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Insulating foundation with XPS without drywall?


IBreakStuff's Avatar
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12-01-13, 09:41 PM   #1  
Insulating foundation with XPS without drywall?

I want to stick some rigid XPS board on the interior of some foundation walls, however I need a fire barrier such as drywall. Is there a cheap(er) alternative to having to hang drywall & still be compliant?

 
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Gary in WA's Avatar
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12-02-13, 11:18 AM   #2  
THERMAX? Sheathing
Check with local AHJ.

Leave top 2" open for annual termite inspection, if required; Termite Basics: Activity By Region

Gary

 
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12-02-13, 11:25 AM   #3  
IL under IBC, and they want an ignition barrier per local amendments; Chapter 26 - Plastic

1. Chapter 26 - Plastic

2. Chapter 26 - Plastic

3. Chapter 26 - Plastic

Gary

 
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12-02-13, 11:38 AM   #4  
Drywall is a pretty cheap option as is .

 
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12-02-13, 11:49 AM   #5  
I guess 'cheap' is the wrong word - just something that required less work than drywall as this is just the furnace/water heater/laundry area. Plus hanging drywall isn't one of my best skills. Was hoping there was just some type of non-flammible sheet of stuff I can roll out on top of the XPS.

I'll look into Thermax as well; I guess I don't necessarily need XPS, it's just what I see recommended for basement foundation wall applications. Will do some research.

 
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12-02-13, 12:44 PM   #6  
Putting up the drywall will be about as easy as installing the foam insulation.
Besides, this gives you a chance to hone your drywall skills and if it's in the mechanical room it's not in plain sight so it's doesn't have to look pretty.

 
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12-02-13, 03:10 PM   #7  
As it is a furnace room, check with your building inspector or Fire Marshal. Many areas for a residence require 5/8" Type X drywall on the ceiling and/or 1/2" Type X on the room walls for fire; Fire Rated Gypsum

Gas burning appliances require supply air- either from the adjoining rooms or outside ducted. Possibly a louvered door, or wall vents you should frame-in before the drywall. Research the proper safety requirements (code is minimum) before you drywall.

Gary

 
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12-13-13, 11:39 AM   #8  
Second question: in the laundry area, there is already electrical & galvanized pipe running alongside the concrete walls (less than an inch gap). I know you don't want a gap between the XPS and the concrete, so is the recommended practice to make cut-outs in the XPS for the plumbing/electrical that's against the wall and then maybe spray foam over them? Or would I just use the really thin (less than an inch) foam board for these areas? Or, (option I don't want to do), I have to rip out the plumbing & electrical and then make them stick out from the wall more to fit the XPS.

Next question is probably a dumb question, but hey, gotta start from somewhere...if I have to hang drywall over the XPS, I can't attach it directly to the concrete can I? Do I have to build a wall?

Next question is: how far up should the XPS be on the concrete wall if the ceiling is already drywalled? Can I stop at that drywall, or do I need to pull that drywall out and make the XPS extend beyond the ceiling drywall?

Final question - can I just use closed cell canned foam on the wall in place of XPS & leave it exposed?

I bet I'm showing my lack of experience, but just want to make sure I don't do something stupid.

 
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