Garage to workshop - insulation/humidity concerns - advice?

[Jim Lafferty]

Hi,

I've got a two car garage that about 1/3rd of it is emerging as my new workspace. I'm now sitting here thinking about the gear I'll be stashing there, including a cast iron topped table saw, a miter saw, a drill press... the table saw especially, and its cast iron top, is what has me concerned. Dangers leaving it to basically freeze and thaw repeatedly over winter? Temps here, upstate NY, get to the teens overnight, sometimes lower... and peak temps hitting 25-35 on many winter days. The garage is currently maybe 5-7 degrees warmer on average, but entirely lacking in insulation, and has some moisture issues in heavy rains in the corner opposite to where the gear will be sitting. It has a pretty open storage area in the rafters, bare cement floor. I'm thinking I should do insulation board and cover it with drywall, but also have been considering if it would be smart to hang some sound proofing rubber sheet to dampen saw noise.

Thanks in advance for your feedback.

[roger wiegand]

Does it need to continue to function as a garage?

I'd advise: 1) control the moisture, whatever that takes. It may be as simple as redirecting downspouts or regrading around the foundation to carry water away from the building, but all else is for naught if you've got water entering the structure. 2) Add insulation, lots. In upstate NY shoot for r45 to 60 in the roof (maintaining air flow from soffit vents to peak), at least r20 in the walls. Consider blown-in cellulose in the stud bays then 2" of rigid foam topped with plywood or OSB on the inside to give you smooth walls you can hang things on. 3) then consider adding a heater that could maintain the space at 40-45 degrees when you're not there. Good insulated garage doors are wicked expensive, so if you can frame in all or part of the opening at least temporarily and air seal and insulate it would be cheaper-- I'd make it easy to tear out when house sale time comes, make an insulated wall inside the existing garage doors.

[Jim Lafferty]

OK, all of that sounds reasonable.

Currently have 15A wired to the garage, and assume it would be smart to switch over to 20A.

Based on what you've written, I'm now considering walling off just a portion of the garage instead of treating the entire thing.

[Jim Becker]

Reducing the conditioned space can make it easier to, um...condition. The downside is that it also has impact on the kinds of projects you can work on as well as the type and size of tools and work surfaces you can leverage for that. This has to be part of your plan before you start any kind of work. You will also need multiple circuits for your shop, even if you use all 120v tools. One for the tool in use and one for dust collection, for example. And those 120v circuits should be 20 amp. Etc.

[roger wiegand]

It's wise to have your lights on a circuit independent of your tools. It's very uncomfortable when the breaker pops and you're in the pitch dark with a still spinning saw.

[Charlie Velasquez]

Controlling humidity and mold was one of my jobs for my school district. All of Roger's suggestions will help. But there are other things you may try.

The goal is to keep the surface temperatures of your tools above the dew point. You can tackle this by addressing the temperature, the water vapor or both.

In the summer it is easiest to address the water vapor. In the winter - the temperature.
Your stated concern was winter, so temperature it is!

Besides Roger's suggestions, you could try a lower tech solution that I used. Given:
A. Iowa, 41° lat. Temps from -20 to 105. RH up to 90% @ 100°.(but we're just worried about winter rh)
B. Slab on grade construction 24'x24' stick built
C. No insulation, open rafters, no heating.
D. Unisaw, 15" floor drill press, Dewalt RAS, tool chest of wrenches sockets

Action
1. Everything on wheels
2. Laid a 4x8x1" sheet of Foamular on the floor (concrete is a giant heat sink). Cover with a sheet of ply.
3. Rolled everything on the insulated ply.
4. Put a chicken coop type heat lamp inside my uni saw
5. Plugged into a timer, on at 3pm, off at 5am.
6. Covered with a heavy tarp

The goal was to keep the tools' surfaces a couple of degrees above the dew point.
I don't do a lot in my shop from December to Feb, but when I did, after moving the tool chest, I could do most things with the tools as theY were.

This was a mini version of Roger's suggestion: control the space and air, insulate as best you can, add enough heat to keep it above the dew point.

[Charlie Velasquez]

OK, all of that sounds reasonable.

Currently have 15A wired to the garage, and assume it would be smart to switch over to 20A.

Based on what you've written, I'm now considering walling off just a portion of the garage instead of treating the entire thing.

Attached or detached?

[Jim Lafferty]

1. Everything on wheels
2. Laid a 4x8x1" sheet of Foamular on the floor (concrete is a giant heat sink). Cover with a sheet of ply.
3. Rolled everything on the insulated ply.
4. Put a chicken coop type heat lamp inside my uni saw
5. Plugged into a timer, on at 3pm, off at 5am.
6. Covered with a heavy tarp

The goal was to keep the tools' surfaces a couple of degrees above the dew point.

This is great. Just randomly was thinking today... "I think I'd do well to put another floor on top of the concrete, just 2-3", and insulate that." Your tip about putting heat lamps on the gear on a timer is fantastic. Ran the idea of isolating a smaller area in the garage by my wife and she thinks we should instead just put our energies and money in to prepping the entire thing. Thanks for your suggestions!

