Attic trusses may need strengthening after many years of wear and tear or damage from rot and other things. Attic trusses can also be weakened by heavy snow mounting up on top of them. This is especially the case if the roof is not slanted enough. Fortunately, there are some fairly uncomplicated ways to strengthen attic trusses using reliable methods which are often used in construction.
If you are comfortably familiar with DIY, you should be able to do the job yourself without too much trouble. Give yourself a couple of days to finish the job. The following steps are for a typical roof of a modern house or large outbuilding. For larger roofs and certain types of designs, plywood sheeting will not be strong enough, and a stronger wood should be used. In some cases, metal bracers should be used. However, the principle of installing them remains much the same.
Step 1 - Take Measurements for the Repair Area
Examine the trusses in your attic, and determine which ones need to be repaired or strengthened. Measure the length and width of the truss. Trusses usually come in standard sizes, but this is not always the case, especially in older buildings. Standard size trusses are either 5.5 inches or 3.5 inches in width.
Step 2 - Cut the Plywood
Apply the measurements to the plywood sheeting. There should be two marks made on one end of the plywood sheeting, and these should mark the width of the truss that you measured. Mark the other side of the length of the truss as appropriate. Remember to cut out the length of the wood along the grain line of the plywood sheeting.
Mark and cut out two sections from this plywood sheeting for each truss. These plywood straps will be used as bracers after installing them onto the sides of the attic truss. You can use a stronger wood if necessary, but in the majority of situations, plywood is perfectly adequate, and it is also very cheap.
Step 3 - Attach the Plywood Bracers
Attach the plywood bracers onto the sides of the attic trusses. Have one on each side, and attach them in place with wood glue to start with. Make sure that the plywood strips are properly aligned with any crack on the truss. Also, make sure that the plywood strips align with the edge of the truss so that they do not look untidy.
When you are happy with their position, clamp them in place using the C clamps. Finally, apply the wood screws. three inch wood screws are ideal for this job. They should be attached every 12 inches or so. Make sure that the screws are not applied in any damaged areas of the truss. The screws should extend through the plywood and attach the strips firmly in place.