Among the many structures used to beautify the grounds of a suburban
or country place, the pergola is seen less than it should be. It is
a luxury, but so is a couch hammock, and many other details of our
modern life might be placed under the same heading. As an arbour for
the training of the vines, the pergola adds more dignity to a place
than any other structure, always assuming that it is well built and
in good proportion. Its length must of course depend on the local
circumstances. It should lead somewhere, as from the house to the
flower garden, or from house to stable. It should, in other words, not
be placed on the grounds simply as an ornament. Its purpose should be
to give a certain amount of privacy to a walk.
The oldest recognized style of architecture is known as post and beam
construction, as suggested in Fig. 219, where two vertical members
support a horizontal one. This style was used by the Egyptians and
Greeks, and was a large factor in deciding the form of the old Greek
temples. The pergola consists of two parallel rows of columns connected
by longitudinal beams and cross beams.
A very artistic one may be built by two boys with the assistance of a
third person in the heavy work of lifting and placing the columns. If a
small-sized structure with 6-inch columns is built, two boys can handle
the whole construction alone.
This small size is not recommended, however, as one of the first
requisites of the pergola is a massive appearance of solidity and
permanence.
The proportions for two sizes are given in the drawing, and they may be
modified to suit the size of the ground, buildings, etc. (Fig. 220.)
Wooden columns in many styles, sizes, and proportions are on the market
and may be bought from any lumber dealer. The bases and caps are
separate and should be ordered to fit the columns.
The construction of the pergola brings the young carpenter in contact
with several new problems. The first is the subject of foundations.
These may be in the form of concrete, which is permanent and solid, and
will not decay, as any form of wooden post will do in time. The ground
should be as nearly level as possible, and should be staked out with
eight stakes, as shown in the drawing. (Fig. 221.)
[Illustration: Fig. 219. The Pergola]
The stakes are three feet from the centre of the columns in each case,
and angle _a c d_ should be made square at the beginning. Measure
distance _a b_ equal to _c d_. From _a_ measure along a line stretched
from _a_ to _b_ three feet, and then three spaces of twelve feet each.
Measure the same distance from _c_ along _c d_, and place stakes at
each point. A line stretched from _e_ to _f_ should pass over the
centre of the stakes marking the centre of each column, as these latter
stakes will be dug out in the process of excavating for the foundation,
while stakes _e_ and _f_ are necessary for the proper location of the
holes.
After digging the first two holes, test their accuracy by again
stretching a cord or masons' line from _e_ to _f_. Proceed with the
next set of holes in the same way, placing new stakes three feet out
from centres to correspond with _e_ and _f_. When the eight holes have
been dug, the arrangement will appear as shown at _g_, twelve stakes
being left in the ground. Should the pergola be longer or narrower, the
same method would be used, the dimensions only being altered. The size
of the holes will depend on the following considerations:
[Illustration: Fig. 220. The pergola]
Assuming that we are building the large pergola with eight-inch
columns, the base will be about twelve inches square. Measure the
base and add two inches to it, making, say, a fourteen-inch square,
the size of the foundation. A box in the form shown at _a_, 14 inches
square inside, must be made. No nails are used on the box. It is held
together by cleats _c c_. They must be made to fit snugly, and are to
be knocked off when the cement has hardened--_i. e._, about four days
after making.
These boxes may be full depth of the hole, three feet, or, as is
sometimes done, the hole is made just the right size and the box, about
eighteen inches in length, wedged into the top as shown at _i_. This
method calls for considerable care in levelling the top of the box and
securing the proper projection above ground, as well as in pouring in
the cement without dislodging it, but the box is removed more easily
than is the case with a full-length one. The decision about this point
determines the size of the hole. In case the short box is used, the
hole must be fifteen inches square and just enough shaved from the
sides at top to receive the box.
If the full length box is used, the hole should be about twenty inches
square, to allow the cleats to be knocked off and boards withdrawn.
[Illustration: Fig. 221. Details of pergola construction]
This weighty question having been decided, prepare to mix concrete.
