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Walls Base off 16" OC with R15 Rockwool

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Discussion Starter · #1 ·
Hi,

So I am starting to finish my basement up and trying to figure out what way I want to go. I have read many sites with reviews about Pros and Cons. I have a basement that is about 60% below grade. I also fall under zone 4/5 on the map for R values. The Foundations is Hollow core Cinder block with a door into the garage and then outside garage is only 30% below grade. I do not have and have no signs of any water ever leaking. I do run a dehumidifier at 50% RH and my Honeywell meter reads between 50 and 60% RH depending on outside temp and the kids leaving basement garage open. My father is a retired carpenter/electrician who has Build many homes and my uncle is a General contractor makes for fun family gatherings.

So they were over about a month ago helping replace some Old wire and update some outlets since then I been reading fact sheets. I asked about what I need to finish the basement and it started a war. So father told me just to put Rockwool R15 with 24" on center studs and leave it about 3/4" off the foundation wall to allow air and a thermal break, that's how he done many homes and never had a problem. Now my uncle said no you need to put XPS on the walls 1" R5 with 16" on center studs and R15 rockwool. I have been looking at both and have read a lot and at this point don't know what I want to do now. I under stand Pink XPS breaks down over time lowing R, and other kinds are better but much more costly or that foil face is much better since its open cell it can take on some water vapor over time.

So lets all be nice and I want to see what others think or if there is a better option. I don't have a budget per say but not anywhere new unlimited founds more money means I have to wait a little longer to get it.
 

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Naildriver
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Applying XPS to the walls and taping all the joints will make for a good thermal break. If the walls are completely underground, they are geothermally correct anyway, but the XPS is always a good addition. Using the XPS, you will need to space your walls out further to accommodate it. Use Rockwool at R15 and 16" centers. Rockwool is waterproof, vermin proof, fireproof, mold proof, and requires no vapor barrier, so it is a plus-plus. I"ve never heard of XPS deteriorating, and would welcome corroboration to the fact. If you have not moisture issues, that is also a plus.
 
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XPS against the concrete block then a framed wall with insulation is the most commonly recommended approach these days. It will reduce condensation and will also allow the foundation to dry to the interior.

24" oc framing is fine and will save a few bucks.
 

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retired framer
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Rockwool R15 with 24" on center studs and leave it about 3/4" off the foundation wall
This is the normal here, our concrete walls are never straight enough for foam board to be effective. We leave an air gap but we do not allow air flow.
We fire stop and add vapour barrier.
 

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Discussion Starter · #6 ·
Applying XPS to the walls and taping all the joints will make for a good thermal break. If the walls are completely underground, they are geothermally correct anyway, but the XPS is always a good addition. Using the XPS, you will need to space your walls out further to accommodate it. Use Rockwool at R15 and 16" centers. Rockwool is waterproof, vermin proof, fireproof, mold proof, and requires no vapor barrier, so it is a plus-plus. I"ve never heard of XPS deteriorating, and would welcome corroboration to the fact. If you have not moisture issues, that is also a plus.
Thanks yes I took the 1inch space into my math with the wall pushed onto the XPS or do I need a small space between XPS and the 2x4 stud?
The walls being house on a hill back wall is
XPS against the concrete block then a framed wall with insulation is the most commonly recommended approach these days. It will reduce condensation and will also allow the foundation to dry to the interior.

24" oc framing is fine and will save a few bucks.
Ya I think I going to go with 16 inch on center just for extra studs since its going to turn into kids (3 girls lol) play area gives me lots of space for shelfs and TV to be mounted and all.
 

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Discussion Starter · #7 ·
Rockwool R15 with 24" on center studs and leave it about 3/4" off the foundation wall
This is the normal here, our concrete walls are never straight enough for foam board to be effective. We leave an air gap but we do not allow air flow.
We fire stop and add vapour barrier.
And that is where my father and uncle go at it LOL. my foundation is pretty straight its only got a 1/4 inch off level from top to bottom.
 

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Discussion Starter · #8 ·
So I am reading over that info and have a questions I saw this before in a forum and cant find it now. So that star I put in blue they talking about putting a sill plate there the roll of blue or pink foam????
661369


Some way to use it some say don't in my mind it makes sense to use it, but the one wall I was going to glue metal track down then build my wall and put it in the plate. Reason being its this wall on the other side has a boiler for heat, hot water tank, washer, and main line of water for house here. My thought was put the track down glue then also tapcon it to floor and then drywall down till at the top of the metal track this way if it ever floods over there the water wont get to the drywall and the frame or go under the frame and into the next room.
661368
 

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I've never used metal framing in a basement, but the sill gasket provides a thermal break. However, any wood framing attached to concrete should be treated, and wood bottom plates in the basement should be treated.

