Help with Shop Design & Wiring: 13'x25' from the ground up

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Forum topic by Dan Lyke posted 03-09-2011 11:55 PM 1670 views 0 times favorited 14 replies Add to Favorites Watch
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Dan Lyke

1520 posts in 4153 days

03-09-2011 11:55 PM

Topic tags/keywords: workshop wiring electrical question

I’m in Northern California, in a small town on the south end of Sonoma’s Wine Country. Land and housing is expensive relative to everything else. We live in a 768 square foot house on a just over 4,000 square foot lot, and we never want to move again.

I’ve been woodworking in the one car 1947 attached garage. It’s tiny, I end up finishing or doing major assembly outside, and no matter how hard we try, the dust gets in the house (and the space is shared with the washer and dryer…). So we’ve decided that we can spare 14’x26’ from the back yard, which means I get an internal size of roughly 13’x25’.

My tools right now are all portable. The Festool saw with table and jigs instead of a table saw, the DeWalt 735 planer on a roll-around table, my router “table” is a platform that cantilevers off my Festool table. I’ll almost certainly end up getting a bandsaw shortly, and my wife is pushing for the Saw Stop contractor’s saw, though I’m expecting I’ll continue to get along with the Festool saw for quite a while and may never get the table saw.

With all of that in mind, inspired by Jerry's "If you had to do it all over..." thread, a few questions:

  1. Walls are going to be 2×6 headers and sills with 2×4 staggered studs on 1’ centers for sound absorption (ie: on each side there’ll be a stud to nail sheathing/drywall to every 2’). I’m doing this rather than running bent channel for sound absorption because it doesn’t seem to have much of a cost premium, and the studs on the inside will be useful for hanging shelves off of. Anyone have additional suggestions on insulation or other easy ways to make it possible for me to run the router table at 2AM without ticking off neighbors?
  2. How many circuits should I run, and how should I lay them out? I’m figuring on running a 100A underground line from our utility drop. Right now I’m figuring on 4 110v circuits: two around the edges at roughly 4’ intervals, and two in the floor, towards the center of the floor. Should I put 4 plugs per box, 2 on each circuit, one circuit in each box (doesn’t save me any connections because they’ll be two legs in one Romex cable), or what?
  3. I’m planning on a slab with treated lumber “joists” run flat on the slab, and floor sheathing over that, because everyone says “wood floor”, but I want to avoid a crawl space. Should that be ¾”? 1”? Should I cover it with something? Is it reasonable to expect to pull it up to run an additional 220v circuit?
  4. 220v: I was going to run one right by where the box is, thinking I might put a bandsaw or dust collector there. How do you plan ahead on these things, especially since If I’m reading code right I can only put one socket per circuit? My thinking was that if I screwed down the floor sheathing, in a pinch I could run additional circuits there.
  5. (How should I get the wiring from the wall to the floor, just cut a hole in the sill plate?)
  6. I’m thinking 6 2-bulb T-8 fluorescent fixtures. Bright enough?

Anything else I’m missing here before I take these plans to the appropriate professionals for sign-off and start movin’ dirt?

-- Dan Lyke, Petaluma California,

14 replies so far

View Howie's profile


2656 posts in 2951 days

#1 posted 03-10-2011 02:29 AM

If you are planning on rolling around equipment much you might want to be sure to take into consideration the circuits(plugs) in the floor(item 2) Do you really want to do this?
Just my $.02

-- Life is good.

View Sawkerf's profile


1730 posts in 3096 days

#2 posted 03-10-2011 03:16 AM

One socket per circuit?? That doesn’t sound right.

If you’ll need a permit for this structure (and I’m sure that you’re supposed to get one), you should talk to you AHJ (Authority Having Jurisdiction) before you get too deep into your plans. Knowing their requirements might answer a lot of your questions – and save you from serious mistakes.

-- Adversity doesn't build reveals it.

