Dirt floor basement – XPS or infill with concrete?
Hi Guys,
Looking for some feedback on a plan for an old dirt floor basement. So here’s what we have.
Old circa 1902 home with a low ceiling (5’8+/-.) The floor has some concrete slab remaining, with other areas being primarily dirt floor.
We are looking to lay a 1″ xps (tape/sealed) over the entire floor, the cover it with one or two layers of 1/2″ ply…
My question is do I have to dig up the existing dirt floor are & inflill it with concrete? Or can I simply lay the xps over the whole thing?
Any thoughts/comments?
Your feedback is greatly appreciated.
~k
Replies
low ceiling (5'8+/-.)
Why do anything? What are you going to use the space for, only storage?
If other than storage, dig out enough dirt so the headroom is the tallest meember of your family plus 7 inches
lay down 4 mil poly on the dirt (if it has been like it is for >100 years, wye bother with a gravel subbase) and put a 2" layer of concrete over it.
Forget the xps and 1/2 ply unless you plan on pressure treated ply, the xps buys you nothing.
@junkhound.
Half of it will be a utility room; so agreed. But I wanted to use the other half as a finished hallway to the 8' tall rec room behind it...basically it will turn into a low ceiling hallway for my kids to get to their rec room.
As for the xps thought it would work as a vapor barrier? No? Am I wrong with this?
poly better barrier, and probably lower cost, and easier to work with.
Depends if you've ever had water problems
If you live in the desert probably no point in putting in a drainage layer. Where are you located?
If you plan to put some kind of flooring down on top of your dirt floor then you have other considerations. If you don't insulate the floor it will tend to be colder than the house assuming you heat the basement and condensation will form on the concrete/dirt surface... if you put carpet on that enjoy mold.
The other thing you could consider is using a geofabric and a smaller layer of gravel. The fabric prevents the drain rock from merging with the dirt and allows a drainage layer without using 4" of rock. Even a layer of rock will provide some insulation from the ground temperature. You could also use the flooring that comes in one foot segments that sits off the floor and provides for an air space (drycore?, can't remember the name off hand).
Poly is cheap, independant of if you go with xps (expensive) I'd definitly do a layer of poly over it and tape the seams. Cheap prevention for radon (again depends on the ground type) but who wants to risk a 10 fold increase in cancer for smokers and at least some increase for non-smokers.
If you are going from 5'8" to 8' rec room, how does the height difference work? I assume the rec room must be lower than the hallway that would join? I just envision any water coming into the hallway and draining into the rec room.