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Basement Walls

I am about to begin finishing my basement and am concerned about the materials I need to use that are in contact with or next to the concrete floor or cinderblock foundation.  My basement is dry, but I think I am required to use pressure treated lumber if the lumber is in contact with masonry or concrete.  Is this a correct assumption?  Should I use pressure treated lumber for the vertical supports if they are next to the masonry foundation, even if I stand the walls off an inch or two from the cinder block?  Does the vapor barrier go between the sheet rock and stud or between the stud and cinder block wall?

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Posted 2011-07-04T02:58:02+0000  by NJsooner NJsooner

Hi there NJsooner and thank you for your question.


I always praise how great social media and these forums are; you get to start a “thread” that can possibly help millions after. Your question is a perfect example. You are at the beginning of the project and you’re concerned about materials being used. Well your concerns are legitimate, some materials shouldn’t be used and some should be installed according to your local building codes and geographical location.


Perfect example and also an answer to your first question would be using unprotected lumber for the bottom plates. You assumption is correct bottom plates should be pressure treated lumber or white lumber installed over some type of moisture resistant barrier in between wood and concrete.


Regular lumber it’s used for vertical supports and top plates. Using pressure treated lumber it’s overkill and from my experience will cause problems due to warping and cupping that is present during drying cycle. Also fasteners used with PT lumber have to be specifically coated to resist chemicals present in PT lumber. All of this and being that vertical supports in correct application are offset from the concrete makes pressure treated lumber unnecessary.


Clearance in between concrete and framing members;


This is a very important step that should not be avoided. Depending on the insulation used a continuous clearance may need to be provided in between framing and foundation walls to allow drying in between vapor barrier and concrete. Clearance should be one inch or greater depending on the plane of the wall. In other words if your wall is out of the plumb you may have one inch clearance on one section but none on the other that is out of the plane.

This rule would apply if traditional unfaced fiberglass insulation is used or similar. Moisture tolerant insulation (XPS) should be installed in contact with concrete and masonry surfaces.


Depending on the number of cold days and geographical location vapor barrier should be either placed on interior or on the exterior side of the wall. Please refer to this link in regards to vapor barrier placement;


Hope this helps and welcome to the community.




Posted 2011-07-05T16:30:22+0000  by George_HD_CHI
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