Costly Flat Roof Leaks – 10 steps to Find and Repair Leaks DIY

Is it the Flashing that causes a leak?

Flashing Definition: sheet metal used in waterproofing making transitions (as at roof valleys or hips or the angle between a chimney and a roof)

Almost 90% of Flat Roof leaks are caused by flashing. The transition from the roof to a vent pipe, skylight, air conditioner curb, and a wall is called “flashing”. Flashing could be metal, rubber, or the roofing material itself.

Metal flashing –

This is a piece of metal that is bent 90% and is placed in the corner where a roof and wall meet. Siding from the wall will cover part of the flashing and a roof membrane will be attached to the other part. The roof membrane can pop loose from the flashing and cause a leak.

Flashing is the number one cause of leaks on flat roofs. Metal flashing that runs alongside a wall, loosens up, or the caulking gives, and a major leak starts. It is the first place to troubleshoot for leaks on a roof. Take a screwdriver or flat bar and see if the caulking that seals the top of the metal flashing, is still holding. The video below will show you exactly how.

Wall Metal Flashing –

It is common to see metal flashing that is cemented into a wall or brick chimney. Below are pictures showing how to install metal flashing into a wall.

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

After cutting a slot into the wall, you can use a drip edge upside down and install it into the groove.

There are many Home Depot’s and Lowe’s as well as Roofing Supply Warehouses to buy products from to make roofing repairs. Make sure you always buy the highest-quality roofing materials to make the necessary flat roof repairs.

Flat Roof Doctor

• 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.
• 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.

Rubber flashing –

This type of flashing is mostly found around vent pipes. Over the years the EPDM Rubber will get brittle and deteriorate braking the flashing apart causing a leak.

Membrane flashing –

Many times a roofer will use the membrane to form the flashing against the wall. This is a continuous membrane that would lay on the roof and go up a wall several inches. This way there is no transition to any metal. The ultra violets tend to beat the membrane in these areas more to cause a leak.

Conclusion on flashing –

Check the flashing on all objects thoroughly and you are likely to detect a place where water can leak in causing damage to the roof substrate or ceiling.

How to look for Flat Roof Leaks on flashing

• Take a trowel or spatula and pry or poke the areas where the metal flashing is attached to the wall
• Check for loose caulking or paint that is peeling above the flashing
• Inspect the rubber boot around a vent pipe to see if it is intact
• Make sure the siding above the flashing is not cracked
• Ensure the rubber membrane that is forming the flashing has not perished
• Check the corners of the roof

How to repair leaky flashing on a roof

• Remove all old caulking and tar
• Take Laquer Thinners and a rag and hard rub the surfaces clean. Make sure to remove all Silicone residues
• Tape off the flashing area that need to be sealed
• Apply one coat of Turbo Poly Seal between the taped off areas
• Install a 4″ polyester fleece over the freshly painted coat of Turbo Poly Seal
• Apply a top coat of sealant over the polyester fleece making sure to cover it completely
• Remove the masking tape
• After 24 hours, apply 1 coat of Silver Coat Protection or any oil or urethane-based paint to protect the Turb Poy Seal against ultraviolets.

Watch this video to see how to repair flashing with Turbo Poly Seal

Four different Roof Systems each with their own leakage problems from seams

EPDM Rubber Membrane –

You can tell it by the look and feel of it. It is smooth and looks like the rubber of an inner tube of a tire. This is the most common roofing material used by most roofing contractors.

Watch this video if you have an EPDM rubber roof

This video will show you how you can save any EPDM roof from failing prematurely, especially at the seams. All EPDM rubber roofs will have seam failures due to the adhesives breaking up from excessive heat.

This video will show you how to extend the life of your roof.

TPO Vinyl Membrane –

This is normally white and has a plastic vinyl feel to it. This type of membrane has gained popularity and is preferred by roofing contractors.

Modified Bitumen Torch Down Rubber Membrane –

This type of rubber membrane comes only three feet wide, So if you see seams every three feet wide you know its some kind of a Modified Bitumen rubber. These membranes are either painted with a Silver paint or have Ceramic granules embedded on the surface.

Metal Roofs –

The overlapping panels on a metal roof create a seam that is sealed with a foam gasket. This gasket will deteriorate over the years and the neoprene washers with the fasteners will also not keep these two panels tight together. The constant moist generated by condensation will cause these seam areas to rust and allow water to leak in.

The video below shows you how to repair Flat Roof leaking on a metal roof seam with Turbo Poly Seal

Conclusion on Roof Seam Leaks:

Torch Down and TPO roofing membranes are heat-welded seams and therefore are less prone to separate and cause leaks.

EPDM Rubber, on the other hand, uses contact cement or adhesives to bond the seams. Because of the extreme heat that is generated on a black EPDM Rubber during summer, the glues start to fail and causing leaks.

How to look for a leak caused by roof seams

• On an EPDM Rubber roof, go to the overlapping seams, with your fingers, see if you can pull up on the EPDM material. When the adhesives fail that is bonding the seams together, then you will easily pull them apart.
• On a TPO roof: use a screwdriver and see if you can drive it in between the seams. If a weld has failed, you will find that a flat screwdriver will easily get into a seam.

• On a Torch Down Rubber Roof: To check the seams if they are causing the leaks, use a round nose trowel and try to pry it in between the seams. You should not be able to move the trowel in the seams more than 1/8 of an inch.

• Metal Roof Seam: Check the overlapping seams of the roof panels and make sure they are tight together. When the seams start heaving up due to the wearing of the neoprene washers and fasteners, it will have leaks.

