Shop flooring question -- Advantech osb over concrete without sleepers

[Jim Becker]

With the gaps caused by leveling the floor with the sleepers, you'd wouldn't have the support of the foam, so 16" OC or closer might be warranted if you do 3/4" material. If you get the heftier 1.25"/1.5" thickness Advantec or LP equivalent, you'd have more support native in the material.

[Zachary Hoyt]

I have 2" of foam and no sleepers, with a 1x8 rough cut board floor underneath and 3/4" Advantech-like product on top. The heaviest thing I roll around regularly is my 1940s Unisaw on 4 casters, and it rolls very easily. I don't have to deal with the moisture questions that come from being on a slab, though.

[Kevin Jenness]

I used 3/4" Advantech over 3/4"x2 1/2" strapping 16" o.c. which has held up fine. If you use thicker material you better eat your Wheaties.

[Peter Franklin]

Hi all,
Thanks for the advice received to date.
I'm leaning towards going with 3/4" advantech over 2" foamular 250 with no sleepers.
A builder has suggested using glue that's used with subfloors for adhering both advantech and the foam board to concrete with nails or anchors "here and there".
Sounds sketchy but given I have no experience with this and tend to err on the side of overdoing things when I don't know anything, thought I'd check in with people with experience here....

[Jim Becker]

Personally, I'd float it. Put down the foam, tape it and then glue up the Advantech as a floating floor. That accommodates expansion/contraction seasonally very nicely and if you're filling up the space, it's not going to move. There's just no reason to glue or nail it down. And not doing so makes it a lot easier to reverse in the future without damaging the concrete should that be necessary by you or a future owner.

[Peter Franklin]

Personally, I'd float it. Put down the foam, tape it and then glue up the Advantech as a floating floor. That accommodates expansion/contraction seasonally very nicely and if you're filling up the space, it's not going to move. There's just no reason to glue or nail it down. And not doing so makes it a lot easier to reverse in the future without damaging the concrete should that be necessary by you or a future owner.

I guess then not such a sketchy idea.... Do you think there would be any issues with moving heavy machines around on that kind of floating floor?

[Charlie Velasquez]

I guess then not such a sketchy idea.... Do you think there would be any issues with moving heavy machines around on that kind of floating floor?

Your average hobbyist’s tools; no.
I have advantech with a unisaw with 2 extension wings, extension table, storage, and a 7’ biesemeier fence on casters (maybe 550#?) and I had a 500# Dewalt GA at about 545#. Never an issue. If you are talking a Bridgeport mill, or other old iron, I would consider 1” or 1.5” advantech

[Jim Becker]

I guess then not such a sketchy idea.... Do you think there would be any issues with moving heavy machines around on that kind of floating floor?

No, I do not expect you will have any issues unless you have "yuge" industrial equipment. That Advantech is pretty tough stuff and when glued together as a floating floor, it's going to be pretty stiff. The dense insulation foam is able to hold a lot of weight, too. Consider my whole 4" thick concrete floor is on top of 2" foam that's just taped together...

[Walter Mooney]

Like Mr. Becker, I’d float the whole thing. And if you go up to the 1-1/8” Advantech, you’ll get much greater rigidity in the floor from panel to panel. When i was buying mine, the price difference was rather small, so went ‘big’! The Advantech decking has a 180-day weather warranty, which, to my way of thinking, means it can stand a whole lot of water for half a year. The amount of ‘water’ / moisture you’d get on the bottom of your panels through your slab has to be so minimal that the product would easily withstand it IMO. And I agree with taping the foam joints. Why not glue the Advantech T&G long edges? And stagger the field to a 50/50 ‘brick’ pattern, or a close to 50/50 as you can get. Maybe even a little glue on the short sides of the panels.

Best of Luck to you!

[Peter Franklin]

Like Mr. Becker, I’d float the whole thing. And if you go up to the 1-1/8” Advantech, you’ll get much greater rigidity in the floor from panel to panel. When i was buying mine, the price difference was rather small, so went ‘big’! The Advantech decking has a 180-day weather warranty, which, to my way of thinking, means it can stand a whole lot of water for half a year. The amount of ‘water’ / moisture you’d get on the bottom of your panels through your slab has to be so minimal that the product would easily withstand it IMO. And I agree with taping the foam joints. Why not glue the Advantech T&G long edges? And stagger the field to a 50/50 ‘brick’ pattern, or a close to 50/50 as you can get. Maybe even a little glue on the short sides of the panels.

Best of Luck to you!

Thanks. This is the direction I'm now headed. With poly vapor barrier beneath the foamboard.