How to Fix a Roof Leak

Find out how to identify, locate, and repair roof leaks to prevent mold growth, rot, and lasting water damage.

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• Working Time: 6 hours
• Total Time: 1 day
• Skill Level: Intermediate
• Estimated Cost: $100 to $300

The home is a place for relaxation that offers security and protection against pests, heavy rain, ice storms, and other inclement weather. The roof plays a vital role, in preventing rain and meltwater from entering the house while redirecting the flow of water to the gutter system and away from the foundation. However, if the roof develops a leak, it can lead to significant problems, including mold, mildew, wood rot, and severe structural damage. Use this guide to learn how to find and fix a roof leak.

How to Find the Leak

Seeing signs of a leak inside the home doesn’t necessarily mean locating the leak from outside will be easy. Start by heading up to the roof to perform a quick visual inspection. Check the shingles around the area where the leak appeared inside, but also inspect any vents, chimneys, joints, or flashing, as these are prime areas for roof leaks.

Flashing under the gutters and along dormer windows can be a point of entry for a leak. Additionally, roof valleys and roofing sections where debris tends to collect are prone to roof leaks. If you can’t find the damaged area, you may need to recreate the leak with a garden hose.

Have a helper stand by inside the house, and then use a garden hose to soak a portion of the roof in the general area of the leak. It may take several minutes to over an hour for any signs to appear. Have the helper yell when a drip becomes visible to indicate that you are close to the leak. Confirm the location by checking nearby joints and flashing or by prying up shingles to inspect the underlying roof paper and roof deck for signs of discoloration, water stains, or rot.

Safety Precautions

Repairing a roof can be dangerous if you don’t take the proper steps to ensure your safety. All it takes is a simple slip or trip to send you tumbling toward the edge of the roof, followed by a short drop and painful impact with the ground. To avoid this, take a few precautions before and during the repair.

Make sure to have a ladder tall enough for the DIYer to climb onto the roof without standing on the top two steps. A second person should hold the ladder in place when it is in use. After the DIYer on the roof steps off the ladder, the person on the ground should back up until they can see the DIYer on the roof. This makes it easy to communicate and watch for any problems.

The DIYer should wear soft-soled boots and a Personal Fall Arrest System (PFAS) that slows and catches the DIYer if they fall off the edge or a Fall Restraint System that prevents the DIYer from even reaching the edge of the roof.

What You’ll Need

Equipment / Tools

• Ladder
• Caulking gun
• Trowel
• Putty knife
• Pry bar
• Hammer
• Utility knife
• Blow dryer
• Circular saw
• Tin snips

Materials

• Roof sealant
• Roof cement
• Roofing nails
• Shingles
• Roof paper
• Plywood
• Silicone caulk
• Roof vent
• Roof flashing
• Ice and water barrier

Instructions

How to Fix a Roof Leak

The type of roof repair depends on the type and extent of the damage. Repairing a few cracked shingles is relatively simple, but if the damage is widespread, it may be a sign to redo the entire roof. Additionally, a professional roofer should assess and repair severe rot, mold, and structural damage to avoid future issues.

