Figs. 4 and 5 respectively, and, as shown,
are merely end sections of riser and tread.
[Illustration: Fig. 6. Side Elevation of Finished Steps with Return
Nosings and Cove Moulding.]
[Illustration: Fig. 7. Front Elevation of Finished Steps.]
Fig. 6 is a side elevation of the steps as finished, with return
nosings and cove moulding complete.
A front elevation of the finished step is shown in Fig. 7, the nosing
and riser returning against the base of the newel post. Often the newel
post projects past the riser, in front; and when such is the case, the
riser and nosing are cut square against the base of the newel.
[Illustration: Fig. 8. Portion of a Cut and Mitered String, Showing
Method of Constructing Stairs.]
Fig. 8 shows a portion of a cut and mitered string, which will give an
excellent idea of the method of construction. The letter _O_ shows the
nosing, _F_ the return nosing with a bracket terminating against it.
These brackets are about 5/16-inch thick, and are _planted_ (nailed) on
the string; the brackets miter with the ends of the risers; the ends of
the brackets which miter with the risers, are to be the same height as
the riser. The lower ends of two balusters are shown at _G G_; and the
dovetails or mortises to receive these are shown at _E E_. Generally
two balusters are placed on each tread, as shown; but there are
sometimes instances in which three are used, while in others only one
baluster is made use of.
An end portion of a cut and mitered string is shown in Fig. 9, with
part of the string taken away, showing the _carriage_—a rough piece of
lumber to which the finished string is nailed or otherwise fastened.
At _C_ is shown the return nosing, and the manner in which the work
is finished. A rough bracket is sometimes nailed on the carriage, as
shown at _D_, to support the tread. The balusters are shown dovetailed
into the ends of the treads, and are either glued or nailed in place,
or both. On the lower edge of string, at _B_, is a return bead or
moulding. It will be noticed that the rough carriage is _cut in_ snugly
against the floor joist.
[Illustration: Fig. 9. End Portion of Cut and Mitered String, with Part
Removed to Show Carriage.]
Fig. 10 is a plan of the portion of a stairway shown in Fig. 9. Here
the position of the string, bracket, riser, and tread can be seen. At
the lower step is shown how to miter the riser to the string; and at
the second step is shown how to miter it to the bracket.
Fig. 11 shows a quick method of marking the ends of the treads for the
dovetails for balusters. The templet _A_ is made of some thin material,
preferably zinc or hardwood. The dovetails are outlined as shown, and
the intervening portions of the material are cut away, leaving the
dovetail portions solid. The templet is then nailed or screwed to a
gauge-block _E_, when the whole is ready for use. The method of using
is clearly indicated in the illustration.
=Strings.= There are two main kinds of stair strings—_wall strings_ and
_cut strings_. These are divided, again, under other names, as _housed_
strings, _notched_ strings, _staved_ strings, and _rough_ strings.
_Wall strings_ are the supporters of the ends of the treads and
risers that are against the wall; these strings may be at both ends
of the treads and risers, or they may be at one end only. They may be
_housed_ (grooved) or left solid. When housed, the treads and risers
are keyed into them, and glued and blocked. When left solid, they
have a rough string or carriage spiked or screwed to them, to lend
additional support to the ends of risers and treads. Stairs made after
this fashion are generally of a rough, strong kind, and are especially
adapted for use in factories, shops, and warehouses, where strength and
rigidity are of more importance than mere external appearance.
_Open strings_ are outside strings or supports, and are cut to the
proper angles for receiving the ends of the treads and risers. It
is over a string of this sort that the rail and balusters range; it
is also on such a string that all nosings return; hence, in some
localities, an open string is known as a _return string_.
[Illustration: Fig. 10. Plan of Portion of Stair.]
[Illustration: Fig. 11. Templet Used to Mark Dovetail Cuts for
Balusters.]
_Housed strings_ are those that have grooves cut in them to receive
the ends of treads and risers. As a general thing, wall strings are
housed. The housings are made from ⅝ to ¾ inch deep, and the lines at
top of tread and face of riser are made to correspond with the lines of
riser and tread when in position. The back lines of the housings are so
located that a taper wedge may be driven in so as to force the tread
and riser close to the face shoulders, thus making a tight joint.
_Rough strings_ are cut from undressed plank, and are used for
strengthening the stairs. Sometimes a combination of rough-cut strings
is used for circular or geometrical stairs, and, when framed together,
forms the support or carriage of the stairs.
_Staved strings_ are built up strings, and are composed of narrow
pieces glued, nailed, or bolted together so as to form a portion of
a cylinder. These are sometimes used for circular stairs, though in
ordinary practice the circular part of a string is a part of the main
string bent around a cylinder to give it the right curve.
_Notched strings_ are strings that carry only treads. They are
generally somewhat narrower than the treads, and are housed across
their entire width. A sample of this kind of string is the side of a
common step-ladder. Strings of this sort are used chiefly in cellars,
or for steps intended for similar purposes.
[A] NOTE.—The measure for the rise of a stairway must always be taken
from the _top_ of one floor to the _top_ of the next.
=Setting Out Stairs.= In setting out stairs, the first thing to
do is to ascertain the locations of the first and last risers, with
the height of the story wherein the stair is to be placed. These
points should be marked out, and the distance between them divided off
equally, giving the number of steps or treads required. Suppose we have
between these two points 15 feet, or 180 inches. If we make our treads
10 inches wide, we shall have 18 treads. It must be remembered that
_the number of risers is always one more than the number of treads_, so
that in the case before us there will be 19 risers.