[Jim Lafferty]

Attached or detached?

Detached. About 30 ft from my house.

[Charlie Velasquez]

Detached. About 30 ft from my house.

Detached building ... garage...
The NEC has rules about detached buildings and detached buildings that will be used to put autos and stuff in.

Garages must have a dedicated 20 amp circuit for convenience receptacles. Only receptacles are allowed on that circuit.
You must also have lights, but it can not be on your convenience circuit. You may have additional receptacles on this lighting circuit.
You can have more circuits, but you must have those two.

Now, detached buildings may only have one circuit or feeder going to it (with a couple of unique exceptions).
There is a special circuit called a multi-wire branch circuit that is actually two circuits that count as one. So to get your two required circuits you must either run a mwbc or a feeder and install a sub panel.
Since you would be trenching for either, it makes a lot of sense to install a sub panel.

[Alex Zeller]

It's not the dead of winter that's the problem. It's when temps are close to freezing and go back and forth at a pretty fast speed. As things warm up the snow melts and creates lots of extra moisture. Heavy steel in tools don't warm as fast as the air so they attract the water. I have a few tools (like a cast iron router table) that aren't in use and are stored in the garage. After reading the advice of a fellow creeker I bought some magnetic sign material. I put that on the machined surfaces. The tools are on plywood to keep them away from the cement. Also I put those cheap Harbor Freight moving blankets on top of the tools. I've never had a problem with rust.

[roger wiegand]

A layer of foam and plywood on the floor will make the shop vastly more comfortable for you as well as for your tools. Second the motion!

We did a deep energy retrofit on the old part of our house and built a fairly large, heavily insulated addition. My shop is in a 1910 barn where the only feasible approach was spray foam for the walls and roof, but when I put in a new floor I put down 4" of rigid foam, a slab, then sleepers and a plywood subfloor and hardwood flooring. Both buildings are amazingly comfortable to live and work in, with the nice side effect that our utility bills are miniscule. I've become a real advocate for putting in as much insulation as you can manage, everywhere. Having your feet not freeze while you're working is priceless!

[Charlie Velasquez]

A layer of foam and plywood on the floor will make the shop vastly more comfortable for you as well as for your tools. Second the motion!

We did a deep energy retrofit on the old part of our house and built a fairly large, heavily insulated addition. My shop is in a 1910 barn where the only feasible approach was spray foam for the walls and roof, but when I put in a new floor I put down 4" of rigid foam, a slab, then sleepers and a plywood subfloor and hardwood flooring. Both buildings are amazingly comfortable to live and work in, with the nice side effect that our utility bills are miniscule. I've become a real advocate for putting in as much insulation as you can manage, everywhere. Having your feet not freeze while you're working is priceless!

And, standing on wood is a lot more comfortable than standing on concrete.

In your scenario I would forego the sleepers. 2x4s flat at 16" centers means about 25% of your floor will have an r-value just slighty higher than 1.
Just butt the insulation boards down and cover. No nails, no glue.
Foamular has compressive strengths ranging from 25psi and up. Choose an appropriate psi with a sheet of 1" avantech osb over it and you should be good for just about any load you put on it (a car's tires' floor contact at 36 psi will be distributed to a larger area by the osb). The advantech is almost impervious to the melted snow or rain your wife's car will bring in. They guarantee it not to swell for a year's storage outdoors, even if sitting in a puddle.

[Matthew Hills]

Currently have 15A wired to the garage, and assume it would be smart to switch over to 20A.

20A is a good idea for a lot of tools (1.5hp table saws, or shop vac + hand power tool).

If you use the shop during winter months, what do you expect to use for heating?

I'm expecting a single 20A circuit may be marginal for running anything substantial along with the table saw.
(E.g.., heater or dust collector). A 2nd circuit (230V may be even better) may be good to consider if that matches with your shop ambitions.

Good lighting is a good idea.

Matt

[Jim Lafferty]

Interesting - I'll look into this. Most of the secondary floor build outs I've seen suggest a plastic moisture barrier, then sleepers, then foam and OSB to finish. Is the moisture barrier advised? And without sleepers or something similar, how do you keep things from shifting?

No cars will be parking in this garage. Half is gardening tools/storage, half will be the woodworking area. Def looking forward to having a more forgiving and insulated floor.

And, standing on wood is a lot more comfortable than standing on concrete.

In your scenario I would forego the sleepers. 2x4s flat at 16" centers means about 25% of your floor will have an r-value just slighty higher than 1.
Just butt the insulation boards down and cover. No nails, no glue.
Foamular has compressive strengths ranging from 25psi and up. Choose an appropriate psi with a sheet of 1" avantech osb over it and you should be good for just about any load you put on it (a car's tires' floor contact at 36 psi will be distributed to a larger area by the osb). The advantech is almost impervious to the melted snow or rain your wife's car will bring in. They guarantee it not to swell for a year's storage outdoors, even if sitting in a puddle.