View jack1's profile


2107 posts in 4055 days

#3 posted 03-10-2011 03:34 AM

You are probably referring to 1 socket/220 circuit but I could be wrong (won’t be the first time ;0) ]. I would consider 3 or more 220 lines. 1 for a big table saw, 1 for AC (I live in CA too) and one for just in case… Definitely 4 plugs/box on the 110 circuits, (heck I’d consider 6 on the box near a work bench). The only other thing I would think about is to make all 110’s 20amp circuits and maybe a few 30amp ones too. I run my 1 3/4 hp hybrid table saw off of one 30amp and it really makes a difference when torque is needed. My 2ยข… ;0)

-- jack -- ...measure once, curse twice!

View Roger's profile


20929 posts in 2832 days

#4 posted 03-10-2011 04:12 AM

I agree with what jack1 says.
something to consider:
check with your electric service. you may be able to get a book o their rules n regulations for one thing. then you can make your wiring plan. do it on paper 1st, so you can physically see what’s what. I’d definately put a few 220 receptacles for sure, in appropriate spots. I’d use nothing less that 12/3 w/20amp breakers for receptacles.
my $.02 :)

-- Roger from KY. Work/Play/Travel Safe. Keep your dust collector fed.

View Pop's profile


427 posts in 3974 days

#5 posted 03-10-2011 05:22 AM

In my little 600 sq. ft. shop everything is on wheels. I even have a space called the parking lot were machines sit until their needed. Because of this method of operation my 120 are all 20 or 30 amp. I have dedicated plugs for: my RAS, detail bench & workbench. My main 120 VAC is a 4 plug box on a 15 ft. # 10 wire extension cord. Very heavy cord and steel box on wood base. My 220 VAC is also an extension cord I can’t remember the wire size but it’s a heavy duty 12 ft. cable made up with twist-lock plugs. This works, but I’m designing a new shop and I’m trying to not use any extension cords.

Side Note, After untangling portable power tool cords for many years all my portable stuff have 6 inch cords with plugs. I have a pile of 6 to 10 ft. cords made up to use these tools.

I’m not saying this is the way to do it. In fact I’m not sure it’s a good idea at all. It’s just the way I do it.


-- One who works with his hands is a laborer, his hands & head A craftsman, his hands, head & heart a artist

View Dan Lyke's profile

Dan Lyke

1520 posts in 4153 days

#6 posted 03-10-2011 07:04 AM

I’m in the process of drawing up plans right now, and I’m probably drawing them to a level that goes beyond what my city’s planning department wants, but I’m going to be swinging the hammer, so I want to make sure that I know everything that I have to do to pass the building inspection. I’m also having an architect look over the plans, and because there are a few funky features to the building will probably need to have a professional engineer sign off on them.

I know I’m way over code on the electrical so far (the requirement for a building like this is a socket every 12 feet, and it could be one circuit for electrical, one for lighting), my questions are more about “what’s useful”.

Jack’s emphatic “4 plugs/box” is exactly the sort of reminder I need: If I’m running 12/2 and I need to make a junction in all 3 wires per box anyway, I should just do two of one circuit, two of the other, and then I never have to worry about plugging and unplugging anything.

Sawkerf and Jack: Yes, if I’m reading the code right, I think I get one socket per 220 circuit. I think it’s 10 per 110 circuit at or under 20 amps. Now worst comes to worst I can always run the wire and the socket and not put a breaker on it for starters, but it does mean I should figure out where I might put those accessories to begin with.

I’m figuring 20 amp circuits on 12ga wire, though I may have to sneak in 20 amp sockets (perpendicular pins) on a few of those after the inspector leaves, I haven’t talked to my building department on that detail yet, in the literature there’s some disagreement about doing that in a residential building.

Jack, we live a quarter mile from tidal water (the north end of the SF Bay), and between the morning fog and the afternoon ocean breezes do with only a window air conditioner that we drag out of the attic for that one or two weeks a year that we need it for the house, so I think that with the insulation and roof structure I’ve got planned I can get away without an air conditioner, but it does strike me that I may want 3: Dust collector, band saw, and table saw. What I don’t know is how to figure out where to run them to. Maybe I just bite the bullet and buy an extra two rolls of Romex and put ‘em in each corner.

Pop, one of the advantages of Festool is the Plug-It cords: They detach at the tool, so I generally just leave one zip-tied to my portable dust collector hose. I’m planning on the band saw by the big door (8’ wide, 8’ high) so that I can use outside as my run-out space, but, yeah, everything but the lumber racks and small tool shelves will be movable.