The height of the story is next to be exactly determined, being taken
on a rod. Then, assuming a height of riser suitable to the place, we
ascertain, by division, how often this height of riser is contained in
the height of the story; the quotient, if there is no remainder, will
be the number of risers in the story. Should there be a remainder on
the first division, the operation is reversed, the number of inches
in the height being made the dividend, and the before-found quotient,
the divisor. The resulting quotient will indicate an amount to be
added to the former assumed height of riser for a new trial height.
The remainder will now be less than in the former division; and if
necessary, the operation of reduction by division is repeated, until
the height of the riser is obtained to the thirty-second part of an
inch. These heights are then set off on the story rod as exactly as
possible.
The _story rod_ is simply a dressed or planed pole, cut to a length
exactly corresponding to the height from the top of the lower floor to
the top of the next floor. Let us suppose this height to be 11 feet 1
inch, or 133 inches. Now, we have 19 risers to place in this space, to
enable us to get upstairs; therefore, if we divide 133 by 19, we get 7
without any remainder. Seven inches will therefore be the width or
height of the riser. Without figuring this out, the workman may find
the exact width of the riser by dividing his story rod, by means of
pointers, into 19 equal parts, any one part being the proper width.
It may be well, at this point, to remember that _the first riser must
always be narrower than the others_, because the thickness of the first
tread must be taken off.
The width of treads may also be found without figuring, by pointing
off the _run_ of the stairs into the required number of parts; though,
where the student is qualified, it is always better to obtain the
width, both of treads and of risers, by the simple arithmetical rules.
Having determined the width of treads and risers, a _pitch-board_
should be formed, showing the angle of inclination. This is done by
cutting a piece of thin board or metal in the shape of a right-angled
triangle, with its base exactly equal to the run of the step, and its
perpendicular equal to the height of the riser. It is a general maxim,
that the greater the breadth of a step or tread, the less should be the
height of the riser; and, conversely, the less the breadth of a step,
the greater should be the height of the riser. The proper relative
dimensions of treads and risers may be illustrated graphically, as in
Fig. 12.
[Illustration: Fig. 12. Graphic Illustration of Proportional Dimensions
of Treads and Risers.]
In the right-angle triangle _A B C_, make _A B_ equal to 24 inches,
and _B C_ equal to 11 inches—the standard proportion. Now, to find
the riser corresponding to a given width of tread, from _B_, set off
on _A B_ the width of the tread, as _B D_; and from _D_, erect a
perpendicular _D E_, meeting the hypotenuse in _E_; then _D E_ is the
height of the riser; and if we join _B_ and _E_, the angle _D B E_ is
the angle of inclination, showing the slope of the ascent. In like
manner, where _B F_ is the width of the tread, _F G_ is the riser, and
_B G_ the slope of the stair. A width of tread _B H_ gives a riser of
the height of _H K_; and a width of tread equal to _B L_ gives a riser
equal to _L M_.
In the opinion of many builders, however, a better scheme of
proportions for treads and risers is obtained by the following method:
Set down two sets of numbers, each in arithmetical progression—the
first set showing widths of tread, increasing by inches; the other
showing heights of riser, decreasing by half-inches.
TREADS, INCHES RISERS, INCHES
5 9
6 8½
7 8
8 7½
9 7
10 6½
11 6
12 5½
13 5
14 4½
15 4
16 3½
17 3
18 2½
It will readily be seen that each pair of treads and risers thus
obtained is suitably proportioned as to dimensions.
It is seldom, however, that the proportions of treads and risers are
entirely a matter of choice. The space allotted to the stairs usually
determines this proportion; but the above will be found a useful
standard, to which it is desirable to approximate.
In the better class of buildings, the number of steps is considered in
the plan, which it is the business of the Architect to arrange; and
in such cases, the height of the story rod is simply divided into the
number required.
=Pitch-Board.= It will now be in order to describe a pitch-board
and the manner of using it; no stairs can be properly built without
the use of a pitch-board in some form or other. Properly speaking,
a pitch-board, as already explained, is a thin piece of material,
generally pine or sheet metal, and is a right-angled triangle in
outline. One of its sides is made the exact height of the rise; at
right angles with this line of rise, the exact width of the tread is
measured off; and the material is cut along the hypotenuse of the
right-angled triangle thus formed.
The simplest method of making a pitch-board is by using a steel square,
which, of course, every carpenter in this country is supposed to
possess. By means of this invaluable tool, also, a stair string can be
laid out, the square being applied to the string as shown in Fig. 13.
In the instance here illustrated, the square shows 10 inches for the
tread and 7 inches for the rise.
[Illustration: Fig. 13. Steel Square used as a Pitch-Board in Laying
Out Stair String.]
To cut a pitch-board, after the tread and rise have been determined,
proceed as follows: Take a piece of thin, clear material, and lay the
square on the face edge, as shown in Fig. 13. Mark out the pitch-board
with a sharp knife; then cut out with a fine saw, and dress to the
knife marks; nail a piece on the largest edge of the pitch-board for a
gauge or fence, and it is ready for use.
Fig. 14 shows the pitch-board pure and simple; it may be half an inch
thick, or, if of hardwood, may be from a quarter-inch to a half-inch
thick.
Fig. 15 shows the pitch-board after the gauge or fence is nailed on.
This fence or gauge may be about 1½ inches wide and from ⅜ to ¾ inch
thick.
Fig. 16 shows a sectional view of the pitch-board with a fence nailed
on.
[Illustration: Fig. 14. Fig. 15. Fig. 16.
Showing How a Pitch-Board is Made.
Fig. 15 shows gauge fastened to long edge; Fig. 16 is a sectional
elevation of completed board.]
