Dormer Window Repair

By Michael Huffman

A couple of years ago, I noticed that the bottom member of the double-hung window in my office dormer had begun to rot.

Knowing it would be difficult to buy a matching replacement, I decided to repair the window using WEST SYSTEM® Epoxy and fiberglass. I removed the sash from the frame and took it to my shop. The first step was to remove the rotted wood. It turned out the damage was extensive, affecting the wood all the way through the bottom member and into the vertical member.

Although the outside surface of the bottom member was flat, the inside surface incorporated a groove about a half-inch wide. Using thin aluminum sheet metal, I fashioned a mold that duplicated the shape of the groove and the bottom surface of the bottom member. After applying mold release, I attached the mold pieces with some sheet metal screws to the good wood outside of the damaged area, then sealed the edges with masking tape.

I then proceeded to wet precut pieces of fiberglass cloth, leftover from another project, with WEST SYSTEM 105 Epoxy Resin® and 206 Slow Hardener®.
I laid them into the damaged area. This ultimately filled up the mold completely. I then screwed and clamped the final mold piece in place.

After the epoxy had cured, I removed the mold pieces and found the repair had been successful, accurately duplicating the shape of the repaired area.

I did a small of amount of handwork with a rotary tool to recut the seal groove in the bottom of the window. Then I sanded the repaired areas and applied latex primer and finish paint before reinstalling the hardware. The window looks good as new.

Editor’s Note: When working in warm weather, you may want to use 209 Extra Slow Hardener® for filling large voids to prevent excessive exotherm.