Most post-frame buildings utilize a permanent wood foundation comprised of pressure-treated posts or laminated columns that are embedded directly into the ground. Post-frame buildings may also be bolted onto a reinforced concrete slab or a traditional cast-in-place concrete or masonry block foundation.

Post-frame buildings may also utilize innovative products that provide alternatives to placing wood directly in ground contact. Post-frame buildings may utilize enhanced wood treatment techniques and wood protection products developed specifically for post-frame buildings, such as plastic sleeves or boots, and concrete posts or piers.

Whether you choose the time-tested and proven method of embedding treated wood directly in the soil or you select a concrete masonry wall or one of the other products developed specifically for post-frame foundation use, you can be confident that a post-frame building will provide a permanent building solution.

Innovative Post-Frame Foundation Products

In addition to the traditional, preservative-treated wood post foundation, there are a variety of products that offer post-frame foundation options. 

Pre-cast reinforced concrete columns designed specifically for post-frame construction utilize a bracket that extends 18 inches above grade to which a solid-sawn post or laminated column is affixed.

• A standard non-treated wood column can be bolted into the “U” shaped connection bracket, eliminating the need for treated wood.
• Reinforced concrete columns are made of 10,000 p.s.i. pre-cast concrete with built-in corrosion and freeze/thaw protection. This special blend ensures superior durability to the standard 3,000-4,000 p.s.i. concrete typically found in most building foundations.
• With an innovative uplift system, no ready-mix concrete is needed for installation. This allows the builder to combine the efficiency of post-frame construction with the durability of concrete. 
• Pre-cast reinforced concrete columns maintain their value and give the building owner peace of mind. 

Poured-in-place concrete pier systems use a pier bracket placed over a hole filled with concrete. Once the concrete sets, the post-frame is bolted onto the brackets.

• Poured-in-place concrete pier systems utilize a bracket that has an engineer’s stamp, assuring code compliance.
• A commercial bracket that also carries an engineer’s stamp certifies that it can carry the moments and the forces of a 6 x 8” laminated column.
• Concrete piers provide a neat, clean look on the inside, without columns being spliced and roof purlins run continuous end-to-end.
• Piers are on grade, which allows prefabricated walls installed on the ground.
• Builders can put trusses on end walls with door headers pre-installed, which saves labor. 

HDPE plastic barrier wood protection systems for enhanced protection of copper-based chemical-treated wood posts and laminated columns

• A plastic sleeve with an enclosed bottom covers the embedded portion of posts or columns.
• Offers a low cost, simple to use and beneficial enhancement to embedded treated wood posts.
• HDPE plastic used in the product is completely resistant to moisture, organic matter, concrete, most chemicals (including wood preservatives), animal wastes, etc.
• The sleeve is designed to fit posts cleanly while still allowing ventilation. Builders don't have to alter construction methods or worry about fit and finish of other framing members.
• Cuts easily with snips, saw, or knife.
• Consultation, research and construction confirm the product’s performance.

• Also available to cover post-frame skirtboards with a barrier between corrosive treated woods and metal trims and siding. 

• Provides moisture and insect protection from footer to above finished floor grade.
• Molded to provide post uplift protection.
• Allows for safe concrete post encasement.
• Prevents chemical leaching from treated posts into soil or ground water.
• Post venting system allows the post to breathe.
• Simple slide-on installation and framing-friendly design.
• Strong, yet pliable and lightweight
• Easy to ship, store and handle
• Attractive coloring and wood grain texture

Other options:

• Creates a foundation-strength base for post-frame buildings
• Provides uplift protection and a way to pour footings
• Finished post and footing is fully enclosed and protected from pests and moisture for the lifetime of the building

• The surface of the wood is coated with asphalt, and a heavy-duty polyethylene shrink film is factory applied to offer a durable protective outer layer.
• The barrier protection system retains chemical penetration and enhances the service life of wooden posts treated with all types of water-borne wood preservatives.
• Provides a technically viable and building code compliant alternative to chemically-treated lumber in weather-protected applications such as post frame construction.
• An uplift restraint notch is pre-applied to the posts prior to the application of the barrier system.
• May be used on solid-sawn, nail-lam and glue-laminated posts.

 
Treated Wood for Post-Frame

Many post-frame buildings use treated wood embedded directly in the ground to form a permanent wood foundation. Post-frame buildings that use the proper treated wood products suitable for post-frame foundations have a long history of success.

Many people think all treated wood is the same, and are not aware there are many types of wood commodities available that have been treated in various ways to meet specific purposes. Because decks and playground equipment are not generally considered crucial building structural elements, treated wood for those applications is not produced to the same specifications as for post-frame buildings. Properly treated and installed posts will ensure a post-frame building will last.

