Shed 8'x12' Gambrel Roof

These wood working plans include:

The following drawings:

  • Front Elevation showing the gable end framing and door opening.
  • Wood Foundation showing the floor joist and foundation.
  • Concrete Slab showing the profile and anchor bolts in the slab.
  • Truss Layout showing the angles of the cuts for the trusses, their lengths as well as the size of the gussets.
  • Side Elevation showing the layout of the trusses on the side walls.

The plans have a List of Materials, which includes size and quantities for:

  • Exterior trim
  • Studs
  • Plates
  • Trusses
  • Joists
  • Gussets for the trusses
  • OSB for the walls and roof
  • Roofing.

The Instructions include the following topics:

  • The Foundation
    • Concrete Slab: Discussing the placement of anchor bolts; the thickness of the concrete slab and perimeter as well as the material under the slab.
    • Concrete Block: The size of footings required; design of the forms; how to install anchor bolts and the sill plate.
    • Wooden Floor: The wood foundation; the layout of the floor, size of joists, their centers, squaring the floor, how to install tongue and groove (T&G) plywood - staggering and nailing the sheets.

  • The Walls: Installing the bottom plate; layout of the studs, door and windows; headers; constructing the walls, fastening them to each other; bracing the walls.

  • The Trusses: Laying out the trusses full size from the drawings; framing the gable ends and door.

  • Putting it Together: Bracing the walls; laying out the trusses on the walls; erecting the trusses.

  • Sheathing the Walls: Framing and sheathing the gable ends; installing sheathing on the walls.

  • Making the Roof: Sheathing the roof; installing the overhang.

  • The Trim and Door: Trimming the roof, door; constructing and hanging the door.

Drawing of our 6 foot gambrel barn roof shed project.

List of Materials:

  • 9 - 1x4x8'
  • 4 - 1x6x8'
  • 10 - 2x4x6'
  • 27 - 2x4x8'
  • 4 - 2x4x12'
  • 2 - 2x6x12'
  • half sheet 1/2" plywood for gussets
  • 6 sheets 4x8x3/8" OSB for walls
  • 6 sheets 4x8x1/2" OSB for roof
  • 3 - 3" galvanized hinges
  • 1 - padbolt or 6" hasp
  • 160 square feet of asphalt shingles or equivalent roofing materials

Wood Foundation:

  • 2 - 6x6x12'
  • 2 - 2x6x12' box or rim joists
  • 10 - 2x6x8' floor joists
  • 3 - sheets 4x8x5/8" T & G (tongue and groove) plywood
  • 2 lb 2" common nails
  • 2 lb 3 1/4" common nail


The Foundation

There are two kinds of foundations that are practical for this type of shed—a concrete slab on grade or a wooden floor supported on pressure treated 6x6s. The easiest and most mobile is the wood foundation. Once concrete is poured it is permanent.

Concrete Slab:

See the foundation drawing. Place the anchor bolts on 4 foot centers or less around the outside perimeter. Make sure they are in the center of the 2x4 when placed flush on the edge and are at least 2" high. These bolts are usually placed after the concrete is poured. Depending on where you live and how cold the winters are, the perimeter of the slab should be built up in thickness, 12" being the minimum thickness and 12" in from the edge as well.

Wooden Floor:

Refer to the Wood Foundation drawing. The wood floor is typically 5/8" tongue and groove plywood on 2x6s at 16" centers on 6x6s, pressure treated to last for 40 years. Put these 6x6s on a bed of about 6" deep compacted gravel to help in drainage. Make sure the center one is level and true with the outside ones. The 6x6s are 12' long and placed 7' apart to the outside, giving an overhang of 6"on each side, to shorten the span. Cut 2 - 2x6s 12'-0" and lay them both out together for the box joists. Start at the left end, measure 15 1/4" and place a mark with an X on the right of the mark. Now move the tape to this mark and continue to mark and place an X in the same manner at every 16" mark on your tape, until you run off the 2x6. Cut the 10 - 8 foot 2x6s to 7'-9" to allow for the combined 3" for the box joists on each end, as shown in the above drawing. When you nail the joists onto this box joist the left edge of the joist will be on the mark covering up the X.

After nailing on all the joists you should be able to place your tape on the edge of any joist, except the first one, and read a multiple of 16" at the center. This will enable the plywood to end on the center of the joist. When the joists are all nailed on, measure their diagonals to be sure the floor is square. Bump one 6x6 to the left or right until the diagonals are the same and the floor is square. Go ahead and nail the plywood on. When using 5/8" tongue and groove (T & G), start with the tongue flush with the outside of the floor and the groove towards the inside of the floor. Notice the stamp on the plywood, it usually says place this side down (the tongue is thicker on the bottom). Nail on the first sheet. Just use a few nails to keep the plywood in place and mark where the joists are. Keep them back from the groove side by at least 6" to allow the next sheet to slip into the groove easier. Cut the second sheet in half - 4'x4' and start on the left, the way you laid out the joists. Place the tongue up to the existing groove get your helper to stand on the tongue and groove together while you hammer lightly with a sledge hammer against a 2x4 against the groove side of the third sheet. The sheet should slip into the groove of the one nailed on. Now install the third sheet (full size) at the end of the half sheet. This is called staggering your sheets so the joints are not in the same line. Nail or screw on the plywood securely: nails spaced 6" apart on all joints and 12" apart in the middle.

The Walls

After the foundation is made start on the side walls. Lay them out in place-2x4 studs 45" long. The studs are nailed to a top and bottom plate. Each plate is a 2x4 that is 12' long.