Leaving a space between the drywall and the floor is definitely good.
 

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Discussion Starter · #10 ·
I've never used metal framing in a basement, but the sill gasket provides a thermal break. However, any wood framing attached to concrete should be treated, and wood bottom plates in the basement should be treated.

Leaving a space between the drywall and the floor is definitely good.
Sorry I know it was a little confusing here a photo of what I mean by sitting the wall inside metal. Stilla all wood wall but just inside metal.
661371
 

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Discussion Starter · #11 ·
So last questions with the xps what do most like to do at the top were the floor joist.

Cut foam to bottom of wood and then small blocks for inside the space or cut it into the board making it all one run. Also best way to seal with expand foam or caulk like cutting so there 1/4 inch between wood and foam then call or foam it????
661402
 

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retired framer
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So last questions with the xps what do most like to do at the top were the floor joist.

Cut foam to bottom of wood and then small blocks for inside the space or cut it into the board making it all one run. Also best way to seal with expand foam or caulk like cutting so there 1/4 inch between wood and foam then call or foam it????
There should be a fire stop between the wall and the floor system, different area have different codes to what that should be, Something like a 1/2" plywood above the top plate and sealed to the blocks.
 

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Discussion Starter · #13 ·
Yes I got that sorry I talking about the XPS foam. Would you cut it flat to the top wood then cut small squares and put seam tape, or cut it around each so it fits like a puzzle. Sorry bad art work did it fast black is tape lol.

Also what do you like to do between the foam and the wood. Expansion foam or Caulk sealer?


661418



Kind of like this with the foam around it how much of a gap do I leave to let the foam fill in the area well like 1/2" or 1/4" or more???
661419
 

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retired framer
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I think you are better off with cutting the foam closer to tight and use a sealant to seal around it.
I changed this picture to show the fire stop below the floor joist tight to the foundation, sealant can be used there too.
661420
 

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Discussion Starter · #15 ·
There should be a fire stop between the wall and the floor system, different area have different codes to what that should be, Something like a 1/2" plywood above the top plate and sealed to the blocks.
SO really I could go get sheet of 1/2" ply and cut in strips 4 1/2" x 8ft long (1inch foam and then 2x4 wall) and attach them to the floor joist now seal them in with fire stop calk then cut the pink foam in blocks to fit between each joist 1' 1 3/8" wide by 9 1/2" wall and put them in with some foam. Then cut the large sheet of foam 4' wide by 7' 4" high put them on the foundation wall then stand my wall up and push them tight to the foundation.
 

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retired framer
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SO really I could go get sheet of 1/2" ply and cut in strips 4 1/2" x 8ft long (1inch foam and then 2x4 wall) and attach them to the floor joist now seal them in with fire stop calk then cut the pink foam in blocks to fit between each joist 1' 1 3/8" wide by 9 1/2" wall and put them in with some foam. Then cut the large sheet of foam 4' wide by 7' 4" high put them on the foundation wall then stand my wall up and push them tight to the foundation.
Yes about like that.
 

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Discussion Starter · #17 ·
So I found this on my township website. So I dont see 1/2" on there. But rockwool is on there and they talk about every 10ft need firw blocking as well. Whats easy way to go about that when you have xps on the walls that would break the continuous vapor barrier. Then I would have wood on the foundations.....

Would it be easyer to just use that fire block foam and put that between the stud and the foundation then continue with the XPS foam.
 

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I'm curious about the "every 10 feet". Is that referring to fire-stopping for open truss floors?

I think your first plan will be easier, although a 1/2" of plywood may not meet your local code. Some require 3/4" plywood. But, as shown in Neal's post, installing a strip of fire stopping from the foundation to the outer face of the framing will be easy. If you want to get really thorough, you can also foam or caulk the joint between the fire stop and the foundation wall.
 

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Discussion Starter · #19 ·
I'm curious about the "every 10 feet". Is that referring to fire-stopping for open truss floors?

I think your first plan will be easier, although a 1/2" of plywood may not meet your local code. Some require 3/4" plywood. But, as shown in Neal's post, installing a strip of fire stopping from the foundation to the outer face of the framing will be easy. If you want to get really thorough, you can also foam or caulk the joint between the fire stop and the foundation wall.
Im pretty sure its fire stop.
661498
 

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Yeah, I wasn't questioning that the reference is to fire blocking or fire stopping--I'm just having trouble figuring out the "every ten feet". Maybe I just need more caffeine this morning.
 
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