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Common Problems With Asphalt Roofing

Renowned in the UK for its waterproofing qualities, mastic asphalt has long been a popular material for flat roofing systems.

Despite its durability and hardwearing nature, asphalt roofs, like all flat roof systems, can suffer from common issues. However, these are issues that are generally able to be resolved by asphalt roof repair specialists.

The most common cause of asphalt roof deterioration stems from the UK’s changeable weather. Below we look at the common problems an asphalt flat roof faces, and then how to identify and resolve these issues. All problem sections are subtitled so if you are in a rush you can jump straight to the issue your think your roof is facing, or you can read through each detailed description.

Identifying Problems on your Asphalt Roof


Perhaps you have noticed what appear to be raised areas on your roof top? If you think you have spotted these climbs up onto your roof and have a good look  bumps should be easily identifiable as any raised areas across the flat roof’s surface. Unfortunately, bumps form when moisture becomes trapped underneath the mastic asphalt's surface and these bumps will need to be dealt with quickly.


When looking at bumps make sure you get close for a good inspection, as it is easy to mistakenly identify a blister as a bump. The difference between asphalt blisters and bumps is that blisters have splits running through the bump area. Blisters occur when further damage has happened to a bump and it is important to quickly address and rectify any blistering on your roof top. This is because the crack running across it is at increased risk of allowing water ingress to occur, which then means water is more likely to penetrate through the roof’s surface and potentially cause a leak.

Splits and Cracks

Splits and cracks across the surface of your roofing system is a concern that cannot be ignored, it is strongly advisable that the moment you notice any running along your roofing system you contact a roof specialist for further advice. Splits and cracks need to be dealt with immediately to ensure that water ingresses don’t start to pool with the next lot of rainfall. The big problem with rainwater collecting is that water breaks down the surface of the mastic asphalt roof and puts the roofing system and greater risk of leaks, drastically reducing the lifespan of your roof.

How Does Moisture Get Trapped On An Asphalt Roof?

There are times where moisture does become trapped on flat roofing systems and as explained above it is important to spot the tell-tale signs of when this has happened. But let’s have a look now at why this might have happened.

Problems That Can Occur Whilst The Asphalt Is Being Laid

Dust Pockets

One of the causes of asphalt roofing problems is caused during the process of the mastic asphalt being laid. Workers use metal buckets that are lined with cement (the cement prevents the molten liquid from sticking to the bucket) to pour the heated asphalt onto the roofs surface. On a very rare occasion, as the workers empty their buckets a tiny pocket of dust can mix into the new laid asphalt and cause contamination. Over time this dust pocket can cause the asphalt to spoil and eventually ‘blow’.

Poor Ventilation

Another issue that asphalt faces during the production stage is a ventilation issue. It is highly important to ventilate the asphalt overly- failure to do this can mean that tiny amounts of moisture become trapped amongst the layers of asphalt and, as explained above, when tiny amounts of water are trapped bumps begin to form across the asphalt roof’s surface.

Damage From a Heavy Item Being Dropped On The Flat Roof

Another commonly reported issue is asphalt that has been damaged from very heavy objects being dropped onto the roof. This damage is exacerbated if the accident happens in cold weather as when mastic asphalt is cold it becomes tight and contracted, making it more susceptible to sustaining damage.  Even if the damage shown only seems to be small hairline fractures it is worth getting advice on repair work, as even small cracks will enable water to become trapped into the mastic asphalt’s surface leading to potentially blow outs.

Asphalt Roofing Problems Caused by UK Weather Conditions

Temperature Changes

The British weather can be a common cause of issues for asphalt roofs. One of the biggest issues is the ever-changing nature of our weather were roofs are exposed to drastic temperature changes throughout the day. When asphalt is heated by the sun it responds by expanding its surface area. Although the change in slight and wouldn’t be noticed by the naked eye. The process of it expanding in the heat and then contracting once the sun sets causes asphalt cracks to appear across the roof’s surface. This is something that won’t happen instantly, but over time as the pattern of the roof expanding and contracting repeats.

The Heat of the Sun

Over time the heat from the sun can cause the bitumen within the mastic asphalt to be drawn out and onto the surface. When this happens, it causes the roof to lose its original, slick black colour and leaves a worn grey instead. This should be something that you will be able to easily spot on your roof.

What Can Be Done To Prevent Sun Damage?

Luckily, it is easy to prevent the sun from damaging your mastic asphalt roof. Solar reflective paint works as a natural ‘sun cream’ for your roof’s surface and works as a barrier between the asphalt roof and the sun’s rays. It most commonly comes in a light grey and provides immediate protection for your roofing system. Manufacturing recommendations can vary, but typically, the solar reflective paint has a lifespan of 3-5 year, after this time you will need to then apply a new coat of protection onto your roof.

How To Apply Solar Reflective Paint To Protect Your Asphalt Roof

• Cover all parts of the asphalt roof including your lead flashing1 as lead is conductive so will soak up the sun’s rays. This reaction to the sun’s heat can cause slumping to occur on the roof’s surface.

• Use a generous amount of paint to cover your roof’s surface as this will ensure you are providing the best possible protection.

Side note: Remember, whilst solar reflective paint does offer you a significant level of protection from potential damages of the sun’s rays, unfortunately it cannot provide 100% protection.

We Are Here To Help With Your Asphalt Roofing Problems

Perhaps you feel you have identified the issue with your asphalt roof or maybe you are still unsure, either way do not hesitate to get in touch with us today. We can provide specialist help and advice and are always happy to answer any queries and offer advice you can get in touch via our web form or call now on 07739207726.