Basement subfloor with crawl space

Old 03-29-23, 07:35 PM
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Basement subfloor with crawl space

I have a home in Superior, CO that came with a basement subfloor with a crawl space. It's constructed out of TJI joists and 3/4 tongue and groove. If I want to frame walls on top of the subfloor do I need to float them on top of the subfloor or does the TJI subfloor with two feet of crawl space under it act as the floating walls? Thanks, Will
Old 03-29-23, 07:44 PM
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Colorado has some weird rules on basement finishing, so you may not find someone here that is familiar with that style of framing. Your best bet is to call your local building inspector, explain what you have and ask what they usually do in that situation.

If you want my opinion, I would think that you would frame to the TJI subfloor since it's above grade. As I understand it, the floating basement walls in Colorado are only required when it is framing on slab. But I'm only licenced in Nebraska so don't quote me.
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Old 03-30-23, 06:44 AM
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Many areas of Colorado have a high percentage of a type of clay, otherwise known as bentonite, mixed into the surface soil. It generally occurs in "seams" running parallel or diagonal to the surface. This type of clay can expand when it becomes wet, resulting in swelling or upward heaving.

I expect this is what you are talking about. If your home was on this type of soil then there could be movement in concrete slab floors. Thus the requirements for floating walls to allow for this possibility. Since you have a crawl space this is likely unnecessary. Check with building codes.

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