Insulating Protruding Basement Wall

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badali
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Insulating Protruding Basement Wall

Post by badali » Mon Dec 10, 2018 7:02 am

Hello,

My basement has been underpinned and the lower 2 feet of the wall protrude a few inches.
Basement Wall
Basement Wall
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What's the best way to add moisture barrier on this wall?

The wall was previously made with no insulation so it's already framed, I can remove and rebuild if needed but if there is an easier way that would be great.

jeb101
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Re: Insulating Protruding Basement Wall

Post by jeb101 » Mon Dec 10, 2018 2:07 pm

From the looks of it, I would use spray foam on the bottom part, as you will get the most R value per inch and it can get into the odd shaped areas as well, just make sure it's not leaking and structurally sound to ensure you don't waste time & money.

Looks like the wood studs stick out ~1/2-1 inch from the wood, and if you can, bring it out a bit and it'll give you better insulation. Normally, they say 2 inch of foam is also your moisture barrier. If you only have a small bit of wall like this, I'd get a DIY spray foam kit, do only the bottom part, and add rigid foam to the top to save on money, just make sure the insulation is tight throughout behind the studs. If you can't, simply add roxul between studs and put 6 mill poly as a vapor barrier, and use an adhesive that is compatible with poly foam to glue the vapor barrier to the spray foam.

The least rework method though will be to spray foam the whole thing, you wouldn't need to rework the framing, but it will be by far the most expensive, and probably cheaper to get a pro spray application once you get beyond the 200sqft (1in) packs. You'd maybe pay 100$ more than a 600sqft pack, but you'll get 2x more foam applied also.

I am not a pro, and just speaking from my experience and research.

badali
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Re: Insulating Protruding Basement Wall

Post by badali » Mon Dec 10, 2018 6:53 pm

Thanks for the detailed reply! Can I put roxul between the upper part of the studs without any moisture barrier behind it?

One thing I didn't mention is that a cold cellar was added behind this wall so it's no longer external. I don't have any moisture issues but this area and the floor above it have always been very cold.

Thanks again for your advice!

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Shannon
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Re: Insulating Protruding Basement Wall

Post by Shannon » Mon Dec 10, 2018 6:58 pm

If that is no longer a exterior wall then moisture barrier and Vapour barrier would not be required. You would get the best R value by spray foaming the lower irregular area and Roxul above that. Because you are not needing a moisture barrier it is not necessary to get a full 2" of sprayfoam.
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badali
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Re: Insulating Protruding Basement Wall

Post by badali » Mon Dec 10, 2018 10:32 pm

Thanks Shannon, will one of the canned single component foams on the bottom portion or are those not dense enough?

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Shannon
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Re: Insulating Protruding Basement Wall

Post by Shannon » Tue Dec 11, 2018 7:10 am

No those really are not made to spray and cover a large surface, you you have to use a two component foam kit like i used in one of my videos.https://www.youtube.com/watch?v=6-xPIgRLuBE
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Re: Insulating Protruding Basement Wall

Post by jeb101 » Tue Dec 11, 2018 8:53 am

If you do end up using 2 component spray foam, I didn't end up using it at home, but ended up selling to a neighbor, and we used a water bath to heat the tanks up, for 24/36h. We used a sous vide circulator to set the temp at 32c and we got good coverage and even distribution of the spray. This stuff is VERY temperature dependent, especially one of the components (not sure which). I just used the circulator in a cooler, works like a charm, hotter the room the better, walls are recommended to be above 18c I believe for best adhesion.

badali
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Re: Insulating Protruding Basement Wall

Post by badali » Wed Dec 12, 2018 9:19 pm

Thanks again for all the advice!

There is another finished area of my basement which is unusually cold and it looks like the external wall there is only insulated with a black felt (moisture barrier?) and half-inch rigid foam.

The interior wall is framed right on the 6" x 18" concrete ledge at the bottom of the wall. The drywall is right up against the concrete along the concrete ledge.

Assuming I can only insulate the part of the wall above the concrete ledge (~80") should I expect to see a significant impact?

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Shannon
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Re: Insulating Protruding Basement Wall

Post by Shannon » Wed Dec 12, 2018 10:26 pm

You will have a cold spot for sure.
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badali
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Re: Insulating Protruding Basement Wall

Post by badali » Thu Dec 13, 2018 8:18 am

Any mold issues to be concerned about if I only insulate the upper part? And should I add vapor barrier all the way to the floor (over the concrete)?

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Re: Insulating Protruding Basement Wall

Post by Shannon » Thu Dec 13, 2018 8:49 am

You will get some moisture and mould issues for sure IMO. Can you insulate this with spray foam or something?
Air/ vapour barrier system must cover entire wall or it is useless.
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badali
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Re: Insulating Protruding Basement Wall

Post by badali » Sat Dec 15, 2018 1:24 am

Thanks, I checked out your spray foam video and it didn't look as hard as I expected!

Spray foaming the area above the concrete ledge will not lead to high moisture/mold risk? Does the thick rigid foam need to be removed before spray foaming or can I keep that for extra R-value?

On another note, there doesn't seem to be vapor barrier on my basement walls but it isn't very humid/moist down there -is it possible there has been some type of external insulating method was used?
Last edited by badali on Sat Dec 15, 2018 7:35 am, edited 1 time in total.

