Framing Angled Attic

Begin with a baseline and snap a center line perpendicular to it.

Framing angled attic.

The run or half the building span is the base of the triangle. The polygon roof miter angle is the tangent of the polygon central angle divided by two. Run the plywood down to the top of the knee wall. The tangent of 22 5 41421 laying out an octagon using a framing square we would take 12 on the blade and the number to be taken on the tongue is 12 41421 which is 4 97.

And the line length measurement from the roof peak to the building wall is the hypotenuse. The central angle for an octagon roof is 45. Then add the 2 4 side walls and the roof slope using a square. If you want your attic space to have a flat ceiling you ll need to add collar ties to the framing.

The rise or height of the roof at its peak is the altitude of the triangle. Collar ties are horizontal members that like rafter ties extend from rafter to rafter but. One half of 45 is 22 5. The plywood will create a smooth strong ceiling without having to apply drywall tape and mud to the ceiling.

Use screws to attach sheets of birch plywood to the angled ceiling over the insulation making sure to drive the screws into the ceiling joists. Use the 3 4 5 triangle method to make the 90 degree angle. The framing of a basic gable roof is based on a right angle triangle and the various roof framing components fit the triangle.