How to Duplicate Molding That is Damaged or Missing

I started replacing some rotted woodwork down here caused by a water leak.  Now the baseboard was no problem, I took off the old piece here, and I happened to have a matching piece, which will go right in here.  But I don’t have a matching piece for this casing, and I don’t want to replace the entire door frame, cause it wouldn’t match the rest of the house.  But there is a solution.

This job can get a little messy, so the first job is to mask the floors and adjacent walls.  The material we’ll be using to make this repair is polyester resin or auto-body filler.  It comes in two parts, the resin itself, and a catalyst that’s added from a small tube.  Using the polyester resin, we’re going to be making a casting of the original moulding.  To be sure the resin releases, I’ll first spray the surface with a lubricant like WD-40.  Now, I’ll spread the body filler on the moulding.  You don’t have to worry about being too neat right here.  In just a few minutes, the resin will harden into a semi rubbery state.  Now’s the time to do some trimming, and then remove the new mold. 

To prepare the mold for casting, we put a wooden block on either end and again spray the inside with WD-40.  Another batch of polyester resin is mixed up and poured into the mold.  While the casting is still flexible, it’s removed from the mold, and the excess trimmed off.  Small air bubbles are filled with speckle, and then the pieces sanded.  A little bit of paint, and you’d be hard pressed to tell that replacement from the original.