Subject: Wood Rot
Date: Sat, 26 Dec 1998
I have an older home that has water damage on the ends of the rafters. The ends (6" to 8") of the rafters are decaying. There is still moisture in the wood. I want to sister in same size lumber on either side of the rafters. I would like to do this without cutting out the rotten sections. What can I use to stop the rotting?
You will want to stop the rot in the old wood before doing any
sistering. Otherwise the rot fungi and/or their spores will simply
affect the new wood. And you can't count on preserved wood for
protection -- it doesn't always work.
The old deteriorated wood can be restored and made rot resistant by using our Clear Penetrating Epoxy Sealer (CPES) on both the old wood and the contact side of the new wood used for sistering. To do this the old wood should be reasonably dry. If you protect it from water incursion and drill CPES-access holes it will dry. When time is a factor in these situations, we have used commercial kerosene heater/blowers to generate lots of hot air.
There are fungicides out there that will kill rot fungi, but they in no
way restore bad wood, as CPES does, and they are mostly water-soluble,
which means eventually they can be washed away by moisture. CPES is a
specialized epoxy and is expensive, but it does the job right and
solidifies wood and infuses the wood with an epoxy resin which restricts the ability of the wood to absorb moisture. Without suffcient moisture, the fungi spores can't reproduce.
Come back if you have further questions. We can advise you on the amount
you might need if you give us the size and number of rafters involved.