LEAFLET NO. 52
A POLE BARN
WALTER GRUB, Associate Agricultural Engineer
POLE 3BARNs are here to stay. And,
there are good reasons for their popu-
larity.
Designed for Alabama farmers by
the Agricultural Experiment Station of
the Alabama Polytechnic Institute, the
multipurpose pole barn has these chief
advantages: (1) low in cost, (2) simple
to construct, (3) long lasting, (4) rough
cut lumber is used throughout, (5) no
masonry footing or foundation is re-
quired, and (6) no diagonal bracing is
needed.
The only major disadvantage is the
difficulty in handling and raising the
long, heavy poles.
The barn's structural frame is de-
signed so that it can be adjusted for a
variety of purposes. Variation in pole
spacing can be used to advantage for
machine storage and farm shop, per-
mitting bays of varying width for dif-
ferent size machinery. The barn can be
a cattle shelter; by using taller poles,
it can be used for hay and feed storage.
Another use is for a poultry house; the
pole spacing can be varied for different
widths and arrangements.
Buildings have been constructed from
this plan at the Station's Plant Breeding
Unit at Tallassee and experiment fields
at Alexandria, Tuskegee, and Brewton.
These structures have proved satisfac-
tory during more than 2 years of tests.
Approved by the Experiment Station,
plans are now available (plan Number
BP-6) from the API Extension Service.
Regardless of how good a design or
plan is, a good job of construction is
necessary for a satisfactory building.
This is especially true in the case of
pole barns. Pole type buildings will not
be structurally sound unless proper
construction methods are used. Pre-
sented in this leaflet are detailed in-
structions, based on the Experiment
Station's design research, on each step
in pole construction.
MATERIALS
The plan specifies certain types and
sizes of materials to be used. It is un-
wise to substitute other sizes, grades,
or types without checking the advisa-
bility of each substitution. If inferior
AGRICULTURAL EXPERIMENT STATION
l/he ALABAMA POLYTECHNIC INSTITUTE
N ~;~ A~-I ~~- ~ IG~~ MI\ TI;~~A1~CI1 II~~A
MAY 1957
E. V. Smith, Director Auburn, Alabama
materials are used, the'building may be
unsatisfactory.
Poles
The poles are the most critical ma-
terial used in this type of construction.
As the main supporting members, they
supply rigidity and strength to the
structural frame, and the lower ends of
the poles serve as footing and founda-
tion.
The poles are in direct contact with
the soil. Therefore, they must be prop-
erly treated to prevent damage by
wood-destroying fungi, bacteria, and
termites and to assure a long building
life. A quick dip or paint treatment is
not satisfactory because the wood pre-
serving chemicals do not penetrate
deep enough into the pole to serve any
practical purpose. For a pole life of 35
to 50 years, a pressure treatment with
No. 1 creosote or a 5 per cent solution
of pentachlorophenol to a retention of
8 pounds per cubic foot of wood is re-
quired. Such treated poles can be pur-
chased from most building supply deal-
ers and lumber yards.
Poles having a small end diameter of
about 5 inches are needed. Smaller
poles do not provide sufficient area for
holding the nails that fasten the rafters
to the poles. Larger poles are too heavy
and difficult to handle. Length of the
poles will depend on their location in
the building. They must be about 2 feet
longer than the distance from the bot-
tom of the hole to the roof to allow for
low places and slope. This extra pole
length is cut off after the roof framing
is in place.
Framing Members
Side wall nailing girths that come in
contact with the ground require the
same pressure treatment as the poles.
All other framing members, both roof
and side wall, can be rough cut, yard
dried, No. 2 yellow pine or equal.
Dressed lumber may be used but it is
more costly, and when used as rafters
and purlins, it has only 70 to 75 per
cent of the strength of rough cut lum-
ber.
The commercial grade of yellow pine
known as No. 2 Common is recom-
mended. Rafters and purlins containing
knots that appear objectionable can be
rotated so that the knots are on top.
