Foaming basement walls

[EatenByLimestone]

I'm seriously looking into insulating my block basement walls. By code, the foam will need to be covered. The easiest way to do this is to Ramset a 2x onto the floor and then place a vertical attached to evert floor joist on top, and toed into the board on the floor. Then I can spray behind it and all is great, right?

Then I start over thinking this...

I don't need a stud every 16", I'm not finishing the basement off and it's not structural. 24" should be ok, but would be more difficult to attach solidly on top. 32" on center, or every other joist, might let the drywall sag or something. Has anybody spanned this far between framing? I'm thinking I'll just do 16" oc just to keep it easy.

Also, I've noticed on new houses there is a piece of what looks like foam between the foundation and sill. Would it be a good idea to incorporate this between the floor and 2x?

Matt

 

[velvetfoot]

I'm no expert, but is that for rotting purposes? You're not going use pressure treated so why not buy a roll of the foam stuff? I'm not a builder though.

 

[EatenByLimestone]

I think it's a vapor barrier. That would keep moisture out of the wood and help prevent rot.

 

[mass_burner]

I think it's a vapor barrier. That would keep moisture out of the wood and help prevent rot.

I read an article where they used azek decking for the bottom, doesn't rot.

 

[velvetfoot]

My crappy basement stairs have been resting on bare concrete for 10 years with no ill effects.

 

[EatenByLimestone]

My crappy basement stairs have been resting on bare concrete for 10 years with no ill effects.

Exactly! Mine have been touching the concrete since 1946 without any issues. Over thinking!

 

[mass_burner]

Exactly! Mine have been touching the concrete since 1946 without any issues. Over thinking!

Yea, but isn't PT code. I bet a lot of ungrounded electric houses never caught fire either.

 

[velvetfoot]

I know that this doesn't answer your questions, but I'm in the basement looking at temperatures and thought I'd take a picture of the cross section of my basement walls. Again, not what you're looking at, but you could take a run at that wall and bounce off.

 

[EatenByLimestone]

PT might be code, but I planned to treat them with bora care. It is safer, fire resistant, and steel is not eaten by it.

 

[sportbikerider78]

I know that this doesn't answer your questions, but I'm in the basement looking at temperatures and thought I'd take a picture of the cross section of my basement walls. Again, not what you're looking at, but you could take a run at that wall and bounce off.

View attachment 171658

So, party at your house?
I don't think too many will doubt that is the best way to do it, but what is that 2 sheets of 2" XPS? Each board is $25 per 4x8 and you have two of them. That makes $50 per 4' of wall...without labor, without framing...ect. Nice,,but pretty pricey.

 

[velvetfoot]

I purposely didn't add up the cost...just went to HD every once in a while a bought some pieces, lol.
For me, there was no framing, just furring strips. And, the original poster is going to get someone in there to foam the wall, so that's not cheap either. Maybe only use one layer?

 

[dja950]

I'm seriously looking into insulating my block basement walls. By code, the foam will need to be covered. The easiest way to do this is to Ramset a 2x onto the floor and then place a vertical attached to evert floor joist on top, and toed into the board on the floor. Then I can spray behind it and all is great, right?

Then I start over thinking this...

I don't need a stud every 16", I'm not finishing the basement off and it's not structural. 24" should be ok, but would be more difficult to attach solidly on top. 32" on center, or every other joist, might let the drywall sag or something. Has anybody spanned this far between framing? I'm thinking I'll just do 16" oc just to keep it easy.

Also, I've noticed on new houses there is a piece of what looks like foam between the foundation and sill. Would it be a good idea to incorporate this between the floor and 2x?

Matt

As far as needing to cover it for code, they make a fire retardant paint you can apply over the foam that meets code. I believe it's has a 3 or 4 hour fire rating

 

[Bret Chase]

As far as needing to cover it for code, they make a fire retardant paint you can apply over the foam that meets code. I believe it's has a 3 or 4 hour fire rating

Sherwin Williams - DC315. One of my clients does everything.. ahem... "Basementy"... it is what they use over sprayed in place poly-iso, when a conventional fire barrier (like 5/8 type X sheetrock, or Dow TherMAX) isn't spec'd..

