Avoiding Using Pressure Treated Wood
Pressure preservative treated wood remains a mainstay in modern wood construction. United States’ manufacturing and sales of pressure treated wood has become a multi-billion dollar industry. Even with all of this, there are some skeptics.
Reader DIANE in MORGANTOWN writes in:
“ I want to avoid pressure treated wood. Even the newer and safer versions. Can any alternate material be used? Concrete? Metal? Thank you!”
I personally have full faith in current formulations of pressure preservative treatment chemicals for wood to be both environmentally friendly, safe for myself and my loved ones, and to provide excellent longevity. With this being said everyone should do their own due diligence of any product and develop their own opinions based upon such research.
From 2015 IBC (International Building Code):
“2304.12.2.2 Posts or columns.
Posts or columns supporting permanent structures and supported by a concrete or masonry slab or flooring that is in direct contact with the earth shall be of naturally durable or preservative-treated wood.
Exception: Post or columns that are not exposed to the weather are supported by concrete piers or metal pedestals projected at least 1 inch (25mm) above the slab or deck and 8 inches (203 mm) above exposed earth and are separated by an impervious moisture barrier.”
Column holes can therefore be completely concrete filled with wet set brackets placed on top of concrete allowing use of untreated wood columns (as long as column isolated from concrete per Code or weather protected, it does not have to be preservative treated). https://www.hansenpolebuildings.com/2012/09/concrete-brackets-2/
A splash plank will be required around post frame building base in order to provide a form for any concrete slab poured upon grade and/or to be an anchorage point for siding. Typically this a pressure treated 2×8. In your case, an untreated board of cedar or redwood could be used, as they are somewhat naturally decay resistant. Keep in mind untreated cedar or redwood has a lifespan much shorter than treated wood.
“We have a Building Official asking for a termite shield for a post frame (pole) building. The building utilizes pressure preservative treated columns embedded in the ground with a treated splash plank around the base of the walls. At the bottom of the steel wall siding is what is known as base trim, it is steel and extends outward from the splash plank 1-1/2″ with the outer edge being a downward bent lip. This should serve to function just like the steel termite shields we have viewed online. 4-5/8″ of the pressure preservative treated splash plank is visible below the base trim. There is a product called a plastiskirt which is vinyl and designed to wrap the splash plank. In your opinion, what would be the best design solution to protect the building from termites as well as to meet the requirements of the Building Code?”
