Shop Remodel Question of the week #4 - Insulating Concrete Floor

[Joe A Faulkner]

I have a 20x20 detached, unheated, cinder block garage that has been my shop for the past 16 years. The shop has evolved over this time with little or no planning. I have decided that my next, perhaps most ambitious wood working project to-date, needs to be a shop remodel. Here are my immediate priorities:
1) Heat; therefore insulation
2) Central Dust Collection
I have several questions I’d like to submit to the collective wisdom and experience of the creek. I thought rather than ask them all at once, I would try a question of the week format. I have really appreciated the feedback on questions #1 - tool covers, #2 -framing & insulation , #3 - prefered wall surfaces. Now on to #4 - Insulating Concrete Floor

I'm strongly considering putting down 3/4" decking over sleepers and rigid foam w/visqueen vapor barrier under the sleepers and foam. The motive is comfort for the legs & knees as well as better insulation for the shop. I might even run one or two 220 and 110 circuits to the middle of the floor for the table saw, jointer and planer.

I'd love to hear from those of you who have done something similar. What decking did you go with - OSB or ply? How is it holding up? How did you finish it? Any regrets? Anything you would do differently. Curious to know what thickness of foam you went with, as well as spacing and width of your sleepers.

[Michael Heffernan]

Joe,

I insulated my shop floor as you have described. I have a 22' x 22' garage shop.
1. Laid down 6 mil plastic over the slab (a few dabs of construction adhesive every few feet to hold it in place).
2. Built a 4 sections of sleeper frames (11' x 11' square, like building a deck) out of 2x3s over the plastic. I laid the sleepers out 16" OC. Using a laser level, I shimmed the sleepers level and screwed the four sections together and then to the wall studs.
3. I filled all the sleeper bays with 2-1/2" of rigid foam insulation (the expensive stuff, SUPER TUFF-R 4 x 8 Polyisocyanurate Rigid Foam Insulation -has the highest R-value)
4. I decked it with Advantech, a T&G resin impregnated OSB, available at HD. It's dense and hard, not your typical OSB. Screwed it down and painted it with a few coats of Sherwin Williams waterbased ArmorSeal.

One thing I didn't do and wished I had, is to run electrical boxes under the floor to the middle of it for my table saw. You should definitely do that to a couple of locations. Just make sure you get a floor rated box, with a dust cover. Rolling machinery over it is inevitable, especially in smaller shops where space is at a premium.

I love this floor; it's easy on the feet and legs, and it's extremely warm.
I recommend going this way.

[Joe A Faulkner]

Thanks Michael. How long has your floor been in service? Did you run any wiring in the floor, or are you using drop cords to your table saw?

[Michael Heffernan]

Joe,

I installed the floor 1-1/2 years ago. My business is furniture making, so it has been in daily use since then. It's rock solid and has held up extremely well.
I did not run electrical under the floor. Wish I had.



Thanks Michael. How long has your floor been in service? Did you run any wiring in the floor, or are you using drop cords to your table saw?

[Darren Almeida]

Joe,

Mine floor is similar to Michael's. However, I used PT 2x4's for sleepers and put them down wide side down and used tapcons to secure them to the concrete floor. I put them 16" on center and put 1.5" rigid foam insulation in the bays between the sleepers. I also used 3/4" Advantech T&G plywood for the decking. As Michael said, it is very dense and not normal OSB. I then primed it and painted it with 2 coats of deck paint.

It is much better on the feet and knees than concrete. Plus it made a huge difference with heating the space. I have two electric heaters in the space and with the concrete floor, I cuold run the heaters for hours on end and the temp would only go from 38 to 44. With the insulated wood floor I can raise the space from 38 to 60 in less than 1 hour. I knew it would make a difference, but it is way better than I expected.

I did not run electrical under the floor. I have only been using the floor for a few months, but so far I am very happy with it.

So glad I took the time to do it.

Good luck.

