Roof framing can be done about as many different ways as there are
mechanics. But undoubtedly the easiest, most rapid and most practical is
framing with the “square.” The following cuts will illustrate several
applications of the square as applied to roof framing, and all who are
interested in the subject can, by giving it a careful study, be able to
frame any ordinary roof the mechanic comes in contact with.
Fig. 33 is an illustration that could well be given much thought and
study. It not only gives the most common pitches, but also gives the
degrees.
Most carpenters know that half-pitch is 45 degrees, yet few know third
pitch is nearly 34, and quarter-pitch about 27 degrees.
A building 24 feet wide (as the rafters come to the center) has a
12-foot run and half-pitch the rise would also be 12 feet, and the
length of the rafter would be 17 feet (the diagonal of 12). Length,
cuts, etc., could all be figured from the one illustration.
[Illustration: Fig. 33.]
[Illustration: Fig. 34.]
Fig. 34 illustrates a way to cut rafters with the square.
A roof 14 feet wide would have a run of 7 feet, third-pitch would rise 8
inches to every foot run. Therefore, place the square on 8 and 12 seven
times, and you have length and cuts.
Fig. 35. For the octagon rafter, proceed same as common rafter, only use
13 for run (in place of 12 for common rafter).
[Illustration: Fig. 35.]
Fig. 36, hip or valley rafter. As these rafters run diagonal with the
common rafter and as the diagonal of 1 foot is practically 17 inches,
use 17 for run, and proceed same as common rafter.
[Illustration: Fig. 36.]
Length of jacks. If there are to be five, divide the common rafter into
six equal parts, use that for a pattern, and it gives the length very
nicely. But that will not always work. To get all the different lengths
might at first look difficult even to many good mechanics, but it is
very simple as illustrated in Fig. 37. If the first jack was one foot
from corner apply the square same as for common rafter, and it gives
length and cut (mark the length for starting point on next), and if it
is 17 inches from the other move the square up to 17, if the next is 15
move up to 15 and so on.
[Illustration: Fig. 37.]
Fig. 38. The side cut of jack to fit hip, if laid down level would, of
course, be square miter, but the more the hip rises the sharper the
angle. Measure across the square from 8 to 12, and it is nearly 14½,
which is the length of rafter to one foot of run. Length and run, cut on
length, gives the cut.
[Illustration: Fig. 38.]
[Illustration: Fig. 39.]
Fig. 39, octagon jack. As the octagon miter on level surface is 5 and
12, it must raise same as common jack, and is, therefore, raised to
length, or 14½, and 5 cut on length.
[Illustration: Fig. 40.]
Fig. 40, hip rafter, is also length and run, cut on length.
[Illustration: Fig. 41.]
Fig. 41. To bevel top of hip take length and rise and mark on rise.
Fig. 42 is another practical way, which is simply to lay the square on
heel or hip. The illustration, explains itself.
[Illustration: Fig. 42.]
Perhaps the most practical way of all to frame a roof, the simplest to
understand, easiest to remember, and most rapid to apply is simply to
always take the rise and run, measure across the square which gives
length. Rise and run give cuts, so you have it all.
[Illustration: Fig. 43.]
Fig. 43 illustrates a roof 25 feet wide and a rise 10 feet, 9 inches,
run 12 feet, 6 inches. Measuring across the square from 10¾ to 12½ gives
16½, or 16 feet, 6 inches is the length of rafter.
Fig. 44. If the run of common rafter is 12½, the run of the hip will be
diagonal of 12½ which is 17 8-16, as is plainly illustrated.
[Illustration: Fig. 44.]
Fig. 45. As the rise is 10¾ and run 17 8-12, the length will be 20 feet,
2 inches.
[Illustration: Fig. 45.]
Fig. 46. When a roof must go to a certain height to strike another
building at a given point, as in additions, porches, etc., don’t forget
in getting the rise from plate to given point to allow the squaring up
of heel as illustrated; and also remember to allow for ridge whenever
one is used.
[Illustration: Fig. 46.]
Fig. 47 illustrates the cut of top of quarter-pitch rafter to lay on top
of roof just mentioned. To apply the square first lay it on 12 and 6,
which is quarter-pitch, and gives plumb-cut. From plumb-cut lay off
pitch of main roof 10¾ and 12½, which gives cut.
[Illustration: Fig. 47.]
Anyone that has studied this with determination will have no trouble in
framing any ordinary roof, as the general principles apply to all roofs,
pitches, etc. So I will not take up any more space with roof framing at
this time, but remember all sheathing, studding, cornice, etc., are made
on the same cuts. In fact a hopper is also exactly on the same
principle.
Division B.
SOME POINTERS ON ROOF FRAMING.
No matter what people may say to the contrary, there is no method or
methods that has ever been devised that is so effective in roof framing,
or results so rapidly achieved, as those which are obtained by the use
of the steel square. I have shown in some of the earlier pages of this
work how rapidly the length, and bevels of any common rafter may be
obtained by the simple application of the square, any determined number
of times. Thus for a building of, say, 30 ft. in width, which is to have
a roof of any given pitch, we arrange the pitch as I have shown, with so
many inches on the blade for the run, and so many on the tongue for the
rise. This settled, we apply the square fifteen times to the rafter, 15
being half of the width of the building. This then gives the length of
the rafter, and a line drawn along the edge of the tongue of the square
will give the proper bevel for the top or plumb cut. If there is to be a
ridge board on the roof, then half the thickness of such board must be
measured back on the line drawn, and the rafter must be cut at that
point, this provides for the ridge board being nailed on the face of the
cut without in the least changing the pitch.
