How to find and repair Flat Roof Leaks

Flat Roof Leaks are common because of many factors. The most likeliest cause of leaks is flashing. Wherever there is a transition from the roof surface to an object, like a vent pipe, wall or drain, flashing is present. When you look for what is causing the leak, then look at cracks at all the flashing on the roof.

Type of roof?

Before fixing and Flat Roof Leak, you must determine what type of flat roof repair you need to make by determining the roofing materials – is it an EPDM, TPO, Tar, and Gravel or a Torch Down?
EPDM Rubber material

What is the roof age?

Find out how old the roof is – EPDMTPO does not last much longer than 15 years. Torch Down can continue indefinitely. It is important to determine the age of the roof before making any repairs. If you try to fix a roof that is too old then you are just wasting time.

Obvious Problems

Look for apparent problems around vents, drains and other objects
Skylight Leak - Design flaw Causing A Leak - Darien CT - Flat Roof Repair

Inspect Objects like:

Check the pitch pockets, flashing, cracked skylights, storm damage, holes made by flying debris from a storm
Pitch pocket filled with tar. The pipe leading through the pitch pocket will cause leaks

Clean Roof to make it easier

Clean or wash the roof to expose issues easier

Roof Drains

 Clean out drains and gutters regularly to avoid water pooling causing leaks
Debris Around Flat Roof Drain Strainer

Seal potential leak areas

 Apply compatible sealant like Turbo Poly Seal where holes, cracks are visible causing leaks
Repairing a metal roof with Turbo Poly Seal

Vent boots:

Repair cracked skylights and vent boots with Super Silicone Seal
Busted vent boots often cause leaks

DIY or Experienced Roofer

Most of the time you can repair almost any leak on your roof. With new products on the market like Turbo Poly Seal and Super Silicone Seal you don’t need a roofing contractor anymore for repairs. Turbo Poly seal 1 gal 50 M 1 1

It takes an experienced person to find the cause of Flat Roof Leaks. If you are a novice, then following the tips and guides on these pages will help you narrow down the area and also instruct you on how to go about making a necessary repair.

See how flaking paint can cause a roof leak

This video explained how to look for a leak above the wall flashing

What is the best product to repair a leak on a Torch Down Rubber Roof?

Turbo Poly Seal is a combination of Bituminous and urethane resins. Therefor is is comparable with Torch Down Rubber materials
Turbo Poly seal 1 gal 50 M 1 1

What is the best product to repair a skylight leak?

Super Silicone Seal is by far the best for repairing Skylights. The reason is that the sealant sticks to plexi glass, glass and metal.
Super Silicone Seal used to repair a skylight leak

What is the best product to use for making general repairs on a roof?

We use Turbo Poly Seal for almost all our repairs
Turbo Poly Seal poured out to repair a metal roof

What is the best product to use to repair a chimney crown?

We have used both Turbo Poly Seal and Super Silicone Seal to seal chimney caps. Turbo Poly Seal is brown and Super Silicone Seal is white.
Chimney Crown seal with Turbo Poly Seal A chimney cap being coated with Super Silicone Seal

What is the best product to use to repair a metal roof?

Our go-to product for repairing metal roofs is Turbo Poly Seal with a Polyester Fleece. You can repair rusted through metal and rusted seams and it will last
The best product to use for repairing metal roofs is Turbo Poly Seal

What is the best product to repair a chimney?

We use Turbo Poly Seal to repair the flashing on all the chimneys we work on
Using Turbo Poly Seal  to repair the flashing on a chimney

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.

Metal Flashing - copper bend at a 90 degree angle making the transition between the roof and chimney
Metal Flashing – copper bend at a 90-degree angle making the transition between the roof and chimney

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.

Use an angle grinder to cut a slot into the wall

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

Inserting a drip edge upside down can serve as flashing on a wall

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.

Vent Pipe Flashing - Rubber boot that is the flashing
Vent Pipe Flashing- It is made from rubber and ultraviolets will deteriorate it over time

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.

EPDM Rubber Roofing Materials are damaged by UltraViolets
EPDM Rubber Roofing Materials are damaged by Ultra Violets. The membrane is used instead of metal flashing

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
This video demonstrates how to go about repairing flashing
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