Patio sliding door sub sill

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  #1  
Old 05-29-15, 07:31 PM
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Patio sliding door sub sill

I have continuous pour concrete slab from rec room out to patio. Am installing new vinyl sliding door and want to know if sub sill is necessary or can I just install door right on slab?
 
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Old 05-29-15, 08:44 PM
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Does it rain on this patio??? And are you saying the concrete in the rec room is the same level as the concrete on the patio outside? If so it sounds like a leak potential.

But generally, no, you do not need to put any kind of sub sill down under a patio door. Generally the pad outside the door is lower, however. If it isn't, there is nothing to keep water from blowing under or around the door (through the rough opening).
 
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Old 05-30-15, 04:46 AM
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Yes it s a continuous pour from inside to out, so same height. The patio does have gutters to help with water.
So if I do a sub sill, what is general height to go.... 1"?
I've seen I can do caulked/wrapped pressure treated, but doesn't that become potential leak source as well or would that actually be more of a barrier than door to concrete?
Doing concrete sub-sill seems best option, but hole would have to be open overnite as I don't believe I could set door on that poured concrete same day.

The patio is about 2' from a 6"drop to another patio area which is at ground level. Had seen where some had cut channels into the concrete by patio door for water run-off. Thought about doing that or
trench drain/strip drain used on patios around in-ground pools.
 
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Old 05-30-15, 05:47 AM
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The best thing to do would be to put down a sill pan, which provides a dam for the entire rough opening without raising the height of the door. Normally there is a drop off at the outer edge of the rough opening (which you would not have) but since it can't turn downward in front, your sill pan would need to be shaped like an L, not like a dripcap or z-flashing. The back part is turned up about 1" where the interior edge of the door will sit, and the sides are turned up to protect the sides of the RO, which makes a "pan" that water can't get past. The sill pan gets caulked down to the rough opening with some good sealant, usually a polyurethane sealant is best. The difficulty will be setting the door into the sill pan before the caulk has had a chance to set up, because it will want to slide around a little. If you have wood framing, the sides of the sill pan could be nailed to the RO, which would help fix it in position. You also caulk on top of the sill pan and set the door on top of it.

Putting a subsill down to raise the door up, and sealing it to the opening is one way to create a "dam", which is similar to the purpose of the sill pan, but the subsill would raise the door, making the tripping hazard greater. No one likes stepping over a noticeably high door threshold because its awkward. If you feel this is more within your capability than a sill pan, then yes, this would probably be a better option than no sill pan at all.

A door can be caulked right to the pad, but the problem that creates is the sides of the rough opening, since water can go around the door. You "can" make a dam out of caulk, and block up the gaps on each side of the door, but the potential problem with that is that if you ever get water leaking down from above, (this happens occasionally with wind driven rain and vinyl siding) it can't get out, and the dam on the outside of the opening will force that water to run into the house.
 
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