Ponding or Standing water on a Flat Roof can cause leaks

1. Skylights on flat roofs

Making Skylight Repairs on a flat roof can be tricky. Here are a few tips where you can begin.  Check the following on a skylight:

• Skylight flashing – make sure that the rubber membrane has not come loose from the metal flashing. In some cases, the rubber membrane is the flashing as well and is tucked underneath the skylight frame. In other circumstances, the membrane is attached to the skylight flashing. Pull up on the membrane and see if you can lift it from the flashing. It should be tight and secure
• Skylight Dome and Frame – when the glass or plexiglass dome of the skylight is secured with a metal frame, then it is likely that the rubber gasket that seals between the glass and the frame has dried and cracked

• Corners on skylights – In many cases where the rubber membrane is galvanized around the corners of the skylight, can cause leaks due to the seams separation
• Cracked Plexiglass – The plastic or plexiglass domes on skylights crack due to ultralight exposure

A List of Manufacturers of Skylights:

• Wasco Skylights

• VELUX Skylights

• Bristolite Daylighting Systems

• American Skylights: Custom Skylights

• Commercial Skylight Manufacturer – Architectural Skylights | Plasteco

2. Bathroom Vent pipes – Flat roof repairs

Vent pipes piercing through a rubber membrane can become the cause of a flat roof leak. The rubber gasket or “roof boot” deteriorates over time and crack causing the leak.

• Check the “roof boot” around the vent pipe
• Check the rubber membrane and seams that attaches to the metal flange of the “roof boot”
• Sometimes the “tar” that is used to seal the  pipe to the rubber, gets dry and crack, causing the leak

3. Pitch-Pockets on flat roofs causes leaks

A Pitch-Pocket is a bottomless container that is placed on a flat roof where airconditioner pipelines and wires are fed through. After the wires and pipes are fed through, the container is filled with liquid “tar” or roof cement to seal around the wires and pipes.

• Check the pitch-pocket and see if it is full to the brim with tar. Many times this tar will dry and shrink and cause a low spot in the container. When it rains, this low spot will collect water, and water will eventually leak through where the wires and pipelines are.
• Check the foam insulation that covers the pipelines. This foam deteriorates and causes openings where water can leak through the Pitch-Pocket.
• As a precautionary step, these pitch-pockets should be filled to the brim at least once a year.
• When looking for a leak on a flat roof, always check the pitch pockets to see if the tar in them is filled to the brim.
• Flat Roof Repairs can easily relate to a Pitch-Pocket that has wires and pipes going through it, and all you need to do is make sure the insulation foam around the pipes is not the cause of the leak.

4. Flashing on flat roofs causing leaks

Flashing is probably the biggest cause of flat roof leaks. Many roof technicians will not take their time and make a proper flashing transition from a rubber membrane to flashing. This can be attributed to lack of experience or did not charge enough for the job.

• Counter flashing – whenever flashing is used where a roof meets a wall, there must be proper counter flashing. Counter flashing is when siding or stucco or any other methods are used to cover the flashing from the top side. One should never be able to see the edge of a flashing.The vertical section should be covered by stucco, wood siding, or even other metal. The horizontal part that lies flat on the roof, should be covered by the rubber membrane.
• Test the rubber adhesion on the metal – try to pull the rubber membrane away from the metal, if it comes up easily, then that could be the cause of the leak.
• Check for cracked stucco or siding – If the siding or stucco has cracks in it, then the counter flashing is compromised.

Flat Roof Repair – Installing Counter Flashing

The brick wall in the image shows that the membrane was brought up the wall about 12 ” high. They then adhere the roofing membrane to the wall. This way of making flashing doesn’t work. The membrane will eventually pull away from the wall. We cut a slot into the brick wall at a 30 degrees angle.

After the slot was cut, we inserted a metal counter flashing that hang over the membrane. This is what counter flashing is and how it is done.

Flat Roof Repairs mostly involves flashing on flat roofs that were not done correctly.

5. Chimneys – the Cause of Flat Roof Leaks

The counter flashing on chimneys is always a problem on chimneys. Many times, the counter flashing has to be embedded in the stone or brick wall. This is where most people don’t get it right.

• Check if the sealant that is used on the counter flashing still holds
• Check if the counter flashing is still intact
• Check for cracks in the chimney
• Inspect the chimney crown – This is the topmost part of the chimney – Most of the time, these cement slabs crack and causes leaks.
• Make sure the rubber membrane is properly attached to the flashing on the chimney.

In the image, notice where the metal flashing meets the cement grout. That little crack is where water leaks from on a flat roof

7. Drains – Flat roof repairs around drains

When a drain is leaking, it is not always necessarily what causes the leaking. Because the drain is normally lower than the rest of the roof, a leak could start somewhere else and flow towards the drain underneath the roof membrane.

To locate a leak around a drain area do the following:

• Try to open the ceiling where the drain is coming through the roof and make a visual inspection
• Clean all debris that has accumulated around the drain and strainer
• Remove the strainer to make a visual inspection of the drain pipe from above
• Make a close-up inspection of the roofing membrane and the drain flange to see if it hasn’t separated
• If you cant find an obvious problem, call an experienced roofing technician to find and repair the leak

8. Dripedge – Locating the roof leak at the perimeter of the roof on the drip edges

Drip edges are made of metal and make the transition from the roofing membrane to the gutter or edge of the roof

Things to inspect to see if the drip edges are causing roof leaks:

• Inspect to see if the membrane is still attached to the metal edging on the perimeter of the roof
• Check where two drip edges overlap for a potential gap or crack on the roof
• Make sure the drip edges are still properly attached to the substrate
• If gutters are present, make sure the drip edges are pointing into the gutter and not behind the gutter