Howie, good point. That’s why I’m asking the questions. I thought I wanted that because I generally work with the Festool table set up in the middle of the room, put the vacuum under the table, plug it into the floor. I’ll have to see how flush the floor-mounted sockets can be. I think all of my casters are large enough that it wouldn’t be a dealbreaker, but it might be annoying.

Thanks, guys, I’ve already got a few places where you’ve convinced me to spend more money (4 sockets, 2 circuits, per outlet), this is why I asked!

-- Dan Lyke, Petaluma California,

View Gregn's profile


1642 posts in 3011 days

#7 posted 03-10-2011 07:07 AM

First thing you might want to do is go to your city offices to the code office an ask if they have a copy of the local code book. This will have all the codes for new structures.

1. Walls: If you are planning on somewhat sound proof the walls I would use 2×6 studs for the walls on 16” centers. Then create a baffle system in the wall. This is done by cutting foam insulation to fit the void space then nailing a 1×2 for the next layer and creating an air pocket between the layers of foam insulation. Cheapest way I know to deaden noise and insulate at the same time.

2. Electrical: It sounds like you plan to have a 100 amp sub panel. Run 120 volt 4 outlets per box 4’ apart and 4’ off the floor on all the walls and single 240 outlets 2 per wall 4’ off of the floor. It wouldn’t hurt to put outlets in the ceiling for a air filter and other accessories you might want to hang from the ceiling. This will provide you with an outlet within easy reach any where in the shop and eliminate the need for running wiring under the flooring.

3. Flooring: A pressure treated grid of 2×2’s with 3/4” plywood should be sufficient for a wood floor. This should provide enough give yet allow you to move equipment around the shop.

This is what I would do, in fact I’m in the process of doing the electrical as described earlier.

-- I don't make mistakes, I have great learning lessons, Greg

View TopamaxSurvivor's profile


18291 posts in 3704 days

#8 posted 03-10-2011 11:28 AM

You should plan on running any motors larger than 1 hp on 240 V. By that I mean any motor that drawns more than 16 amps on 120 volts, not necessarily a 3 hp router that draws 15 amps. It is not a 3 hp motor!

-- Bob in WW ~ "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence

View agallant's profile


551 posts in 2914 days

#9 posted 03-10-2011 04:22 PM

Lessons learned from building my 14X18 shop.

1. Put outlets around all of the walls every 4 feet
2. Put in a dedicated circuit for your table saw
3. I have 2X dual 8 foot lights (4 total) which is pleanty of light.
4. After you insulate and drywall hang peg board everywhere
5. I wish I did not use OSB for anything.

View Dan Lyke's profile

Dan Lyke

1520 posts in 4153 days

#10 posted 03-10-2011 05:29 PM

Greg, on walls, the stuff I read says that the best thing you can do for noise transmission is to make sure that there’s no direct contact between the inside walls and the outside walls, which is why I’m planning on the staggered stud construction. Do you have resources on wall assemblies and sound transmission measurements?

I do like that baffle system insulation method, in fact you could probably do something like that with strips of foam glued in squares to separate the layers. I’m going to have to see what rigid insulation costs and see if I can find a little bit more about building optimal baffles.

It also sounds like I’m going to have to suck it up and run a couple extra coils of Romex for my 220v just in case. I guess I can always put in covered junction boxes and just install the socket where I’ll actually have a tool.

And the consensus definitely seems to be calling for a really high socket density, time to double what I’ve got on my drawings…

agallant, what have your problems been with OSB? I’m up in the air over it, my wife won’t let me use it for anything in the house, but I thought it might be okay for sheathing…

-- Dan Lyke, Petaluma California,

View DIYaholic's profile


19623 posts in 2703 days

#11 posted 03-11-2011 03:30 AM

You can get flush mount floor boxes with outlet covers (not sure if they make a shallow version, though). The covers can be screwed on and off or they can be hinged. Personally I’d go with the screw cover, the hinged ones always seem to get broken off.

