An 8 x 8 ft cold room in a garage: 2x4 walls lined with 2 in foam board, a foam ceiling, an insulated door and a window cooling unit.
Draft plan, generated from the model. Not yet build-tested.
94 x 94 inFootprint
84 inHeight
2 in foam, R-10Insulation
35 to 40°FTemperature
20 to 30 hrBuild time
~$1,609.22Materials, part estimate
Drawings All dimensions in inches
3D viewfinished3D view, framingsiding and roof removedFront elevationRight elevationPlan viewfrom above
Cut list: lumber Long-point lengths; angles noted
Qty
Stock
Length
Part
Cut
1
2x4
94
Front top plate
laid flat
1
2x4
94
Back top plate
laid flat
7
2x4
94
Ceiling joist
on edge, across the top plates
1
2x4
87
Left top plate
laid flat
1
2x4
87
Right top plate
laid flat
7
2x4
77 1/2
Front stud
7
2x4
77 1/2
Back stud
7
2x4
77 1/2
Left stud
7
2x4
77 1/2
Right stud
1
2x4
32
Front door header
laid flat
1
2x4 PT
94
Front bottom plate
laid flat
1
2x4 PT
94
Back bottom plate
laid flat
1
2x4 PT
87
Left bottom plate
laid flat
1
2x4 PT
87
Right bottom plate
laid flat
Cut list: sheet goods
Part
Stock
Size
Note
Front foam 1
foam
48 x 78 1/2
door is the cutout, re-hung
Front foam 2
foam
39 x 78 1/2
door is the cutout, re-hung
Back foam 1
foam
48 x 78 1/2
Back foam 2
foam
39 x 78 1/2
Left foam 1
foam
48 x 78 1/2
Left foam 2
foam
35 x 78 1/2
Right foam 1
foam
48 x 78 1/2
Right foam 2
foam
35 x 78 1/2
Ceiling foam 1
foam
48 x 87
Ceiling foam 2
foam
39 x 87
Lumber cutting diagram Lengths chosen for the lowest cost; 1/8 in kerf, 1/2 in end trim
2x4 x 10 ft
Left top plate 87Front door header 32
2x4 x 8 ft
Front top plate 94
2x4 x 8 ft
Back top plate 94
2x4 x 8 ft
Ceiling joist 1 94
2x4 x 8 ft
Ceiling joist 2 94
2x4 x 8 ft
Ceiling joist 3 94
2x4 x 8 ft
Ceiling joist 4 94
2x4 x 8 ft
Ceiling joist 5 94
2x4 x 8 ft
Ceiling joist 6 94
2x4 x 8 ft
Ceiling joist 7 94
2x4 x 8 ft
Right top plate 87
2x4 x 8 ft
Front stud 1 77 1/2
2x4 x 8 ft
Front stud 2 77 1/2
2x4 x 8 ft
Front stud 3 77 1/2
2x4 x 8 ft
Front stud 4 77 1/2
2x4 x 8 ft
Front stud 5 77 1/2
2x4 x 8 ft
Front stud 6 77 1/2
2x4 x 8 ft
Front stud 7 77 1/2
2x4 x 8 ft
Back stud 1 77 1/2
2x4 x 8 ft
Back stud 2 77 1/2
2x4 x 8 ft
Back stud 3 77 1/2
2x4 x 8 ft
Back stud 4 77 1/2
2x4 x 8 ft
Back stud 5 77 1/2
2x4 x 8 ft
Back stud 6 77 1/2
2x4 x 8 ft
Back stud 7 77 1/2
2x4 x 8 ft
Left stud 1 77 1/2
2x4 x 8 ft
Left stud 2 77 1/2
2x4 x 8 ft
Left stud 3 77 1/2
2x4 x 8 ft
Left stud 4 77 1/2
2x4 x 8 ft
Left stud 5 77 1/2
2x4 x 8 ft
Left stud 6 77 1/2
2x4 x 8 ft
Left stud 7 77 1/2
2x4 x 8 ft
Right stud 1 77 1/2
2x4 x 8 ft
Right stud 2 77 1/2
2x4 x 8 ft
Right stud 3 77 1/2
2x4 x 8 ft
Right stud 4 77 1/2
2x4 x 8 ft
Right stud 5 77 1/2
2x4 x 8 ft
Right stud 6 77 1/2
2x4 x 8 ft
Right stud 7 77 1/2
2x4 PT x 8 ft
Front bottom plate 94
2x4 PT x 8 ft
Back bottom plate 94
2x4 PT x 8 ft
Left bottom plate 87
2x4 PT x 8 ft
Right bottom plate 87
Sheet cutting diagrams Dashed = openings to cut out
