Building Foundation Types & Designs
Note: The goal of this page is to help you understand different types of
concrete foundations used in barn construction. Always consult with an engineer and
your local municipality before doing foundation for your building. Keep in mind that all types of
foundations must be designed according to the latest IBC (International Building
Codes) and soil bearing capacity. In addition, building size, number of
stories and intended use of the structure must also be considered in foundation
Concrete Pillars Foundation
Use: This type of foundation is mostly used on buildings with post & beam
style (or similar) construction where main supporting posts are spaced far apart. It is important to have
the pillar under each supporting wall
post. Pole barns may also be built with this type of foundation to protect
posts from rotting.
Advantages: Very affordable foundation
Disadvantages: Can not be used with conventional
construction where walls are framed with studs, unless a heavy structural grade
beam is installed first.
Cost: Approximately $150 - $300 per each pier, depending on size
and depth of pier.
Notes: For storage barn or garage use, concrete slab and
piers are poured at the
same time to create a single Monolithic Style Frost Protected Foundation.
How to Do (piers & slab): Level the site (taking all of the top soil off), drill
a hole with an auger bit
under each supporting post, prepare stone base (see
site preparation), set up concrete slab form using 2x6 lumber for a 5-½" thick slab,
place two re-bars in each hole (bend the top of each re-bar at 90°), put wire mesh in place
(see image on left), pour piers and slab with
#3500 concrete mix. Finish concrete.
How do Do (piers only): For horse barns where concrete slab is not
needed, after drilling all of the holes, install construction tubes (higher than
the ground level) and secure tubes in place so they don't move when concrete is
poured. Next, using transit or rotating laser level, mark each tube at the
top making sure that the tube at the highest elevation point is 4" above ground
(might be higher at the lowest point if site is off level), cut the tube off at each mark, making
sure each cut is straight. After this, pour concrete, make the top of each
pier smooth and level and wait for at least 3 days for concrete to set.
After concrete is set, spread stone between piers and compact it, making sure
that the top of your stone base is almost even with the top of piers.
Size of Piers to Use: The most common sizes are 18" - 24" in diameter.
Exact size of each pier must be determined by an engineer.
Depth of holes to drill depends on your area's frost line. Make sure to
drill holes below frost line.
Also known as a Slab-On-Grade Foundation and sometimes referred to as a
Use: Mostly used in warmer climates where ground does not freeze and
also in rocky areas when it's hard or impossible to drill holes or dig trenches
below the frost line. Also, often used for smaller buildings and sheds.
Advantages: More affordable than conventional foundation and may be
converted into FPSF (Frost Protected Shallow Foundation) by adding Ridgid Foam
insulation around perimeter.
Cost: Depends on size, slab thickness, region, etc.
Note: Call your local municipality to find out if this type of
foundation is allowed in your area and consult with an engineer to properly
design it for your area.
Ho to Do: Level the site taking top soil off, dig 12" - 16" deep
trenches around perimeter sloping the inside of the trench wall (as shown) and
compact the soil. The bottom of the trench should be at least 12" wide.
Next, prepare the stone base (see
site preparation), install concrete form (we
recommend 5"-6" thick slab) and place all of necessary re-bars and wire mesh in
place. We recommend at least (3) #4 re-bars inside the trench and a wire
mesh for the slab. Pour concrete and finish the slab.
Use: This type of foundation is more expensive to do, but may be used
in different construction applications. This foundation can be used for
barns, garages, houses and for many other buildings.
Advantages: Provides a very sturdy frost protected foundation.
May be done with either cement blocks or as a complete poured concrete wall.
Cost: Depends on the depth, size of footing and the area you live in. Also
depends if the foundation is done with cement blocks or as a poured concrete
Note: The width and the thickness of the footing must be designed
according to IBC, soil bearing capacity and the intended use of your structure.
The depth of foundation must be below your area's frost line. Normally,
the footing width varies from 12"-18" in width and 6"-8" in thickness.
How to Do: Prepare the site (see
site preparation), dig the
trench below frost line, compact the bottom of the trench (optional), set up the
form for the footing (keeping the top level), install two or three #4 re-bars in place
and pour concrete. After the concrete is hard & cured (2-3 days) set up
the form to pour foundation wall with all of the necessary vertical re-bars, and
then pour concrete. After the concrete is poured, install anchor bolts and
finish the top of your foundation making it smooth and level. Another
option is to lay 8" or 10" cement blocks on top of the concrete footing, keeping
at least one course of the blocks above ground. Later, you'll need to pour
cement inside the blocks and install anchor bolts.
Final Notes: To prevent a water penetration through your foundation
wall, Conventional Foundations (and sometimes Slab-On-Grade Foundations) require
outside of the foundation wall to be coated with a water resistant coating.
Installation of drain pipes might also be required to divert water away from a