I'm planning on applying foam-panel insulation over my basement's concrete wall. I'm told a fire barrier is required over that, either plasterboard or decently-thick plywood.

I've been considering making the bottom few inches a separate piece, so it can easily be replaced if we get a Water Event. Simpler than having to cut it free and might reduce wicking upward.

My question is, is there something else I could consider using as this "baseboard" which would have the needed fire rating and be likely to pass inspection but be inherently waterproof? Obvious thought would be to build up a few inches of of brick or concrete inner wall... but I'm sure someone out there has a better answer.

Or should I just put in french drains and trust the sump pump?


I'd consider fiber cement trim board. Almost all of it is Class 1 (A) fire rated, it's easy to find at the big box stores in a variety of dimensions, and it will most likely pass for baseboard if it's thicker than the "plasterboard or decently-thick plywood".

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  • Also a very reasonable idea... How does one cut that stuff? – keshlam Dec 25 '15 at 19:27
  • @keshlam - Some manufacturers claim you can use a thin kerf carbide blade circular saw, but if you try that I'd treat the blade as disposable. I cut the stuff with a diamond abrasive blade (although a masonry abrasive blade would work just fine too). – Comintern Dec 25 '15 at 19:33

First thought was 2x treated on edge? Install a "J" channel on the drywall bottom with a squirt of silicone. Composite decking is sold in several thicknesses and can be routed/shaped to an appealing profile to be used as trim or wall base. The foam panel should be semi-permeable if you expect water to infiltrate the basement wall.

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  • Not sure about the fire rating of repurposed composite decking in this orientation, but it's definitely an interesting idea. – keshlam Dec 25 '15 at 19:26

Use cementboard for this. It's, well, a board of cement! if it gets wet, it doesn't mind.

In fact, I would recommend making everything in the finished basement out of a non-moisture-sensitive material. Use cementboard instead of drywall; 4" blocks instead of wooden studs; beveled tiles instead of baseboards; tile or stained concrete instead of hardwood, etc. This way, if the basement floods, it doesn't actually matter!

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  • Interesting thought, but I think overkill for my needs...? – keshlam Dec 25 '15 at 19:49

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