If you want additional support for wood framed roofs with concrete or clay tiles, add rafter collar ties. Collar ties are also useful in areas that get a large amount of snow. Rafter ties are installed in the attic on every other set of opposite rafters under the roof peak or ridge.
You should be able to install rafter ties yourself. Here are tips to install roof rafter ties.
Prepare to Work
For this project, you need:
- work gloves
- safety goggles
- tape measure
- 16D nails
- circular saw
- framing square
- tie plates
- two by six or two by four plywood three-fourths inch thick
Construct two catwalks out of plywood above the insulation. The extra catwalk is for the assistant. Don't touch insulation with bare hands. Be aware of HVAC ducts.
Trim a plywood board to two feet long and ninety-six inches wide with the saw. Place the board down starting at the attic entrance on the ceiling joists under the roof ridge. Move the catwalks as needed.
Measure vertical length from the top of the joist to the roof ridge, then divide this figure by three to get the height of the collar ties. Make a mark on a rafter sixty-four inches above the joist. Move the catwalk, and mark sixty-four inches from the joist on the opposing rafter.
Measure between the opposing roof rafter and divide this result in half to get the number of ties that need installing. Measure horizontally between the marks on opposing rafters, Note the numbers of opposing rafters at the ridge, and divide this number by two to get the number of collar ties needed.
Install the Collar Ties
Mark the horizontal measurement on the plywood, and cut the board to fit with the circular saw. It isn't necessary to cut angles, unless it is required by the building codes or architect of record. If angles are needed, find the pitch of the roof with the framing square, and mark the angle on the collar tie, and draw the line across the board.
Get an assistant to help you attach the other end of the collar tie. Place the collar tie flat against the marks on the lower edge. Use a level to ensure evenness.
Nail in the rafter collar ties, so it forms a triangular pattern on each end. Install additional collar ties in the same manner. Nail a tie plate on the joint between the rafter and collar tie, ensuring all the nail holes in the plate are filled. Each collar tie needs a tie plate on two sides, top, and bottom.
Your roof will be able to support more with with rafter collar ties. If the roof is seriously damaged, contact a roofer from a company like HomeTowne Roofing if you don't trust your skill.