How to Frame a Cross Hip Roof
Of all the different roof designs, a hip roof frame is one of the most challenging roof styles to build. This is because a hip roof does not have any flat sides. Instead each side of the roof slopes downward to meet the walls of the house or building. While this may be difficult to build, the roof style offers more protection in areas that are prone to high winds and hurricanes. A cross hip roof presents even more of a challenge due to the fact that it is almost as if you are putting two hip roofed buildings together.
Step 1 – Create your Plan
Before you begin framing you should consult a professional carpenter, home builder or architect. Any of these people will be able to assist you with the floor plans and give you some idea of the correct elevations and slope of the roof. During the planning process, contact the city to find out what permits, if any, are needed. The new roof will have to meet all city building codes; therefore it is good to know of any restrictions up front.
Step 2- Measure and Calculate
You need to know the area of the roof in order to purchase the correct amount of materials. Area is the length multiplied by the width. Measure the length and the width of the roof and multiply the numbers. This will give you the square footage of the roof and when you take this measurement to the lumber yard, the staff will be able to assist you in determining how much material you need.
There is wastage in every building project and if this is your first project of this nature, you will probably make a few mistakes. Add on an extra 10 to 15% to the calculation of needed material to allow for this.
Step 3 – Cut the Ridge Boards
A ridge board is the board that runs along the top edge of all the rafters of the roof and holds them in place. There is a simple formula to determine how long your ridge board should be. Take the measurements of the roof you had in Step 2 and subtract the width from the length. This is the measurement of the ridge board that you need to cut. Depending on the size of the roof, you may need to join several boards together to achieve this measurement. Cut the boards once you have your measurements. You will need to have two of these for the roof because they have to be placed at a 90 degree angle to each other.
Step 4 – Frame the Rafters
First, lace the ridge boards in position so that they are perpendicular to each other. Nail these boards in place.
Second, cut the common rafters. The common rafters that you need for the roof must be cut to the same measurement as you cut the ridge boards in Step 3.
Third, to start nailing the common rafters in place, you must start with the ridge board. Nail a rafter to each end of this board. Then lift the ridge board and attach two rafters on the opposite end. Line up the walls by pushing the ridge up until the seat cut – a notch in the rafter where the bottom part of the rafters rests on top of the wall - lines up the walls. Secure the rafters in place by nailing them.
Fourth, now nail two rafters to the ends of the ridge boards and nail another one in the center of the end walls. The purpose of this is to make sure that the ridge board stays in place. Continue framing the roof by nailing two rafters to one end of the cross-hip ridge board. Raise the ridge into place, while at the same time making sure that the seat cut is lined up with the ridge board.
Finally, continue adding rafters to both hips. Locate the intersection made by the ridge board and the first set of rafters you nailed in place. Use this as the point at which you will nail the rest of the rafters with them coming from the outside corners of the building.
Step 5 – Finishing
Place the fascia boards and the collar beams where they need to be. Nail on the material you are using for sheathing to close in the roof. Install the flashings in the valley of the roof and then proceed to install your underlay and shingles.