Prow roofs constitute a particular type of roof framing that is popular on Viceroy-style houses and many modern log homes. As shown in the photo, the roof is a normal, gable-style framing, but each end (or sometimes only one end) will jut out a few feet farther than the end of the home. This creates a small covered nook and offers added protection for windows and/or siding on houses in harsh environments. Building prow roofs may seem daunting, but with accurate calculations, the process can be carried out by most able-bodied carpenters. If you are building a home and would like to incorporate a prow roof into your design, this article outlines the basic steps in designing and constructing one on an already built wall structure.
Install the prebuilt rafters for the roof, as you would a normal roofing system. Prow roofs really only differ in construction at the ends; thus, you need to mount and nail the middle rafters for your roofing run as normal. Depending on how long your roof will be, you can either install rafters on a 2-foot, 3-foot, or 4-foot center. The longer your roof, the longer each run between rafters should be. Mark each run on the wall's upper sill plate, then have a helper assist in lifting the rafter in to position as you nail it to the sill plate. Be sure to install rafters all the way to the end of the walls.
Mount the roof cap boards onto the tops of the rafters, or the "peak," and let the ends of the boards extend past the ends of the walls. The length of extension you leave is up to personal preference; however, most prow roofs only extend 3 to 4 feet past the edge of the walls.
Measure from the end of the ridge cap boards to the base of the last rafter on each end of the house. This measurement will be the length of your prow side supports. Use the saw to cut two 2-by-4-inch boards to length for each prow end. Use a miter saw to cut a 45-degree angle into the ends of the 2-by-4-inch boards, so they will fit flush on the rafter bottom and ridgetop board.
Nail the prow side support boards to the base of the end rafters, and to the ridgetop board. If the span is greater than 2 feet, add a support crosspiece from the prow support to the rafter.
Cover the entire roof with the plywood to provide a solid base. This step in the construction can go very quickly, as very few angles (excluding the ones on the prow) have to be cut. Nail down each piece securely. Cover the roof with the tar paper, tacking it down with staples or tacks; then install your shingles or other roofing material according to the manufacturer's specifications.
Some roofing companies can even provide prebuilt prow roofing rafters for very reasonable prices. Work with your rafter company to explore the options that may be available to you.
Always wear the proper safety gear when working on roofs. Safety harnesses and sturdy footwear will help prevent accidental falls.