Make a mixing board about five or six feet square of flooring boards
fastened to heavy cleats on the under side. It should have two or three
sides nailed on, as shown at _k_. Also prepare eight wooden blocks, as
shown in drawing. These may be fifteen to eighteen inches long, sawed
from 4 × 4 timber, planed smooth and with a slight taper toward the
lower end. The purpose of these blocks will be apparent later on. The
concrete is composed of four parts clean gravel to one of Portland
cement, and the best is always the cheapest in the long run. Use a pail
for mixing and place four pailfuls of gravel on the mixing board. Pour
over this one pailful of dry cement and mix thoroughly, turning the
whole mass several times. When thoroughly mixed, pour on water, half
a pailful at a time, and turn again with the shovel until the whole
mass is wet. Shovel this into the first box. It will probably take two
such mixings to fill it. Now place in the top of the concrete one of
the tapering blocks, allowing it to project about three or four inches
above the surface of the concrete. The block should be rubbed with
grease or oil before insertion to make it withdraw easily. As soon as
the block is placed, pass the line from stakes _e_ to _f_ and make sure
that the block is exactly at the centre.
In every case it is to be withdrawn in about an hour, or as soon as
the concrete has set, but before it has gripped the block too tightly;
otherwise withdrawal will be a difficult matter. The object of this
performance is to leave in the centre of the foundation a hole about
a foot deep and four inches across. Level the top of concrete with a
trowel and test with the level.
All the foundations are made alike and no effort should be spared to
see that the boxes are level and in line with each other. Test from end
stakes _a b c d_ and from across stakes with the masons' line. This
work will be easier if the four end foundations are made first.
To do the work thoroughly, two boys may count on the process, from the
staking out to the finishing of foundations, occupying about three
days. It is the most important and laborious part of the work and when
finished represents about one third of the labour on the pergola.
The concrete should stand at least four days before it is touched
again, and during that time the timber may be prepared. Besides the
eight columns, there will be needed:
6 pcs. 4 × 6 ins.--16 ft. long
15 pcs. 3 × 6 ins.--14 ft. long
144 ft. (running) 1 × 2 ins.
8 pcs. of 5/8-in. round iron
The iron should be 18 inches longer than the total height of the wooden
columns, including base and cap. This should be determined by actual
measurement. The rods can be obtained from a blacksmith. Have him cut
a thread at each end and provide two nuts for each rod. They are to
extend clear through each column from the bottom of the hole in the
foundation, through the longitudinal timbers that rest on the cap, to
bolt the whole structure together securely.
Columns come either built up or solid. The solid ones have a core bored
out through the centre, so that in either case the rod can easily pass
through from top to bottom. A hole should be bored 3/4 inch diameter
through the centre of both cap and base to allow the bolt to pass
easily.
In ordering timbers, have them dressed on all sides at the mill. Have
the fifteen 3 × 6 inch pieces sawed on both ends as shown at _l_, and
have one end on four of the 4 × 6 inch pieces sawed the same shape. The
two remaining 4 × 6 inch pieces are to be square on the ends.
A week after making the concrete foundations, the boxes having been
removed and the holes filled in with earth well tamped down, the
openings in the top may be cut out with a long cold chisel, as
shown at _m_. This need not be a very particular job. The object is
to dovetail the cement, to be used in filling up the opening to the
foundation, and it can be done roughly. The setting of the columns on
their foundations is performed as follows:
Nail base and cap to each column and slip a long bolt clear through.
At the bottom the bolt will be allowed to project. At the top pass it
through a piece of wood 6 inches high, a 3/4-inch hole being bored for
the purpose.
Fill the opening in the foundation with clear cement mixed with enough
water to bring it to the consistency of paint. Set the column on its
foundation, with the end of the bolt and its nut and a large washer
immersed in the cement. This will harden quickly, making a strong bond
with the foundation and holding the bolt rigid. Plumb the column, and
if it shows a tendency to lean, place thin wedges under it until it
stands true when tested by the plumb and level on all sides.
Treat all the posts alike and when one row has been set, run the
masons' line along the bolts on top and see that they are in line.
Everything should be ready before starting this job, as clear cement
hardens quickly and any moving of the columns that may be necessary in
lining them up must be done before it sets. A good method is to place
the end posts first, tie the masons' line to the bolts and line the
other two posts as they are set.