- darren

[Kris Bjarnason]

Does anyone have pictures of what the plywood floor looks like? I am seriously considering this, although I would probably use standard 1-1/8 tongue and groove plywood, possibly unfinished. How did others deal with entry doors, seeing as the new raised floor would be too high to allow the door to open?

[Ken Shoemaker]

I used DryCore from Lowes for the floor. It's 2X2 OSB squares with a plastic backing for insulation. I did a 22X24' shop in about 4 hours, then sealed it with 2 coats of Poly. I used it all winter with a 1500 watt electric hear and the shop stayed comfortable at 65deg. ( legs and feet really appreciate it too). Of course the walls and ceiling are heavily insulated as well.

The walls are 5/8 OSb primed with Kilz and painted white. This is the best thing I ever did. I can mount anything anywhere. I put two steel insulated double doors so I can get any sized item in and out with no problem, but the insulation value remained.

Good luck with your remodel. It is exciting to get a new place.

Ken

[Bob Riefer]

Michael - Really good description of your method. I was wondering though.. with the vapor barrier already in place, why not use loose fill insuation? seems that would have been really inexpensive and given nice R value. But I'm not knowledgeable on the subject, just wondering

[Michael Heffernan]

Bob,

Not sure what you mean by 'loose fill' insulation. Do you mean, blown insulation or fiberglass? Anyway, neither of those give the R-value that the rigid foam does (2.5" equals about R-16.5 value).
Besides that, a loose fill, IMO, would be a mess and difficult to keep in between the sleeper bays as you lay down the deck.
I am extremely happy with my floor. Even in the dead of winter it stays comfortable.



Michael - Really good description of your method. I was wondering though.. with the vapor barrier already in place, why not use loose fill insuation? seems that would have been really inexpensive and given nice R value. But I'm not knowledgeable on the subject, just wondering

[Joe A Faulkner]

Thanks to everyone who has shared of their experience and those who have posted additional questions. Michael, if you were to run wiring in the floor, what would you have done, simply flush mounted outlet's in the floor? (I'm not sure code would allow this in my area) or would you have built a short wall, maybe 12"18" shy of center with a couple of 220 and 110 outlets? I am toying with this idea, maybe 4 220 outlets, all on the same circuit - I'll never run more than one machine at a time, and maybe another 4 110 outlets. I'm planning a router table and SCM station against the walls, along with drill press and band saw, but the table saw, planer and jointer will be in the middle of the shop.

[Michael Heffernan]

Joe,

You can run outlets in the floor. At least here in the Philadelphia area it's up to code. But you need to use an outlet box rated for floor installation. I recommend ones with a brass or stainless cover and an outlet cap or pop-up access door. You don't want sawdust getting into the unused outlets.

Here is a link to the kinds of boxes I'm talking about:
http://www.arnev.com/Round-Floor-boxes-for-wood-and-concrete-floors-in-Brass-Aluminum-Nickel-Silver-Stainless..html

The reason I didn't install them is that I only used 2x3 sleepers (2-1/2" depth) and I couldn't find any shallow enough to fit under the deck. If you are using 2x4s, 3-1/2" is deep enough to recess the box. Most are 3-1/8" deep.
They're not cheap. But you want to get a heavy duty type that won't crush in the event that you roll a piece of machinery or work cart over them.
I wish I had taken some photos during the construction process. It was too cold and dark at the time (no heat or good lighting at the time of the build-out). Now it's well lit, have a direct vent counterflow furnace and a rugged, comfortable floor.
Definitely post some pics during your build.



Thanks to everyone who has shared of their experience and those who have posted additional questions. Michael, if you were to run wiring in the floor, what would you have done, simply flush mounted outlet's in the floor? (I'm not sure code would allow this in my area) or would you have built a short wall, maybe 12"18" shy of center with a couple of 220 and 110 outlets? I am toying with this idea, maybe 4 220 outlets, all on the same circuit - I'll never run more than one machine at a time, and maybe another 4 110 outlets. I'm planning a router table and SCM station against the walls, along with drill press and band saw, but the table saw, planer and jointer will be in the middle of the shop.

