insulate a slab on the interior side
DonSWW
| Posted in Energy, Heating & Insulation on
A customer has a shed he wants converted to an office. The shed is very well built on a slab that is at least 6″ thick. He will heat this Boston area office with eletric heat so I’m recommending lots of insulation, R54 on roof and R36 in walls.
I’m wondering if we should install 1″ poly iso on slab topped with 3/4″ underlayment. Could I nail the underlayment thru the polyiso and a layer of 6 mil plastic into the concrete and then install carpet on top?
Thanks,
D
Replies
Probably. Not sure about how to fasten the underlayment to/through the insulation. Someone else can provide details, I bet.
Basic question ... can you tolerate an increased floor elevation of 1 3/4"? That's often the big factor in situations like yours.
Probably be easy
to drill holes and drive Tapcons in carefully, trying to avoid puckering the plywood.
Well, not *easy*, but certainly do-able.
Do you think the iso board would hold up to foot traffic above even with 3/4" ply on top? I would consider SM foam.
I would think so, easily. Put flooring over the subfloor and I'd think there'd be no question at all. We put concrete over that kind of stuff all the time. Iso and EPS have similar densities, I think.
>>>Iso and EPS have similar
>>>Iso and EPS have similar densities, I think.
Ok, thanks for that. No experience with it yet, but might come in handy in the future.
Both are routinely used for commercial roofing applications and placed under the roofing itself w/ nothing in between. People walk on those all the time w/ no issues ... although it is recommended to use walking pads. But I'm on that stuff almost daily and it's not an issue.
My internet connection is slower than dialup at the moment, so I can't research this, but my memory is that many people that have put insulation and a floor over existing concrete just use two pieces of plywood overlapped to form a continuous underlayment that just floats on the insulation board. The crush strength in that situation is a lot greater than you probably think with the plywood distributing the load. Several years ago one of the past editors of Fine Homebuilding did an article on converting a basement with insulation on the concrete. There are a number of articles in the Fine Homebuilding archives on doing such a project. I think you could also use several sheets of eps or polyiso and cut channels in the top sheet to place tubing for hydronic heat.