How to stop dry rot up on a roof.
Here is an example of a poorly installed dutch barge rafter that never had a chance to perform. As you can see the rafter lays right on the roof. This is not good because it allows moisture to soak up into the wood causing dry rot as you can clearly see in this picture. Most horizontal cuts like this should be 3/4 of an inch off the roof. This barge rafter was installed raw and never has seen paint on the underside because it rest on the roof shingles. When replacing this rafter I advise using a pre-primed 2×6, make the correct cut, prime and paint the wood prior to the installation. This gives the customer a good chance of having this dutch barge rafter perform for years and years without dry rotting.
The same goes for any wood touching the roof. This picture to the right is of a chimney chase with T-1-11 siding that has also dry rotted. Even being 3/4 of an inch off the roofing shingles the installer created a dam on the right corner at the 1×4 trim. This allowed moisture to wick up the trim boards and dry rot both the 1×4 trim and the siding. When replacing this I also advise pre-priming and painting all the cuts and the back side of the siding and trim up two feet from the roof. This is now protected and will stop any moisture from walking up the back side and causing dry rot. The trim board also must allow water to move freely down the roof and not cause any damming.
Painting wood before it is installed is big a hassle for the roofer but if you think about it, it needs to be painted anyway. Having the raw wood sealed with paint is just a better job. It is easier to paint on the ground than on a roof. There will be some touch work to be done but the time you save and removing the risk of spilling paint on your new roof or worse fall off the roof have been greatly reduced by pre-painting.
In short, Try to cut any wood 3/4 of an inch off the roof and maintain the wood with a normal paint job ever few years and you won’t see dry rot up on the roof.
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