When they are all on their foundations at last you will begin to
realize for the first time the value and beauty of the task you have
undertaken. Our boys were so excited that every member of the family,
and some of the neighbours, were dragged out as spectators. It did not
seem possible that two boys could handle such a large proposition, but
there it stood as if it were intended to stand for a century. Harry was
for putting on the superstructure at once, but Ralph had to warn him
not to touch it until the cement had thoroughly hardened.
They allowed it to stand two days before they removed the 6-inch blocks
from the bolts at the top and began the work of placing the long 4 ×
6 inch timbers. These members were lapped as shown in the drawing,
3/4-inch holes being bored to receive the bolts.
When all the timbers on one side were in place, the nuts were screwed
down snug on each bolt with a monkey wrench. The work, with the
cutting, fitting, and boring, consumed a whole day, and a second day
was used up on the second row. It was not necessary to call the family
out again. The boys had all the help that could be desired in lifting,
and were also blessed with a continuous audience.
The cross timbers were gained out to a depth of 1-1/2 inches, and
fitted over the long 4 × 6 inch pieces, as shown at _n_. There was one
over the centre of each column, and an additional piece was removed
to provide for the nut, which was thereby entirely concealed. The
remaining cross pieces were spaced three feet apart on centres, and all
spiked securely to the 4 × 6's. It was found advisable to bore 1/4-inch
holes for the spikes, and to sink their heads below the surface with a
nail set.
It only remained to nail on to the cross pieces five rows of 1 × 2 in
the position shown.
All nail holes and cracks were puttied, and the entire structure down
to the cement foundation was given three coats of white paint. Built
in this manner, the pergola will stand for many years, and already the
boys have planted wistaria, honeysuckles, crimson rambler, trumpet, and
other vines to cover it.
The columns themselves may be easily made of concrete. The form may
be made of six or eight inch iron pipe. When this is bought, have it
split in half lengthwise at a machine shop. Six-inch pipe cut in this
way will cost about a dollar a foot, but it will last a lifetime if
protected from rust, and very often the concrete posts may be sold, so
that the form will soon pay for itself.
Have a blacksmith make two iron bands, as shown at _o_. Have a
5/16-inch hole drilled at _a_ through both ends. These bands are used
to hold the two halves of the iron form together, and are tightened by
a bolt and nut at _a_.
Dig a pit for the form to stand in, so that the cement may be easily
poured in. This pit may be about three feet deep by two feet square,
and the sides supported by a box without a bottom.
To make a column, clamp the two bands about the form, and place in
the bottom end a circular piece of wood, with a hole in the centre to
insure the iron rod being in the middle. Place the form upright in the
pit, and secure it firmly by nailing strips of wood across the top
of the box. Place the iron rod in the centre, passing it through the
hole in the bottom. Pour in the cement quite wet, and tamp it down
occasionally until full. It will settle a little, and will need to be
filled to the top. A circular piece of wood, similar to the one at the
bottom, may be used to centre the rod at the top. This must be done as
soon as the form is filled, before the concrete has had a chance to set.
Use four parts of fine, clean sifted gravel to one of cement. Allow
the form to stand four days. Remove the clamps, and draw the form out
on the ground. Tap it gently, and remove one half of the iron pipe.
Roll it over upon two pieces of board, and remove the other half. The
concrete will be very heavy, and the assistance of a full-grown man may
be needed to draw the form out of the pit.
The inside of the form should be cleaned and thoroughly oiled. This
should always be done before making a column to insure its coming out
easily, as concrete forms a strong bond with iron, and otherwise the
column may be broken in trying to get it out. The result will be a
perfectly round but not perfectly smooth column. It should be coated
with a wash of clear cement and water, using a wide brush. The colour
may be made white by adding a lump of lime to the cement and water,
and two coats of this solution about the consistency of milk will be
necessary. The last coat may be put on after the columns are on their
foundations. The placing of the posts on the square foundations is
heavy work and the help of a labourer should be secured.
These plain posts are not as ornamental as wooden columns, with their
bases and capitals, but they make a very substantial structure that
cannot decay and will last a century.