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Shannon
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Re: Insulating Protruding Basement Wall

Post by Shannon » Sat Dec 15, 2018 6:55 am

Spray foaming that entire wall ,even with the old foam left in place should be completely fine. It is doubtful you could tell the difference with insulation on the exterior. You need a air/vapour barrier unless you completely seal the interior with at least 2" of closed cell sprayfoam. If you are doing more then that entire wall I would have a pro come give you a price
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Re: Insulating Protruding Basement Wall

Post by badali » Thu Dec 20, 2018 10:10 pm

So it looks like my basement is incorrectly insulated in several areas... Spray foam is starting to make more sense.

In my case the studs are so far in front of the wall that I will need to just foam the whole concrete wall behind the studs.

I was advised to vapour barrier from floor to ceiling in front of the concrete ledge. Do you agree?

(pic below is getting rotated but that's from behind the wall.)
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Shannon
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Re: Insulating Protruding Basement Wall

Post by Shannon » Fri Dec 21, 2018 8:02 am

You will need a air/vapour barrier from bottom of upper floor to bottom of wall . If you use a min. of 2" of closed cell spray foam on the entire wall and floor joist area then a separate air/vapour barrier should not be needed.
I would also note that unless you open the ceiling as well you will never get a proper air/vapour barrier, you need access to the spaces above the wall cavity as well.
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badali
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Re: Insulating Protruding Basement Wall

Post by badali » Tue Jan 01, 2019 11:30 pm

I finally took down the drywall on one of the walls mentioned above and it's really something else...
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I removed the drywall carefully and this is exactly how it was...Just thought I would share for entertainment purposes.

Thanks again for all the help!

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Shannon
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Re: Insulating Protruding Basement Wall

Post by Shannon » Wed Jan 02, 2019 7:49 am

What a mish mash of stuff. Not pretty
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Re: Insulating Protruding Basement Wall

Post by badali » Sat Jan 05, 2019 12:12 am

Probably shouldn't be too much of a suprise but after removing that insulation the wall doesn't appear to be in the best shape.

Here is a pic for context,
IMG_20190105_000646.jpg
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The concrete below the window is cracking, I think this window was added recently and poorly cut. The sill is also framed with steel studs so definitely not original.
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IMG_20190105_000654-01.jpeg (57.17 KiB) Viewed 283 times
On the left side there are large gaps and there was.moisture and mice were nesting here so I believe there is outside exposure.
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IMG_20190105_000701-01.jpeg (80.7 KiB) Viewed 283 times
So a bunch of questions,

1. Can I parge the cracked rocks around the window and then foam seal?

2. The wall was covered with roofing paper. Is it worthwhile to reinstall this? Based on your video I'm planning 1" rigid foam, then rockwool and then vapour barrier.

3. I can get rigid foam behind everything but the very bottom plate - which is actually offset but there is some concrete mixture which was poured in the space between the wood and the foundation wall. Is it worthwhile to reframe it? The sill is very deep so thinking it will be best if I bring it down to allow more light in. Sound ok?

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Shannon
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Re: Insulating Protruding Basement Wall

Post by Shannon » Sat Jan 05, 2019 8:08 am

Well that certainly is a mess. That poor patch job of the concrete wall is going to give you trouble unless it is fixed well. Simply parging the inside will not be a permanent fix. Is this window below grade and in a window well out side ?

The paper is not needed and the 1" form will be enough to act as the moisture barrier.

With an older damp basement I would really recommend removing and properly separating the untreated wood from contact with concrete. I know you do not plan to do the entire basement but I would do what you have torn apart now for sure. Place 1" foam on the exterior concrete wall and get the wood plate off of direct contact with the concrete by placing either poly between them or foam sill gasket. Also replace the bottom plate wood do not re use it . It will have mould on it or spores at the very least. Same goes for the drywall left around the window, i can see mould on it and again this is because of no insulation between it and the concrete and likely some direct contact as well.

If it were me I would look at maybe cutting that window opening lower and getting rid of that bad spot in the wall all together. increasing the window size and excavating and installing proper drainage ,water proofing and window well out side that area. Its a lot of extra work but other wise this area is going to cause you issues .
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badali
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Re: Insulating Protruding Basement Wall

Post by badali » Sat Jan 05, 2019 1:41 pm

Thanks for all the feedback!

The window is above grade bit I don't think I can do anything practical on the exterior (check it out).
IMG_20190105_143633-01.jpeg
IMG_20190105_143633-01.jpeg (86.72 KiB) Viewed 269 times
Redoing the framing isn't too much work so I can easily do that.

That mold was very concerning to me as well - I checked carefully it's isolated to that area. Given the terrible way the fiberglass was jammed in right against that corner there I'm somewhat optimistic it's localized.

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Re: Insulating Protruding Basement Wall

Post by Shannon » Sat Jan 05, 2019 9:55 pm

That window would be a pretty big project to do but honestly if any water /snow sits in that area out side it will make its way through that mess of rubble they patched that hole with. I guess do as best you can do but I would not make any promises. I would use hydraulic cement to fill that ugly patch in better. Spray foam will not do much to hold moisture out so make the hydraulic cement work as best you can.

I would pull that dry wall still and replace and see if you could at least get maybe some 3/4" or better rigid foam around that opening first then refinish.
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