Remove Siding, Repair Flashing

The vinyl siding on my house was not properly installed (no insulating board, no house wrap, no caulking). I can now see exposed plywood sheathing in a large gap between the edge of the siding panel and the edge of the vinyl window. How can I seal this gap around the windows so that it is water proof, but still allows for the expansion/contraction of the vinyl siding panel?? Thanks in advance.

Rex, Seattle, WA

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Hi Rex.

I’m not sure that anything you put at that vinyl siding gap is going to be completely waterproof. Vinyl siding is a deterrent to water, but it’s the materials behind the siding that actually prevent moisture from entering your home. Caulking the gap between the siding and your vinyl windows may improve the cosmetics of your home, but I don’t think it’s a solution for making it watertight — especially with Seattle’s reputation for damp weather.

If you can see plywood in the gap, that’s a pretty good indication that your vinyl windows don’t have proper weather stripping. While it’s more expensive than just using a bead of caulk, I suggest removing the siding around your windows and installing rubber flashing material at the flanges.

Rubber, Self-sticking Flashing

Vinyl siding comes off fairly easily and depending on the number of windows involved, it may not be a huge project as it will only be the siding pieces at the windows. Of course, an even better solution would be removing all of the siding and installing house wrap along with the window flashing. However, that could get fairly costly.

While having a contractor install the window flashing may cost a few dollars, it could save you a lot of expensive repairs down the road if you have water intrusion around the windows. It’s a shame the vinyl siding installation wasn’t done properly initially.

Removing and installing vinyl siding is fairly DIY friendly and the rubber flashing is easy to install so you may be able to save a little by doing the project yourself. The flashing normally comes in rolls and is self-adhesive. However, if you have a two story home and ladders are involved, hiring an experienced contractor might be a wise move.

The Right Measurement

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