Sheet 1: 2 in foam board, 4 x 8 ftSheet 2: 2 in foam board, 4 x 8 ftSheet 3: 2 in foam board, 4 x 8 ftSheet 4: 2 in foam board, 4 x 8 ftSheet 5: 2 in foam board, 4 x 8 ftSheet 6: 2 in foam board, 4 x 8 ftSheet 7: 2 in foam board, 4 x 8 ftSheet 8: 2 in foam board, 4 x 8 ftSheet 9: 2 in foam board, 4 x 8 ftSheet 10: 2 in foam board, 4 x 8 ft
Shopping list $1,139.22 checked / $470.00 estimated
Item
Store
Qty
Each
Line
Note
2x4x10 stud, SPF
Home Depot
1
$5.46
$5.46
see lumber cutting diagram
2x4x8 stud, SPF
Home Depot
38
$4.15
$157.70
see lumber cutting diagram
2x4x8 ground-contact pressure-treated
Home Depot
4
$4.68
$18.72
see lumber cutting diagram
2 in foam board, 4x8 sheet
Home Depot
10
$64.84
$648.40
see sheet cutting diagrams
Prehung steel exterior door 30 x 80 in
Home Depot
1
$249.00
$249.00
Cooling controller and window air conditioner, 5,000 BTU
Home Depot
1
$420.00
$420.00
window AC and controller
Vapor barrier tape and foam sealant
Home Depot
2
$25.00
$50.00
foil tape and sealant
Exterior wood screws #9 x 2.5 in, 5 lb box
Home Depot
2
$29.97
$59.94
Total before tax
~$1,609.22
Filled dot: price read from a store listing on Oct 20, 2026. Hollow dot: estimate. Prices come from the master price list, so they change when it changes.
Build steps
Pick a corner of the garage with a level concrete slab and an outlet. Chalk the 94 in square on the slab and check both diagonals for square.
Frame the four walls flat on the floor with pressure-treated bottom plates and studs 16 in on center. Frame a 32 in wide opening for the door in the front wall.
Stand the walls and screw the bottom plates down to the slab with masonry anchors. Screw the corners together.
Screw the ceiling joists on edge across the top plates, 16 in on center.
Screw the 2 in foam board to the inside of the studs with 3 in screws and washers, with the joints on studs. Tape every joint with foil tape and seal the edges with foam sealant.
Fit the foam ceiling panels under the joists and seal the same way. Set the prehung door in the opening, with weatherstripping all round.
Cut an opening in the foam and the wall for the window air conditioner, and fit it with the cooling controller. Hang a thermometer inside; the target is 35 to 40°F.
Before you start
A cold room holds roots, cabbages, apples and cheese at 35 to 40°F at 85 to 95 percent humidity. Add a tray of water on the floor, and wet the floor now and then.
The cooling unit and controller are in the list as one item at an estimate. The controller overrides the AC's thermostat, which stops at 60°F.
Seal every gap: a leaky cold room is a loss of money. Keep the room's door shut and the vapor barrier unbroken.
A cold room draws 10 to 15 kWh a day in summer; plan the circuit with an electrician.
The foam board, door, and cooler prices are estimates; check before you buy.
Draft drawings generated from the model. Build one before selling this plan.