220v Floor outlet in workshop?

[Sam Dotson]

I am turning a 2-car garage in my new home (in Texas) into a workshop. I am finalizing my electrical plan for a sub panel and several 110 and 220 circuits, and I'm wondering if there is a "code correct" way to install a 220 circuit flush mount in the floor. Sine I don’t have a basement, and my shop floor is cement, I am adding a wood floor over the slab by laying pressure treated 2x4's on the cement (attached with glue and nails), then 6-mil plastic sheeting, and then 3/4" ply wood over that. This should give 2 1/2 inches for conduit and an electrical box. Assuming I have the room under the floor, what does the code say about this?

Sam

[Chris Damm]

How are you going to keep dust out of the outlet?

[Sam Dotson]

I'm assuming the plug that is plugged into it will do that whan something is plugged in. When nothing is plugged in, I'm assuming I can find a recepticle with a spring loaded or screw-in cover.

Notice all the assumptions? That's why I am posting here. :)

Sam

[Todd Burch]

IIRC, fire code disallows a wood floor in a garage built for parking cars.

[Todd Burch]

On another note - a 2 car garage is not that big. Why not just a longer power cord? Will the machine be in a fixed place? If so, I would stub out a short receptacle to be positioned up inside cabinetry or other enclosure that is part of the fixed machine.

Todd

[Joe A Faulkner]

Search for recessed brass outlet boxes or recessed outlet boxes.

Here's one example: http://www.acehardwareoutlet.com/productdetails.aspx?sku=998003692

You will note these are expensive, but they are designed to be recessed in a floor and provide for some "crush resistence". Seems like this shoudl work for a 20 amp outlet.

I was considering these a while back for my shop remodel. I've since backed off on the idea of putting in the wooden floor for two reasons: 1: materials alone would run me about $800 and I have to weigh that against or lets see, a tablesaw upgrade, a bandsaw, a lathe, a workbench and decided I'd just buy better quality shoes for the shop. 2: While I don't have any immediate plans to move, it isn't out of the question and I'm not sure the wooden floor would be as valuable to a buyer as it is to me.

[Sam Dotson]

IIRC, fire code disallows a wood floor in a garage built for parking cars.

Once the wood floor is installed, it would be intended for parking cars any longer. Surely just because it was built for parking cars, this doesn’t mean I can’t put down a wood floor and use it for something else.

Sam

[Sam Dotson]

Thanks Joe, I will check out that outlet box.

The wood floor is more to protect dropped hand tools (like planes and chisels) and to allow floor mounted power for tools in the middle of the floor than to protect my feet. I have another three car garage for parking, so I’m hoping the wood floor would be an issue for a potential future buyer. If it turns out to be, I can always remove the floor I guess :eek:

Thanks


Sam

[Luther Oswalt]

Once the wood floor is installed, it would be intended for parking cars any longer. Surely just because it was built for parking cars, this doesn’t mean I can’t put down a wood floor and use it for something else.

Sam

I would check with your local codes office because it is not just wether it is in the fire code the codes folk and tax folk may come calling on you. That's a sure thing if you are building and have a permit.

[Richard Jones]

IIRC, fire code disallows a wood floor in a garage built for parking cars.

Code here in VA doesn't allow a wood floor in a garage, but this will no longer be a garage. Wouldn't be a problem in my jurisdiction, have done quite a few like this.

Also, floor boxes must be rated, listed and labeled for the intended use.

Rich

[Thom Porterfield]

The problem I have with floor boxes is that they're not always in the right place...and then you have extension cords again. To solve that problem in my shop I put in trenches instead. Granted, my floor is a concrete slab, but my solution (following) shouldn't be that difficult to implement in a wood floor.

What I did was install 4" x 4" x 12' trench drains, but I replaced the slotted covers with sheets of plywood. I can make those covers any length I want (up to 8' long) and put a power cord-sized hole at whatever location is convenient for my tools. My shop is 18 feet square, approximately, and I have two such trenches parallel to one another, 4' apart in the center of the room. I installed 2" conduit pull chases under the slab to the wall where the service panel is located and each terminates in a junction box. I can run non-metallic cable to either trench and locate a junction box and receptacle for either 110 or 220 power. Then the pigtail from the tool need only drop into the trench through the cover. As it happens, my table saw, jointer and router table sit directly over one or the other trench and there are no cords laying about on the floor.

I suppose, if I wanted to, I could install a floor outlet, such as described above, in the plywood, but I haven't yet found the need.

[Dan Hintz]

I would not want to spill any liquids near a surface-mount outlet...

[Joe Angrisani]

Sam... Where will the dust collection be coming from? I'm in the "no floor outlet in a dusty environment" camp, so I'd suggest bringing the power down from the ceiling along with the dust collection ductwork. If the ductwork will just come across the floor, I'd run the saw's power cord through one of those "no trip" strips in the same area as the dust ductwork (if you have to step over a duct, you'll never notice a power cord coming through in the same place).

