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Community and Q&A

exterior door threshold slopes towards door

Trevor Lambert | Posted in General Questions on

I’ve recently discovered that the threshold on the door leading to my “flat” roof balcony is not only not properly sloped, if anything it actually slopes toward the door. The door threshold is really deep, about 18″, so this makes the problem even worse. I’ve been trying to figure out what to do about it, and at a loss. Do I have any options besides removing the door, tearing up the deck membrane and doing it all over again? The builder is long gone and of no help.

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  1. User avatar
    Michael Maines | | #1

    Trevor, unfortunately, door sills/thresholds are already vulnerable parts of the building envelope; if yours is sloping in the wrong direction I don't know of a solution other than taking it out and starting over. A skilled carpenter can remove the threshold without removing the entire door, but unless you have very high-value finishes, it's probably easiest to bite the bullet and pull the door.

    It's not uncommon on balconies to need to raise the door up on a plinth in order to flash it properly; the building code is a little murky when it comes to required details on this, but I believe it's ok to have the sill up to 7 3/4" above the floor on either side. A photo of your situation would help a lot.

  2. Trevor Lambert | | #2

    I will take a photo when I get home tonight. The deck is well below the door threshold, so there's no reason to have not done it (he said he was going to, must have had a broken level).

  3. Trevor Lambert | | #3

    Here are a couple of photos.

  4. User avatar
    Michael Maines | | #4

    Trevor, those photos help a lot. It's not really what I was picturing. If your goal was to create a water collection device, I'd say your contractor did a pretty good job. The area outside the door is likely raised because it's the interior floor system carrying through, and the deck surface was framed a couple of inches lower.

    If door frames were totally waterproof, maybe you could bring a new slope up to the front of the door sill, but it's much safer to have a pan that extends under the door with a backdam on the interior. Especially when there is little to no step-down on the exterior side of the door.

    That leaves your options as:
    1. Remove the door, create a new slope outside the door and a pan extending under the door, or
    2. Remove the membrane and re-frame the area outside the door with a slope toward the rest of the deck. I'm not familiar with the roofing membrane used; EPDM is still standard in my area, but it looks like it's weldable. Depending on your floor framing system, there is a chance you could remove some material to create a slope, but you should have an engineer look at it if you choose this route.

  5. Trevor Lambert | | #5

    That area outside the door is not part of the interior floor system. It was all done very quickly while the decking guy was waiting to do his job, so I only have a fuzzy memory of what it looked like, but it had to be just a piece of exterior plywood set down as they were finishing the deck roof and installing the door. Can you link me to any pictures of what a pan with a back dam looks like? Option 2 seems like the easiest option. It's vinyl, and heat weldable. It would mean the membrane would just butt up to the door frame rather than go under it. Is that ok, as long as it's sloped correctly?

  6. User avatar
    Michael Maines | | #6

    Trevor, it's interesting that it's not part of the floor system. What were the exterior walls built on? Assuming you know your own house better than I do, I'd suggest reading: (a piece I wrote long ago; in the meantime flexible pans are now the norm)

    Several wise contractors have told me "doors always leak." Even high-performance, triple-glazed european doors are not immune. I'm embarrassed to say that the Thermatru entry door I installed on my own, antique house leaks when the rain hits it just right (a larger roof overhang would help, but not against the driving rain we sometimes get). Others say that their doors don't leak. It's always safer to include a sill pan, but if you're feeling lucky, and especially if you're in an area that's not windy and rainy and you have a roof overhang, you might be fine without one.

  7. User avatar
    Michael Maines | | #7

    Got it, thanks for the explanation. I'm sorry this happened; good builders can be hard to find.

  8. Trevor Lambert | | #8

    The house is made of pre-fabricated wall panels. The second level walls rest directly on the lower level walls, and the floor is entirely within that footprint, attached with joist hangers onto an LSL header.

    I realise I need to remove the door and get a sill pan under there. Just another in a long list of grievances I will never get to file with the builder.

    I'm also realising this isn't going to be a straightforward fix. The width and extra depth of the door frame probably means I'm making the pan myself.

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