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Re-siding / re-sheathing a 30-year-old double-stud house

krom | Posted in Energy Efficiency and Durability on

I’m in Zone 6. My mother’s house was built from the late 70s to the early 80s (not a guess — it took that long).

Walls are 2×6 and 2×4 staggered studs with pink glass, poly, and sheetrock on the inside, rough-sawn board sheathing, rough-sawn board-and-batten siding. Andersen 2-pane casement low-e windows.

It’s time to replace a bunch of siding, as the bottom is rotting where it is close to the deck (rain splashing up in the summer, and constant snow contact in the winter, my guess).

The house has always leaked air — not enough to get frost on the outlets, but quite a bit, and its always had a rodent problem. (It’s only 100 feet from the house to fields in 3 directions.)

I’m looking for suggestions on tightening it up. I’ve considered going to a taped plywood, or Zip sheathing, but really dread the thought of removing all the window trim and windows.

Any suggestions would be greatly appreciated!

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Replies

  1. GBA Editor
    Martin Holladay | | #1

    Trevor,
    Your mother's house sounds like a lot of homes that I'm familiar with from that era (including a few I built). Back then, builders thought that the best way to improve the performance of a house was to make the walls thicker and add more fiberglass batts. Many of us didn't understand the importance of air sealing, so we ended up building houses like the one you describe.

    If I were you, the first thing to do is to decide whether you will be replacing the windows. It's possible to keep the existing windows, of course -- but keeping the existing windows makes the flashing challenge a little trickier.

    I would certainly remove the siding and inspect the existing board sheathing. Assuming the existing sheathing is sound, I would install a new layer of sheathing over the boards -- either ordinary OSB, Zip sheathing OSB, or plywood -- with carefully taped seams. Detail the perimeter of each wall, and the penetrations, carefully -- both from a moisture-management perspective and an air-sealing perspective.

    Then it would be a good idea to install a layer of housewrap or asphalt felt as your WRB. (Even if you choose Zip sheathing, I think that housewrap or asphalt felt is worth it, because these products make it easier to integrate the WRB with the window flashing.)

    Window flashing details depend, as I wrote before, on whether you are installing new windows or making do with the existing windows.

    New siding can be board-and-batten or a different siding, as you prefer. To address splashback problems, consider installing roof gutters, or install a band of metal flashing at the base of the wall (with about 4 or 6 inches of flashing exposed) -- assuming you don't mind the look of exposed metal -- and keep the bottom course of siding (or the bottom of your new board-and-batten siding) raised above the deck a few inches.

  2. GBA Editor
    Martin Holladay | | #2

    Trevor,
    Although you are focusing on walls, you also asked for "suggestions on tightening up" the house. I feel duty-bound to inform you that tightening up an old house usually requires air-sealing work in the basement (or crawl space) and the attic.

    Here are links to two articles on tightening up an old house:

    Air Sealing a Basement

    Air Sealing an Attic

  3. krom | | #3

    Martin,
    Thanks.
    We will be keeping the existing windows (they've held up fantastically, only 1 panel in the entire house has needed replacement from fogging internally) the budget isn't there to replace them all.
    The sheathing looks sound except for the bottom board near the deck. The new siding will be board and batten.

  4. Dana1 | | #4

    If you're stripping the siding you may be able to dense-pack (or at least dens-er pack) the walls drilling from the exterior. If you can't get a dense packing hose into the cavities due to interference with the existing fiberglass you may have to drill 3 or maybe even 4 holes per bay to get a high enough density to achieve the air-tightening and gap filling you're looking for. Dense packing will drive fiber insulation into every air leak & seam, and while it's not as perfect an air seal as caulk, it's does quite a lot for reducing air infiltration. And by compressing out the fiberglass it makes the fiberglass more air retardent to boot.

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