1. Reattach Curled Shingles One of the simple fixes is reattaching curled shingles. Sometimes, shingles curl up on the bottom or sides, but they can usually be smoothed out and reattached in warm weather. Use a blow dryer if the shingles are too stiff to move. Then, smooth out the curled shingles and apply roof sealant under the raised edges using a caulking gun. Press the shingle down firmly and apply roof cement to the edges of the shingle with a trowel.
2. Patch Clean Cracks with Roof SealantWhen the leak comes from a cracked shingle, the solution is to replace the shingle or patch the crack. Usually, clean cracks can be fixed without needing to replace the shingle.Use a caulking gun to apply a bead of roof sealant under the crack and press down firmly on the shingle to ensure there are no gaps. Next, apply a second bead of sealant over the crack. Then, spread the sealant with a putty knife to seal both edges of the crack. You can use a small handful of loose asphalt granules to disguise this repair.
3. Replace Broken or Missing Shingles. If the shingles are broken or missing, you need to get replacement shingles that match the color of the existing roof. Lift the front edge of the damaged shingle. Then, slide a pry bar under the shingle and carefully pry the shingle up to loosen the nails. Remove the nails with the pry bar or a hammer, including the nails from the shingle above. Slide the damaged shingle out. Scrape the area to remove any leftover roofing cement and slide the new shingle into place. Use a blow dryer if the surrounding shingles are rigid, and round the back corners of the new shingle with a utility knife to make the shingle easier to install. Secure the new shingle with roofing nails and replace the nails that were removed from the above shingle. After the new shingle is in position, apply roof cement over the nail heads and the edges of the new shingle to complete the repair.
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4. Remove and Replace Damaged Roof Deck When a leak is left for too long, the water can cause significant damage to the roof paper, roof deck, and any interior material, such as insulation or drywall. This type of repair may be too involved for some DIYers, so consider your skills and limitations before starting this job. Remove the shingles with a pry bar to access the roof paper and roof deck. Use a utility knife to cut away torn or damaged roof paper, but keep as much intact as possible. Cut out the damaged section of the roof deck with a circular saw. Pry out any nails with a hammer or pry bar and remove the damaged section of roof deck. Use this piece of plywood as a template to measure and cut the roof deck patch. Place the roof deck patch in position and secure it with roofing nails. Lay down new roofing paper and install replacement shingles starting from the bottom-most row of the affected area. Leaf the new shingles into the existing shingles from left to right to maintain the established rows. Nail down the shingles and apply roof sealant to prevent leaks. Finish the repair by adding a bead of roofing cement along the bottom and edges of the shingles.
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5. Fix Gaps at Joints, Vents, or Chimneys Leaks can form around flashing joints, chimneys, and vents, so it’s a good idea to inspect these areas if you have a leak. Fixing gaps is relatively straightforward. Start by scraping away old sealant and cleaning any debris around the area. Next, use a thin, flexible putty knife to fill small cracks with roof cement. If the gaps or cracks are located at the metal or rubber collar of a pipe or vent, use a waterproof silicone-based caulk to mend the joints. Keep in mind that any gaps wider than 1/4 inch cannot be fixed with this method.
6. Reattach Loose FlashingIf the flashing comes loose, water may seep into the home. The good news is that reattaching loose flashing is relatively simple. Apply a bead of roofing cement under the flashing and press it down firmly into place. Check to see if any nails are loose or missing. Replace loose or missing nails, and then seal the nails with roof sealant to prevent leaks.
7. Replace Damaged Flashing When the flashing isn’t just loose or slightly cracked, the DIYer must replace the damaged flashing to fix the leak. Use a pry bar to pry off the damaged flashing carefully. Scrape away old roof sealant and cement with a chisel or putty knife. Measure the affected area to determine the correct size and shape for the new flashing, and then use a set of tin snips to cut the flashing to fit the joint. Ideally, flashing should overlap the joint by about 4 inches on each side. Apply strips of ice and water shield to the joint before laying down the flashing. Make sure the ice and water shield strips extend about 4 inches up for any objects that protrude from the roof, like a chimney. Wrap the flashing around the joint and nail it in place. Seal the flashing with roofing cement to prevent water from leaking into the home. How to Install Roll Roofing
8. Remove and Replace Damaged Vents. In some cases, ice, sticks, or years of accumulated rust may have damaged the roof vents. If a damaged vent is the source of the leak, the DIYer should remove and replace the vent. Use a pry bar or hammer to pull out any nails that secure the vent. Then, use the pry bar to lift and pull back any shingles covering the base of the vent. Have a second person hold the shingles out of the way while the DIYer removes the damaged vent. Scrape away roofing cement, sealant, or any other debris to prepare the area. Apply a bead of roofing cement or roof sealant to the vent flashing. Slide the new vent into position and press down firmly to ensure there are no gaps in the sealant. Nail down the vent at all corners and every 4 inches along each side. Apply roof sealant or cement to the nails and edges of the vent. Lower the shingles back into position, and use roof cement to secure the shingles and prevent water from leaking through the roof.

How to Prevent Roof Leaks

The best way to keep the roof from leaking is to regularly inspect the shingles, flashing, joints, vents, and chimney for any damages. Make repairs as soon as you notice the damage to it from worsening.

Beyond regular inspections and repairs, homeowners should keep the gutters clean and free of ice, leaves, sticks, and other debris. Additionally, homeowners need to keep up with the maintenance of nearby trees to prevent sticks, leaves, and other debris from collecting on the roof.