Mike writes
I'm looking to have a cement block retaining wall replaced. Several contractors have suggested using 6x6 pressure treated lumber to build a tie wall. (This wall will butt up directly against my foundation wall, and under my deck) I've always be taught that wood with ground contact is never a good idea. Is pressure treated wood really termite and carpenter ant resistant? Are there any other products I can use with the PT lumber just for added protection? I was looking at Bora-Care, but the Q&A points out it won't soak into PT lumber.
You should definitely use pressure treated wood when it is in contact with the soil. Eventually though, pressure treated lumber will lose their pressure treated qualities and eventually be susceptible to termite damage. Unfortunately, there is nothing you can do to the wood now that will work. You cannot apply wood treatment products to pressure treated wood because PT wood does not allow moisture into the wood and the products that are used on wood are required to be able to move through the wood to work. You should either not use wood on your retaining wall or be prepared to do something else or treat the wood in about 8 years when it starts to lose its pressure treated qualities.
Answer last updated on: 07/28/2011
