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Quattro 01-22-2008 10:01 AM

Exterior treatment for NW facing exposed foundation?
Hey all,

as some of you know, I've been piece-mealing the work needed in my basement where the exposed portion of the foundation tended to get frosty in cold weather. I've been putting up 1.5" and 2" XPS on these surfaces, and framing for walls interior of that. So far, it's going well, but a few choices I made may come back to haunt me...we'll see.

This question deals with the EXTERIOR of the same exposed foundation (poured concrete) on the N/NW side of the house. In the winter, this corner of the house is the coldest, and is a big reason my basement is colder than it should be. So I'm taking steps to insulate from the inside, but I want to do something on the outside as well. Options?

Would a 1" layer of XPS or other "foamboard" product work here? Just glue it to the exposed concrete? Would that actually do anything? What about an adhesive "wrap" of some sort that would at least act as a water/wind barrier? This side of the house takes most of the weather as well, and there are signs that the concrete is taking a beating (water mostly) some sort of barrier might help. This is the street-side of the house, so the solution would have to be something that could be made pretty. :)

I'm not looking to tackle this problem now, rather wait until this spring/summer.


Quattro 01-22-2008 11:00 AM

Something like this available at stores?

glennjanie 01-22-2008 11:02 AM

Hello Quattro:
I hear you on the North West corner; that's where most of us get the bad weather from in the winter.
I would not insulate the outside because roaming dogs and cats would tear it up. I might consider painting the foundation or using a skim coat of portland cement and sand; brushed on will work too.
The frost is on the inside, right? That's the place to insulate and the 2" foam board should do the trick. If you are adding a wood frame inside the basement walls you could consider using fiberglass batts between the studs for additional insulation.

Quattro 01-22-2008 11:32 AM

Yes, the frost is/was on the inside. That's where I've been placing the XPS. I just noticed that one little area I missed had frost on it...and it got me worried that there was frost behind the XPS I just put up. There shouldn't be, but...

Man I wish I had X-ray eyes! :-)

I'm not worried about cats/dogs, as the insulation would be covered by something...just not sure what that is yet (fiberglass panel?). I like the skim-coat idea, but I don't think that adds any insulating power. Should help seal up any major cracks, though.

Maybe I just need to go peruse the stores and see what's out there.

It's just amazing to me how the NW corner is so bad, and the rest of the above-grade foundation in the basement is frost-free...and not even that cold to the touch.

Quattro 02-04-2008 10:05 AM

A little update on this thread.

I found that when it's below about +10F, there are many areas of the interior exposed foundation that get frosty...not just the NW corner of the house, although that does seem worse. I found it in several other places where the insulation at the band joist (or rim joist) just wasn't enough. So, I'll be putting in 1.5" XPS in each band joist pocket, follwed by R-30 fiberglass batt. That brings the insulation right out flush with the 1.5" XPS on the foundation wall. That *should* take care of the frost problem. What a pain, though! It'll be worth it in the end...I just can't see the end! An hour here, half-hour just never seems to get anywhere. Ah well, could be worse I suppose. Our TV room is downstairs, and since the writer's strike there hasn't been anything good to watch anyway! :)


inspectorD 02-04-2008 05:52 PM

Sounds good. Also sealing the area between the foundation and the foundation plate, is a great fix.
Usually in older homes they would build it up with a small concrete edge. But the wood shrinks and you still have a 1/8 gap....cold. I used a small amount of great stuff all around that joint before insulating the band joist...rim joist...outside box....all the same thing.(for those of you in different areas of the world)
Even caulk will help like you would not believe.
New homes have sill seal insulation put down before any wood is attached to the foundation.

Imagine a 1/32 hole in your boat.....issue?:D For about 50 linear feet.:eek:

It is the small stuff folks.

Quattro 02-05-2008 08:58 AM

I guess some homes are built with a sill plate (a piece of lumber on top of the foundation that the rim joist is attached to), but not mine. The rim joists and ends of the floor joists sit directly on the top of the foundation, with only a 1" layer of fiberglass insulation between...which of course is squished down to nothing.

fred333 04-30-2008 08:59 AM

That is a great suggestion.

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