[Rob Russell]

Sam,

Because you're installing a raised floor, I would run conduit under the floor and feed a surface mounted subpanel. From that subpanel, you can run whatever you want for circuits in surface-mounted conduit. That's all easily removeable when you sell the house and gives you the flexibility to add circuits as you need.

Rob

[Sam Dotson]

Sam... Where will the dust collection be coming from? I'm in the "no floor outlet in a dusty environment" camp, so I'd suggest bringing the power down from the ceiling along with the dust collection ductwork. If the ductwork will just come across the floor, I'd run the saw's power cord through one of those "no trip" strips in the same area as the dust ductwork (if you have to step over a duct, you'll never notice a power cord coming through in the same place).

That's a good point Joe, since there should be a dust collection run to every "island" in the workshop, I will consider ceiling mounted outlets with twist lock cords dropping down beside the dust collection run.

Thanks!

[Rob Russell]

That's a good point Joe, since there should be a dust collection run to every "island" in the workshop, I will consider ceiling mounted outlets with twist lock cords dropping down beside the dust collection run.


Remember that hanging cords need to have strain-relief connectors.

[Michael Heffernan]

Sam,
I did the same thing you want to do in my two car garage. I laid pressure treated sleepers, 12" O.C. on my slab, covered with 3/4" plywood. As I am in a cold clime (Philadelphia), I fitted 1.5" rigid foam between the sleepers to keep the floor warm in the winter. You write that you are going to put the 6 mil plastic between the sleepers and the ply deck. From my research, and what I did, was put the plastic on the slab, then laid the sleepers. You want the vapor barrier between the concrete and the wood. If your slab was poured with a vapor barrier below it, then you shouldn't need the plastic above and shouldn't do it. You will be creating a sealed envelope around the concrete with no way for the moisture to evaporate. But if no barrier below the slab, put the plastic on top, then the wood.
As for the floor outlet, I placed a 220v 'floor box' just behind my table saw. I planned out my shop and knew that I wouldn't be moving it from that location. I ran the NM cable from the panel and stapled to the sleepers to the sealed box. Since there is only one outlet, and the saw is plugged in all the time, I'm not concerned with dust getting in the box. If I do remove the plug (as I do sometimes roll the cabinet saw out of the way), I put the brass screw cap on the box plate. I'm glad that I don't have a cord running along the floor to a wall outlet waiting for me to trip over it or crush it with a tool or lumber.


I am turning a 2-car garage in my new home (in Texas) into a workshop. I am finalizing my electrical plan for a sub panel and several 110 and 220 circuits, and I'm wondering if there is a "code correct" way to install a 220 circuit flush mount in the floor. Sine I don’t have a basement, and my shop floor is cement, I am adding a wood floor over the slab by laying pressure treated 2x4's on the cement (attached with glue and nails), then 6-mil plastic sheeting, and then 3/4" ply wood over that. This should give 2 1/2 inches for conduit and an electrical box. Assuming I have the room under the floor, what does the code say about this?

Sam

[Sam Dotson]

Remember that hanging cords need to have strain-relief connectors.

does a twist lock plug count as strain-relief?

Sam

[Sam Dotson]

Michael,

With the plastic on the slab, how did you attach the sleepers to the slab? Did you use tapcon screws or powder actuated nails?

Sam

[Larry Browning]

I have a crawl space with t&g plywood decking and I installed several floor mounted plugs. I wanted to avoid saw dust getting into a flush mounted plug, so I mounted a metal plug box to a small 2x4 block, then drilled a 3/4 inch hole thru the block. I then drilled a hole in the floor, ran the wire up into the box and screwed the block to the floor. That way the plug is vertical and I only have a small 3/4 hole in the floor. If I want to move the plug I can fill the floor hole with a 3/4 dowel and drill a new one where needed. I always place these under or very close to the tool so that I won't trip on it. Seems like you could do the same in your raised floor. I'm not sure if that would violate some code, but it works for me.

[Don Jarvie]

I did the same thing as Mike but the floor floats. I screwed the sleepers to the sill plate after I got the sleepers level. I didn't want to drill into the slab for fear I'll start getting condensation. I did the sleepers with insulation then plastic over that and then screwed T&G OSB over that. My back is liking the wood floor. The OSB looks kind of ugly and will flake but when you need to push a plane you won't slip and slide.

I ran a few lines under the floor to the center of the roon, 20X20. I have my TS and an assembly table as one so the lines go into a junction box attached to the table and then split out from there. All I have is the line coming out of a hole in the floor. The lines are under my extension table so they aren't a tripping hazard. I wouldn't put a box directly in the floor due to dust getting in it.