Sheath the walls while they are laying down. Make sure they are square. Stand these walls up, then nail a 12' long 2x6 onto the top plate making the inside flush and overhanging the outside by 2". This 2x6 acts like a strong back to strengthen the wall and keep it from bowing out from weight on the roof as well as forming an overhang for the roof.

The Trusses

Next layout the trusses, full size on the floor. Layout from the measurement on the Truss Layout drawing. Snap a line for the roof where it sits on the 2x6. This line should be longer than 8' - 4". Label it line #1.

Snap another line, #2, up 3' and parallel to line #1. Mark in the center of this layout a point up 10 5/8" from line #2. Square a line down from this point to the bottom line. This is the center line of the truss.

From the center line measure 2' - 8" along line #2 each way out from center, and mark these points. From the center line and along line #1 in both directions mark points at 4' - 2". Connect these three points on each side of the center line. This is the outside line of the truss. Are the measurements of the 2x4s close to mine on the plan? They should be 33 5/8" and 40 1/4".

Now cut these 2x4s to length using your layout as a guide.

You'll notice that the top roof has a 4/12 pitch so the plumb cut for that 2x4 is 4/12 on your square, or 18.5 degrees. Also, the lower part of the roof has a 12/6 pitch. The joint between the two is an equal miter that should be 22.5 degrees if you have a cutoff saw or 4 7/8"/12 on your square for those using a circular saw. The bottom cut on the 40 1/4" piece is 26.5 degrees. Adjust these angles slightly to fit your layout. Be accurate, when you're happy with the joints, mark the two pieces as a pattern (pat) and mark the remaining 2x4s using the pattern. Cut a total of 20 pieces each.

Make your gussets from 1/2" plywood (don't use OSB, K-3 particle board or multicores). Cut them 12" long with the grain running length ways. Nail each side of the gusset with 8 - 2" galvanized nails, spreading them out and making sure the joints of the 2x4s are tight. Glue isn't required here, as there's too much expanding and contracting due to temperature changes.

Make six trusses with the gussets nailed to both sides of each truss. Make two more trusses with the gussets nailed to one side only. These are the gable trusses, which are gussets on the inside of the building. Make two more trusses to trim the overhang. These gussets should be trimmed flush on both edges of the 2x4.

Putting It Together

Now brace up the two outside walls so they are plumb and straight. Notice the Side Elevation drawing and the layout of the trusses to enable the plywood or OSB ends to rest on the center of the truss.

On the top of the walls layout the trusses as shown on this drawing. Extend your tape out 6" from the end of the wall and mark a point at 23 1/4". Place an "X" next to this point so that this point represents the edge of the truss and the truss sits on top of the X, centered on 24". From this point continue marking points along the wall at 24" and an X where the truss will sit. The X's should be on the same side of all the points. Remember to put a gable truss flush with the outside of the wall at each end (with the gussets facing the inside of the building).

To hold the trusses in place before you sheet the roof, nail a 1x4 along the trusses near the ridge. This is where a friend comes in handy to give you a hand. Leave the two overhang (trim) trusses on the ground for now.

To hold that first awkward truss up, brace it temporarily either to a stake pounded into the ground or to the inside of a wall. Nail the bottom of the truss securely into the 2x6 with 3" nails. When all the trusses are up and tied together with a 1x4 near the ridge and braced up nice and plumb go have a coffee.

Sheathing The Walls

Now let's finish off the back wall. With the trusses forming the shape of the roof, just nail studs to the underside of the truss to a plate nailed on the floor. If the shed is not going to be insulated, place these 2x4s on the flat. If insulated place them on edge in the wall. They should be placed at 2' centers and kept flush with the outside of the truss.

On the front end lay out the door jamb, keep it plumb and use straight 2x4s. The header over the door should be at 6' - 8" clearance. Make the header long enough so you can nail each end of it to the inside edge of the truss. It's best to put the header board up and mark its ends along the actual sides of the truss so you are sure to get an exact fit.

Apply the wall sheathing when the framing is complete. The wall sheathing should go over the trusses as well. Nail it well to the truss and to the header, especially around the joints. This is why you didn't put gussets on the outside of the truss, the sheathing takes their place.

Making The Roof

Start ripping the roof sheathing to the measurements required. Start at the bottom, allow an extra 1" for the first row of sheathing to overhang the truss where it sits on top of the 2x6. It isn't necesary to miter the joints in sheathing, butt joints are good. Keep the sheets separate from each other the thickness of a 3" nail to allow for expansion (about 1/8").

Nail up the sheathing at about 12" center in the middle of the sheets and about 6" centers along the ends. Get your friend to help you again by holding up the overhang trusses flush with the end of the roof sheathing, forming a 6" overhang, with the gussets on the inside.

Install your choice of roofing. I prefer fibreglass/asphalt laminated shingles. Follow the manufacturer's very explicit instructions included with their shingles.

The Trim And Door

Now nail the 1x6 trim on the ends of the trusses at the front and back, flush with the top of the roof sheathing.

Nail the 1x4 trim on around the door.

Nail a 1x4 on the inside of the latch-side jamb (the side opposite the jamb the door is hinged to). Offset the 1x4 so it extends about 3/4" out from the door-opening edge of the 2x4 (all along the length of the 2x4). This makes a door stop on the latch side of the door so the door can be securely latched closed.

The door can be made of a framework of 2x4s on the flat and sheathed with OSB to match the walls as shown in the front section drawing. Nail 1x4 trim over the sheathing in the same locations as the 2x4s.

Attach the door to the frame with 3" galvanized strap hinges screwed to the door trim and jamb trim with 2" screws.

For security, I'd recommend a 6" hasp and padlock or heavy duty padbolt (barrel bolt that accepts a padlock).

Build a little ramp to the door to wheel the mower in and you are all set.

Enjoy your new shed!


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