Published on November 14th, 2012 | by Henri


Plywood soffit keeps buckling and peeling

Q.    The second floor of my 20-year-old house overhangs the first floor by two feet. Every few years sections of the plywood cover at the bottom of the overhang buckle and peel. I keep replacing them but would like to find a solution to this problem.
I have noticed that the Kraft paper of the insulation faces down. The insulation itself seems to be dry. Is venting required and how would it be done since the joists are perpendicular to the length of the house? Or should the insulation be turned over?

A.    No venting should be done. If you have noticed water stains covering the entire side of the plywood that is up against the insulation, you may have a condensation problem. It is probably due to warm, moist air from the first floor migrating into the overhang and condensing on the cold plywood.

The simplest solution, next time you have to replace a section of the plywood soffit, is to cut pieces of 1-inch-thick rigid insulation to fit tightly in each joist space and push them into the inside line of the first-floor wall. Then, caulk all four sides to seal the spaces. Turn the insulation over so the kraft paper is against the second floor subfloor but make sure that the entire joist spaces are filled with the insulation, even if you have to add some or replace what you have.

If you notice water stains concentrated on the outside edge of the soffit sections and fading as they progress toward the first floor wall, you may have a different problem. If you have ice dams at the eaves of your roof and you do not have a special waterproofing membrane under the shingles, there may be leakage into the second floor walls that works its way down to the overhang soffit. In that case, you should also have noticed some leakage at the window heads. This is obviously more serious and you should deal with it appropriately by either having Grace Ice & Water Shield (or equivalent) installed under the shingles or insulating and venting the attic to eliminate the ice dams. You should also make sure that there are no convective paths in the second floor ceiling that allow warm air to get into the attic.

In either case, paint the new sections of plywood on all sides before nailing them back in place.

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