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-   -   Replacing drywall on an exterior wall (http://www.diychatroom.com/f19/replacing-drywall-exterior-wall-65069/)

MarkHaley 02-22-2010 10:23 AM

Replacing drywall on an exterior wall
 
Hello all, and thank you in advance for any help you can provide.

I work for a theater that is house in an old grange hall (built in 1860). We are currently renovating room-by-room as our budget allows. The next project we are working on is our box office, at the front of our building. We will be taking down the old horsehair plaster and putting up drywall. My question is regarding insulation and air/vapor barriers.

Currently, the building has no insulation (which makes for rough New Hampshire winters). I'm looking to insulate at least to the outside during the project since we'll have the walls down anyway. I was wondering A) what kind of insulatiing materials people would recommend, and B) what I should do in terms of vapor/air barriers to the outside.

I have a follow-up question as well. The walls have wainscotting on them, which we would prefer to leave alone, so I'm wondering how that factors into to insulation and vapor barrier issues.

Thanks again!

Mark Haley

Bondo 02-22-2010 12:04 PM

Ayuh,... That sounds like the perfect situation for Sprayed Foam...

ccarlisle 02-22-2010 12:14 PM

There are 3 issues you ought to be looking at: insulation per se (like what type and how much etc), air movement and a vapour retarder/barrier of some sort.

Now I assume you're doing this to bring things up to standards of today rather than a 'historical restoration' project - one would be more costly than the other - and so, first, you'll have to gauge to what extent you can cut down air drafts from the outside. Nowadays we wrap exterior walls in some sort of plastic sheet (eg "Tyvek") to repel rainwater and to prevent an excess of cold air blowing in; that goes underneath the siding.

If you can't access underneath the siding, then you'll have to cut down air drafts from the inside. So, now we turn to the plaster etc. Now the best idea here is to tear out the old plaster and replace it with drywall, taking advantage of the opportunity to add thickness to the walls, insulate well, add electrical needs and seal out the drafts I spoke of earlier. We would use spray-foam polyurethane (expensive!) in kits at this point as it does a few things at the same time; otherwise, we'd settle for unfaced fibreglass batts (cheapest) or better still polystyrene boards depending on how thick the wall is meant to be. I'd aim for 6" of fibreglass batts (easiest) on outside walls or 4'' of polystyrene...

Then, I'd put up 6 mil plastic vapour barrier and seal the seams with red tape, then drywall, then prime and paint.

Paulie 02-22-2010 08:28 PM

Since the budget is the issue, batt insulation, 6mil vapor barrier, drywall. Hope your not tearing out any decorative plaster, that would be a shame.

Stillwerkin 02-22-2010 09:42 PM

+1 on the sprayfoam. Complete sealing of drafts and vapor barrier in one. About 5-7R value per inch.

If you DIY and buy a kit, make sure to wear complete protection. For large jobs, I've heard the price is about the same.
There is slow-rise and extention nozzles for deep spaces, and fast-rise for the flat areas. Nozzles seem to clog quickly, and the containers need to be at proper temp for the chemicals to work.


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