Roof Inspection, Flashing Repair, and Shingle Replacement
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Most roof problems start small: a cracked shingle, a loose piece of flashing, a clogged valley. Left alone, they let water under the roofing and into the sheathing, where rot and mold spread invisibly for years. A twice-yearly inspection from the ground with binoculars, plus a closer look after major storms, catches most problems before they turn into five-figure repair bills.
Ground-Level Inspection
Walk the perimeter of your house and scan the roof with binoculars. You are looking for missing or curling shingles, visible gaps in flashing around chimneys and vents, sagging sections along the ridge line, and debris piled up in valleys. Pay particular attention to the south-facing slopes, where UV exposure degrades shingles fastest. Manufacturer specs from companies like GAF and CertainTeed note that direct southern exposure can reduce shingle lifespan by 15-20% compared to north-facing surfaces.
Check the gutters for granule accumulation. Asphalt shingles shed granules as they age. A handful after a heavy storm is normal, but thick deposits in the bottom of the gutter indicate the shingles are nearing end of life. If you find more than a light coating after each rain, start planning for replacement rather than spot repairs.
Inspect the attic if you have access. Look for daylight coming through the sheathing, water stains on rafters or sheathing panels, and damp insulation. A leak shows in the attic long before it shows on the ceiling below. Bring a flashlight and check carefully around any roof penetration points: vent pipes, chimneys, and exhaust fan housings.
After storms with hail or high winds, look for dents in metal flashing, missing shingles, and debris impact marks. If you find storm damage, file an insurance claim promptly. Most homeowner policies have time limits on storm damage claims, typically 12 months from the event.
Replacing Damaged Shingles
Work on a dry, warm day. Cold shingles crack when bent, and hot shingles tear under foot traffic. The sweet spot is 50-70 degrees Fahrenheit. Most shingle manufacturers, including Owens Corning and IKO, recommend installation within this temperature range for proper adhesive activation.
Lift the edges of the surrounding shingles to expose the nails holding the damaged one. Use a flat pry bar to pull the nails. Each shingle is held by two rows of nails: one through the shingle itself and one through the overlapping shingle above it. Pull both sets and slide the old shingle out. A 10-inch flat bar works better than a claw hammer here because it distributes force without cracking adjacent shingles.
Slide the new shingle into position, aligning it with the surrounding courses. Nail it with four roofing nails placed one inch from each side edge and just above the adhesive strip line. Use 1-1/4 inch galvanized roofing nails for standard three-tab shingles or 1-3/4 inch nails for architectural shingles, which are thicker. Press the overlapping shingles down over the nail heads.
Apply a dab of roofing cement (DAP or Henry's are common brands, about $6 per tube) under the edges of the new shingle and the surrounding shingles you lifted. This reseals the adhesive bond that was broken during the repair. The sealant strip on the shingles needs sustained heat to rebond on its own, so the cement provides immediate hold.
Match the replacement shingle to the existing roof as closely as possible. Shingles darken with age and UV exposure, so new shingles from the same manufacturer and color line will still look different for 6-12 months until they weather to match. Buy a bundle of matching shingles and keep the leftovers for future repairs.
Flashing Repair
Flashing is sheet metal (usually aluminum or galvanized steel) installed where the roof meets a vertical surface like a chimney, wall, or vent pipe, or where two roof planes meet in a valley. Its job is to direct water over the shingle surface rather than letting it seep underneath. Flashing failures are the second most common source of roof leaks after shingle damage.
Step flashing consists of L-shaped pieces along a chimney or wall. If one piece has slipped out of position, push it back and seal the top edge with roofing cement. If the flashing has corroded through, replace it by sliding out the old piece, sliding the new one into the same slot, and nailing through the vertical leg into the wall sheathing. Use aluminum step flashing pieces (available in 10-packs at Home Depot or Lowe's for $8-12) to match standard shingle courses.
Vent pipe boots are the rubber collars around plumbing vent pipes. They crack from UV exposure after 10-15 years. User reviews commonly report this as one of the first failure points on an otherwise sound roof. When the rubber splits, water runs down the pipe directly into the attic. Replace the entire boot assembly rather than trying to patch the rubber. Pry up the surrounding shingles, pull the old boot off the pipe, slide the new one over, and reshingle around it. Oatey and Perma-Boot both make replacement boots in standard pipe sizes ($10-20 each).
Valley flashing comes in two types. Open valleys have exposed metal running down the valley line. If a seam has opened, clean the area and seal it with roofing cement reinforced with a patch of matching metal. Closed valleys (shingled over with no visible metal) are more difficult. Water infiltration in a closed valley usually means the shingles in the valley need to be torn up and the valley re-done, which is a job for a professional roofer.
