The Rot Doctor


Subject: Rot around downspouts?
Date: Sat, 12 Jun 1999

Dear Dr. Rot,

I'm a first time homeowner who has just bought a nearly-flat-topped mid-1950s house with beam-and-post construction and a tar-and-gravel roof. The roof has some small membrane penetrations along 5' of its overhanging edge on one side. There are a couple of rafters that show thin black areas between the boards, but the boards seem solid otherwise (except for some 1" deep soft black areas around two of the downspouts and a bit of mildew on the painted surfaces).

Roofing companies say that I need to pull up the roof, replace these 2 or 3 rafters and their adjacent edge fascia, and then put in a new roof and downspouts (at $8K). It looks to me like the boards are only marginally deteriorated -- my house inspector said that they "looked worse than they really are" when he prodded them. Can these boards be saved, so I could just patch the roof leak and install new downspouts?
Thanks for any advice...


They surely can. If the wood is dry (and wait until it is) then the application of CPES (Clear Penetrating Epoxy Sealer) to the boards, discolored ones as well as the ones that show rot, will return substance to the wood and make the wood highly resistant to rot fungi. A 1-2" deep soft spot is no problem at all. It's best if the CPES can be applied from above, but getting at the wood sideways will work as well. We do have a syringe and/or spray unit to help application.

One coat of CPES will be fine for the marginal boards, but we'd recommend 2 coats where the wood is soft. The CPES should be sufficient, but if you have to deal with the inspector again you could add a coat of the L&L Resin to give everything a hard finish. Not really necessary, and don't spend the money unless you're having to get his approval. Unfortunately, not all building inspector understand or have knowledge of the interaction of epoxy and wood.

After the CPES, patch the roof and install the new downspouts and you'll be fine.

Hard to say how much CPES you would need. It's a very thin mixed liquid and penetrates deeply, so you'll just have to estimate. It does store indefinitely if unmixed and kept from freezing.

Come back if we can be of further help.