I damaged one of my attic roof trusses by accidentally knocking out a large knot from the main cross member. Although it seems sound, I think that the strength of the truss has been weakened. If I want to add a sister repair to the truss, how should I do it?
Ian ~ Virginia Beach, VA
Ian, if you are concerned about the structural integrity of your attic roof truss, then you could add some additional support to the damaged cross member. One way to do this would be to glue and screw a 2x4 to each side of the damaged area, which would basically sandwich the damaged truss chord between two stronger pieces of lumber. The length of the new pieces of wood will depend on which portion of the truss is damaged, but in general longer boards should increase the strength of your repair more than short boards.
When installing the new boards, use a heavy duty construction adhesive and some stout decking screws that have sheer strength (meaning: don't use drywall screws!). Another option would be to install two steel carriage bolts on either side of the repair, which would secure together the damaged truss chord with its two new "sister" boards. Although your repair may be more than adequate for the weight of the load that the truss is actually supporting, you could always hire a structural engineer who works in the Virginia Beach area to inspect the repaired truss and offer their informed opinion.