[Bob Riefer]

Btw, you're totally right about better R value from the Rigid foam as opposed to the loose fill (which apparently is meant for attic applications where you can pile it high to get the insulation level you need). Good call and thanks for answering my question

[Tim Cleary]

All sorts of great ideas here-

Just one quick suggestion from my own experience: there are a couple dimpled HDPE products (delta-FL is what I used) which are a good alternative to DriCore. Not that Dricore is a bad solution but I preferred just rolling out and taping the seams of the Delta-FL and then laying over larger OSB sheets cut as needed vs. the smaller DriCore tiles that would have more readily transmitted the non-flatness of the slab to the floor, if that makes sense.

It was an easy installation. To create an even softer/warmer floor, I suspect you could put extruded polystyrene butted on top of the Delta-FL and then cover that with OSB. As otherwise, a few long tapcons on each sheet at least are a good idea. If you want more detail pm me - just wanted to highlight one alternative.

[Joe A Faulkner]

Does anyone have pictures of what the plywood floor looks like? I am seriously considering this, although I would probably use standard 1-1/8 tongue and groove plywood, possibly unfinished. How did others deal with entry doors, seeing as the new raised floor would be too high to allow the door to open?

In my case, the building originally had two 8x7 garage doors without a service door. I removed one of the garage doors, framed in a wall with two small windows and door. I left the bottom plate in place when I hung the service door, so I have about 2 1/4 in. clearance for the service door. For the garage door, it plan to take the new raised floor flush to the interior side of the garage door. Since this building is being dedicated to wood working, I will only use the overhead door for the occasional moving in of sheet goods, lumber or moving out projects. In my area there is one regionally owned lumber yard. The staff there will/can order a custom size steel door. So it would be possible to get a shorter door if you needed one.

[Joe A Faulkner]

Joe,

You can run outlets in the floor. At least here in the Philadelphia area it's up to code. But you need to use an outlet box rated for floor installation. I recommend ones with a brass or stainless cover and an outlet cap or pop-up access door. You don't want sawdust getting into the unused outlets.

Here is a link to the kinds of boxes I'm talking about:
http://www.arnev.com/Round-Floor-boxes-for-wood-and-concrete-floors-in-Brass-Aluminum-Nickel-Silver-Stainless..html

The reason I didn't install them is that I only used 2x3 sleepers (2-1/2" depth) and I couldn't find any shallow enough to fit under the deck. If you are using 2x4s, 3-1/2" is deep enough to recess the box. Most are 3-1/8" deep.
They're not cheap. But you want to get a heavy duty type that won't crush in the event that you roll a piece of machinery or work cart over them.
I wish I had taken some photos during the construction process. It was too cold and dark at the time (no heat or good lighting at the time of the build-out). Now it's well lit, have a direct vent counterflow furnace and a rugged, comfortable floor.
Definitely post some pics during your build.

Michael, thanks for passing this on. I will be limited to 1.5 inch sleepers. Though your suggestion has me considering framing in a "chase" in the floor to simply run extensions under, or maybe I'll just scrap this idea. More decisions ... fortunately I like having options to consider.

[Joe Cowan]

I am starting my floor project next week. I posted the same question a couple of months ago and am tentatively planning on doing it this way. Vapor barrier, 2x4 dry PT 2x4's on 16" centers, but the 2x4's will be cut no longer than 3' and positioned so that the butt joints are not opposite one another and allowed to "float" (no tapcons"). The guy that recommended this said he was advised by professional gym flooring installers to do it this way. I will cut some 1/2" ply up into 3 1/2" strips and place that on top of the 2x4's to make the depth 2" and then place the rigid foam in between the 2X4's. Then the 3/4" subfloor and last a utility grade hickory 3/4" floor from Lumber Liquidators. I have the wires coiled up against my shop wall to run under the floor for my Table saw (220 volt) and also for a 110 outlet. Unless I change my mind (I may just put 1" foam down and not build up the 2x4's to 2" think) this is it.