Vent pipes are necessary to vent drains from bathrooms. These pipes penetrate the roof. When any object sticks through a roof, some kind of flashing is needed.

In most cases, bathroom vent pipes have a vent boot that makes the transition from the pipe to the roof. These roof boots are made out of EPDM Rubber and will deteriorate and get brittle over the years.

One way to repair these roof boots is to hire a roofing contractor to replace it.

Another method to fix this problem will be to use Turbo Poly Seal or Super Silicone Seal.

Both Super Silicone Seal and Turbo Poly Seal are excel very pliable and will outlast any EPDM Rubber material. They are also easy to use. Watch these videos on how it is done.

Using Super Silicone Seal to make repairs on Vent pipe leaks

Super Silicone Seal will last over 15 years with no issues. It adheres to wood, plastic, metal, glass, paint.

How to check Vent Pipes for leaks

• Make a visual inspection to see if the rubber boot is still intact
• If any caulking was used making temporary repairs
• Take a close look to see if the seal around the pipe is very tight. There should be no gaps
• Make sure the roof membrane is attached to the metal flashing of the vent pipe

How to repair a leaking vent pipe on a metal roof

Metal roof vent pipes can be hard to repair due to the standing seams. Watch this video to see how easy it is to make repairs

How to Repair a leaky Vent Pipe

• Clean the pipe and roof area so it is free from debris
• Tape a square area off with masking tape approximately 10″ from the pipe
• Take a disposable brush and paint 1 coat of Super silicone Seal inside the taped off area and also up the pipe
• Cut tabs in a polyester fleece and install it into the wet painted surface covering the pipe and roof at the same time
• Paint a final coat over the fleece
• Remove the masking tape

The counter flashing on chimneys is always a problem with 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.

How to check a chimney for leaks

• Make sure 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 More on Chimney Repairs

The most overlooked problem on a chimney is the flashing. Cement does not adhere to metal and does not create a watertight seal. This issue has been around for a long time. Most people will either use Caulking or Tar to try and seal it.

The best product we have found to remedy this problem is Turbo Poly Seal or Super Silicone Seal. Watch the video on how to repair the flashing on a leaky chimney.

Chimney Crown

Most chimney crowns have a thin non reinforced cement slab on the top. This cement slab cracks over time causing the chimney to leak. This type of leak is noticeable inside the fireplace or sometimes in the basement.

Watch the next video to see how to seal or waterproof a chimney crown.

When a metal roof is newly installed, there is a rubber or foam gasket placed in between the overlapping seams that seal the overlapping seams from leaking.

Fasteners are used to compress this gasket causing a tight seal between the metal panels. These fasteners have a neoprene washer that deteriorates over time causing the fastener to loosen up and in turn taking pressure off the gasket between the panels. This allows then water to leak in through the fasteners and seams.

This picture shows what most people do when they repair a metal roof. Tar is the Go-to product. Tar will always dry out and crack.

Watch this video to see how to fix a metal roof seam that is rusted and leaking

How to Repair a Metal Roof Seam with Turbo Poly seal

• Remove all existing tar and caulking
• Remove the hexagon fasteners
• If a metal band exists, remove it
• Use an angle grinder with a wire brush to prepare the surface
• Use flat head screws and screw tight both overlapping panels
• Take a disposable brush and apply a coat of Turbo Poly Seal approximately 3″ on either side of the seam
• Install a 4″ wide polyester fleece over the seam
• Apply a final coat of Turbo Poly Seal covering the entire fleece
• After 24 hours, apply 1 coat of Silver Coat Protection over the Turbo Poly Seal to protect it against ultraviolets

Pitch Pocket Maintenance

It is important to check older Pitch Pockets once a year and top them off with fresh tar. The tar that is used in Pitch Pockets will shrink and crack. This leads to a hollow Pitch Pocket that can collect water and leak.

An overlooked cause of roof leaks are Pitch Pockets

Notice in the image above how the pipe insulation has broken off. The seal around the pipe is now compromised and causing leaks.

Pitch Pockets can have different types of filling. More modern ones have a silicone fill instead of tar.

Five Tips on maintaining Pitch Pockets

• Check whether the roof is flashed properly
• Make sure that old cut pipelines are properly capped off
• 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, fill pitch pockets yearly.
• 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.

Very often a roof leak can be fixed by simply topping off the pitch pockets on a roof. This is a very common problem on commercial flat roofs.

Skylights on flat roofs

Making Skylight Repairs on a flat roof can be tricky. Here are a few tips where you can begin.

  How to check for Skylight Leaks

• 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

From our experience, it is better to use Super Silicone Seal to make a skylight repair than Turbo Poly Seal

Below is a video where Turbo Poly Seal is used to make a leak repair

An Atrium Style Skylight

These atrium-style skylights will; need to be replaced because of the plexiglass cracking causing leaks

How to inspect a roof drain for leaks

A-List of Manufacturers of Skylights:

• Wasco Skylights
• VELUX Skylights
• Bristolite Daylighting Systems
• American Skylights: Custom Skylights
• Commercial Skylight Manufacturer – Architectural Skylights | Plasteco

The skylight in the above picture is the most problematic skylights and are very hard to repair. From experience, these skylights will always leak due to a faulty design.

A Plexiglass Domed Skylight

Ho to locate a leak around a drain:

Roof Drains that are clogged will cause leaks

Watch the 3D video explaining how a roof drain should really work

How to inspect a roof drain for leaks