Also, I strongly suggest that you build your shop in my back yard. I have plenty of room and I wouldn’t want you to lose any valuable yard space or scenic views. Just trying to help out a fellow LJ!

-- Randy-- I may not be good...but I am slow! If good things come to those who wait.... Why is procrastination a bad thing?

View RTim's profile


60 posts in 2720 days

#12 posted 03-11-2011 04:48 AM

Not sure if this is in your plans but are you putting a panel or sub-panel in the new shop? This makes reconfiguring electrical if you ever buy new machinery much more flexible!

Instead of Romex, why not go with EMT (half inch elctrical tubing that uses set-screw fittings) and individual wires. You can get multiple circuits through the same runs of tubing. If you still plan on Romex, use 12/3 to carry two 20A circuits per run. I just finished wiring up my basement shop and I put in 5 quad (double duplex) receptacles on 2 separate circuits for one side of the shop and I plan to do the same for the other side of the shop once I finally get everything put away.

I would definately plan single runs of romex for each large stationary tool (table saw, dust collector, etc.) as that same cable can be a 120v or a 240v circuit depending on the breaker you put it on.

I’m not a big fan of floor receptacles. The covers eventually leak and the receptacle fills up with all manner of detritus making a potential fire risk. If you have no support columns then outlets for the center of the room are harder, making floor receptacles a necessity, or suspend them on cords with strain relievers from the ceiling (depending on ceiling height) This is useful for sanders and other handheld power tools if you don’t want to limit the need to drape extension cords across the floor.

It sounds like you have plenty of general lighting but you may want to consider additional task lighting if you have a workbench along a wall.

Whatever you end up deciding, I’m sure you’ll thoroughly enjoy your new shop!

-- Tim from MA -- "Well done is better than well said." - Benjamin Franlin

View oluf's profile


260 posts in 3067 days

#13 posted 03-11-2011 05:23 AM

If you are going to have under floor space I would think it would be a good idea to run a 4” pvc dust collection line from end to end with at least three stand pipes to floor height. With this set up wou would never be too far from an outlet for dust removal . It would sure beat pipes and long hoses all over your work space.

-- Nils, So. Central MI. Wood is honest.Take the effort to understand what it has to tell you before you try to change it.

View Dan Lyke's profile

Dan Lyke

1520 posts in 4153 days

#14 posted 03-11-2011 05:32 PM

Randy, thanks, I was actually thinking that if I didn’t find what I was looking for I could cut squares out of my floor sheathing, frame around them (underneath) put a weatherstripping gasket on the frame and have lift-out covers. And, yes, I’m going to have a sub-panel, so adding circuits should be easy, but if I can do all the wiring before I put up the drywall that’s much better. So it’s even reasonable for me to run the wiring and not bother to put in the breakers ‘til I get the machines.

And your suggestion on location is noted, unfortunately stepping out the back door to do a little woodworking would take more time than I have.

RTim’s observation on floor receptacles is a good one, and even if I can find one with good covers might make my idea of gasketed lift-out panels worth pursuing a bit. My main reason for floor mounted is that in my current layout I have my portable dust collector under my work table, my tools plug into that, and it’d be nice if I could have full walk-around freedom.

I’m going to have to do a little googling and see if anyone makes temperature breakers for sockets. My sister (in the midwest) just had a nasty basement flood, so the family is suddenly passing around all sorts of tips on special purpose sensors and alert systems; something that tripped if the temperature in the box got over 160°F or so would be perfect.

It’s a small enough space that, despite the heavy load I’m putting on the roof (the plan is a living roof), I’m wanting everything as a clear span. I’ll use EMT (probably ¾”) to get the power from the walls to the lights, but as much as possible I was trying to keep the space generally clear.

Nils’s comment echoes what a guy who owns a local woodworking shop mentioned to me yesterday. I was thinking that I was just going to lay treated lumber on edge and have 1½” clear space between the concrete and the floor sheathing (a friend of mine is about to redo the outdoor storage area at a marina and has asked if I know anyone who wants ten thousand feet of treated lumber, I’m thinking that’s my sills and floor joists), but y’all are making me think I should give up a few more inches of vertical height and run sub-floor ducting.

-- Dan Lyke, Petaluma California,

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