What to Do About a Sagging Roof?

Causes

• A complex network of ceiling joists, alternate beams, ridges and rafters make up standard roofing systems in homes. The joist and rafters configure a triangle or truss unit that helps support the rooftop, and forms the ceiling above each floor of the house. Joists function as beams that provide vertical support for the ceiling, as well as counter the horizontal load of rafters. However, if the ceiling joints are not installed properly over walls, they can loosen and pull apart. As a result, load-bearing walls begin to move outward and cause the roof rafters to shift. This outward movement causes the roof to drop or sag. Cracks can also form in the ceiling drywall near areas where the ceiling joists are strained. Ceiling joists that are not aligned with rafters can also contribute to a sagging roof.

Solutions

• Ideally, it is best to work from the top of the roof to repair damaged roof trusses, decking and rafters. Remove roof sheathing, underlayment and roof decking to access the damaged truss members underneath. Use structural steel channels to restore the shape of roof rafters and truss members. Remove debris such as splintered wood before mounting the steel channel to the truss or rafter. Position the channel to the damaged members using lag bolts tightened with washers. Add supports to provide extra reinforcement where the members have been repaired or reconnected. Replace damaged or broken gusset plates with plywood gussets on each side using a pneumatic nailer. Plywood panels can also be used as a temporary solution to cover damaged roof decking.

Prevention

• Regularly inspect your roof at least twice a year to catch signs of sagging or cracking in the roof. Start your interior search in the attic. Look for water damage including leaks, dark spots and trails. Note any cracks and holes. On the exterior of the roof, flag blistering, rotting, curling or missing roof shingles. Scan for loose materials and erosion around chimneys, vents and pipes. Also note any signs of rot, algae growth and mold caused from dripping water and excess moisture. Other inspection tasks include ensuring gutters and downspouts are attached securely, and that house vents lead outside rather solely into the attic.

Considerations

• If you are experienced with structural repairs, select a time during the year that will allow you to repair your roof quickly and safely. Getting to the damaged area during icy, snowy or wet weather will cause delays and obstacles. Instead, contact a professional contractor to properly assess damage and brace weak areas along the roof.