 

[moey]

I have 2 inches XPS glued up and screwed tight with 1 * 3s then drywall. Night and day difference in temp now I did it over the course of the last year the foam panels are around $28 drywall around $8 screws and boards $6. It adds up probably $40 for a 4*8 sheet. Of course framing it out would add up as well. I had a lot of obstructions to spray foam would have been tough.

 

[Warm_in_NH]

I've read a bit on this as I have an old stone foundation and I know people who have stayed theirs and it's made a HUGE difference in temperature and humidity levels.
The theory is, in most cases, these older foundations aren't sealed on the exterior so they wick in moisture, it's just the nature of rock and block. This moisture is then "exhausted" to the interior where it becomes part of the air in the basement.
Once you seal this inside wall, the moisture that gets into the stone or block now only has one direction to go, up, now it may get exhausted above grade to the exterior or the theory is it'll get wicked into your sill plates and start rotting them out. Most stone block foundations don't have sill seal between the foundation and plates thus allowing this to happen.
I've had a lot of long discussions on this with friends in the trades, I'm in the wait and see boat, some have gone for it, some will never do it. I suggest doing a bit of research before pulling the trigger on this (see the pun there...trigget, foam gun, ha.....) it's not as simple as I laid it out, but that's a rough outline to give ya an idea of the theory.

 

[TradEddie]

As far as needing to cover it for code, they make a fire retardant paint you can apply over the foam that meets code. I believe it's has a 3 or 4 hour fire rating

Where was this advice two years ago when I needed it?

All I did was glue XPS to the block wall and glue drywall to the XPS. Quick and easy, but paint would have been easier.

TE

 

[Babaganoosh]

Where was this advice two years ago when I needed it?

All I did was glue XPS to the block wall and glue drywall to the XPS. Quick and easy, but paint would have been easier.

TE

lol, painting sucks though. I hate it.

 

[semipro]

All I did was glue XPS to the block wall and glue drywall to the XPS.

I did this in one area where I needed the space for code clearance next to a toilet and it has worked surprisingly well.

 

[sportbikerider78]

I've read a bit on this as I have an old stone foundation and I know people who have stayed theirs and it's made a HUGE difference in temperature and humidity levels.
The theory is, in most cases, these older foundations aren't sealed on the exterior so they wick in moisture, it's just the nature of rock and block. This moisture is then "exhausted" to the interior where it becomes part of the air in the basement.
Once you seal this inside wall, the moisture that gets into the stone or block now only has one direction to go, up, now it may get exhausted above grade to the exterior or the theory is it'll get wicked into your sill plates and start rotting them out. Most stone block foundations don't have sill seal between the foundation and plates thus allowing this to happen.
I've had a lot of long discussions on this with friends in the trades, I'm in the wait and see boat, some have gone for it, some will never do it. I suggest doing a bit of research before pulling the trigger on this (see the pun there...trigget, foam gun, ha.....) it's not as simple as I laid it out, but that's a rough outline to give ya an idea of the theory.

Interesting.
I guess you could always take some moisture data from around the sill, spray foam, then keep taking data to monitor it. The assumption they are making is that the moisture will wick up instead of out because there is more water to wick because it is not getting into the basement. I think they are grossly overestimating how much water goes into the air on a normal basement. Or they are looking at a situation were sprayfoam shouldn't be used in the first place to hold back large amounts of water....a problem with an outside solution.

 

[Warm_in_NH]

Interesting.
I guess you could always take some moisture data from around the sill, spray foam, then keep taking data to monitor it. The assumption they are making is that the moisture will wick up instead of out because there is more water to wick because it is not getting into the basement. I think they are grossly overestimating how much water goes into the air on a normal basement. Or they are looking at a situation were sprayfoam shouldn't be used in the first place to hold back large amounts of water....a problem with an outside solution.

As of now they're all just long term theories from what I can see. Some interesting reads on it though, none the less.
Building trades aren't any different than anything else, new stuff is out there all the time, some is great some is garbage, I stick with the wait and see approach. Let someone else be the guinea pig...