Flat Roof Leak Repair – Repairing a Leaky Roof

This video shows flashing that causes leaks on a roof and How to go about repairing it.

How to find and repair Flat Roof Leaks

  1.  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?
  2. Find out how old the roof is – EPDMTPO does not last much longer than 15 years. Torch Down can continue indefinitely
  3. Look for apparent problems around vents, drains and other objects
  4. Check the pitch pockets, flashing, cracked skylights, storm damage, holes made by flying debris from a storm
  5. Clean or wash the roof to expose issues easier
  6.  Clean out drains and gutters regularly
  7.  Apply compatible sealant where holes, cracks are visible causing leaks
  8. Replace broken skylights and vent boots
  9. Find an experienced roofer – not a handyman, to make the necessary repairs

How to detect leaks on a flat roof:

It takes an experienced person to find the cause of a leak on any roof. 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.

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 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.

See how flaking paint can cause a roof leak

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

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 leak 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

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