Comments on: Finished Basements – Insulation Method

By: Todd

Todd — Tue, 27 Dec 2011 12:46:45 +0000

I recommend you just “ignore” the exterior insulation and consider it a “cherry” on top. I would still recommend the 1-1/2″ minimum foam, sealed properly, then supplemental insulation to meet code. The reality is it’s very hard to get a continuous layer on the outside and have it work seamlessly with the exterior siding/insulation.

Good luck.

By: Dmsnaz

Dmsnaz — Tue, 27 Dec 2011 07:08:17 +0000

Question,
I am just starting on finishing my basement. The house is relatively new and has 2″ extruded foam with a moisture barrier on the outside of the foundation. Given that level of insulation, would you recommend also applying the extruded foam on the interior? Do you think that would typically be a code requirement? If you suggest yes to the interior foam, would your recommended width be less than 1 1/2″ for the foam?

If the foam is not needed on the interior due to the exterior insulation, would you be ok with batt insulation?

I read the building science report on insulation, and it states that the exterior extruded foam would cover the entire concrete of the foundation and connect to the exterior siding. However, on my house it appears they stopped the insulation at ground level and there is no insulation from ground level to the siding (about 2 feet). Is there anything I should do to rectify this shortfall?

Thanks!

By: David

David — Mon, 01 Aug 2011 22:42:18 +0000

Thanks, Todd!

By: Todd

Todd — Mon, 01 Aug 2011 10:21:43 +0000

David – Glad to hear you’re working on your basement project. Foam board must be covered in order to meet most current building code requirements. The issue at hand is a flame spread issue which really means you’re trying to keep an open flame from starting a quick fire. Many products can be used to meet the criteria. To the best of my knowledge I’m not aware of a tongue & groove product that’s been UL tested to meet that. However, there are plywoods that have been tested.

So I’d check with your local building code official first and see what they think. If they want to see a UL tested assembly then I’d put 7/16″ OSB up (be sure it has the certification) followed by the T&G. The wood would certainly breath well down there and do very well.

Good luck.

By: David Burns

David Burns — Mon, 01 Aug 2011 04:12:18 +0000

I’m working on that basement project you gave me some advice about back in February. I’m using the 1.5 inch Dow insulation boards with the cut outs for furring strips. Does this have to be covered with drywall for fire safety, or can it be covered with tongue and groove cedar boards or something like that? Would one or the other be better in a basement environment, in terms of any mildew or odor? If I need to use drywall, it it worth using that moisture resistant drywall that is sold for use in bathrooms? Thanks!

By: Todd

Todd — Mon, 28 Feb 2011 19:23:19 +0000

You are quickly learning why basements are such a royal pain! There is no perfect answer. DRIcore works pretty well especially with slabs that have a proper vapor barrier under them. Most of this discussion depends on the type of flooring you want to use, how much head room you have, and ultimately budget.