In Fig. 17 the manner of applying the pitch-board is shown. _R R R_
is the string, and the line _A_ shows the jointed or straight edge
of the string. The pitch-board _P_ is shown in position, the line
8⅓ represents the step or tread, and the line 7¾ shows the line of
the riser. These two lines are of course at right angles, or, as the
carpenter would say; they are _square_. This string shows four complete
cuts, and part of a fifth cut for treads, and five complete cuts for
risers. The bottom of the string at _W_ is cut off at the line of the
floor on which it is supposed to rest. The line _C_ is the line of the
first riser. This riser is cut lower than any of the other risers,
because, as above explained, the thickness of the first tread is always
taken off it; thus, if the tread is 1½ inches thick, the riser in this
case would only require to be 6¼ inches wide, as 7¾-1½ = 6¼.
The string must be cut so that the line at _W_ will be only 6¼ inches
from the line at 8⅓, and these two lines must be parallel. The first
riser and tread having been satisfactorily dealt with, the rest can
easily be marked off by simply sliding the pitch-board along the line
_A_ until the outer end of the line 8⅓ on the pitch-board strikes the
outer end of the line 7¾ on the string, when another tread and another
riser are to be marked off. The remaining risers and treads are marked
off in the same manner.
[Illustration: Fig. 17. Showing Method of Using Pitch-Board.]
Sometimes there may be a little difficulty at the top of the stairs, in
fitting the string to the trimmer or joists; but, as it is necessary
first to become expert with the pitch-board, the method of trimming the
well or attaching the cylinder to the string will be left until other
matters have been discussed.
Fig. 18 shows a portion of the stairs in position. _S_ and _S_ show
the strings, which in this case are cut square; that is, the part of
the string to which the riser is joined is cut square across, and the
butt or end wood of the riser is seen. In this case, also, the end of
the tread is cut square off, and flush with the string and riser. Both
strings in this instance are open strings. Usually, in stairs of this
kind, the ends of the treads are rounded off similarly to the front
of the tread, and the ends project over the strings the same distance
that the front edge projects over the riser. If a moulding or _cove_
is used under the nosing in front, it should be carried round on the
string to the back edge of the tread and cut off square, for in this
case the back edge of the tread will be square. A riser is shown at
_R_, and it will be noticed that it runs down behind the tread on the
back edge, and is either nailed or screwed to the tread. This is the
American practice, though in England the riser usually rests on the
tread, which extends clear back to string as shown at the top tread in
the diagram. It is much better, however, for general purposes, that the
riser go behind the tread, as this tends to make the whole stairway
much stronger.
Housed strings are those which carry the treads and risers without
their ends being seen. In an open stair, the wall string only is
housed, the other ends of the treads and risers resting on a cut
string, and the nosings and mouldings being returned as before
described.
[Illustration: Fig. 18. Portion of Stair in Position.]
[Illustration: Fig. 19. Showing Method of Housing Treads and Risers.]
The manner of housing is shown in Fig. 19, in which the treads _T
T_ and the risers _R R_ are shown in position, secured in place
respectively by means of wedges _X X_ and _F F_, which should be well
covered with good glue before insertion in the groove. The housings are
generally made from ½ to ⅝ inch deep, space for the wedge being cut to
suit.
In some closed stairs in which there is a housed string between the
newels, the string is double-tenoned into the shanks of both newels,
as shown in Fig. 20. The string in this example is made 12¾ inches
wide, which is a very good width for a string of this kind; but the
thickness should never be less than 1½ inches. The upper newel is made
about 5 feet 4 inches long from drop to top of cap. These strings are
generally capped with a subrail of some kind, on which the baluster, if
any, is cut-mitered in. Generally a groove, the width of the square of
the balusters, is worked on the top of the subrail, and the balusters
are worked out to fit into this groove; then pieces of this material,
made the width of the groove and a little thicker than the groove is
deep, are cut so as to fit in snugly between the ends of the balusters
resting in the groove. This makes a solid job; and the pieces between
the balusters may be made of any shape on top, either beveled, rounded,
or moulded, in which case much is added to the appearance of the stairs.
[Illustration: Fig. 20. Showing Method of Connecting Housed String to
Newels.]
[Illustration: Fig. 21. Method of Connecting Rail and String to Bottom
Newel.]
Fig. 21 exhibits the method of attaching the rail and string to the
bottom newel. The dotted lines indicate the form of the tenons cut to
fit the mortises made in the newel to receive them.
Fig. 22 shows how the string fits against the newel at the top; also
the trimmer _E_, to which the newel post is fastened. The string in
this case is tenoned into the upper newel post the same way as into the
lower one.
The open string shown in Fig. 23 is a portion of a finished string,
showing nosings and cove returned and finishing against the face of the
string. Along the lower edge of the string is shown a bead or moulding,
where the plaster is finished.
A portion of a stair of the better class is shown in Fig. 24. This is
an open, bracketed string, with returned nosings and coves and scroll
brackets. These brackets are made about ⅜ inch thick, and may be in
any desirable pattern. The end next the riser should be mitered to
suit; this will require the riser to be ⅜ inch longer than the face of
the string. The upper part of the bracket should run under the cove
moulding; and the tread should project over the string the full ⅜ inch,
so as to cover the bracket and make the face even for the nosing and
the cove moulding to fit snugly against the end of the tread and the
face of the bracket. Great care must be taken about this point, or
endless trouble will follow. In a bracketed stair of this kind, care
must be taken in placing the newel posts, and provision must be made
for the extra ⅜ inch due to the bracket. The newel post must be set out
from the string ⅜ inch, and it will then align with the baluster.
[Illustration: Fig. 22. Connections of String and Trimmer at Upper
Newel Post.]
[Illustration: Fig. 23. Portion of Finished String, Showing Returned
Nosings and Coves, also Bead Moulding.]
[Illustration: Fig. 24. Portion of Open, Bracketed String Stair, with
Returned Nosings and Coves, Scroll Brackets, and Bead Moulding.]
