How to Build Dormers Using Structural Insulated Panels

Structural insulated panels, or SIPs, are building materials manufactured for residential and light commercial construction. SIPs have a foam core sandwiched between two boards, usually made of a material called oriented strand board. These boards are used as an alternative to wood, and provide superior strength and durability as well as premium insulation. Using SIPs to create dormers for your second-story building project produces an attractive update while saving you time and money. There are several brands of SIPs available through building supply stores and websites.

Snap chalk line
Crowbar
Tape measure
Pencil
SIP boards
Saw
Nails
Nail gun
2-by-4-inch pieces of wood

Instructions

- 1
  Lay out the dormer according to your measured drawing on the floor of your attic or second story before opening the roof and beginning the construction project. This will be a dry-fit model of the project that you can look at and make adjustments to before building.
- 2
  Mark snap chalk lines on your roof where the dormer will be installed according to your measured drawing.
- 3
  Remove the shingles from the roof with the crowbar from the area where you will be building. Save the shingles if they are still in good shape to use when finishing the dormer. Cut the sheathing board on the roof along the chalk line with your saw, cutting from the bottom to the top and leaving a hole where the dormer will be attached.
- 4
  Draw lines, according to your measured drawing of the dormer, on the floor of the attic or second story underneath the hole you cut in the roof. Use a level and plumb line to make sure everything is plumb before cutting away the rafters in the section of the attic where the dormer will be located. Add new rafters around the edges of the opening where the dormer will be located for additional support.
- 5
  Cut the SIP board for the side and front walls and two pieces for the roof of your dormer according to the measured drawing. Leave an opening in the front wall for the window that will be added later.
- 6
  Set in the SIP side walls into the space cut for the dormer and attach them to the new rafters with nails and a nail gun. Attach the front wall with the window cut out the same way.
- 7
  Frame the roof of the dormer using 2-by-4s cut to the length required by your measured drawing. Lay out the roof frame and attach to the SIP side boards with nails and a nail gun.
- 8
  Attach the SIP roof boards to the dormer roof frame with nails and a nail gun, nailing through the roof board into the 2-by-4 inch roof frame at two-inch intervals along the width of the roof board.
- 9
  Finish by setting in the window. Secure the window to the dormer according to factory directions and seal up any gaps with all-weather window caulking. Add shingles to the dormer with roofing nails and a nail gun.

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