How to Build the Gambrel Garage Page 1 of 3
Following classic barn designs, this 12 x 12-ft. garage-size storage shed has several features that make it a versatile storage shed or workshop.
Following classic barn designs, this 12 x 12-ft. garage-size storage shed has several features that make it a versatile storage shed or workshop. The garage’s 144-square-foot floor is a poured concrete slab with a thickened edge that allows it to serve as the building’s foundation. Designed for economy and durability, the floor can easily support heavy machinery, woodworking tools, and recreational vehicles.
The garage’s sectional overhead door makes for quick access to equipment and supplies and provides plenty of air and natural light for working inside. The door opening is sized for an 8-ft.-wide x 7-ft.-tall door, but you can buy any size or style of door you like—just make your door selection before you start framing the garage.
Another important design feature of this building is its gambrel roof, which maximizes the usable interior space (see The Gambrel Roof). Beneath the roof is a sizeable storage attic with 315 cubic feet of space and its own double doors above the garage door. Note: we added a patio section to the front of this shed. This optional slab will appear throughout the how-to photos.
The Gambrel Roof
The gambrel roof is the defining feature of two structures in American architecture: the barn and the Dutch Colonial house. Adopted from earlier English buildings, the gambrel style became popular in America during the early 17th century and was used on homes and farm buildings throughout the Atlantic region. Today, the gambrel roof remains a favorite detail for designers of sheds, garages, and carriage houses.
The basic gambrel shape has two flat planes on each side, with the lower plane sloped much more steeply than the upper. More elaborate versions incorporate a flared eave, known as a “Dutch kick,” that was often extended to shelter the front and rear facades of the building. Barns typically feature an extended peak at the front, sheltering the doors of the hayloft. The main advantage of the gambrel roof is the increased space underneath the roof, providing additional headroom for upper floors in homes or extra storage space in outbuildings.
How to Build the Gambrel Garage - Step 1
Build the slab foundation at 144" x 144. Set J-bolts into the concrete 13⁄4" from the outer edges and extending 21⁄2" from the surface. Set a bolt 6" from each corner and every 48" in between (except in the door opening). Let the slab cure for at least three days before you begin construction.
How to Build the Gambrel Garage - Step 2
Snap chalk lines on the slab for the wall plates. Cut two bottom plates and two top plates at 137" for the sidewalls. Cut two bottom and two top plates at 144" for the front and rear walls. Use pressure-treated lumber for all bottom plates. Cut 38 studs at 92 5⁄8", plus two jack studs for the garage door at 78 1⁄2" and two window studs at 75 7⁄8". Note: Add the optional slab now, as desired.
How to Build the Gambrel Garage - Step 3
Construct the built-up 2 x 8 headers at 99" (garage door) and 63" (window). Frame, install, and brace the walls with double top plates one at a time, following the FLOOR PLAN and ELEVATION drawings. Use galvanized nails to attach the studs to the sole plates. Anchor the walls to the J-bolts in the slab with galvanized washers and nuts.
How to Build the Gambrel Garage - Step 4
Build the attic floor. Cut ten 2 x 6 joists to 144" long, then clip each top corner with a 1 1⁄2"-long, 45° cut. Install the joists as shown in the FRAMING ELEVATIONS, leaving a 3 1⁄2" space at the front and rear walls for the gable wall studs. Fasten the joists with three 8d nails at each end.
How to Build the Gambrel Garage - Step 5
Frame the attic kneewalls: Cut four top plates at 144" and two bottom plates at 137". Cut 20 studs at 26 5⁄8" and four end studs at 33 5⁄8". Lay out the plates so the studs fall over the attic joists. Frame the walls and install them 181⁄8" from the ends of the joists, then add temporary bracing. Option: You can begin building the roof frame by cutting two 2 x 8 nailers to 144" long. Fasten the nailers to the kneewalls so their top edges are 32 5⁄8" above the attic joists.
How to Build the Gambrel Garage - Step 6
Cover the attic floor between the kneewalls with 3⁄4" plywood. Run the sheets perpendicular to the joists, and stop them flush with the outer joists. Fasten the flooring with 8d ring-shank nails every 6" along the edges and every 12" in the field of the sheets.
How to Build the Gambrel Garage - Step 7
Mark the rafter layouts onto the top and outside faces of the 2 x 8 nailers; see the FRAMING ELEVATIONS.
How to Build the Gambrel Garage - Step 8
Cut the 2 x 6 ridge board at 168", mitering the front end at 16°. Mark the rafter layout onto the ridge. The outer common rafters should be 16" from the front end and 8" from the rear end of the ridge.
How to Build the Gambrel Garage - Step 9
Use the RAFTER TEMPLATES to mark and cut two upper pattern rafters and one lower pattern rafter. Test-fit the rafters and make any needed adjustments. Use the patterns to mark and cut the remaining common rafters (20 total of each type). For the gable overhangs, cut an additional eight lower and six upper rafters following the GABLE OVERHANG RAFTER DETAILS.
How to Build the Gambrel Garage - Step 10
Install the common rafters; then reinforce the joints at the knee walls with framing connectors. Also nail the attic joists to the sides of the floor rafters. Cut four 2 x 4 collar ties at 34", mitering the ends at 26.5°. Fasten them between pairs of upper rafters, as shown in the BUILDING SECTION and FRAMING ELEVATIONS.