I need to repair the corner of an exterior door sill for my son. The left-most 8" is cracked and starting to show signs of serious decay. The rest of this door sill is perfectly solid, so I don't really want to remove the door, frame, sill, etc. The deteriorating area is actually not under the door, per se, but more of a decorative extension. Small weathering cracks in a poor paint job seem to have enlarged and now trap more moisture.....
Any suggestions for a repair/filler material to save having to tackle a major construction job? Looking for something that would penetrate and seal a soft section, then be stable enough to stand up after a good quality paint job. Ideas?
I would suggest you saturate the wood with an effective preservative. Find some Boracare or use Borate wood preservative rods. These little rods ar about a 1/4" in diameter and 1/2" long. Drill a hole into the affected area and insert the rods and then fill the holes. You might want to drill some holes and soak the wood with wood hardener Or water thin epoxy. Fill the surface and sand and paint. If you don't kill the fungus first, Bondo and paint will barely slow it down. The woodis rotting much further than it appears.
I would coat all cracks with epoxy first, to seal everything with deep penetration. Then I'd use minwax filler. The epoxy will prevent the cracks from expanding and give it strength, and by sealing it will prevent further decay but....everything needs to be dry in order to work. This is a permanent fix and has to be done in stages. Even 2 coats of epoxy if needed.
I built a log cabin and some logs had dry rot. I coated with epoxy to the questionable areas and that ended the problem. It's been 14yrs now and no sign of continued damage.