How To Patch a Leaking Rubber Roof

Flat and low-pitch roofs are especially vulnerable to roof leaks and water damage, but homeowners can help to prevent these by patching up rubber coverings. With just a few tools, you can fix up a rubber roof to prevent it from leaking. Learn how to patch a leaking rubber roof in our step-by-step guide below, and watch the video above for tips from This Old House general contractor Tom Silva.

Understanding Rubber Roofs

Rubber roofs, also known as EPDM (ethylene propylene diene monomer) roofs, are popular because they’re durable and cost-effective. You can frequently find these roof types on flat or low-slope structures. They can last up to 30 years if you maintain them properly.

These roof types come with certain challenges and maintenance needs, though. Below are some reasons rubber roofs might leak.

• Age-related deterioration
• Damage from foot traffic
• Improper installation
• Punctures from falling debris
• Seam separation

You can usually fix a leak that’s caused by a puncture, tear, or seam separation yourself. The first step is to find the leak.

Identifying the Leak in a Rubber Roof

Find the source of the leak before you patch your rubber roof. Inspect carefully and take your time, as water can run through the underlayment and cause damage some distance away from the leak itself.

Visual Inspection of the Roof

Examine the roof surface for signs of damage. Inspect thoroughly for the potential issues below.

• Cracks or tears in the rubber membrane
• Loose or separated seams
• Punctures or holes
• Standing water

Interior Inspection

Check your attic or the rooms directly below the roof for signs of water damage. Internal signs, such as those below, can provide clues to the leak’s location.

• Damp insulation
• Mold or mildew growth
• Water stains on ceilings or walls

Remember that you may not find damage directly beneath the leak, but that’s a good place to start looking. Contact a professional roofer if you can’t find the leak.

Preparing for the Repair

Once you’ve identified the leak, gather the tools and materials below in anticipation of the repair process:

Tools

• 3-inch paint brush
• 3-inch paint roller
• Caulk gun
• Drill/driver
• Framing square
• Measuring tape
• Utility knife

Materials

• EPDM rubber roofing material
• High-density fiberboard substrate
• Lap sealant
• Membrane cleaner
• Rubber-to-rubber contact cement
• Screws and metal washers

Safety Tips

Keep yourself safe by following the tips below, whether you’re working on a flat roof or a pitched roof:

• Ask someone to hold the ladder securely as you climb it. 
• Avoid working on the roof during wet or windy conditions to prevent slips or accidents.
• Cover any skylights with plywood so that you don’t step through them.
• Wear gloves to protect your hands from sharp tools and materials.

Patching the Rubber Roof

Follow the steps below to patch your leaking rubber roof. Remember to only cut materials off the roof or on top of a piece of scrap fiberboard. Otherwise you may cause another leak.

1. Cut around the damaged area: Use a utility knife to carefully slice through the rubber roofing around the leak. Create a square or rectangular opening.
2. Remove the old roofing: Peel back the section of rubber roofing to expose the substrate.
3. Replace damaged substrate: If the fiberboard substrate is wet or damaged, remove it by unscrewing the metal washers that hold it in place. Cut a new piece of high-density fiberboard so that it fits the area.
4. Install new substrate: Place the new substrate into the opening and secure it with screws and metal washers.
5. Prepare the patch: Cut a piece of EPDM rubber roofing that’s about 12 inches longer than the repair area on all sides.
6. Clean the surfaces: Apply membrane cleaner to the roof area around the repair and the underside of the rubber patch so that the patch adheres properly.
7. Apply contact cement: Use a paint roller to apply rubber-to-rubber contact cement to half of the repair area and half of the rubber patch. Allow it to dry for about 10 minutes.
8. Position the patch: Carefully align the rubber patch with the repair area. Press it down firmly without stretching the material.
9. Complete the patch: Fold back the unglued half of the patch and apply contact cement to the remaining areas. Once the contact cement is dry, press the second half of the patch into place.
10. Seal the edges: Apply a bead of lap sealant around the entire perimeter of the patch to create a watertight seal.

Tips for a Successful Repair

You must carefully prepare and handle rubber patching materials to successfully make repairs. Follow the tips below to successfully stop leaks:

• Apply even pressure when you adhere the patch to eliminate air bubbles.
• Avoid stretching the rubber patch. This can lead to future leaks.
• Clean the repair area thoroughly before you apply any adhesives.
• Work on a dry, calm day so that moisture doesn’t interfere with adhesion.

Maintaining Your Rubber Roof

Maintain your rubber roof regularly to extend its life. 

Maintenance and Cleaning

Follow the steps below to keep your rubber roof in top condition. 

• Clean the surface with a mild detergent and water to remove dirt and organic growth.
• Inspect your roof twice a year and after severe weather events.
• Keep the roof clear of debris, which can puncture the membrane.
• Reapply lap sealant to seams and edges every few years.
• Trim overhanging tree branches to prevent damage from falling limbs.

Regular Inspections

Conduct regular inspections to identify potential issues before they escalate. Consider the tips below.

• Check for any new cracks or tears in the rubber membrane.
• Hire a professional to perform an inspection once a year.
• In the fall, remove fallen leaves and inspect for any damage that summer storms have caused.
• In the spring, check for damage from winter weather, such as ice or snow buildup.
• Look for signs of aging or wear, such as brittleness or discoloration.
• Make sure you have secured seams and edges, and that they show no signs of separation.

When To Call a Professional

Many types of rubber roof repairs can be do-it-yourself projects, but some situations warrant professional help. Call a professional if any of the variables below apply to your roof. 

• Extensive damage that covers a large area of the roof
• Multiple leaks or systemic issues
• Structural damage to the roof deck
• Your roof is 30-years-old or older

If you’re uncomfortable working at heights or lack the tools necessary to complete repairs, call a professional. Look for licensed and insured roofing contractors that have experience with rubber roof repairs. Check reviews and references to make sure the contractor you hire has a good reputation. Request estimates from multiple contractors, and compare pricing and services.

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