How to Repair a Flat Roof

When repairing a flat roof, you must first find out where the leak is coming from. Since flat roofs are made up of multiple layers of tar and roofing felt, leaks may be more likely to occur at low spots or in areas where a roof is visibly damaged. If you’ve already found the source of your leak, skip ahead to the flat roof repair steps below.

Finding a Flat Roof Leak

While flat roof leaks are commonly located directly beneath the damaged area on the roof, finding where the leak originated can sometimes be tricky. If the leak isn’t as obvious, you can use the following tips to help find the source of the flat roof leak:

  • Clear all debris and examine the roofing membrane to search for tears, blisters, worn areas, loose seams, and other flaws.
  • Examine roof flashing, caulk, and collars around vents. Check for any cracks, decay or overlaps. If you find any cracks, this is likely the source of the flat roof leak.
  • Where you found the water leak, doesn’t necessarily mean that is where the source of the leak is. Water can enter the roofing membrane and then travel a short bit of distance until it has found a seam to enter. Since most flat roofs are very slightly rounded, you’ll want to inspect the area where the leak entered and then up the slope – as water could have traveled down.
  • Run water with a garden hose along any areas of concern. Wait inside for a few minutes so the water has had time to make its way down the roof to the potential leak. If you’re still unable to pinpoint the source of the leak, you can also try hosing the roof in sections.
  • If you’re still unsure of exactly where the flat rook leak is coming from, it may be time to call a roofing professional. Some roofing contractors offer free inspections to come out and look at your flat roof to analyze damages.

Things You’ll Need for Flat Roof Repair

To successfully complete this simple project, you’ll need the following items for your flat roof repair:

How to repair a flat roof leak

  • Rags for soaking up water
  • Utility knife
  • Safety goggles
  • Asphalt roof cement
  • A trowel
  • 6d galvanizing roof nails
  • Hammer

Preparing to Repair a Flat Roof Leak

Before you begin to repair a flat roof leak, you’ll want to check if water has pooled in the leak area. If water is pooled over a leak on a flat roof, soak it up before attempting any repairs.

Allow the surface of the roof to dry completely and brush off any residual gravel. Take this time to assess the roof for obvious cracks in the felt or large blisters that have separated the top layer of roofing materials.

Steps for Flat Roof Repair

Once you find a visible blister on a flat roof, you can use these steps for a quick and efficient repair:

Step 1:

Cut a blister with a utility knife down the middle; cut deep enough to penetrate the depths of the blistered layer without cutting through the felt underneath.

Step 2: 

Lift up the cut edges of the blister and squeeze out any accumulated water from the edges toward the center.

Step 3: 

Soak up water completely and open the edges of the blister to allow roofing layers to dry.

Step 4:

Spread a thick layer of roof cement over the bottom edges of loose felt and press in place against the perimeter of the blister.

Step 5:

Nail the blister closed with 6d galvanizing roofing nails in lines along both sides of the cut.

Step 6:

Spread more roofing cement over the blister to ensure that nail heads are sealed completely.

As a note, if you open a blister on a flat roof and find a large amount of collected water, the problem may be much bigger than you can handle on your own. If water has leaked into a flat roof from the adjoining surface of a pitched roof, a professional roofing company will be needed to assess the extent of the damage.


Professional Flat Roof Repair

Need help repairing your flat roof leak? A & J Reliable, Inc. offers immediate roof repair services throughout the tri-state area, including New York and New Jersey. As one of the leading roofing contractors in the industry, we’re dedicated to saving our customers money by solving small problems before they become costly replacements. For more information about our flat roof repair services or to schedule a free inspection, please contact us today.