Basement Walls + firestopper


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Old 02-11-03, 06:07 PM
rcw1202
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Basement Walls + firestopper

I'm preparing to frame a basement wall that's below grade. 1) should I put plastic sheeting across the wall as a moisture barrier? 2) I have a small vertical crack that gets damp when it rains. There's mineral deposits along the crack. How do I patch it? 3) My local code, based on BOCA, requires a firestopper above the header. It shoudl be either 5/8 drywall or 3/4 plywood. But they don't tell me how far, if any, it needs to extend beyond the framing and into the room space. I understand it needs to be flush to the masonry wall. Any experience with firestoppers?
Thanks.
 
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Old 02-11-03, 06:35 PM
Doug Aleshire's Avatar
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rcw1202,

First, you should seal any leaks that you currently have. This can be done by various means, hydraulic sealer injection, Drylok products as examples. This is a must or all the work you do is going to be damaged.

Second, you have options with vapor barrier. I guess this is the best and most economical way to construct walls that would be placed on the exterior. I prefer to see 2x4 but as mentioned by others they can get 2x3's. You still need that W/T plate. Doing the framing 16" O.C. provides a solid base for your 1/2" drywall. If using traditional framing method, frame your new wall 1" from the vertical block/masonry surface if using R-13. The reason to keep the wood out from the walls is the moisture that could damage them. If using insulation like R-19 and only 2x4 studs, the insulation would touch the walls. I have stated before that if a homeowner did put thicker insulation in, and the wall was only 1" from the masonry surface, I have recommended hanging a vapor barrier between the back of the wall and masonry surface. This doesn't allow for the insulation to touch the wall and air movement is not restricted but at least you won't create damage to the insulation or wood. If you do want to increase the R value, move the wall out further or use the R-13 and then apply a rigid insulation over the studs (warm side) then drywall (not paneling) *Code advises a 15 minute fire rated material over any rigid insulation - 1/2" Drywall*.

Kraft Faced insulation is fine to use in the above scenario. No need for the poly and you can do everything easily. You may find this easier and I would do this versus unfaced and vapor barrier because I don't like to play with it any more than I have to.

Let me add one other thing, rigid insulation used on a concrete/masonry surface is fine. Considerations to make in using this is;

1. If you are just using 1 1/2" rigid and furring strips - A. You need W/T strips to protect the wood. B. The strips can be adhesively applied but they must be solid - mechanical anchors may have to be used to insure that if shelving is installed it will hold. Problem with this is, the penetration into a sealed concrete/masonry surface is damaged and subject to leaking. C. Any electrical boxes will have to be shallow - sometimes makes it hard to wire. D. You must use a fire retardant material over this as per Code.

(Most books, articles about rigid and furring strips fail to say anything about the use of W/T and this will get destroyed and be a good source for mold/mildew with the slightest hint of moisture)

2. Alternative which does add cost is to apply full rigid sheets to the concrete/masonry walls, adhesively applied, then place frame wall against the rigid, then insulate between studs and cover with drywall. The Rigid insulation does then act as a the vapor barrier. Do not tape/seal the seams. This allows it to breath and dry up any condensation that may form.

This link should help you on firestopping;

http://www.co.fairfax.va.us/gov/dpwe...ments.htm#CODE

Hope this all helps!
 
 

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