Few home repairs are as important as repairing a missing roof shingle. The roof, after all, keeps us out of the rain and snow, and it does so by acting as a unified system of several layers. The system works best when each layer is intact.
A missing shingle allows water to penetrate the wooden layers below. Even if things have not reached the point of breaking out the buckets because it’s raining indoors, moisture that gets past the shingles will quickly start to compromise the entire system. Wood and water are never a good mixture.
A torn shingle can cause similar problems, but it may not need replacement if it is in decent shape otherwise. Instead, apply roofing cement beneath the tear, press the shingle down into the cement and apply another bead of cement on top of the tear. That may be enough to hold things together.
If the shingle is missing or too far gone, it needs to be replaced. For that job, you will need a pry bar, a hammer and a utility knife. You will also need roofing nails and, unless this is a large-scale job that needs gallons of cement, a tube of roofing cement. Finally, you need a new shingle. If you do not have shingles left over from the original roofing job, your only option is to buy a bundle of new shingles that are the closest possible match.
When shingles are first installed, roofers work from the bottom up, nailing down one course at a time until they reach the peak. As a result, replacing a shingle starts from the top down.
Begin by sliding the pry bar under the row above the missing shingle and lift that upper shingle enough to loosen it. Loosen the next row above in the same way, since nails from that row go through the layer to be replaced.
Using the pry bar, remove the nails that are holding the damaged shingle in place. If the shingle is completely gone, remove the nails that would prevent you from sliding a new shingle into place. The goal is to install the new shingle directly onto the roof’s wood sheathing.
If the edges of adjacent shingles are ragged, use the utility knife to straighten those edges. Use the same tool to cut the replacement shingle to fit.
Next, add a bit of cement to the back of the new shingle and slide the shingle into place so that it goes beneath the two rows of shingles above. While holding the upper shingles away from the replacement, nail the shingle to the sheathing. It never hurts to apply a dab of cement to each of the new nails and to add some to the back of the new shingle along its bottom edge, so that it adheres to the row below.
The upper rows of shingles that were loosened can now be nailed down in their original positions. If the original nail holes were not used, cover each of those spots with a dab of cement.
Sometimes shingles are reluctant to lay flat after they have been raised. In that case, use cement where anything is curling and place a brick on any problem area overnight.
Repairing a missing shingle is relatively straightforward, but roof work can be dangerous. Take sensible precautions and avoid working when the roof is icy or wet and when the weather is especially windy.