Flat Roof Leak Repair – Repairing a Leaky Roof

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.

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 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