Step between concrete floor and patio
deerefan
| Posted in General Questions on
I would like to ask for a “best practice” guideline.
There are 2 long sliding glass doors in the home I am building. On the inside is concrete floor level with door track, outside will be a stone patio in one location and Trexx deck in another. Both sliding doors have 1.5″ deep sillpans with 1.5″ PVC drainage systems. I would like to achieve as smooth of a transition between inside and outside as is possible but would like to avoid water entry. Could you please advise me as to what would be the minimum safe step between the plane of the outside surface and inside concrete floor? Thank you.
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...one step.
I apologize if I worded the question poorly. I meant what vertical height difference between the 2 planes (inside and out) would be minimal recommended to keep rainwater from trying to come in during heavy rain and wind. Thank you again.
deerefan,
This is another one with an "it depends" answer. The code restrictions only apply to finished grade where there are no paved walkways or patios. Some houses, particularly those using glazed sliding panels like Nana-walls, have completely flush thresholds. Whether they are safe depends a few things.
- The way the sill is detailed. Some rely on weep-holes to drain water that has made it's way down the door. The outside needs to be low enough for them to be kept clear, and also low enough that any surface water that may build up can not make it's way into the sill, or need to rely on those weep holes.
- The way the patio is detailed. If you have a strip (or trench) drain at the door, it is much safer than having the patio itself abut the door frame.
- The amount of roof-overhang and slope of the patio. You want those elements to do the heavy lifting in keeping the walls and roof free from wind-blown rain, and not put that task on the more vulnerable door-sill.
If after wading through all that you still want a number, I'd say in most circumstances leave an 1 1/2" of the foundation wall exposed above the patio slab, and build the deck entirely flush.
Malcolm,
We have a very robust drainage for the sliding walls: 1.5" deep subsillpan with 1.5" PVC drains every 6' connecting to a closed 2" diameter drainage pipe leading away from the foundation. I can definitely install a narrow trench next to the patio door. The overhang is 6' over the patio and 8' over the balcony.
The balcony walkway connects to the patio and so it would be ideal to have both be the same level. Given the details above, do you think it would be unwise to have both be flush with inside grade?
Even if the balcony and patio are not the same level, couldn't the walkway between them have a small gradual grade so no steps are necessary in the walkway?
In the house I built, a tiled concrete patio was at the same height as the finished height of a sliding door sill (typical Andersen 8' slider). The patio had a slight grade away from the house, so water on the patio would drain water away from the house. There was also a gap between the sliding door and the patio, so even if ice, snow or something were to allow water to pool on the patio, it couldn't drain directly into the doorway, even though the door was at the same level. Water would fall into that gap between the door sill and patio. The patio door sill also extended out past the edge of the foundation below. So there wasn't much chance of anything falling down into that gap between the door sill and the patio. Although there was an upper level deck and a roof overhang above the doorway, they did little to prevent rain or snow from landing on the patio. We never experienced a problem, other than having to shovel snow on the patio (would be better to have been at least a partly covered patio).
However, this house is in a dry climate, which is helpful too. You didn't mention your climate. Malcolm builds in a wetter maritime climate and knows his stuff so I'd defer to his analysis.
For this house, the biggest problem may have been the possibility of tripping on the door sill itself, which is not completely flat, but has tracks for the sliding door. Never happened but a possible hazard. But I'd guess much less of a hazard than a step down right at the door. Generally its good practice to have at least a 3' horizontal area between a door and a stair(or stairway) to avoid falls at the door. Although exceptions are made for an exterior door, its still a good idea to have no step, as you are attempting to do.
Elsewhere on this site, Martin Holladay notes the danger of single steps:
https://www.greenbuildingadvisor.com/article/bad-stair-design-contributes-to-falls
In my experience, single steps at doorways are not a hazard like the ones Martin discussed in his article. Single steps in open floors are a hazard because people often don't see them. In an exterior doorway, we expect the surfaces to be uneven, so we are paying more attention.
That said, flush transitions are still nicer to navigate. I would second Malcolm's point about draining the gap between the door sill and the patio/deck. It sounds like you've got good roof cover and that should protect the area as well. The last question I would have is: are you in a hurricane or other high wind/rain region? If so, wind can blow water up against the doors, even if drains are present. 100 mph winds can blow water up several inches against walls and doors. In seashore areas, I always try to have a step of 4"-6" at doors for this reason. if people really want a flush transition, we install the deck surface flush with the door, but maintain a large space under the deck to capture and drain the water.
I think that you guys have helped me make the decision to keep everything flush, ensuring correct detailing of the overhangs, drainage system and separation to help prevent water intrusion. Thank you.