We have now described several methods of dealing with strings; but
there are still a few other points connected with these members, both
housed and open, that it will be necessary to explain; before the young
workman can proceed to build a fair flight of stairs. The connection
of the wall string to the lower and upper floors, and the manner of
affixing the outer or cut string to the upper joist and to the newel,
are matters that must not be overlooked. It is the intention to show
how these things are accomplished, and how the stairs are made strong
by the addition of rough strings or bearing carriages.
[Illustration: Fig. 25. Side Elevation of Part of Stair with Open, Cut
and Mitered String.]
[Illustration: Fig. 26. Plan of Part of Stair Shown in Fig. 25.]
Fig. 25 gives a side view of part of a stair of the better class, with
one open, cut and mitered string. In Fig. 26, a plan of this same
stairway, _W S_ shows the wall string; _R S_, the rough string, placed
there to give the structure strength; and _O S_, the outer or cut and
mitered string. At _A A_ the ends of the risers are shown, and it will
be noticed that they are mitered against a vertical or riser line of
the string, thus preventing the end of the riser from being seen. The
other end of the riser is in the housing in the wall string. The outer
end of the tread is also mitered at the nosing, and a piece of material
made or worked like the nosing is mitered against or returned at the
end of the tread. The end of this returned piece is again returned on
itself back to the string, as shown at _N_ in Fig. 25. The moulding,
which is ⅝-inch cove in this case, is also returned on itself back to
the string.
The mortises shown at _B B B B_ (Fig. 26), are for the balusters. It
is always the proper thing to saw the ends of the treads ready for the
balusters before the treads are attached to the string; then, when the
time arrives to put up the rail, the back ends of the mortises can be
cut out, when the treads will be ready to receive the balusters. The
mortises are dovetailed, and, of course, the tenons on the balusters
must be made to suit. The treads are finished on the bench; and the
return nosings are fitted to them and tacked on, so that they may
be taken off to insert the balusters when the rail is being put in
position.
Fig. 27 shows the manner in which a wall string is finished at the foot
of the stairs. _S_ shows the string, with moulding wrought on the upper
edge. This moulding may be a simple ogee, or may consist of a number of
members; or it may be only a bead; or, again, the edge of the string
may be left quite plain; this will be regulated in great measure by the
style of finish in the hall or other part of the house in which the
stairs are placed. _B_ shows a portion of a baseboard, the top edge of
which has the same finish as the top edge of the string. _B_ and _A_
together show the junction of the string and base. _F F_ show blocks
glued in the angles of the steps to make them firm and solid.
[Illustration: Fig. 27. Showing How Wall String is Finished at Foot of
Stair.]
[Illustration: Fig. 28. Showing How Wall String is Finished at Top of
Stair.]
Fig. 28 shows the manner in which the wall string _S_ is finished at
the top of the stairs. It will be noticed that the moulding is worked
round the ease-off at _A_ to suit the width of the base at _B_. The
string is cut to fit the floor and to butt against the joist. The
plaster line under the stairs and on the ceiling, is also shown.
[Illustration: Fig. 29. Showing How a Cut or Open String is Finished at
Foot of Stair.]
Fig. 29 shows a cut or open string at the foot of a stairway, and the
manner of dealing with it at its junction with the newel post _K_.
The point of the string should be mortised into the newel 2 inches,
3 inches, or 4 inches, as shown by the dotted lines; and the mortise
in the newel should be cut near the center, so that the center of
the baluster will be directly opposite the central line of the newel
post. The proper way to manage this, is to mark the central line of
the baluster on the tread, and then make this line correspond with the
central line of the newel post. By careful attention to this point,
much trouble will be avoided where a turned cap is used to receive the
lower part of the rail.
The lower riser in a stair of this kind will be somewhat shorter than
the ones above it, as it must be cut to fit between the newel and the
wall string. A portion of the tread, as well as of the riser, will also
butt against the newel, as shown at _W_.
If there is no spandrel or wall under the open string, it may run down
to the floor as shown by the dotted line at _O_. The piece _O_ is glued
to the string, and the moulding is worked on the curve. If there is
a wall under the string _S_, then the base _B_, shown by the dotted
lines, will finish against the string, and it should have a moulding on
its upper edge, the same as that on the lower edge of the string, if
any, this moulding being mitered into the one on the string. When there
is a base, the piece _O_ is of course dispensed with.
The square of the newel should run down by the side of a joist as
shown, and should be firmly secured to the joist either by spiking or
by some other suitable device. If the joist runs the other way, try
to get the newel post against it, if possible, either by furring out
the joist or by cutting a portion off the thickness of the newel. The
solidity of a stair and the firmness of the rail, depend very much upon
the rigidity of the newel post. The above suggestions are applicable
where great strength is required, as in public buildings. In ordinary
work, the usual method is to let the newel rest on the floor.
[Illustration: Fig. 30. Showing How a Cut or Open String is Finished at
Top of Stair.]
Fig. 30 shows how the cut string is finished at the top of the stairs.
This illustration requires no explanation after the instructions
already given.
Thus far, stairs having a newel only at the bottom have been dealt
with. There are, however, many modifications of straight and return
stairs which have from two to four or six newels. In such cases, the
methods of treating strings at their finishing points must necessarily
be somewhat different from those described; but the general principles,
as shown and explained, will still hold good.
=Well-Hole.= Before proceeding to describe and illustrate neweled
stairs, it will be proper to say something about the _well-hole_, or the
opening through the floors, through which the traveler on the stairs
ascends or descends from one floor to another.
Fig. 31 shows a well-hole, and the manner of trimming it. In this
instance the stairs are placed against the wall; but this is not
necessary in all cases, as the well-hole may be placed in any part of
the building.
