5 tell-tale signs it’s time to repair or replace your asphalt or felt flat roof

Bitumen roofs have been around for a long time. They have a proven track record that can be counted on, and the good news is: a longer lasting roofing material has a lower environmental impact.  The bitumen used in flat roofing is a by-product of refining crude oil for use as petrol, diesel and gas. Therefore, it’s better for the environment and your pocket to renovate and maintain your roof rather than just replacing it.

So how do you assess the condition of your asphalt or felt flat roof?

A visual inspection will give an indication of the general condition. Internally you are checking for tell-tale signs of water ingress or damp inside on ceilings, and outside: check the roof covering for the following:

  1. Age or thermal movement often causes cracks and splits in bitumen felt. After 20+ years of expansion and contraction and exposure to the elements, bitumen felt will lose its elasticity. Your roof expands and contracts with heat and cold, but the felt won’t. It has become hard and brittle. Humps may have appeared on the joints made on the joists where the felt is being forced to rise, giving the illusion of a dip or hollow in the roof decking itself.

When these occur above standing water they won’t cause too many problems, but will sometimes be opened up when water freezing and expanding over successive winters.

Even when your roof is old, if the damage is in a particular area, for example one exposed to sunlight due to lack of grit a repair might be possible. More modern felts have a mineral finish whilst older felt roofs will often have loose chippings covering the field areas to protect the roof from UV rays.  A patch flat felt roof repair with a paint-on waterproof may provide you with a solution that would last a year or even two.

2. Lifting or badly stuck joints – Dry joints can be due to poor materials,  workmanship, or again through age. A small amount of paint on water-proofer will again provide a temporary flat felt roof repair.

3. Blisters or bumps in asphalt roof – Are caused by moisture trapped underneath the roof surface which then expands with the heat and lifts the felt away from the roof. Again, these don’t mean the roof is condemned, unless they burst and become hollow, or sit below lying water (ponding). It could be feasible to apply a layer on top. This is called an overlay and can provide a solution to get a few more years out of your roof.

4. Leaking flashings – often occurs where your flat roof joins with a wall. Water blown against the wall will run behind it and into the property. Taking care not to damage the roof, one option might be to remove the old mortar and repoint with the correct mix.  A different flashing option could also solve the problem. 

Check the joint where the flashing is ‘chased’ into the wall, especially if it is rendered wall. Water can enter and find its way behind the flashing and onto the roof boards beneath. In certain cases, it will be possible to mastic this joint instead of using a sand and cement mortar. If you use mastic be prudent and use a recognised brand / type such as those used for lead flashings or a polysulphide based mastic as these are highly flexible unlike standard silicon mastic.

5. Condition of the roof deck substrate (the roof timber below the covering). If this is rotten or deteriorated, it means the roof and decking that supports it is no longer viable. Unless you have a visible hole localised in the area of the roof leak, a flat felt roof repair is a waste of money. 

Again, it’s worth knowing the age of your roof. In many cases older roofs were installed with chipboard decking. This is fine when it’s kept dry, but chipboard fails very quickly when wet and will cause a bigger problem if left and water spreads further into the roof. You might also come across Stramit or ‘straw’ boards which don’t perform well when sodden. 

Plywood or OSB3 (oriented strand board) is recommended as decking. It will maintain its strength for a longer period even if there is a leak and is easily repaired after ensuring the decking is dry and sound.

When replacing your asphalt or felt flat roof is the only option…

If your roof is nice and firm underfoot and is a built up felt roof, it will either strip successfully and a new Torch-on felt or asphalt roof can be installed, or there are other roof cover solutions to consider. GRP and EPDM rubber roofing, which, once laid, are seamless (so the chances of water leaking through joints is minimal); and liquid systems, with reinforced matting, which provide alternative solutions to traditional bitumen felt. Read more about them in our guide to flat roof options here.

All said and done, if you inspect your roof and need to carry out minor repairs there are products available which will work, provide a quick fix and time to allow you to explore your options, get quotes and above all else, budget for your new roof.

Investing in the best possible option with roofers’ guarantees and manufacturers’ warranties are worth it for your own peace of mind. If you need further information on product warranties, not use our LiveChat function now.