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DeputyDog 08-20-2011 03:08 PM

Foundation/sill plate coating
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I have an exterior foundation/sill plate finishing question. 100 year old shingle-style house, 2 storeys with no basement in Pacific Northwest. The cement foundation is solid, no water penetration issues but low to the ground, ie. normally I believe there’s a 6” gap between the grade and bottom of the siding, but I’ve less than that and in some cases no gap due to a slight slope to the lot. I have hardie board siding on top of wood sheathing (?) and at the bottom of the siding is a 2 x 6 vertical board (‘base board’) with metal flashing running on top of it (below the last course of siding over the top of the base board). Please see first picture for clarity. I can pull the base board off (pictures 2 - 4) and apply a coating or material from the bottom of the flashing over the old sheathing, sill plate and down to the foundation, then re-attach the base board.

What kind of material should I use to cover the space between the top of grade to the bottom of the siding? Needs to cover the cement foundation, wood sill plate and wood siding up to the bottom of the hardie board siding.

I’ve read about various possible coatings including parging, spray-foam, caulking, Blue Skin, Blue Seal. I’m mainly trying to prevent bugs, rot, rodents and cold air from penetrating the space.

Any advice is greatly appreciated. Thank you.

BridgeMan 08-20-2011 10:42 PM

Why not 2 courses of Hardiplank, with the bottom course attached to short vertical furring strips of treated wood and the top course tucked in under the flashing, attached to the existing base board? You'd have to come up with a special clip designed for the attachment, or be willing to live with visible screw-heads, caulked and painted over. Or possibly use some super-strong adhesive, impervious to moisture.

I like Hardiplank, although it can be a bugger to work with.

nealtw 08-21-2011 09:12 PM

Keep in mind the concrete wicks water below grade and evaporate in this area above grade so sealing with blueskin is not a good idea.
In B.C. you can buy bug screen in 6" rolls , staple it behind the tarpaper and goop to the concrete with acoustical sealer close to the top of concrete and change the facia board with one 2" wider to hide the screen.

DeputyDog 08-23-2011 12:27 AM

Thanks for the suggestions. The screen is a good idea to keep out the bugs and rodents. and the acoustical sealer along the sill plate would keep out the cold air.

nealtw 08-23-2011 01:07 AM

The screen is for the bugs, you don't really want to stop air movement there!

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