How to Help a Sagging Roof

Examine the interior of the roof from the attic. Note the location of any damaged rafters, joists or truss gusset plates.

Lay down tarps around the foundation of the house. Climb a ladder to the roof, and remove the shingles in the sagging areas with a shovel. Place the shingles on the tarps.

Cut out any wet or rotted plywood decking with a handsaw. Reinforce any wood framing that has small cracks with new boards. Fasten the boards into place over the cracks with framing grade screws or nails.

Wedge propping boards from floor to ceiling on either side of a large crack. Remove the damaged wood with a handsaw. Fasten the new wood into place with framing grade screws or nails. Replace any damaged truss gusset plates. Remove the propping boards from the repair.

Replace the damaged plywood roof decking with new decking by nailing it in place to the roof frame from above. Lay down an underlayment such as tar paper, and nail it into place on the roof decking. Nail the roof shingles into place. Screw in ice shields on the lower edges of the roof to prevent water damage to the roof decking.