Decayed Log

Q: I have a 200-year-old chestnut log cabin from Tennessee, and several logs have extensive decay. One is 12 feet long with a 2-foot decayed area. I have tried Bondo to fill the area. Could you suggest any other products? Support, at this time, is not a problem, but if it decays any further it will affect the dovetail. I have already waterproofed and filled cracks. Thanks for your help.  
– Bob Marsh, via e-mail

A: Congratulations on owning a classic piece of American history! Schroeder Log Home Supply suggests the following process to restore decayed logs.

First, cut out the rotted areas and coat the inside of the logs with a preservative that will halt the decay as well as kill insects and fungi. Then use a strengthener and primer such as LiquidWood to seal the wood and to prepare it for a later application of wood filler. Next, if the decayed area is on the end of a log, shape a new piece of wood to fill the cavity in the rotted log. Use either new lumber or a piece of straight-grained salvage or another similar material to make a “plug.” You could also use the strengthener/primer mixed with sawdust to fill in the cavity. Coat the plug with the preservative and when it has dried, coat it with strengthener/ primer and insert it into the cavity. Use an epoxy wood replacement compound to fill in around the plug and the cavity. To color the new area, use dry pigment mixed in with the epoxy to match the rest of the building. If the repaired area is on the end of a log, use a sealant to seal the ends.
 
If at any point in its distinguished lifetime someone painted your cabin with house paint, it will need to be stripped or sandblasted before using any of the products mentioned above.

If the decayed area is especially large, you may want to consider half-log inserts or log replacement. For that you will probably need to hire a professional. (See “Cabinitis: Log Gone” in the Feb/March 2003 issue of Cabin Life for a first-hand account of replacing a log.)