I live in West Texas and I have a house built circa 1940. I’m in the midst of remodeling room by room and I’ve just torn into the kitchen walls and I’ve found myself in a bit of a conundrum. The interior of the house is clad in tongue and groove clapboards which I’ve removed to access the walls and I discovered that the exterior of the wall has no sheathing or clabboards, just nailers for what I’m assuming is some sort of vapor/air barrier and the supports for the stonework. The barrier on the exterior has a number of holes in it and is far from air tight. Since the house is stone I can’t tear it down to access it from the outside, so I’m going to have to find a way to deal with this from the inside. I can’t afford spray foam and I’m not sure that it’s economical to do it room by room. I know I need to maintain a space between the stone and wall for a drainage plane so that rules out spray foam anyways. There is not any water damage (or anywhere in the house for that matter) that I can see, we don’t see a lot of rain here and and I have decent overhangs. So how should I go about dealing with this? My first thought was to cut foam board to fit tight in the stud bays and spray foam the edges to seal it tight. I want to fur out the wall to 2×6 depth to have more room for insulation. My other thought was to fill the bays with r-13 fiberglass, foam board over the whole wall for air sealing and thermal break, then add furring strips for the drywall. Any thoughts out there? I spent my twenties as a carpenter, framing and trim carpentry. I’m pretty well versed in most construction methods but this is a situation where I’m really scratching my head. Any help or advice would be much appreciated!
Replies
Stone Walls?
I am not sure that I understand?
Are you writing that you have solid stone walls, no cavities, and that someone has lined the walls with t&g boards?
If indeed the walls are solid stone? Then the only problem you are likely to have is, wind blown rain, seeping through the mortar.
Solid stone walls are not effected by condensation, it merely passes through. If you want to insulate solid stone walls, then the best way is to stick sheets of polystyrene to the walls (this avoids heat bridging) and finish by sticking dry wall to the polystyrene. A wet plaster skim coat will give you a high quality finish to decorate.
Having dealt with this type of thing on a few remodels and knowing what a pain in the butt it is to try to fit foam boards between old studs that are never straight or even and filled with wires and whatnot, I'd say you're best bet is to fill the stud bay with fiberglass, and install 2' wide foam board at least an inch thick horizontally with a nailer every 2' and around the perimeter for sheetrock.
You don't need a vapor barrier - the foam takes the place of that, so get unfaced bats that will install 2x as quick. Add a nailer at floor level and wall sides and door/window openings, then lie down a 2'x8' piece of insulation and use that as your spacer for the next nailer (easy and no gap). Repeat until you get to the top and hang sheetrock. Fill any small gaps with cans of spray foam or buy a resuable foam dispenser and larger cans of the same spray foam.
That's the big picture.
Make sure your nailer matches the height of your sheetrock joint - adjust the width of a layer of foam so it works out correctly.
It's much better to have your nailer 1/16" proud of the foam than 1/16" short since the foam won't compress enough to allow the sheetrock to sit directly on the nailer and that will cause wierd things to happen when installing sheetrock screws.
Some electrical boxes will need to be changed out - see what's available since the design has to allow the box to extend through the foam and sheetrock. Cutin boxes are not always the best way to go, but they may be for some situations. Old wiring cut short and crammed into small boxes doesn't always play well with cutin boxes - big square metal boxes with plater rings are often what I go with - plenty of room to get things right.
Hi, dkerbn – I’m Doug Walden and the product manager of air sealing at Owens Corning. I just wanted to jump in and hopefully provide a solution.
Assuming the existing stud is 3½ inches, fur it out with a ¾-inch furring strip to make it 4¼ inches, which would be your cavity.
Then, use a ¾-inch piece of polystyrene rigid foam insulation, flush with the exterior face of the original framing and sealed at the edges with can polyurethane foam, as you’ve suggested. Then fill the remaining 3½-inch cavity with R-13 fiberglass batt insulation.
Hope this helps.