The arrangement of the trimming varies according as the joists are at
right angles to, or are parallel to, the wall against which the stairs
are built. In the former case (Fig. 31, _A_) the joists are cut short
and tusk-tenoned into the heavy trimmer _T T_, as shown in the cut.
This trimmer is again tusk-tenoned into two heavy joists _T J_ and _T
J_, which form the ends of the well-hole. These heavy joists are called
_trimming joists_; and, as they have to carry a much heavier load than
other joists on the same floor, they are made much heavier. Sometimes
two or three joists are placed together, side by side, being bolted
or spiked together to give them the desired unity and strength. In
constructions requiring great strength, the tail and header joists of a
well-hole are suspended on iron brackets.
If the opening runs parallel with the joists (Fig. 31, _B_), the timber
forming the side of the well-hole should be left a little heavier than
the other joists, as it will have to carry short trimmers (_T J_ and
_T J_) and the joists running into them. The method here shown is more
particularly adapted to brick buildings, but there is no reason why the
same system may not be applied to frame buildings.
Usually in cheap, frame buildings, the trimmers _T T_ are spiked
against the ends of the joists, and the ends of the trimmers are
supported by being spiked to the trimming joists _T J_, _T J_. This is
not very workmanlike or very secure, and should not be done, as it is
not nearly so strong or durable as the old method of framing the joists
and trimmers together.
Fig. 32 shows a stair with three newels and a platform. In this
example, the first tread (No. 1) stands forward of the newel post
two-thirds of its width. This is not necessary in every case, but it is
sometimes done to suit conditions in the hallway. The second newel is
placed at the twelfth riser, and supports the upper end of the first
cut string and the lower end of the second cut string. The platform
(12) is supported by joists which are framed into the wall and are
fastened against a trimmer running from the wall to the newel along the
line 12. This is the case only when the second newel runs down to the
floor.
[Illustration: Fig. 31. Showing Ways of Trimming Well-Hole when Joists
Run in Different Directions.]
If the second newel does not run to the floor, the framework supporting
the platform will need to be built on studding. The third newel stands
at the top of the stairs, and is fastened to the joists of the second
floor, or to the trimmer, somewhat after the manner of fastening shown
in Fig. 29. In this example, the stairs have 16 risers and 15 treads,
the platform or landing (12) making one tread. The figure 16 shows the
floor in the second story.
This style of stair will require a well-hole in shape about as shown
in the plan; and where strength is required, the newel at the top
should run from floor to floor, and act as a support to the joists and
trimmers on which the second floor is laid.
Perhaps the best way for a beginner to go about building a stairway
of this type, will be to lay out the work on the lower floor in the
exact place where the stairs are to be erected, making everything full
size. There will be no difficulty in doing this; and if the positions
of the first riser and the three newel posts are accurately defined,
the building of the stairs will be an easy matter. Plumb lines can be
raised from the lines on the floor, and the positions of the platform
and each riser thus easily determined. Not only is it best to line out
on the floor all stairs having more than one newel; but in constructing
any kind of stair it will perhaps be safest for a beginner to lay out
in exact position on the floor the points over which the treads and
risers will stand. By adopting this rule, and seeing that the strings,
risers, and treads correspond exactly with the lines on the floor,
many cases of annoyance will be avoided. Many expert stair-builders,
in fact, adopt this method in their practice, laying out all stairs on
the floor, including even the carriage strings, and they cut out all
the material from the lines obtained on the floor. By following this
method, one can see exactly the requirements in each particular case,
and can rectify any error without destroying valuable material.
[Illustration: Fig. 32. Stair with Three Newels and a Platform.]
=Laying Out.= In order to afford the student a clear idea of
what is meant by _laying out_ on the floor, an example of a simple
close-string stair is given. In Fig. 33, the letter _F_ shows the floor
line; _L_ is the landing or platform; and _W_ is the wall line. The
stair is to be 4 feet wide over strings; the landing, 4 feet wide; the
height from floor to landing, 7 feet; and the run from start to finish
of the stair, 8 feet 8½ inches.
The first thing to determine is the dimensions of the treads and
risers. The wider the tread, the lower must be the riser, as stated
before. No definite dimensions for treads and risers can be given, as
the steps have to be arranged to meet the various difficulties that
may occur in the working out of the construction; but a common rule
is this: Make the width of the tread, plus twice the rise, equal to
24 inches. This will give, for an 8-inch tread, an 8-inch rise; for a
9-inch tread, a 7½-inch rise; for a 10-inch tread, a 7-inch rise, and
so on. Having the height (7 feet) and the run of the flight (8 feet
8½-inches), take a rod about one inch square, and mark on it the height
from floor to landing (7 feet), and the length of the going or run of
the flight (8 feet 8½ inches). Consider now what are the dimensions
which can be given to the treads and risers, remembering that there
will be one more riser than the number of treads. Mark off on the rod
the landing, forming the last tread. If twelve risers are desired,
divide the height (namely, 7 feet) by 12, which gives 7 inches as the
rise of each step. Then divide the run (namely, 8 feet 8½ inches) by
11, and the width of the tread is found to be 9½ inches.
Great care must be taken in making the pitch-board for marking off
the treads and risers on the string. The pitch-board may be made
from dry hardwood about ⅜-inch thick. One end and one side must be
perfectly square to each other; on the one, the width of the tread is
set off, and on the other the height of the riser. Connect the two
points thus obtained, and saw the wood on this line. The addition of a
gauge-piece along the longest side of the triangular piece, completes
the pitch-board, as was illustrated in Fig. 15.
The length of the wall and outer string can be ascertained by means
of the pitch-board. One side and one edge of the wall string must be
squared; but the outer string must be trued all round. On the strings,
mark the positions of the treads and risers by using the pitch-board as
already explained (Fig. 17). Strings are usually made 11 inches wide,
but may be made 12½ inches wide if necessary for strength.
