Shop and Garage Spray Foam Insulation

An uninsulated shop in North Texas is two buildings: an oven from June to September and a cold, damp box on winter mornings. A steel shop adds a third problem, condensation that drips on tools, trucks and anything stored inside. Spray foam on the roof and walls fixes the drip, takes most of the heat out of the building and makes it possible to cool the space with a small mini-split.

Steel shops: closed cell on the panels

For a steel shop or metal garage, closed cell foam goes directly on the inside of the roof and wall panels, between the purlins and girts. At 2″ (about R-13) it stops condensation, seals every lap and screw hole, and keeps the panels from pinging and drumming. If you plan to air condition the shop, 3″ on the roof is worth considering. More detail is on our metal building insulation page.

Wood-framed garages and shops

A detached garage or shop with a wood roof deck and stud walls can take either foam. Open cell is the economical choice for a deep roof deck. Closed cell gives more R-value in thin 2×4 walls and adds stiffness. Many owners pick open cell for the roof and closed cell for the walls.

Attached garages and rooms above them

In many DFW homes, the garage ceiling is the floor of a bonus room or bedroom. That room is often the hottest in the house because a 120°F garage sits under it. Spraying closed cell on the garage ceiling, if it is open, or along the band joists if it isn’t, helps. So does spraying the garage roof deck when the garage attic connects to the main attic. We’ll look at how your garage connects to the house on the measure.

Making a mini-split work

A mini-split in an uninsulated metal shop runs all day and never catches up. Once the roof and walls are foamed and the gaps are sealed, a much smaller unit can hold the shop at a comfortable temperature. Insulate first, then size the unit for the insulated building. Ask your HVAC contractor to size it after we spray.

What a shop costs

A 30×40 shop with 12′ walls and a 4/12 roof has about 3,100 square feet of walls and roof to spray. See what that and other sizes come to on our spray foam cost page, or enter your shop’s size in the calculator.

Shop and garage questions

Will spray foam stop my shop from sweating?

Yes, if the foam is closed cell sprayed directly on the steel. Sweating happens when humid air reaches steel that is colder than the air’s dew point. With foam bonded to the panels, that air can’t reach the metal, so water has nowhere to form.

Do I need to empty the shop?

Not completely. We cover tools, benches, vehicles and stored items with plastic and mask off what we can’t move. Anything easy to move out is worth moving, and anything with a finish you care about should be covered or taken out.

What about the garage door?

We don’t spray garage doors, because the foam would add weight and could affect the springs and opener. Insulated garage doors or door insulation kits are the way to go, and we can mask and seal around the door frame.

Does foam in a shop need to be covered?

It depends on how the space is used. In many shops and garages, exposed foam needs an ignition barrier coating, and in some uses it needs to be covered by drywall or an approved coating. Your quote lists what applies to your building.