Klaus Larsen LLC Case Studies: Installing a Vented Deck in Old Saybrook Roofing System
Challenge
Our initial inspection of this roof found some leaking, as well as very soft plywood. This lead us to believe that there was a serious moisture problem here. The homeowners informed us that not only did they have ice dams, but that they also had a mold problem in part of the attic. They had a fan installed, which began to take care of the mold, but were still facing a condensation issue. Our plan was to incorporate ventilation, however this is what is considered a 'hot roof.' This means there was no way to exhaust air from the bottom of the roof to the top. Like a canned soft drink on a summer day, the strong temperature differential was causing moisture to condensate on the underside of the decking. Water was then being absorbed into the plywood, which was causing it to delaminate. It had gotten so bad that we were actually able to pull the roof up and peel it away, as the nails were no longer holding.
Solution
We had to create a thermal break between the inside of the house and the outside, to alleviate that temperature difference. After removing the old roof and getting it down to the bare plywood deck, we added two layers of foam insulation board on top. We then laid a furring strip on top of the foam, and a new plywood deck on top of the furring strips. With a strip laid every 16”, we have created an air path where we can get air from the eave to the ridge. There is now also an eave vent at the bottom and an Owens Corning Rolled Ridge Vent at the top. This takes care of the condensation and prevents ice dams from forming.
