Workshop Update Questions

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Forum topic by pete79 posted 04-18-2011 07:10 PM 1461 views 0 times favorited 7 replies Add to Favorites Watch
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154 posts in 3165 days

04-18-2011 07:10 PM

I’m starting with the task of insulating my garage workshop and have a few questions before I get too far:

1. I’m planning to put up a vapor barrier and insulation, covered by plywood or OSB on the walls. I’m not sure what to do with the ceiling. I currently have your typical vaulted garage roof, with no ceiling. Do I put in joists and a ceiling, or do I just insulate the existing roof and leave it vaulted? Puting in a ceiling would leave me with about a 8 foot ceiling. Also, should I use drywall or plywood/OSB for the ceiling?

2. Wiring – I haven’t updated my electrical service yet…but that’s coming in the future. I want to wire the garage to accomodate for that. I will likely run a 50amp subpanel to the garage when I do it. That being said, should I just run all lights on 14/3, 15amp lines, and do all the plugs on 12/3, 20 amp lines? Or is there a better method to follow? Not really knowing what tools will go on which outlets, I’d like to at least have the proper load capacity in the wires in the walls. I’d also like the flexibility to have at least one or two lines on 240v if I choose to go that route.

Just looking for opinions or lessons learned from others here.

-- Life is a one lap race.

7 replies so far

View NewfieDan's profile


50 posts in 2673 days

#1 posted 04-18-2011 07:44 PM

1. If it were my garage I would put in a ceiling with joists. This give your roof more room to breathe and prevent any moisture from building up on the underside of your roof sheathing. Allow room at the edges for air flow. Most home improvemnt stores have insulation stops. These allow you to insulate right to the outside edge of the studs but maintain a gap for air movement. The opposite is also true. The stops will also help to keep your shop cooler in summer by allowing the excess heat to escape from inside the attic space. For the inside ceiling material I am looking at using 3/4” thick tongue and groove pine. It applies similar to hardwood flooring but you don’t have to hoist full 4X8 sheets over your head. It also gives teh ceiling amore finished look with out the need for paint or plaster.
2. I would update the electrical before the insulation goes in. Trust me on this one. If you can affford it do it now then think about the insulation after that. It is much harder to wire after the insulation is done.

I am at the same stage with my new garage and this is what I am looking at doing.

View ocwoodworker's profile


209 posts in 3029 days

#2 posted 04-18-2011 07:48 PM

As a Calif. state building inspector IMHO I would say that there is no need to drywall the ceiling. If you are looking to keep your garage cool during summer and warm in winter, then just insulate. If you do decide to put in a ceiling, check your spans of existing rafters and the loads you will impose on them. Most garages are 20’ spans and would require that you upgrade the joist system to at least DF #1 2×6’s (which will give you as span of 19’-11”) and that’s only for carrying the dead load of the drywall. If you plan on hanging things or storing things on it, I would seriously consider going to DF-SS 2X8’s as long as you don’t go into the anvil or bowling ball storage business, in which case upgrade to 2×10’s.
As for electrical, you got the right idea but a 50 amp panel to me is undersized. I have several 220V machines and each carry 15 to 30 amps. If you use a DC and a TS at the same time you are already pushing 45 amps. (and that isn’t including the misc. power consumption of lights, radio and the mini fridge to hold our precious adult beverages we consume between cuts). Given that you rate your panel to 80% of the load as ideal, you might want to go to a 100 amp sub panel if possible. And as a side note, make sure you do decide where you want your electrical equipment. Trying to put in a dedicated power source is always tricky once the walls are up.

-- I'd like to believe Murphy's Law haunts my woodshop, because if it's Karma it would mean I had something to do with it. - K.R.

View ClayandNancy's profile


519 posts in 3040 days

#3 posted 04-18-2011 08:34 PM

Best to check your local electrical codes first to make sure you have it right. I’m sure it would make your insurance company happy. I agree with Kevin go with the 100 amp service if you can, just gives you room to expand if necessary in the future, (You know you will add more stuff).

View Gregn's profile


1642 posts in 3008 days

#4 posted 04-19-2011 03:20 PM

To answer question #1 we used to insulate vaulted ceilings the same method as the walls with the exception of adding Styrofoam vents that were 12” wide and 36” length. We would come in after the electrical and plumbing contractors were done. We would first install the Styrofoam vents so that one end would be in the soffet area and against the roof decking to provide ventilation between the decking and the insulation. We would then install the insulation and then a plastic vapor barrier, then the sheet rockers would come in after us. As to use OSB or sheet rock that would be a personal choice.

As for the electrical I would have to agree with the 100 amp sub panel myself. My shop is 12×30 check out my blog The Electrical Journey as to what I have done. I have wired for any possible electrical need I may have. Hope this helps you some.

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

View Bill White's profile

Bill White

4948 posts in 3985 days

#5 posted 04-19-2011 03:33 PM

100 amp w/o a doubt. Anything less and you’ll be speaking in unknown tongues first time ya trip a breaker.


View agallant's profile


551 posts in 2911 days

#6 posted 04-19-2011 06:15 PM

I have 60 amp out in my work shop and I think it is just fine. I have my lights running on 12/2 15amp and my TS/VAC on a dedicated 10/2 20amp circuit, all other outlets in the shop are on a 12/2 15 amp circuit. I like knowing that I have more capacity if I need it.

As for insulation I built my shop with the idea that I would not insulate it and changed my mind. I put insulation in the walls and drywalled it. I with I put some in the attic, I am sure I will get to that later this year.

View SnowyRiver's profile


51457 posts in 3505 days

#7 posted 04-20-2011 10:30 PM

If you are the only one working in the shop I think 60 amp would be fine too. I have 60 amps and run my lights, cabinet saw, air filter, and dust collector at the same time without any problems. I have never tripped a breaker and the lights dont flicker.

Most machinery can run off of 120 VAC 20 amp circuits, but if you have a cabinet saw, 2 or 3 hp or above, you might want to put in a 30 amp/220 VAC breaker to reduce the current drain.

On the ceiling, I would insulate it, but leave it vaulted. Its nice to have a high ceiling especially if you have a cabinet standing on the work bench…the extra head room is nice. Its also nice when hanging air filters from the ceiling, running dust collector pipe, and when moving long boards around…you wont keep hitting the ceiling.

-- Wayne - Plymouth MN

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