The strength of these framing mem-
bers is not appreciably affected when
knots are located in this position.
Roofing
Metal roofing is nailed directly to
the roof purlins, which are spaced 24
inches from center to center. Metal
roofing material that requires closer
purlin spacing can be used if the purlins
are spaced according to the require-
ments of the manufacturer. For non-
rigid roofing, a solid wood deck is
nailed to purlins.
Side Walls
Exterior siding, such as vertical
rough cut boards and battens, exterior
grade building boards, or metal siding
may be used. These materials are nailed
directly to the horizontal nailing girths,
which are spaced from 24 to 42 inches
from center to center depending upon
the siding used. Any of these materials
will prove satisfactory. They should be
selected on the basis 
of cost, durability,
and ease of application.
LOCATION q BUILDING
The building is made part of a good
farmstead plan and oriented to give
maximum protection from prevailing
winds and rains. A level, well drained
building site is selected and any neces-
sary grading completed before con-
struction is started.
Batter boards are next set in place
about 3 feet beyond the proposed
corners of the building and lines are
strung between the batter boards to
represent the outline of the structure.
These lines can be squared by setting
up a contractors transit over the corners
or by measuring from one corner a dis-
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FIGURE 1. Lines outlining the building are strung between batter boards located about
3 feet beyond the proposed corners of the building. Corners are squared as shown in
the diagram above,
tance of 3 feet along one line and 4
feet along the other, Figure 1. If the
corner is square, the distance between
these points will measure exactly 5 feet.
If the distance between these points is
not 5 feet, one string is moved until
the correct measurement is obtained.
This process is repeated on each adja-
cent corner until all four corners are
square. One further check for square-
ness is then made by measuring the
distance between the diagonal corners
of the building. These distances will
be equal if the comers are square. If
the measurements are not the same, the
foregoing process is rep'eated until the
building outline is square.
Stakes are then driven into the
ground to locate the center of each
hole, Figure 2. The outside edge of
each exterior wall pole should just
touch the line forming the outline of
FIGURE 2. To locate the center of each hole, stakes are driven into the ground a
distance of one-half the pole diameter from the line marking the side of building.
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the building. To obtain this pole posi-
tion, the center of the hole is positioned
in from the line one-half the diameter
of the pole. This point on the ground
is found by dropping a plumb bob from
the desired position on the guide line
and measuring the required distance.
At this point a short stake is driven into
the ground to mark the center of the
hole. The same procedure is used for
locating the other stakes. Interior poles
are located by stretching lines from a
stake on one wall to the corresponding
stake on the opposite wall and measur-
ing in from the guide lines. When all
of the stakes are driven, their positions
are checked by sighting along each line
of stakes to make certain no erroneous
measurements were made. Special care
in laying out pole positions will prevent
having to redig holes and relocate poles.
STEPS CONSTRUCTION
Holes
Depth of the holes depends on type
of soil and height and weight of the
building. The holes generally are dug
4 feet deep in soil of compact sand and
gravel, shale, or dense sandy silt. If
the soil type is sand, clay, silt, or muck,
the holes are dug 5 feet deep for extra
rigidity and strength. In either case the
holes must be dug to undisturbed sub-
soil and all loose dirt removed from the
bottom of the holes.
The diameter of the holes is dug 6 to
8 inches wider than the butt diameter
of the poles. This allows room for rais-
ing and positioning of the pole, and for
tamping the backfill soil. If the building
is located on muck, clay, silt, or sand,
the diameter of the holes must be in-
creased and the hole backfilled with
bank or stream-run gravel. If the soil
is compact sand and gravel, shale, or
dense sandy silt, it may be used as the
backfill material.