The USDA Forest Products Laboratory has conducted long-term tests in the harshest environments found within the continental U.S. Chromated Copper Arsenate (CCA) type II at retention level .26 pcf treated test stakes have showed no signs of failure since their installation in 1949. Modern post-frame buildings typically use the newer, improved formula CCA type III at retention level .60 pcf.

Specifying Treated Wood by Use

Wood treatment is governed by standards set by the American Wood Protection Association (AWPA). Treated wood for post-frame skirtboards should be treated to AWPA use classification standard UC4A; a larger amount of treatment chemical is forced more deeply into the wood for UC4A than is for deck, playground and other common uses. Laminated columns and solid-sawn posts should be treated to at least UC4B, or a minimum of .60 pcf CCA. If you feel an extra level of wood protection is needed, you may order wood treated to UC4C, or .80 pcf CCA. Kiln Drying After Treatment (KDAT) also improves the performance of treated wood products.

Employ a quality contractor who will use the proper materials – a minimum of .60 CCA or UC4B for columns, and a minimum of UC4A for skirtboards and other members above ground.

AWPA now organizes standards according to its Use Category (UC) system.

CCA-Treated Wood Still Allowed for Post-Frame

CCA-treated wood is still allowed in most types of post-frame construction in accordance with the 2001 AWPA Treated Wood Commodity Standards, which may only be applied to CCA. The table below describes where CCA may be used, according to EPA guidlines.

Commodity Standard/Building Type	Typical Post-Frame building use, including residential, agricultural, etc.	Structure in some marine environments	Agricultural fence posts (rounded)	Residential decks, gazebos, playground equipment, etc.
Solid sawn posts and commodity lumber (including skirt boards, splash boards, and foundation sill plates) less than 5” on any side (C16).	No*	Yes	Yes	No
Solid Sawn 5x5” & larger Posts (C16, C18, or C24) or nail/glue laminated columns (C28).	Yes	Yes	Yes	No
Plywood and wood shingles (C9)	Yes	Yes	Yes	Yes**
Decking, railing, fence pickets, skirt boards, splash boards, sill plates, etc. (C15)	No	No	No	No

Solid-Sawn Timbers and Laminated Columns

Some builders prefer solid-sawn columns, and others prefer the performance of laminated columns.

Solid-sawn posts were key to the early development of the post-frame industry. With improved treatment techniques and new chemical preservatives, solid-sawn posts offer an economical and practical solution to quickly erect a post-frame building.

The species and grade of solid-sawn posts used may affect a building’s quality. Solid-sawn posts of poor quality may warp, twist, split or become otherwise dimensionally unstable. Quality builders who use solid-sawn posts select high-grade timbers to ensure greater dimensional stability and quality.

Southern Yellow Pine is one of the easiest species of lumber to treat because it contains more sapwood and less heartwood than many other species. Heartwood is more difficult to treat than sapwood. Lacerations may be mechanically etched into species with more heartwood, so treatment chemicals may penetrate more deeply into wood fibers. Treaters who produce wood commodities for post-frame should conduct random core sampling to ensure their processes are providing the amount of chemical penetration needed to comply with wood treating standards.

Instead of solid-sawn posts, many post-frame builders today use laminated columns. Laminated columns typically consist of three or more plies of 2x dimension lumber fused into one large member using nails, glue, or both nails and glue. Laminated columns made specifically for post-frame may have warranties that span several decades, or that offer a lifetime guarantee.

Mechanically-laminated columns are used in many post-frame buildings. Laminated columns may be fabricated to any length by splicing shorter pieces of wood together. They are fabricated to be straight and are inherently more stable because of the laminating process. Finger-jointing may increase the stiffness characteristics of a laminated column. Laminated columns are able to deal with increases in bending moment because weak areas in one layer of a laminated assembly are supported by adjacent layers. 

Because laminated columns are composed of lumber that is usually less than 2” wide, there is a larger surface area for treatment chemicals to pass through compared to solid-sawn posts. A laminated column will generally have more chemical retained within it than a solid-sawn post of the same size. Also, smaller members are likely to have more sapwood, which is most amenable to treatment chemical penetration.

A quality builder will know manufacturer recommendations for fasteners and connectors to be used with treated wood and electrical barriers that may avoid corrosion of panels. Stainless steel fasteners and panels with a thick galvanizing layer provide the best corrosion resistance.

For more information about foundations, including case studies and additional technical information, click here to request a free copy of The Post-Frame Advantage Handbook.