I am restoring some exterior window sills in my 110 yr old house. There are cracks and splits that require filling/bonding. I have been using a kneading type two part epoxy putty, but it is pretty dear at $5/oz. Someone suggested using Bondo, but I wondered if it adheres to wood well. Any suggestions appreciated.

 

I have used Bondo for years in making repairs to furniture. It will adhere to just about any UNFINISHED surface.

I use masking tape and paint paddles to 'form' it when needed. I also apply several coats of aerosole lacquer to the paint paddles and let that dry first - this prevents the Bondo from sticking to the 'form'.

I would suggest doing as much shaping as possible before the Bondo completely hardens. After it sets up, it's harder than most woods and may be difficult to sand out flat.

It can be primed and coated just like any other exterior surface.

FYI: in the furniture repairs, I use artists oil colors to color the repair toward the wood color, then finish as needed.

 

I think I'll make the switch to Bondo. Those are some neat tips that you included. I have noticed with the epoxy putty that it is also harder than the surrounding fir and hence hard to sand flat. However, on exterior window sills I don't need a furniture grade finish.

 

Will Bondo stick to Zinnser oil primer?? Secondly, do you have any opinions on oil primer vs Peel Stop. This house has a lot of peeling and alligatored paint.

 

You might want to look into Home Fix Super Strength Universal Repair Filler (100773), made by Evercoat (a division of Illinois Tool Works). It is fortified with glass fibers, and will not shrink or crumble. I like it because: one can fill large voids, if necessary, without time-consuming layering; it can be tinted or painted; it can be drilled, routed, and shaped (I matched surrounding wood grain on fascia). The Evercoat web site did not list Home Fix, but I contacted them by email and they directed me to current dealers (I think they were either Ace or True Value). My current can of Home Fix lists 513-489-7600 as a contact number.