Home>Discussions>EXTERIORS>Need Information: Sealing a concrete slab to house framing
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BearClaw66
Need Information: Sealing a concrete slab to house framing

Parents looking to replace wood deck with a concrete slab. From grade foundation wall is about 30" above grade. Then 10" from top of founation to bottom of door sill. With parents getting older they would like to walk out the back door onto back deck/ concrete slab. Looking for some information on how to flash/seal edges of a concrete slab, being up against wood shelthing. Any help would be appreciated.
Thanks
BearClaw

dj1
Re: Need Information: Sealing a concrete slab to house framing

Generally speaking, when ever you attach a cement product (masonry, stucco, mortar, etc.) to wood, a water proof moisture barrier of some sort (tar paper, house wrap, sheet meta, etc.) must be installed first.

But, I'm having a hard time to visualize your situation correctly. When you said "wood shelthing" did you mean "wood sheeting" or "wood sheathing"??

You have 10" from grade to door sill and you want a slab flush to the door sill. If I guess correctly, this is what you can do, after you remove the old deck and refinish the exterior wall - fill holes, etc.:

1. Waterproof/wrap the house from grade to door sill. Do it correctly so it's 100% water tight. Not done correctly, you'll have troubles galore.

2. Back fill from grade to 6.5" below door sill with imported dirt. Compact it well.

3. Add 2" gravel.

4. Form and pour 3.5" concrete, with sufficient slope for proper drainage away from the door.

Now you will a slab which is 1" below the door sill against the waterproof exterior wall.

There is no room for mistakes, so if you are not sure, hire a pro.

Sombreuil_mongrel
Re: Need Information: Sealing a concrete slab to house framing

I can't give the citation, but I think code requires a 2" minimum step on an exterior patio to the interior floor height. This is to prevent water running inside under the threshold. You can have a ramp, however, to facilitate the "Universal design" aspect.
Heed the above warning about properly isolating the wood sills from the masonry; we usually use copper flashing over Ice & water shield brought up the walls, so melting snow drifts won't seep in behind. The wood siding should be at least 2" above the patio floor so splashing of rainwater can run off. We leave that as exposed copper, which ages dark and looks unobtrusive.
Casey

HoustonRemodeler
Re: Need Information: Sealing a concrete slab to house framing

You might get away with a "handicap" style ramp at the doorway, but raising an exterior masonry slab to interior floor level is not a good idea, even if the slab is pitched away from the house slab. The huge problem you'll be facing is rain water getting onto or into the house from the slab. In my fair city there is a 6" minimal exposure of the foundation above any grade. The only exception is for handicap ramps. In the case of the ramps, care still needs to be taken to prevent water from infiltrating the structure.

Mastercarpentry
Re: Need Information: Sealing a concrete slab to house framing

Here in the upstate of SC wind-driven rain is an issue, as are leaves that pile up clogging water run-off paths. I do enough ADA work to know that you're practically inviting problems with anything new going up to sill plate level so I avoid that- better a dropped slab with a ramp than a rotted sill or siding. If a ramp is poured take the time to open up the door trim and seal the heck out of everything under and around there where water may be driven in during a storm. Also 'crown' the ramp slightly like a road so water can drain off the sides better. Water kills homes and there is no overkill in waterproofing.

Sombreuil_mongrel
Re: Need Information: Sealing a concrete slab to house framing

Hi I was thinking a removable temporary ramp used as needed.
Casey

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