Fibreglass insulation on the outside of a foundation???

Question Icon
Posted by: from Newmarket
11/30/2011 at 8:43:46 PM

I'm not sure if this would be better to ask in the Contractor Talk section but here goes:

I was at a customer's today to do some external painting. He mentioned that his basement is leaking and asked me to look at it. When I examined the outside, I noticed a crack and dug a bit of the dirt away from the foundation to get a better look. While I was digging (only about an inch or three), I noticed that there is fibreglass insulation against the outside of the foundation. I have seen rigid foam insulation on the outside but never fibreglass. The owner said he bought the house new 8 years ago and has done nothing so assumes the builder did this. Has anyone ever heard of fibreglass on the outside of the foundation below grade?

I am in the Toronto area.

User Icon
Kevin from Urban Improvements in Orono
Date/Time11/30/2011 at 9:09:53 PM

I've definitely never seen fiberglass insulation since I've been a contractor

As far as I know it must be a 2" rigid foam that is designed to be below grade. Fiberglass will simply rot!!

Rigid foam is also a water barrier along as a thermal barrier so I just don't understand what your homeowner has below grade.

Definitely worth checking out for their sake.

User Icon
Date/Time11/30/2011 at 10:21:05 PM

Hi Brett,

The fiberglass is compressed and treated to resist water. It is probably about 1 - 1.5" thick and is used as a drainage board over the water proofing. It serves the same purpose as the dimpled plastic products but has an actual insulation value. This is one of the products available.

If the owner hasn't done anything since moving in, I would guess some settling has occurred around his foundation and changed the grading so the water is running towards the house instead of away. You could also suggest downspout extensions to get the rainwater at least 6 ft. away from the foundation.

I have seen homeowners put in raised beds around the foundation and just pile dirt up against the house wall. This will hold water and it will eventually work its way into the house through the brick and concrete. It is also probably slowly cracking apart their foundation / bricks / mortar as it goes through freeze / thaw cycles.

The more water you can get rid of on the surface, the less chance it has of leaking into the basement.

Good Luck with it!

Jim Kuzma

Kettleby Handyman Services

Search the TrustedPros directory and discover the best contractors in your area.

Find your home service pro
Great renovations start with a great contractor.

Since 2004, TrustedPros has been helping homeowners find the right contractor for their home improvements and repairs.

Post Your Project

Within hours you'll be comparing offers from top-rated professionals. It's free to post and you're under no obligation to hire.

Trustedpros Inc. does not warrant the accuracy, completeness, safety, legality or usefulness of any Content, or Whether Content is Current and up-to-date, and TrustedPros Inc. Shall have no liability whatsoever with respect to your use or reliance upon any content or for content being removed or otherwise ceasing to be available. Please refer to the terms and conditions of use of this websites for more details.

Get Free Estimates

Post your project and compare offers from top-rated pros.