Common Problems and Their Causes
Ice dams form when heat escapes through the roof and melts snow, which then refreezes at the cold eaves and backs water up under the shingles. The fix is to improve attic insulation and ventilation so the roof surface stays cold and even. Heat cables and ice dam removal products treat symptoms, not the cause. According to the U.S. Department of Energy, proper attic insulation (R-38 to R-60 depending on climate zone) combined with adequate soffit and ridge ventilation eliminates most ice dam problems.
Moss and algae appear as green or black growth on shingles, particularly on shaded north-facing slopes. Moss holds moisture against the roof surface and can lift shingle edges over time, creating entry points for water. Remove it with a 50/50 bleach and water solution sprayed on and rinsed off. Do not pressure wash the roof. Pressure washing strips protective granules from the shingles and voids many manufacturer warranties. To prevent regrowth, install zinc or copper strips along the ridge line. Rainwater washing over the metal creates a solution that inhibits moss and algae growth for 10-15 feet downslope.
Ponding water on flat or low-slope roofs accelerates membrane degradation. Standing water for more than 48 hours after rain indicates a drainage problem. Check drains and scuppers for blockages first. If the roof structure has sagged, adding a cricket (a small peaked diverter) or tapered insulation to direct water toward drains is the proper structural fix. Flat roof ponding is beyond typical homeowner repair and should be addressed by a commercial roofing contractor.
Safety on the Roof
Falls from residential roofs are a leading cause of serious homeowner injury. The Consumer Product Safety Commission reports thousands of ladder and roof-related emergency room visits each year. If you go on the roof, wear rubber-soled shoes with good tread, work only on a dry day, and use a fall-arrest harness tied to a ridge anchor or a solid anchor point on the opposite side of the roof.
Never walk on a wet, frosty, or moss-covered roof. The surface is as slippery as ice and there is no way to recover from a slip on a pitched surface. Even experienced roofers avoid wet roofs.
Extension ladders should extend at least 3 feet above the roof edge and be set at a 4:1 angle: the base placed 1 foot out from the wall for every 4 feet of height. Secure the base on firm, level ground and have someone hold the ladder while you transition onto the roof. Werner and Louisville both make residential-grade extension ladders rated for 225-300 pounds in the $150-300 range.
For steep roofs (8:12 pitch and above), professional roofers use roof jacks and scaffold planks to create a working platform. This is not standard homeowner equipment and requires experience to set up safely. Hire a professional for any work on steep-pitch roofs.
When to Hire a Roofer
Some roof work falls outside the scope of safe and practical homeowner repair. Hire a professional for: large areas of missing or damaged shingles (more than a few), any structural issue like a sagging ridge or spongy sheathing, flashing work on multi-story chimneys, full valley re-shingling, any work on steep-pitch roofs, and any work on tile, slate, or metal roofing. These materials require specialized skills and different tools than asphalt shingles.
Get multiple quotes from licensed roofers. A reputable contractor will inspect from the roof (not just the ground), provide a written estimate with materials and labor itemized, and pull permits for full replacement jobs. Expect to pay $350-500 per square (100 square feet) for a standard asphalt shingle replacement including tear-off, based on 2026 national averages. Prices vary significantly by region and roof complexity.
Check references and verify licensing. A roofer should carry general liability insurance and workers' compensation coverage. Ask for proof of both before work begins.
Frequently Asked Questions
How Long Do Asphalt Shingles Last?
Three-tab shingles last 15-20 years. Architectural (dimensional) shingles last 25-30 years. Premium and luxury shingles can last 30-50 years. These are manufacturer estimates under ideal conditions. Harsh sun exposure, poor attic ventilation, and repeated ice dam damage all shorten lifespan. Regardless of the rated lifespan, begin annual inspections after the 15-year mark to catch degradation early.
Can I Put New Shingles Over Old Ones?
Building code typically allows one layer of new shingles over an existing layer. The benefits are lower cost and faster installation since there is no tear-off labor. The drawbacks are real: the added weight stresses the roof structure, the overlay hides problems in the sheathing underneath, and trapped heat between the layers degrades the new shingles faster, reducing their effective lifespan. If you already have two layers, code requires a full tear-off down to bare sheathing before new shingles go on.
How Do I Find a Roof Leak From Inside the Attic?
Water enters the roof at one point but can travel along rafters and sheathing for several feet before it drips down to the ceiling below. In the attic, trace the water stain upward along the rafters toward the ridge. The actual entry point is usually a nail penetration, a flashing failure, or a crack in the sheathing. Mark the spot from inside, then go outside and look for the corresponding damage from above. On a dry day, you can also have someone spray a garden hose on sections of the roof while you watch from the attic to identify exactly where water enters.