Your Flat Roof Problems Solved

FLAT roofs, which are usually built up with layers of roofing felt and asphalt or coal tar, should be recoated every two to four years, unless they are covered by a layer of gravel or other stone chips. About two times a year, the roofs should also be inspected for blisters, cracks and other flaws that can lead to leaks.

Coating waterproofs and protects the original roofing. It is available in five-gallon containers as a black or metallic liquid. The material is thicker than paint, but not as thick as tar. It is applied with a long-handled brush resembling a small push broom.

Both types of coating contain asphalt, which seals the roof against moisture. Metallic coating also contains aluminum, which reflects sunlight, protecting the asphalt from ultraviolet radiation and deterioration. In addition, aluminum reflects heat that can weaken roofing materials and increase cooling costs.

High-quality aluminized roof coating is a better product than coating of equal quality without aluminum. But poor-quality aluminized coating is not as good as high-quality coating containing just asphalt.

 

3 Types of Flat Roofs

  1. Built-Up Roof (BUR)

The traditional hot-tar-and-gravel roof is built from three or more plies of waterproof material alternated with hot tar and ballasted by a layer of smooth river stone. Once made of tar paper, these types of roofs gradually are using more-advanced materials such as fiberglass membranes.

  1. Modified Bitumen

A single-ply rolled roof similar to ice-and-water shield, but impregnated with a mineral-based wear surface. Torch-down systems involve heating the adhesive as the material is unrolled. Newer peel-and-stick systems are safer and easier.

  1. Rubber Membrane

EPDM (short for ethylene propylene diene monomer) is a true rubber. The durable material resembles an inner tube, but it’s engineered to resist damage from sunlight. EPDM can be mechanically anchored with fasteners, ballasted with stone, or glued.

 

Here are 7 flat roof problems to look out for:

  1. Ponding

As the name suggests, a pond of water on your roof is a very bad sign. Long standing water will always find a means of escape and that often means through the roof.

  1. Watermarks

Water may have escaped into the roof or evaporated after a long period of ponding. Either way it will often leave the tell tail signs of patches of a lighter or darker colour depending on the surface you are looking at.

  1. Vegetation

Moss, fungus, lichen and weeds are all signs that there has been a build-up of water.

  1. Cracking or stretching at joints or corners

With age, the flexible materials that make up the waterproof layers of your roof can crack (due to drying out or stretching), rip or just wear away. This is most common with roofs made of rubber or EPDM (Ethylene-Propylene-Diene-Monomer).

  1. Blistering

This is when you see a bubble appear in the roof membrane. One day it might burst giving water direct access into your home.

  1. Movement

All properties suffer from some degree of movement but in most cases it’s minuscule. However, subsidence and land heave can often cause significant movement to a building’s structure. A moving wall will stretch the roof which will often lead to tears and cracks in the waterproof membrane.

 

What are common flat roofing problems, and how do you fix them?

The solution to ponding water

The best way to combat ponding water is to be proactive and keep the roof well maintained. It’s important to ensure your gutters and drains are maintained, and any blockages cleared as quickly as possible to prevent ponding water. Additionally, ensuring the person installing your roof is experienced and professional can help to remove any potential for ponding water.

Placing patches over a small ponding area can be a simple and quick fix to prevent further build up of water. Dry the water out using rags or towels and leave to dry. Cut a 12 inch circle of rolled asphalt, spread roofing cement to the bottom of the patch, and place onto ponding area. Then cut more circles out, each time increasing the circle size by 4 inches, until you have 10 circles. Each time place the patch on top of the previous one, using roofing cement. When complete, apply a thick rubber or elastomeric coating to seal, and once dry test it by adding water on top of it.

If there are numerous pools of water, or it is a large area of pooling, it may be the case that the whole roof membrane needs to be replaced

The solution to blistering

Generally, as long as they stay intact you don’t need to worry too much about the blistering. Keep a close eye on them, and if they pop you can then replace or repair them. To repair blisters, cut away the blistered material up to the point that it is attached tightly to the roof still. Then reapply new membrane material, extending it at least 6 inches over the edge of the blister to prevent leakage.

It’s important to keep your roof well maintained and cleaned regularly – any build up of moss or algae can contribute to trapped moisture or water that may cause blistering.

 Alligatoring

Alligatoring is the term used to describe the cracking of a coating or surfacing bitumen on a flat roof, which causes a pattern similar to the hide of an alligator.  This can be caused due to water, debris or long term exposure to the sun. The cracking will eventually split and develop further if left unrepaired, meaning that water can get into the roofing and cause leaking, moisture and more damage.

The solution to alligatoring

To fix alligatoring, one solution is to apply a new coating to the roof. First, clean the roof thoroughly, removing all dust, dirt and anything else that is loose. Then apply a primer, and once the primer has dried apply the coating.

Thermal movement

Temperature changes can cause the roofing material to expand and contract, which is relatively normal. However, you must keep an eye on your roof for evidence of this, as continual expansion and contraction can weaken the roof and potentially cause leaks. This thermal movement can also occur on the flashing, resulting in it pulling away from the edges of your roof over time – this leaves room for leakage and moisture entry into your roof.

The solution to thermal movement

Ensure you use good quality flashing and roofing materials, and that they are installed properly, with regular maintenance. If you notice some flashing pulling away from the edges of the roof or house, its best to replace the flashing.

 

How to Prevent Problems with Flat Roofs

Rainwater can be a pretty serious threat to a low-sloped or flat roof. Unlike a steeply pitched roof, these surfaces don’t always have the power of gravity working with them to carry runoff down to the ground. Drainage systems on a flat roof can be overwhelmed quickly by falling debris—and anytime there is standing water on a roof, issues will abound. The water weighs your roof down, which can cause it to collapse. Additionally, standing water provides an opportunity for leaks to occur, especially in hairline cracks that may form over time from constant water exposure. Here’s how to protect your roof—and help it live its best life yet.

  • Inspect and Clean Gutters Frequently—Even if You Have Leaf Guards
  • Sweep Leaves and Dirt Off the Roof Regularly
  • Replace Your Roof Every Ten Years
  • Have Your Roof Sealed with a Waterproof Coating
  • Have Your Roof Inspected Frequently
  • Take Care of Cracks as Soon as Possible