[Illustration: Fig. 33. Method of Laying Out a Simple, Close-String
Stair.]
After the widths of risers and treads have been determined, and the
string is ready to lay out, apply the pitch-board, marking the first
riser about 9 inches from the end; and number each step in succession.
The thickness of the treads and risers can be drawn by using thin
strips of hardwood made the width of the housing required. Now allow
for the wedges under the treads and behind the risers, and thus find
the exact width of the housing, which should be about ⅝-inch deep; the
treads and risers will require to be made 1¼ inches longer than shown
in the plan, to allow for the housings at both ends.
Before putting the stair together, be sure that it can be taken into
the house and put in position without trouble. If for any reason it
cannot be put in after being put together, then the parts must be
assembled, wedged, and glued up at the spot.
It is essential in laying out a plan on the floor, that the exact
positions of the first and last risers be ascertained, and the height
of the story wherein the stair is to be placed. Then draw a plan of
the hall or other room in which the stairs will be located, including
surrounding or adjoining parts of the room to the extent of ten or
twelve feet from the place assigned for the foot of the stair. All
the doorways, branching passages, or windows which can possibly come
in contact with the stair from its commencement to its expected
termination or landing, must be noted. The sketch must necessarily
include a portion of the entrance hall in one part, and of the lobby
or landing in another, and on it must be laid out all the lines of the
stair from the first to the last riser.
The height of the story must next be exactly determined and taken on
the rod; then, assuming a height of risers suitable to the place,
a trial is made by division in the manner previously explained, to
ascertain how often this height is contained in the height of the
story. The quotient, if there is no remainder, will be the number of
risers required. Should there be a remainder on the first division,
the operation is reversed, the number of inches in the height being
made the dividend and the before-found quotient the divisor; and the
operation of reduction by division is carried on till the height of the
riser is obtained to the thirty-second part of an inch. These heights
are then set off as exactly as possible on the story rod, as shown in
Fig. 33.
The next operation is to show the risers on the sketch. This the
workman will find no trouble in arranging, and no arbitrary rule can be
given.
A part of the foregoing may appear to be repetition; but it is not, for
it must be remembered that scarcely any two flights of stairs are alike
in run, rise, or pitch, and any departure in any one dimension from
these conditions leads to a new series of dimensions that must be dealt
with independently. The principle laid down, however, applies to all
straight flights of stairs; and the student who has followed closely
and retained the pith of what has been said, will, if he has a fair
knowledge of the use of tools, be fairly equipped for laying out and
constructing a plain, straight stair with a straight rail.
Plain stairs may have one platform, or several; and they may turn to
the right or to the left, or, rising from a platform or landing, may
run in an opposite direction from their starting point.
When two flights are necessary for a story, it is desirable that each
flight should consist of the same number of steps; but this, of course,
will depend on the form of the staircase, the situation and height of
doors, and other obstacles to be passed under or over, as the case may
be.
In Fig. 32, a stair is shown with a single platform or landing and
three newels. The first part of this stair corresponds, in number of
risers, with the stair shown in Fig. 33; the second newel runs down
to the floor, and helps to sustain the landing. This newel may simply
be a 4 by 4-inch post, or the whole space may be inclosed with the
spandrel of the stair. The second flight starts from the platform just
as the first flight starts from the lower floor, and both flights may
be attached to the newels in the manner shown in Fig. 29. The bottom
tread in Fig. 32 is rounded off against the square of the newel post;
but this cannot well be if the stairs start from the landing, as the
tread would project too far onto the platform. Sometimes, in high-class
stairs, provision is made for the first tread to project well onto the
landing.
If there are more platforms than one, the principles of construction
will be the same; so that whenever the student grasps the full
conditions governing the construction of a single-platform stair, he
will be prepared to lay out and construct the body of any stair having
one or more landings. The method of laying out, making, and setting up
a hand-rail will be described later.
Stairs formed with treads each of equal width at both ends, are named
_straight flights_; but stairs having treads wider at one end than the
other are known by various names, as _winding stairs_, _dog-legged
stairs_, _circular stairs_, or _elliptical stairs_. A tread with
parallel sides, having the same width at each end, is called a _flyer_;
while one having one wide end and one narrow, is called a _winder_.
These terms will often be made use of in what follows.
The elevation and plan of the stair shown in Fig. 34 may be called
a _dog-legged_ stair with three winders and six flyers. The flyers,
however, may be extended to any number. The housed strings to receive
the winders are shown. These strings show exactly the manner of
construction. The shorter string, in the corner from 1 to 4, which is
shown in the plan to contain the housing of the first winder and half
of the second, is put up first, the treads being leveled by aid of a
spirit level; and the longer upper string is put in place afterwards,
butting snugly against the lower string in the corner. It is then
fastened firmly to the wall. The winders are cut snugly around the
newel post, and well nailed. Their risers will stand one above another
on the post; and the straight string above the winders will enter the
post on a line with the top edge of the uppermost winder.
[Illustration: Fig. 34. Elevation and Plan of Dog-Legged Stair with
Three Winders and Six Flyers.]
_Platform stairs_ are often constructed so that one flight will run
in a direction opposite to that of the other flight, as shown in Fig.
35. In cases of this kind, the landing or platform requires to have
a length more than double that of the treads, in order that both
flights may have the same width. Sometimes, however, and for various
reasons, the upper flight is made a little narrower than the lower; but
this expedient should be avoided whenever possible, as its adoption
unbalances the stairs. In the example before us, eleven treads, not
including the landing, run in one direction; while four treads,
including the landing, run in the opposite direction; or, as workmen
put it, the stair “returns on itself.” The elevation shown in Fig. 36
illustrates the manner in which the work is executed. The various parts
are shown as follows:
[Illustration: Fig. 35. Plan of Platform Stair Returning on Itself.]
