I have an old house with a stone foundation and ~6x6 sill plate. The deck used to butt right up to the siding. I cut the deck away about 18" in order to get access to the area for some weatherization... removed some courses of clapboards, sheathing boards (T&G), and did some spray foaming. My question now is, should I take any measures to protect the foundation, sill, and siding from moisture - particularly snow that will fall from above and/or drift?

I was thinking several inches high metal flashing extending to an inch or two below the sill to a few inches above it. But then how would I attach the clapboards? Is there a better alternative? Or will I just have to live with replacing those clapboards sooner than the rest of them?

Here's a schematic (side view) to illustrate:

enter image description here

The vertical line represents proposed flashing.

1 Answer 1


better than metal flashing and its excellent ability to repel water/moisture is self-sticking rubberized flashing. Although 15 pound roof felt also is acceptable. Either product should be lapped over by the (if any) house wrap and fastened with minimal nails ,etc. I'm not sure about the problem you have in regards to re-installing the clapboards? Won't they re-install with the original fasteners? or is there concern about nailing through the metal flashing?

  • BTW, there was tar paper under there before, but I believe the deck raised the snow up enough to prevent it from puddling underneath. Anyway, yes, my concern was in nailing through metal flashing - both in terms of buckling the flashing and in the unsealed holes it'd create. Using the adhesive flashing, is there any concern about creating too tight a barrier for moisture? there's spray foam along the inside of the sill, so I want to be sure there's room to breathe all up in there.
    – aaron
    Nov 2, 2015 at 19:57
  • the adhesive flashing is self-sealing so any penetrations (nails) through it won't allow water. Regarding it being a barrier to moisture, well it's great for keeping it out when installed correctly. It is a good choice over metal flashing, but can be used in conjunction with it, too.
    – ojait
    Nov 2, 2015 at 23:54

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