Building an Addition With Used Pressure Treated Lumber and Cement Blocks

Can old Pressure Treated Lumber and Cement Blocks be use in New Construction?

By Mark J. Donovan

Question: I am building a 20’x30′ addition with a crawlspace onto my concrete block house. I have a possible source for used pressure treated lumber (several 20′ 6×6 beams, lots of 2x8s and some 2x4s and 2x12s too). Would this be good to use for frame construction/floor joists/rafters, etc? Would I be better off doing some sort of post and beam design with the 6x6s? I also have an old block building on my property, and I wanted to know if I should use this instead for free material to build the addition. How difficult would it be for me to tear it down myself and prepare the blocks for the new construction? Is the labor on block construction more expensive than frame construction?

Answer: I would first check with your local building inspector to see if there are any issues using pressure treated lumber in framing your home (particularly older PT lumber). Because of the preservatives in pressure treated wood, particularly pressure treated wood older than 2004, the EPA banned the use of CCA (Chromated Copper Arsenate) pressure treated lumber in home construction.

The new pressure treated wood products use a copper based chemical known as Alkaline Copper Quaternary (ACQ).

ACQ is less harmful to the environment however care needs to be used in what type of nails/fasteners you use with it. Galvanized or stainless steel nails / fasteners are required. If your PT lumber is newer and allowed to be used in your home’s construction use these types of fasteners.

Note that the American Wood-Preservers Association (AWPA) has approved certain types of pressure treated lumber for enclosed / interior framing applications.

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However, for enclosed structural framing purposes, the pressure treated lumber must be dried after treatment to a moisture level of no more than 19% before the building is enclosed. Again, check with your local building inspector on determining specifically what type of treated lumber you can use in your enclosed framing.

Even if you get the all clear from your local building inspector, I still have my reservations about the use of pressure treated lumber in enclosed framing applications. I am concerned that either through an out-gassing or leaching process of the lumber, you may be exposing your family to chemicals that may one day be deemed unsafe. My recommendation would be to limit pressure treated lumber to outdoor applications.

Regarding using old cement blocks, I would suggest that you will find it labor intensive, and thus expensive, to breakdown the old wall, clean up the blocks and reinstall them in a new foundation wall.

 Building an Addition With Used Pressure Treated Lumber and Cement Blocks

My recommendation is to bite the bullet and use new material on your addition project. In the end, you will save time and money, and not risk exposing your family to any environmental concerns.

For more help on building a family room addition, see’s Room Addition Bid sheet. The Room Addition Bid Sheet  provides you with the knowledge on how to plan a room addition project, and what to look for when hiring contractors for your new home construction. It also includes a detailed cost breakdown table and spreadsheet for estimating your own room addition building costs.

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