Roof Leaks Are Elusive
Finding roof leaks can be tricky for a couple different reasons. One is the way water behaves once it gets past a shingle, flashing, or joint. Moving generally downhill under the power of gravity, it then flows along the path of least resistance and can cover a goodly distance thanks to surface tension. It can, for example, travel a number of feet along drywall seams or beams before forming a puddle or damp spot where a person is likely to notice. Which is to say, the actual roof leak can be a long way off from the place where you discover dampness or water.
By the same token, roof leaks can admit water for weeks or months before the damage becomes visible to the casual observer. In that time, the water can do significant damage. It can deteriorate building materials and foster the growth of mold.
But Roof Leaks Can Be Found
The good news is that though it may take an expert to locate them, roof leaks can’t hide forever. The experts hunt them down by checking insulation and sheathing, following staining, and scanning the insides of walls. Specialized equipment like thermal cameras, moisture meters, and supplemental lighting is deployed as needed to aid in the search. Once the roof leak is discovered, it’s tarped and roof leak repair begins.
Common Locations of Roof Leaks
Naturally, when undertaking the hunt for roof leaks, it gives you an advantage to know where they often develop. Here, then, are some common locations.
Roof Leaks and the Shingle Field
In older homes, the problem is often in the roof field. If you want to check the roof yourself, be aware that an asphalt roof is easy to walk on. Clay tile, concrete tile, and slate are trickier. Your weight can crack them if you’re not careful.
If you’re checking regular shingles, examine the tops of the vertical knockouts. You’re looking for cracks, missing colored granules, or nails hat have backed out of the roof sheathing.
Roof Leaks and Roof Valleys
Valleys are the low places where two roof planes come together. They can develop links when shingles are incorrectly trimmed. When they are correctly trimmed, the roofer has made two cuts, not just one.
Roof Leaks and Head Wall Flashings
Your roof may end at a wall. If so, the wall needs a metal flashing to aim water down the wall and away from the shingles. The flashing needs to extend over the shingles for at least three inches, and if the wall is made of brick or other masonry, the flashing should bend and extend one inch into a mortar. If you see caulk or roofing cement, you know somebody has tried to plug a roof leak.
Roof Leaks and Wall Step Flashing
Step flashings are found where a roof climbs alongside a vertical wall. A separate step flashing goes over each shingle at the end of a row terminating at the wall. Rust or holes reveal the likely presence of a roof leak.
Roof Leaks and Plumbing Vent Flashings
When plumbing vent flashings combine an aluminum flashing with a rubber seal, the seal can fail in as little as ten years. Look for cracks in the rubber around the plumbing pipe, and make sure the flashing runs up to and under the shingles that extend up roof from the middle of the plumbing vent. The lower half of the flashing should actually cover the shingles.
Roof Leaks and B-Vent or Furnace Flashing
These flashings are much the same as plumbing vent flashings though sometimes with a metal storm collar that should fit snugly around the vertical pipe exiting the roof. When the collars come loose, roof leaks can result.
Roof Leaks and Chimneys
A chimney contains four different kinds of flashings, all of which must be in good working order to prevent roof leaks. The counterflashing in the brick mortar needs to function properly as well. Even a hairline crack can let a lot of water get behind the flashings.
Check soldered flashings for broken corners and holes. If you find them, don’t use caulk to attempt roof leak repair.
Roof Leaks and Ice Dam Problems
Ice dams are a problem for people living in snow country, and they can produce roof leaks even when the roof itself is in good repair. They’re frozen blockage that keeps water from flowing where it’s supposed to. Instead, it backs up and gets under shingles, tar paper, flashing, etc. and from there drips into the interior of a house. The only sure remedy is membranes installed under the roofing to keep the water out.
Roof Leaks and Wind Driven Rain
This is another problem that can result in roof leaks even if the roof is in good shape. The wind can drive rain up and under the roofing materials in much the same way that an ice dam can send it there.
Once again, membranes can protect the house, as can tar paper. Additionally, if the house has metal valleys, hemming the edges gives the hidden edges a 180-degree bend. This moves wind-driven rain back to the bottom of the valley. Roofing cement under shingles at the edge of the roof can help as well.
Roof Leaks That Aren’t
Finally, be aware that the seeming appearance of a roof leak can be deceiving. Condensation, possibly resulting from high humidity, may be the real culprit responsible for dampness in the house. A cracked chimney crown or missing siding can also counterfeit the effects of roof leaks.