To obtain straight building lines, the
straightest poles are used at the corners
and end walls of the building. The
poles are placed butt down and posi-
tioned so that their straightest side just
touches the lines that form the exterior
edges of the building. The poles can
be plumbed with either a builder's
transit, a carpenter's level held against
a straight edge, or a plumb bob. They
are held temporarily in position with
two diagonal braces, Figure 3, that
have been fastened to stakes. The butt
of the pole is secured by backfilling the
hole with two 4-inch layers 
of soil,
each layer uniformly spread and well
tamped. The hole must not be com-
pletely backfilled until after the roof
framing is in place so that minor align-
ments can be made.
The side wall and interior poles are
placed and aligned next. To compen-
sate for a lack of straightness, these
poles are rotated in the holes so that
the straightest surface faces the side of
the building. The poles are then
aligned with the corner and end wall
poles, and the bottoms secured with
two 4-inch layers of soil, each layer
well tamped.
A level grade mark is made on each
FIGURE 3. Poles are held temporarily in
an upright position with diagonal braces
fastened to stakes. Butt of the pole is
secured by backfilling with two 4-inch
layers of well tamped soil.
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pole. It can be made with a string level
or a farm level. From this line, the
height of each rafter is marked on each
pole. Rafters are then cut according to
the plan and fastened into position. For
greater strenuth, the rafters are fast-
ened to the sides of the poles rather
than on top of the poles.
Fastening the rafters is of utmost im-
portance. The joint 
must support the
downward force caused by the roof
and snow load and the upward force
caused by wind. To support these loads
satisfactorily, the rafters must be firmly
fastened to the poles with 40d nails or
spikes.
After rafters are in place, the purlins
are added. To prevent wind damage,
the roof purlins must be securely an-
chored to the rafters. Framing anchors,
shown in Figure 4, are a satisfactory
fastening device. With this type of con-
nection, the full strength of the roof
framing can be utilized.
Purlins can be fastened in place by
two men working on adjacent rafters,
each starting at the cave and working
to the ridge. Tops of the poles are cut
off as nurlins are fastened1 in pos-itlon.
FIGURE 4. Fasteners shown above se-
curely anchor roof purlins to rafters. Thus,
to prevent wind damage.
Backfilling the Holes
After enough purlins have been fast-
ened in place to tie the rafters together,
the holes are completely backfilled. The
slightly moistened soil is evenly distrib-
uted around the pole in 4-inch layers.
Each layer is thoroughly tamped before
the next layer is added.
Finishing the Roof
After the remaining roof purlins are
fastened in place, Figur 5, 2 x niui-
FIGURE 5. Two purlins are placed at the roof ridge with lower sides touching to pro-
vide nailing surface for end of roofing sheets and for ridge roll. A solid deck roof can
be nailed to the purlins if non-rigid roofing material is to be used.
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ers are fastened to the ends of the pur-
lins on each gable endl of the roof. The
building is now ready for the sheets
of metal roofing, which should be
applied according to tile manufacturer's
specifications. If a roofing material re-
quiring a solid roof deck is used, 1-inch
tongue and groove boards or % inch
exterior grade plywood is nailed di-
rectly to the purlins.
Siding
The side wall framing consists of
2X6 members nailed directly to the
outside of the poles. Girths are nailed
in a horizontal position, lapped at the
poles, and spaced from 24 to 42 inches
from center to center depending upon
the siding material used. The girths
that are placed in contact with the
ground are pressure treated with wood
preserving material. No untreated wood
framing or siding material should be
placed any closer than 8 inches from
the ground. Metal siding, vertical rough
cut board and battens, or exterior grade
building boards can be nailed directly
to the side wall girths.
Roof Pitch
The roof pitch can be varied without
any major changes in the structural de-
sign. However, it should conform to
the minimum pitch recommended by
the roofing material manufacturer.
SUMMARY
Pole frame buildings are structurally
sound, low in cost, easy to construct,
and suitable for erection by farm labor
using locally available building materi-
als. Because of the importance of
proper construction, care must be taken
to follow the plan carefully. Competent
advice should be sought before substi-
tuting building materials not specified
on the plans.
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