How to Patch Up a Leaking Flat Roof

Roofing leaks can be frustrating and cause huge amounts of damage in a short time. Flat roofs present an added challenge in determining where the leak is originating. The actual damaged roof can be many feet away from where the leak manifests itself. A little patience and roofing cement will keep the rain right where it belongs--outside.

Difficulty: Moderately Challenging

Instructions

Things You'll Need:

• Drill with screwdriver bits
• Small brush
• Chisel
• Hammer
• Tape measure
• Roofing cement
• Small paint brush
• Garden hose
• Tin snips
• Replacement flashing

Patching Leaks in the Flashing

1. Inspect the roof for loose, worn or damaged flashing. All HVAC (heat, ventilation and air conditioning) units, chimneys and skylights are surrounded by flashing material.

2. Remove the suspect flashing using a drill with a screwdriver bit. Use a small chisel and hammer to pry the flashing loose if it is stuck.

3. Clean the area with a stiff brush. Look for any obvious cracks in the roofing material beneath the flashing.

4. Spread a thick layer of roofing cement over the area beneath the flashing. Force the cement down into any cracks. Extend out from the area being repaired by 2 or 3 inches on all sides. Wait 10 minutes before reinstalling the flashing. Cut any new flashing to fit by using a pair of tin snips. Drill screws in to fit flashing tightly to the roof.

5. Wait the recommended drying time on the roofing cement label and run a garden hose up to the roof. Spray water on the repaired area for 10 minutes and check indoors for leaks.

Patching Due to Roofing Materials Failure

6. Locate all areas of leaking and mark them with a piece of fluorescent chalk, which can be purchased at Lowe's or Wal-Mart. Tim Carter at Ask The Builder gives some great tips for locating flat roof leaks. Check out the resource section at the end of the article for assistance with this. Cut open any obvious areas of cracks, holes or bubbles. These are all a sign of long-term roof leak problems.

7. Clean the area using the stiff brush. Remove any pebbles and loose or damaged roofing materials. Expose all areas that are cracked and in need of roofing cement.

8. Apply a thick layer of the roofing cement up to 3 inches out from the area being repaired. Force cement down into any cracks or obvious areas of damage. Allow recommended drying time and then wet the repaired area with a garden hose for 10 to 15 minutes. Check the inside of the building for leaks.

Tips & Warnings

• Take time to determine exactly where all of the leaks are. It's better to do it right the first time. Clearly mark every leak you have located.
• Follow all safety precautions on the roofing cement label. Be aware of the proximity of the edge of the roof as you move around. Move slowly if you are near an edge.

References

• Monster Guides: How to Repair a Leaking Roof
• Rustic Girls: DIY Home Repair

Resources

• Ask the Builder