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Opinions on This Basement Floor Assembly

rsackiw | Posted in Green Building Techniques on

Hi All,
I have an old cabin with an unfinished basement that I would like to finish. It is basically a 3 season cabin up north, Zone 7a with no heat except a pellet stove and fireplace. The is no insulation under the floor, and the basement is normally dry, but it is on the bottom of a hill, so in the spring with the snow run off, there is a bit of water that comes in between the floor and the walls, and runs toward the sump pit. Lots of clay in the soil so I think it is just a matter of it not being able to move under the floor to the sump pit fast enough, and that is why it leaks in.
I was thinking of putting down delta fl as a vapour barrier and to give the water a channel to travel across the floor. Then 1 1/2″ rigid foam on top. T&G OSB on top of that and finally vinyl plank. Now my question is, Do I need to use 2×4 sleepers and place foam sheets between them? or can I use continuous foam across the floor with just the OSB? I have also seen some people recommend 1×3 strapping across the top of the foam with the osb on that. Basically I am worried that the water heater and pellet stove would compress the foam too much. Other than that the area will just be a games room, with chairs and couches. So nothing else will be heavy enough to cause concern. Or any better ideas? Thanks in advance.

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  1. plumb_bob | | #1

    What about interior foundation perimeter drainage? The water could then be directed from these new drain pipes to your existing sump.

  2. Expert Member
    Dana Dorsett | | #2

    In zone 7A insulating the basement floor of an intermittently heated basement increases the odds of plumbing freeze up.

    Any dimple-mat underlayment under the foam would allow the water to find it's level. With any reasonable subfloor above the pressure on the foam at any dimple would not exceed it's elastic limits.

    There is no point to using sleepers under the foam & subfloor. With double-layer of half-inch OSB glued & nailed/screwed together with staggered seams it can even be floated, with no mechanical fasteners to the slab. With a single layer of OSB it needs be secured to the slab with masonry screws or it will develop "potato chipping" curl as the humidity content of the OSB shifts with the seasons (or tide).

  3. rsackiw | | #3

    Basically cost, this is a remote cabin. Hard to get anyone in to do work in remote places like this. Which is why I am trying to do the finishing myself. And a perimeter drain is more than I would like to take on.

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