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jreed 01-14-2010 02:03 PM

Above grade framing and a few framing question
I am getting ready to frame my walkout basement. On one side of the basement the walls are above grade. Is it ok to butt the 2X4's up againts the walls in these sections? I am going to frame with 2X4's and use fiberglass insulation. In the sections that are below grade I will obvioulsy leave an air cavity.

Secondly, a few walls run parallel with the floor joists. However arent under the joist. It will be between the sill plate and the joist so I have nothing to secure the walls to. Should I run plates from the joist to the sill plate?

These are all of the questions I have right now but Im sure Ill come up with some later :)

tpolk 01-14-2010 05:34 PM

I am going to frame with 2X4's and use fiberglass insulation. In the sections that are below grade I will obvioulsy leave an air cavity.

what does this mean?

jreed 01-14-2010 06:49 PM

I should have said I will install the framing about an inch out from the blocks.

CustomBuild 01-15-2010 08:14 AM

1 Attachment(s)
here is the proper way to do it. Install the plywood before the walls are framed, and be sure the plywood fits tight to the mud sill. The 2x4 blocks give you something to nail the plywood and top plate of your new walls to. This is in compliance with new code. The plywood serves as a draft stop. Some codes ,however, require a fire stop. In that case, substitute the required drywall for the plywood. It prevents a fire from being able to travel from inside the wall to your first floor joist system. Also, as far as the air gap, it is a must. If not to prevent rot, then the air gap will allow you to frame straight walls(concrete is often not straight). If you are concerned with loosing square footage, use 2x3's. Might I suggest closed-cell spray in insulation, as it is a vapor barrier and insulation in one. WELL worth the investment. If you do go this route, have the foam placed AFTER the walls are installed. Also, look around this site for information on sealing and insulating the rim joist. You are going to want to do that before installing the walls, unless you are getting spray foam. Then you will want to frame first, then have it insulated. Regardless, you will notice a difference in the whole house by insulating the rim joist. Hope this helps.
Attachment 16630

jreed 01-15-2010 08:34 AM

Great information there...thank you! What size gap would you leave, is 1" enough? Also, would you do 2X4's or furring strips? Ive gotten mixed reviews on both. Furring strips would be much easier I would think but it seems the cost would be higher due to the high price of the rigid foam insulation.

Gary in WA 01-15-2010 11:40 AM

If you leave a gap, you will have a convective loop in your batts:
It would also allow the moisture to travel along the wall as you really want it to dry to the inside. Remember to fire-stop the studs every 10 lineal feet as well.

Furring strips or studs--- studs, you want the foam to act as a thermal break from the concrete. SPF, 2-3" thick is a Class II vapor retarder which is what you want, not a vapor barrier- Class I: It could be a vapor barrier, 23" thick.

Be safe, Gary

CustomBuild 01-16-2010 10:56 AM

1" is plenty of room for air to circulate. The only reason to leave more would be if the concrete wall has more than a 1" bow in it(check this with a string stretched tight). I have always been a fan of standard framed walls rather than furring strips. I don't like the idea of screwing untreated wood directly to the concrete, and you can never seem to achieve straight walls with this method. The never ending hammer drilling gets on my nerves. Then you have to use shallow electrical boxes which are difficult to wire in. Also, according to drywall standards, the screws need at least 1" of penetration into the studs, which cannot be achieved with a 3/4" thick stud. You have to use 1" screws rather than 1-1/4" screws, because the screw needs to countersink into the drywall, and it can't because it will protrude from the back of the furring strip, and hit the concrete. Therefore, the 1" screws will only give you 1/2" of penetration.

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