[Illustration: Fig. 37 is a section of the top landing, with baluster
and rail.]
[Illustration: Fig. 38 is part of the long newel, showing mortises for
the strings.]
[Illustration: Fig. 36. Elevation Showing Construction of Platform
Stair of which Plan is Given in Fig. 35.]
[Illustration: Fig. 37. Section of Top Landing, Baluster, and Rail.]
[Illustration: Fig. 39 represents part of the bottom newel, showing the
string, moulding on the outside, and cap.]
[Illustration: Fig. 40 is a section of the top string enlarged.]
Fig. 41 is the newel at the bottom, as cut out to receive bottom step.
It must be remembered that there is a _cove_ under each tread. This may
be nailed in after the stairs are put together, and it adds greatly to
the appearance.
We may state that stairs should have _carriage pieces_ fixed from floor
to floor, under the stairs, to support them. These may be notched
under the steps; or _rough brackets_ may be nailed to the side of the
carriage, and carried under each riser and tread.
There is also a framed spandrel which helps materially to carry the
weight, makes a sound job, and adds greatly to the appearance. This
spandrel may be made of 1¼-inch material, with panels and mouldings
on the front side, as shown in Fig. 36. The joint between the top and
bottom rails of the spandrel at the angle, should be made as shown in
Fig. 42 with a cross-tongue, and glued and fastened with long screws.
Fig. 43 is simply one of the panels showing the miters on the moulding
and the shape of the sections. As there is a convenient space under the
landing, it is commonly used for a closet.
[Illustration: Fig. 38. String Mortises in Long Newel.]
[Illustration: Fig. 39. Mortises in Lower Newel for String, Outside
Moulding, and Cap.]
[Illustration: Fig. 40. Enlarged Section of Top String.]
[Illustration: Fig. 41. Newel Cut to Receive Bottom Step.]
In setting out stairs, not only the proportions of treads and risers
must be considered, but also the material available. As this material
runs, as a rule, in certain sizes, it is best to work so as to conform
to it as nearly as possible. In ordinary stairs, 11 by 1-inch common
stock is used for strings and treads, and 7-inch by ¾-inch stock for
risers; in stairs of a better class, wider and thicker material may be
used. The rails are set at various heights; 2 feet 8 inches may be taken
as an average height on the stairs, and 3 feet 1 inch on landings, with
two balusters to each step.
In Fig. 36, all the newels and balusters are shown square; but it is
much better, and is the more common practice, to have them turned, as
this gives the stairs a much more artistic appearance. The spandrel
under the string of the stairway shows a style in which many stairs are
finished in hallways and other similar places. Plaster is sometimes
used instead of the panel work, but is not nearly so good as woodwork.
The door under the landing may open into a closet, or may lead to a
cellarway, or through to some other room.
In stairs with winders, the width of a winder should, if possible,
be nearly the width of the regular tread, at a distance of 14 inches
from the narrow end, so that the length of the step in walking up
or down the stairs may not be interrupted; and for this reason and
several others, it is always best to have three winders only in each
quarter-turn. Above all, avoid a four-winder turn, as this makes a
breakneck stair, which is more difficult to construct and inconvenient
to use.
[Illustration: Fig. 42. Showing Method of Joining Spandrel Rails, with
Cross-Tongue Glued and Screwed.]
[Illustration: Fig. 43. Panel in Spandrel, Showing Miters on Moulding,
and Shape of Section.]
_Bullnose Tread._ No other stair, perhaps, looks so well at the
starting point as one having a _bullnose_ step. In Fig. 44 are shown a
plan and elevation of a flight of stairs having a bullnose tread. The
method of obtaining the lines and setting out the body of the stairs, is
the same as has already been explained for other stairs, with the
exception of the first two steps, which are made with circular ends,
as shown in the plan. These circular ends are worked out as hereafter
described, and are attached to the newel and string as shown. The
example shows an open, cut string with brackets. The spandrel under
the string contains short panels, and makes a very handsome finish.
The newels and balusters in this case are turned, and the latter have
cutwork panels between them.
[Illustration: Fig. 44. Elevation and Plan of Stair with Bullnose
Tread.]
[Illustration: Fig. 45. Section through Bullnose Step.]
Bullnose steps are usually built up with a three-piece block, as shown
in Fig. 45, which is a section through the step indicating the blocks,
tread, and riser.
Fig. 46 is a plan showing how the veneer of the riser is prepared
before being bent into position. The block _A_ indicates a wedge
which is glued and driven home after the veneer is put in place. This
tightens up the work and makes it sound and clear. Figs. 47 and 48 show
other methods of forming bullnose steps.
[Illustration: Fig. 46. Plan Showing Preparation of Veneer before
Bending into Position.]
Fig. 49 is the side elevation of an open-string stair with bullnose
steps at the bottom; while Fig. 50 is a view showing the lower end of
the string, and the manner in which it is prepared for fixing to the
blocks of the step. Fig. 51 is a section through the string, showing
the bracket, cove, and projection of tread over same.
[Illustration: Fig. 47. Fig. 48. Methods of Forming Bullnose Steps.]
[Illustration: Fig. 49. Side Elevation of Open-String Stair with
Bullnose Steps.]
Figs. 52 and 53 show respectively a plan and vertical section of the
bottom part of the stair. The blocks are shown at the ends of the steps
(Fig. 53), with the veneered parts of the risers going round them; also
the position where the string is fixed to the blocks (Fig. 52); and the
tenon of the newel is marked on the upper step. The section (Fig. 53)
shows the manner in which the blocks are built up and the newel tenoned
into them.
The newel, Fig. 49, is rather an elaborate affair, being carved at the
base and on the body, and having a carved rosette planted in a small,
sunken panel on three sides, the rail butting against the fourth side.
