Installing shop flooring on sloped concrete
Hi folks, I saw this article with a method for installing a wood floor over a concrete basement floor:
I’m considering it for my basement shop, but the concrete floor slopes substantially (3″ over 12′) and is uneven. I don’t want to use leveling concrete mixture if I can avoid it because of the mess and the fact I have no experience with it. Hence my interest in this method.
My thought would be to adapt this method by scribing the contour of the floor then cutting the 2x4s with tapers on the bandsaw that effectively cancel out the slope, then fasten them into the concrete per the method. Then put the plywood underlayment on top.
Do you see any issues with this method? Searching online I can’t find any examples of people doing this (or my twist on the idea),which is making my spidey sense tingle a bit, as that’s not usually a good sign!
Thanks for any advice and suggestions.
Replies
I have done that though with less slope than you have. I've also used leveling compound which is easier than you might think. It seeks its own level ..its liquid with only some minor floating on your end on the top. But cutting tapers would work but the slope is 3" , kind of too much in my opinion. Your left with only 1/2" on the high end. You could do both, leveling compound and 2× 4s- but set on the flat ,no tapers but shims to achieve level. Depending on your plywood thickness and I would use t&g plywood--- set your runners at 16" to no more than 24" centers. Shim maybe every foot and set anchors every 2 feet . I like the blue "tapcons" cause they are easier than expansion bolts.
Use full 2x4's and frame it just like you were building a deck but with lots of 2x4 legs along the length and width.
It looks like a good idea and should work pretty well. I would snap a level line along the wall on the down slope side 3 inches up from the floor and use a construction string to determine the cut on your 2x4's. Measure distance to the wall and to the floor at various points. You will probably need to do some scribing here and there.
Not sure how complicated you want to get, but given the thin end only has 1/2" left, have your thought about using 2x6 or 2x8? That also opens up the possibility of running your dust collection and any new wiring under the floor. Kind of a 2 birds with one stone situation.
TBH with that sort of slope, I'd pay the $$ to have someone cut away some of the excess concrete then use levelling compound. Messy yes, but proper. You could also run pipe for wires, add reinforcement, damp-proofing and insulation. The possibility of gaining a bit of head room is also there if you go all out and have the basement fully converted.
If you can afford to lose 4" in height in a basement then your plan will work well. Also it's a great excuse to buy a track saw.
Thanks for all the replies, folks. Super helpful.
Do you think I might develop a mold issue under the plywood with this approach?
In general the basement has a dehumidifier maintaining 50 humidity 24/7 during the humid months, but if it is not on then it gets musty. Not sure if that would dehumidify under the plywood where the concrete is, or whether mold would form?
I think it would be a good idea to roll on a coat of garage paint to seal the concrete before starting. And use treated 2x4's rated for ground contact. I would leave the framing open for awhile to let the moisture from the wood dry out before laying plywood.
I built a shop in an old barn hay loft with slope in both directions.I built a 2x4 frame,12in on centers,across the whole floor.I found the high point,secured it ,and with a 6 ft level went arround the frame leveling it with premade wedges or scrap 2x4.I then went back and either toe nailed the shims and added support where the shims were too far apart.In my case i insulated and plyood over the entire frame