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Water control at ADA patio door?

Debra_Ann | Posted in General Questions on

We’re building our retirement home with some universal design features, as we plan to live there until we kick the bucket. Our foundation is poured concrete foundation wall (for a closed conditioned crawl space), with top load floor trusses.

We have a patio door, and our designer wants to have the concrete patio elevated to just below our subfloor, to make this entrance more accessible for wheelchairs. And he’s having the concrete patio sloping away from the house at just 1 inch drop over 10 feet.

The soil around the house will be graded away at 6″ over 10 feet. That’s too steep a slope for a patio, but I can envision a hard rain being driven uphill towards the door with just a 1″ slope.

This is an exposed north wall (where the main weather hits), and I’m very concerned about water control. The top of the concrete patio would be higher than the concrete foundation, and abutting the wooden floor framing. I’m concerned about water leakage over the years, even with good flashing.

Any thoughts or ideas? The only solution we’ve contemplated so far is installing a wide roof to cover that entrance area. Not sure how big it would need to be, or if there are other better options. Thanks.

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  1. GBA Editor
    Martin Holladay | | #1

    First of all, any wheelchair accessible entrance door needs a wide roof, for exactly the reasons you are worried about (water entry or, in some climates, snow accumulation). If you are at the design stage, plan for a roofed entry porch.

    Second, a concrete ramp adjacent to a rim joist is likely to lead to rim joist rot, unless (a) the roof is very wide, and (b) the rim joist is very carefully flashed. I hope that your designer and builder are aware of these issues.

  2. Debra_Ann | | #2

    Yes, I'm still in the design stage, and trying to catch all these design details. Haven't chosen a builder yet, but our designer hasn't stated that we need an entrance roof for this patio door - though I feel pretty strongly that we need it.

    I also don't like the thought of a concrete slab up against the rim joist area. I'm wondering if we can keep the concrete slab at least a foot away, and use a section of treated wood above a drainage channel to bridge the gap between the door and concrete. Still need really good flashing in that area, though.

  3. Expert Member
    ARMANDO COBO | | #3

    If I understand your foundation, I give you a different option or two, which can be modified to your floor frame specs. See the attached pictures.
    1. In the area where the rim joist would be against the concrete slab for the patio in a crawl space, design a reversed brick ledge where the concrete wall is extended to the floor level.
    2. Before you pour your concrete patio, install flexible tape/WRB against the exposed concrete wall and frame wall, to cover the joint where moisture could come in, however the degree of detailing and quality control is higher.
    3. In either case, design a roof over the patio and make it a porch. 10' patio plus 24"(?) overhang, would give you 12' rain protection.
    4. Install exterior doors with sloping and low thresholds, 1/2" or so. Many manufacturers offer "barrier free" or ADA option, like Marvin, Milgard, ThermaTru, etc.. Look for thermally broken sills.

  4. Debra_Ann | | #4

    Armando, thank you for for suggesting a reverse brick ledge. I like that idea, along with a roof. I'm also thinking about possibly placing the concrete patio about 1 foot from the house and using some kind of treated wood "bridge" for a small ramp from the door to patio.

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