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To caulk or not, above a 1925 redwood window head jamb?

I was just pulling out the caulk gun, when I noticed this head jamb is tapered.

The house is 1925 stucco in USDA zone 10b (San Francisco Bay Area). So did the original builders intend this as a form of weep? Instead of caulk is it actually better to leave the edge open, or cut a weep into the caulk?

The stucco wall in question is settling, and has various patched cracks. So, in theory at least, water may weep down the old tar paper behind the stucco, during the rainy season. The walls are at least partially filled with cellulose, which reduces drying to the interior lathe and plaster.

Caulk historic stucco window.JPG75.21 KB
Asked by Bryce Nesbitt
Posted Jun 11, 2018 6:19 PM ET


3 Answers

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I'm an advocate of caulk-free siding. In general, you shouldn't see any caulk around windows or siding. Free drainage and air movement are what you want when it comes to siding and window trim.

All this presupposes, of course, that the wall has an air barrier somewhere -- either at the sheathing level or the drywall level.

The trouble with an old house is that you don't know what type of water-resistive barrier (WRB) or flashing (if any) is hiding behind the siding. But unless you have a specific problem that you are trying to solve, and you know what you are doing, put away the caulk gun. Save the caulk for the interior of your home.

Answered by Martin Holladay
Posted Jun 12, 2018 5:11 AM ET


Based on elsewhere, the wall is probably lathe & plaster inside, board sheathing, and a single layer of tar paper, then furring nails wire and stucco. Here there's no overhang or roof line above (Mediterranean style). Thus water sheets down the wall, and wind could push a fair amount back into the crack.

The tar paper probably ends on the tapered head jamb with no other flashing. The condition of the tar paper is likely mixed.

In many other buildings that head jam appears to be made from a flat piece of wood. Here it appears to have a deliberate taper out. For a flat jamb would you caulk?

Answered by Bryce Nesbitt
Posted Jun 14, 2018 1:54 PM ET


My answer is unchanged. No caulk -- unless there is a very specific water entry problem, well diagnosed, that you are trying to solve.

Answered by Martin Holladay
Posted Jun 14, 2018 2:17 PM ET

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