[Todd Burch]

I spilled a gallon of lacquer thinner on the floor last week. I wonder what that would have done with a floor plug. :eek:

[Thomas Delpizzo]

I have the same sized shop. I installed a 220 line on 1 wall using conduit for my compressor and made a 220 extension chord. NY code allows me to mount the line on the wall as long as I use conduit. The extension chord can even be used overhead. As I'm only running the chord about 10 feet, it doesn't pose a problem. I will be installing another plug, eventually, on an opposite wall for my eventual dust collector. As others have stated, the floor outlet, if code permits, is really more for stationary tools and workbenches. The best ones are those heavy duty brass ones that you can't get at a big box store, but even those have to be cleaned from time-to-time. Good luck with your endeavor.

[Michael Heffernan]

Sam.

Basically. I built it as a floating floor. My garage/shop is 24' x 22', so I built it in half, each approx. 22' x 12'. The only sleepers I fastened with Tapcons were the outside perimeter, every 2' just to keep it from moving around when I put the framing together. I snapped a line down the center of the space, laid PT 2x4s (one 10', one 12') on center, measured out to the walls to get parallel lines and tacked down the perimeter sleepers over the plastic. I installed the sleepers, 12" O.C. (I felt 16" was too wide as I roll some of my heavy machinery around from time to time). I started tying the sleepers and center/rim plates with Simpson connectors, but found it easier and cheaper to just toe-screw them together. As my slab was sloped considerably toward the center drain in the floor (almost three inches from outer walls to center drain!), I used PT ply (1/4, 1/2, 3/4) and PT 2x6s andv5/4 x 6 decking as shims, fine tuning it with some construction shims to make it level front to back and side to side. I screwed those to the sleepers to keep them from shifting, using PT rated deck screws. I strung some level lines and use my laser level to get it nearly close to level.
With the grid in place, I filled the voids with 1.5" rigid foam, taped the seams and over the sleepers with foil tape, and screwed the 3/4" deck down (AC ply) with 2" deck screws, staggering the boards. Three coats of satin latex porch and floor paint and it was ready to use in a day and a half.
Works well for me, going on two years (did the same at my old garage too) and no issues. Thinking of putting on a touch up coat of paint on the floor, but not till spring.
I made it a floating floor, as I saw no need to fasten it down everywhere and compromise the slab. The screwed down decking and some tapcons around the perimeter is all that is needed. It'll be easy to take up if ever we sell the house (no construction adhesive or nails, just screws). I did use a few dabs of foam board construction adhesive to hold the 6 mil plastic in place on the slab. Easy enough to scrape up if the wood floor does need to come up.
Good luck with your floor.


Michael,

With the plastic on the slab, how did you attach the sleepers to the slab? Did you use tapcon screws or powder actuated nails?

Sam

[Peter J Lee]

First, I would find out what your building inspectors consider a garage. Just saying you won't use it as one any more probably doesn't mean much. What I would expect them to say is what happens when the next owner pulls his SUV onto that wood floor.

But putting that issue aside, there are lots of floor box choices. Besides major manufacturers like Hubbell, there are are companies like this www.lewelectric.com (http://www.lewelectric.com). Most of them have PVC boxes which seems like a good idea, but I can't recall one that is shallow.

[Roy Turbett]

I planned my stationary tool layout before I built my shop and ran electric conduit and 4" PVC for dust collection before I poured the concrete. I used the flush mount brass boxes that have threaded covers for each outlet and I keep a cover on the outlets that aren't in use. I live in Michigan and park my truck in the shop and the building and electrical inspector didn't have a problem with anything I did. I highly recommend you have the work inspected because your home owners insurance company may deny a claim if you don't. I sloped the floor on the half of the shop where I park my truck and put in a drain and dry well. The other half of the shop is where the stationary tools and floor electrical outlets are and in 15 years I've never had a problem with water or dust getting in the outlets. I sweep up the big stuff and use an electric leaf blower to finish up. The one thing I would have done different is use larger conduit with large sweep elbows. I didn't use the long 4" PVC sweep elbows where the dust port comes out of the concrete. This prevents narrow cutoffs from the table saw from getting stuck in a inaccessible spot and on the rare occasion they create a blockage they can be easily cleaned out.

[Justin Jump]

to comment on the code issue with the flooring, if you're not parking in there any more, then the Inspector might be OK if you take out the garage door and frame in a sliding door or french door......

Agree with the comment - what about the next owner.......

[Don Jarvie]

When you sell the house just rip out the floor unless the new owner wants it. I'm leery about putting a flush mount outlet in the floor with or without a cover. Try to get it off the ground a few inches or so.

[Joe Angrisani]

does a twist lock plug count as strain-relief?

Sam

The wire itself needs to have strain relief. I bet you've seen it. It's a wire mesh sleeve that goes around the outer insulation of the dropped cord. Carries the weight of the drop so the electrical connections (in the overhead box and in the twist-lock connectors) do not.

[Peter J Lee]

When you sell the house just rip out the floor unless the new owner wants it. I'm leery about putting a flush mount outlet in the floor with or without a cover. Try to get it off the ground a few inches or so.

Its not so much that you can take it out as it is how the building code is used. Floor outlets aren't unusual.