Building a slanted shed roof

A slanted shed roof is a great roof to increase your living space. This is not a difficult project and it can be done easily if one of the walls is taller then the other one. If the walls are equally high, then you can do two things.

You can raise one wall by installing additional layers of plates, or you can build a wood frame of the wall and install it over it.

Some of the materials required are:

  • Lumber
  • Sliding T bevel
  • Carpentry tools
  • Nails
  • Framing square
  • Reciprocating saw


First of all you will need to measure the span of the roof. You can then calculate the length of the common rafters, by subtracting the thickness of the taller wall from the total span of the shed.

To measure the rise of the roof, take the difference between the two walls. Then add the depth of the common rafters and subtract the value of the seat cut. Transform the value in inches and then multiply it by the length of the run. Divide the result by 12 and you will get the size of the common rafter needed for spanning an external wall and reaching the inner side of the other wall.

Rafter seats

Cut the common rafter seats at the right size. These will help fix the rafters to the wall plates. Use a carpenter’s square and a measuring tape.

Seat cut

Now you can make the cuts for the other seats. Measure the distance between the heel plumb line and then use it to measure the entire run of the common rafters. the two seat cuts will be facing the same side.

Finalizing the construction

Use nails to bind the rafters together. You can also use fillers and block stiffeners. Take the fascia rafters and boards and put them into place. You are advised to use lookouts with ladder framing to go along with the fascia rafters. After the frame is finished, use plywood to cover the entire roof.

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