=Open-Newel Stairs.= Before leaving the subject of straight
and dog-legged stairs, the student should be made familiar with at
least one example of an open-newel stair. As the same principles of
construction govern all styles of open-newel stairs, a single example
will be sufficient. The student must, of course, understand that
he himself is the greatest factor in planning stairs of this type;
that the setting out and designing will generally devolve on him. By
exercising a little thought and foresight, he can so arrange his plan
that a minimum of both labor and material will be required.
[Illustration: Fig. 50. Lower End of String to Connect with Bullnose
Step.]
[Illustration: Fig. 51. Section through String.]
Fig. 54 shows a plan of an open-newel stair having two landings and
closed strings, shown in elevation in Fig. 55. The dotted lines show
the carriage timbers and trimmers, also the lines of risers; while the
treads are shown by full lines. It will be noticed that the strings and
trimmers at the first landing are framed into the shank of the second
newel post, which runs down to the floor; while the top newel drops
below the fascia, and has a turned and carved drop. This drop hangs
below both the fascia and the string. The lines of treads and risers
are shown by dotted lines and crosshatched sections. The position of
the carriage timbers is shown both in the landings and in the runs of
the stairs, the projecting ends of these timbers being supposed to be
resting on the wall. A scale of the plan and elevation is attached
to the plan. In Fig. 55, a story rod is shown at the right, with
the number of risers spaced off thereon. The design of the newels,
spandrel, framing, and paneling is shown.
[Illustration: Fig. 52. Plan of Bottom Part of Bullnose Stair.]
[Illustration: Fig. 53. Vertical Section through Bottom Part of Bullnose
Stair.]
Only the central carriage timbers are shown in Fig. 54; but in a stair
of this width, there ought to be two other timbers, not so heavy,
perhaps, as the central one, yet strong enough to be of service in
lending additional strength to the stairway, and also to help carry the
laths and plaster or the paneling which may be necessary in completing
the under side or soffit. The strings being closed, the butts of their
balusters must rest on a subrail which caps the upper edge of the outer
string.
[Illustration: Fig. 54. Plan of Open-Newel Stair, with Two Landings and
Closed Strings.]
The first newel should pass through the lower floor, and, to insure
solidity, should be secured by bolts to a joist, as shown in the
elevation. The rail is attached to the newels in the usual manner, with
handrail bolts or other suitable device. The upper newel should be made
fast to the joists as shown, either by bolts or in some other efficient
manner. The intermediate newels are left square on the shank below the
stairs, and may be fastened in the floor below either by mortise and
tenon or by making use of joint bolts.
[Illustration: Fig. 55. Elevation of Open-Newel Stair Shown in Plan in
Fig. 54.]
Everything about a stair should be made solid and sound; and every
joint should set firmly and closely; or a shaky, rickety, squeaky stair
will be the result, which is an abomination.
=Stairs with Curved Turns.= Sufficient examples of stairs having
angles of greater or less degree at the turn or change of direction, to
enable the student to build any stair of this class, have now been
given. There are, however, other types of stairs in common use, whose
turns are curved, and in which newels are employed only at the foot,
and sometimes at the finish of the flight. These curved turns may be
any part of a circle, according to the requirements of the case, but
turns of a quarter-circle or half-circle are the more common. The
string forming the curve is called a _cylinder_, or part of a cylinder,
as the case may be. The radius of this circle or cylinder may be any
length, according to the space assigned for the stair. The opening
around which the stair winds is called the _well-hole_.
[Illustration: Fig. 56. Stair Serving for Two Flights, with Mid-Floor
Landing.]
Fig. 56 shows a portion of a stairway having a well-hole with a 7-inch
radius. This stair is rather peculiar, as it shows a quarter-space
landing, and a quarter-space having three winders. The reason for this
is the fact that the landing is on a level with the floor of another
room, into which a door opens from the landing. This is a problem very
often met with in practical work, where the main stair is often made
to do the work of two flights because of one floor being so much lower
than another.
A curved stair, sometimes called a _geometrical stair_, is shown in
Fig. 57, containing seven winders in the cylinder or well-hole, the
first and last aligning with the diameter.
In Fig. 58 is shown another example of this kind of stair, containing
nine winders in the well-hole, with a circular wall-string. It is not
often that stairs are built in this fashion, as most stairs having a
circular well-hole finish against the wall in a manner similar to that
shown in Fig. 57.
[Illustration: Fig. 57. Geometrical Stair with Seven Winders.]
Sometimes, however, the workman will be confronted with a plan such as
shown in Fig. 58; and he should know how to lay out the wall-string.
In the elevation, Fig. 58, the string is shown to be straight, similar
to the string of a common straight flight. This results from having an
equal width in the winders along the wall-string, and, as we have of
necessity an equal width in the risers, the development of the string
is merely a straight piece of board, as in an ordinary straight flight.
In laying out the string, all we have to do is to make a common
pitch-board, and, with it as a templet, mark the lines of the treads
and risers on a straight piece of board, as shown at 1, 2, 3, 4, etc.
If you can manage to bend the string without kerfing (grooving), it
will be all the better; if not, the kerfs (grooves) must be parallel to
the rise. You can set out with a straight edge, full size, on a rough
platform, just as shown in the diagram; and when the string is bent and
set in place, the risers and winders will have their correct positions.
To bend these strings or otherwise prepare them for fastening against
the wall, perhaps the easiest way is to saw the string with a fine
saw, across the face, making parallel grooves. This method of bending
is called _kerfing_, above referred to. The kerfs or grooves must be
cut parallel to the lines of the risers, so as to be vertical when the
string is in place. This method, however—handy though it may be—is
not a good one, inasmuch as the saw groove will show more or less in
the finished work.