A line along the edge of the blade, gives the proper bevel for the level
or horizontal cut. If the bottom end of the rafter is to have a
crow-foot cut on it to fit the plate, the workman will have no
difficulty whatever in cutting the foot of the rafter to suit, as all
the lines will be at right angles to each other, and a section of the
plate may be made on the line of the bevel and the “cuts” laid off to
suit the conditions.
In reviewing an article of mine on this method of laying out a rafter,
an English carpenter took exceptions to it on the grounds that it would
take too much time to lay out the rafters for a whole building by this
“tiresome process,” as he called it. Now the Englishman was right from
his point of view, but no American workman would ever think of laying
out the rafters for a whole building by the process. He would simply
make one rafter as I have shown, for a pattern, and use this pattern for
laying out all the other rafters for that particular pitch and rise on
the same roof. Most workmen, however, make a pattern from thin stuff of
some sort, as it is lighter and easier handled. The reviewer suggested
as a better way “that the pitch be arranged on the iron square, then
measure across the angle from the points of run and pitch, and multiply
this measurement by half the width of the roof to be covered.” Now this
is all right, but, as a matter of fact, entails more labor of a
“tiresome sort” and would use much more time than the method I have
taught now for nearly forty years. The American workman, however, does
not even require a suggestion as to the quicker method. He will see and
adopt it at once without argument.
[Illustration: Fig. 48.]
The method the Englishman would adopt is shown at Fig. 48, where the
points of pitch and run are shown at 12 and 8, which makes the diagonal
line 14½ inches. To get the length of the rafter for our supposed
building then, we must multiply this 14½ inches fifteen times, then we
must use the square at the top and bottom of the timber to obtain the
necessary bevels for the cutting lines.
Regarding this question of preparing rafters for a common roof, an “old
hand” in the use of the steel square writes to me to say: “I do not
think that any simpler method can be given for finding the bevels at the
heel and point of rafters than that which you have explained in your
books, but I do think that the following method for obtaining lengths of
rafters, is somewhat better than yours, particularly when employed for
estimating purposes. The most common width of buildings in my locality
is 24 ft., and with your permission I purpose to take that width for the
practical test of my method. As you have given several ways by which the
same result can be obtained, I will ask you to compare them with mine.
Finding the length of the hypothenuse by the old rule, we obtain for
one-quarter-inch pitch 13:4.99, or, as near as it can be used on the
square 13 feet, 5 inches.
Allowing one inch to the foot and trying your method we find, as a
result, 13 inches and 7-16 scant, or 13 feet, 5 inches. This is a very
simple method, and when the rule is kept perfectly straight, the results
are very satisfactory.
By my way I simply multiply the width of the building by the decimal
.56, 24×.56=13.44, or as near as can be worked by the square, 13 feet, 5
inches.
Let us try the same rule for a greater width—say 60 feet. By finding the
hypothenuse we find as near as can be used by the square, 33 feet, 6½
inches. By my method it would be 60×.56, or 33.60, equal to 33 feet, 7
inches full. By this method the rafters in wide buildings are a little
long. Thus, if the building is 52 feet wide, by the hypothenuse it would
be 29 feet, 1 inch; my way it would be 29 feet, 1½ inches. I consider
this an advantage, as it leaves the point of the rafter very slightly
open.
For one-third I follow the same plan, only using the decimal .6. Unlike
the decimal used for a quarter pitch the lengths are a very small
fraction short; as, for instance, a rafter for a building 60 feet wide,
by finding the hypothenuse, would be 36 feet, 1-16 of an inch. By my
way, 60×.6=36 feet. A slight difference, truly. If building is 48 feet
wide, then by the first method we find 28 feet, 10 inches full; by my
way, 28 feet, 9⅜ inches. A little practice will enable the mechanic to
allow just enough to make up for the slight difference, so that when
rafters are put together the fit will be perfect.
The one-half pitch can be found in the same manner by using the decimal
.71. Taking the 24-foot building, length of rafters by the hypothenuse,
we find 16 feet, 11 2-3 inches; my way they would be 17 feet full.
Again, building 60 feet wide, rafters by the first method would be 42
feet, 6⅛ inches; by my way 60×.71=42 feet, 6 inches. By using this
decimal, the length is so near practically correct, that it may be used
in all cases.
For a full pitch use the decimal 1.12, and as in the preceding mentioned
pitch, and it will be found so near correct that it can be practically
used in all cases.
It will be noticed that I have not made any allowance for projection of
rafters over the plate. In this case gauge from the crowning side of
your rafter the thickness of your projection; allow enough for the
latter, and find the lower bevel according to the way you described in
your last; measure the length of your rafter from where this bevel
crosses the gauge line.
A little practice will enable the mechanic to lay off a rafter in a very
short time. I have used the above myself, and have no trouble whatever.
While I have no fault to find in your methods, as I know them to be
correct, yet it is just as well that workmen should know other methods,
as there are many occasions when the “only method” he possesses cannot
be applied. Hence I submit the foregoing, at your request.