Finishing a new basement....need advice.

clayfarmerFebruary 19, 2008

Hello everyone.

I'm getting ready to finish my basement. There is so much conflicting information out there on the proper way to insulate a basement, I'm confused. But here's what I'm planning to do. Please let me know if I'm on track.

The house was built about 6 months ago. I have already painted Drylok on the walls and floor.

Do I need to use hydraulic cement to seal the joint between the floor and walls?

I plan to adhere 1" rigid foam insulation to the basement walls, and then build stud walls. Between the stud walls I'll use R-13 or R-15 unfaced fiberglass insulation. I'm in south-central this insulation sufficient?

Am I on track? Anything I need to change? Thanks!!!

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The link below goes to the US Department of Energy's recommendations for cost effective insulation levels based on your climate.

According to the map, your basement should have at least R-19 in the walls.

If your home has proper external drainage and a dimpled membrane, I wouldn't worry about the cold joint except maybe for some caulking as an air barrier.

Othwerwise, be sure the baseplate is on an inch of XPS and pay close attention to the rim joist area. You can cut XPS or EPS to fit, then caulk around.

Here is a link that might be useful: Climate Zone Maps

    Bookmark   February 19, 2008 at 12:30PM
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Could you explain further your last sentence..."Othwerwise, be sure the baseplate is on an inch of XPS"
Are you saying I need an inch of XPS on the floor of the basement?

    Bookmark   February 19, 2008 at 12:34PM
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Just score and snap pieces of XPS to put under the plate. This prevents moisture from wicking up through the floor into the wood and keeps the wall above any minor flooding that you may get. To install the XPS, just secure the plate as you would normally with concrete screws or powder actuated fasteners. You might also want to consider paperless drywall.

A must is a dehumidifier to keep the relative humidity at no more than 45% during the summer.

    Bookmark   February 19, 2008 at 6:52PM
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Great advice. Can I ask one more question? I need to adhere the foam to the concrete wall. Any specific suggestions on what I should use?

    Bookmark   February 20, 2008 at 12:10AM
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Adhere the board with either made for the purpose adhesive caulking--carried in the big box stores near the XPS boards--or mechanically with concrete screws and fender washers and/or diminsional lumber, i.e. 2x2s or whatever works best for you. Depends on whether you have a helper or not!

Tongue and groove foamboards work best. Otherwise, seal all joints with building tape and caulk all open areas, if you're cutting around pipes and the like.

    Bookmark   February 20, 2008 at 10:30AM
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Is XPS a brand or a type of board? In other words, is the pink Owens Corning stuff at the box stores the same thing?

    Bookmark   February 25, 2008 at 9:38PM
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Putting the wall on 1" XPS sounds like a pain for fastening the plate. Worthy, how do you attach that?

I'd just use pressure-treated plates glued and ramsetted to the floor. If moisture wick is a concern, then buy a thin roll of foam that I believe is for going under sill plates, which basically serves the same purpose (it's like 1/8 or 1/4 ribbed foam). It's cheap and easy.

    Bookmark   February 26, 2008 at 11:27AM
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Won't powder fasteners crush the XPS and distort the wood? I use green 2x4's which should be fine on top of concrete. I just envision the 2x4 squishing down the XPS at the fastener created a wavey plate.

    Bookmark   March 2, 2008 at 8:36PM
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I think the powdered fastener method wouldn't crush the XPS, but it also wouldn't secure the plate either (do they even have powdered fasteners longer than 2 1/2"?

    Bookmark   March 3, 2008 at 12:21AM
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I was a subcontractor for Basement Experts / Owens Corning for years. Worked my but off for them.
Just a warning for those subs out there considering working for them, in the beginning they pull money from your checks as an insurance policy to make sure you guarantee your work for a year. I can understand that. But once the year passes with no call backs they are to return the money.
Its been 2 years and I still haven't seen my $700.00. Beware subs, they'll screw you the same way they do everyone else.

    Bookmark   October 9, 2008 at 10:58AM
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but it also wouldn't secure the plate either That's how the carpenters on my last project did it. I can't remember the fastener length. Only that it went no more than 3/4" into the concrete, which was radiantly heated. I absolutely didn't want them to penetrate a PEX line!

    Bookmark   October 12, 2008 at 3:32PM
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