[Gerry Grzadzinski]

Why not just use 1-1/2" foam with the 2x4's?

[Joe Cowan]

Why not just use 1-1/2" foam with the 2x4's?

I have not been able to find it locally. That is what I would probably do if available. Buying 1/2" and 1" to make the 1 1/2 piece is more expensive than the 2" one piece unit is. But I could do that and save having to cut and install the 1/2" ply on top of the sleepers.

[Jim Terrill]

I have not been able to find it locally. That is what I would probably do if available. Buying 1/2" and 1" to make the 1 1/2 piece is more expensive than the 2" one piece unit is. But I could do that and save having to cut and install the 1/2" ply on top of the sleepers.

Where are you looking? They don't sell it at the BORG here, but if I go to a quality lumber yard, I can get 1/2" to 2" in 1/2" increments as plain foam or foil faced (which I recommend). Granted this is the north and we are all about insulation, but you should be able to find it.

[Joe Cowan]

I was going to use the blue foam type insulation. Lowes carries the foil backed insulation in the 2" material, that is the most expensive. With the plastic down, I did not think I needed the foil backed insulation.

[Jim Terrill]

I was going to use the blue foam type insulation. Lowes carries the foil backed insulation in the 2" material, that is the most expensive. With the plastic down, I did not think I needed the foil backed insulation.

It adds another few Rs to the insulation. Up to you whether or not it is worth the extra cost, the key when using the rigid foam though is to use the foil tape to prevent air movement.

[Joe A Faulkner]

Joe, please post some pictures as you make progress on your floor system. It sounds like you are forming up a torsion box. I am interested in seeing your frame before you apply the subfloor. I am also interested to hear about your experience with the utility hickory floor. At 89 cents a sq. ft. I'm tempted.

[Rob Fisher]

Joe, please post some pictures as you make progress on your floor system. It sounds like you are forming up a torsion box. I am interested in seeing your frame before you apply the subfloor. I am also interested to hear about your experience with the utility hickory floor. At 89 cents a sq. ft. I'm tempted.

Joe,

I if I understand Joe C. correctly he is just doing a floating floor, no torsion box. The 2x sleepers are dry laid (no tapcons, no glue), and staggered. Then the subfloor is attached overtop as normal. The only thing different is that the line of attachment points will stagger. Meaning when you look at the installed subfloor, the screws (or nails) that attach it to the 2x sleepers will not be in a straight line. They will stagger with the sleepers below. Dry laying the sleepers allows them to expand and contract due to thermal or moisture change (hopefully just thermal), therefore not affecting the subfloor or finished floor above. Hope this makes sense.

Also if there is a vapor barrier installed between the concrete and the sleepers then the foil facing on the insulation is useless.

Rob

[James Stokes]

Here is what I did in my house, it could be done in the shop just as easy.I installed 3/4 t&g blue foam on my floor then installed a laminate floor over it.

[Joe Cowan]

Joe, please post some pictures as you make progress on your floor system. It sounds like you are forming up a torsion box. I am interested in seeing your frame before you apply the subfloor. I am also interested to hear about your experience with the utility hickory floor. At 89 cents a sq. ft. I'm tempted.

I am not making a frame. I will be laying down the 3' pieces of 2x4's in a line, then laying down a row of insulation, followed by another row of 2x4's and so on. The weight of the 3/4 ply and the hickory will be what holds the floor down. Also, I am the landlord for a Lumber Liquidators store. The manager told me the hickory was good stuff. I will ask him again before I order but am leaning toward the hickory.

[Joe A Faulkner]

Now I understand; I'm curious about the decision to cut the 2x4's into 3' pieces; you mentioned a gym floor installer recommended this? What was the explanation? Does cutting these into shorter lengths serve to reduce warping?