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Asphalt Roof Repair

Asphalt Roof Repair Specialists | London Asphalt

London Asphalt offer a complete asphalt repair service for all types of roofs. No matter how big or small your asphalt repair needs are, our professional team will be happy to help you. With a wealth of experience, you can be sure any repair work carried out on your asphalt roofing will be to a high standard, completed as agreed and problem free for years to come.

Problems With Your Flat Roof In Mastic Asphalt?

Whilst asphalt roofing is a fantastic choice for a flat roof because of its durability and the ease of carrying out asphalt repair work. Like any roofing system there are some common issues that can occur. Here we will identify common issues that can happen and address the best course of action to take to deal with them; the good news is that in nearly all cases a defective flat roof can be fixed with a simple asphalt repair.

One of the most frequent problems encountered by a mastic asphalt flat roof is caused by the exposure to the UK’s range of weather conditions. Typically, the prolonged exposure to freezing temperatures or the heat of the sun. We will explore these in more detail below.

Exposure To The Sun

A problem that any roof faces is the heat of the sun. Prolonged exposure from the sun draws the bitumen out of the asphalt and to the surface. An easy way to identify if this has happened is through any discolouration of the asphalt. Once the bitumen has been pulled, over time, onto the surface of the roof, the colour changes to a worn grey, making the asphalt look much older than it is.

However, discolouration is not the only issue the sun can cause. The cycle of the sun’s heat expanding the mastic asphalt coating in the day. And then as the temperature drops the surface contracting. This process of expansion and contraction can cause  cracks to appear in the asphalt surface.

The Simplest Solution To Protect Asphalt Roofing Systems From Thermal Movement?

Solar reflective paint is the simplest way to prevent an roof from needing repair due to thermal movement. It is best to coat the roof immediately after it has been laid. This coat must be re-applied every 3 to 5 years depending on how much sun exposure the roof has to endure. The reflective paint is light grey in colour and is a fantastic defence against the damage that the sun can cause, the best analogy for it is that it is ‘sun cream’ for your roof.

Application Of Solar Reflective Paint

When applying the paint remember to cover all parts of the roof even the sections that are covered by lead flashing and remember to apply the paint liberally. The reason you need to ensure you also cover these sections of the roof is because lead is conductive which means it will hold onto the suns heat and then this will cause slumping to occur on the roof. For complete protection it is advisable that you also cover the lead flashing itself in UV protective paint1.

Of course, like any form of protective paint, the solar reflective paint does not provide 100% protection for the asphalt roof from the sun’s rays, but it does drastically improve the negative impact of the sun’s rays and thus maximise the roofs life span.

Asphalt Flat Roof Repairs Are Often Needed Because Of Trapped Moisture

There are three main causes of moisture becoming trapped in underneath the mastic asphalt coating.

1) The first happens during the roof laying process. Workers use metal buckets to transport the heated mastic asphalt to the roof and in order to prevent this molten liquid from becoming stuck to the metal they coat their buckets in cement dust. However, on rare occasions a pocket of this cement dust can leaves the bucket as the mastic asphalt is poured out to be spread this. In time, this dust pocket can cause the asphalt to ‘blow.’

2) Another issue that can cause asphalt to ‘blow’ is if the asphalt overlay has not been vented. As if any moisture gets trapped between the layers the bitumen is drawn to the top of the surface, eventually creating bumps.

3) If the asphalt roof becomes damaged, e.g. by something heavy being dropped on it, particularly in winter, hairline cracks can then appear. These hairline crakes quickly expand and cause water ingress, again leading to the asphalt roof ‘blowing’.

Common Problems Caused By Trapped Moisture

The best way to inspect your roof is to get up on it and look for any bumps, blisters cracks or wrinkles. See descriptions below for more detail:


It should be fairly easy to identify any bumps as they are raised and so will stand out from the rest of the level roof. Remember, these bumps will have been caused by moisture that is trapped under the mastic asphalt.


Blisters2 may appear to look like bumps at first, but on closer inspection you will notice that the head of the bump has got a split or a crack running through it. Again, you should be able to identify by sight whether you have a blister on your roof.

Unfortunately, blisters are more of a worry as they are the stage on from a bump and their crack or split at the top is more prone to allow water through the roof. Thus, compromising the roofing system from both a safety perspective and how well it can protect the content below it.

Splits and Cracks

Cracks or splits are unfortunately a problem that need to be addressed immediately and by a roof specialist. Cracking and splits are inevitably going to have a very detrimental effect on a roof’s lifespan as, eventually they will allow water to pool and then begin to seep through causing damage to any items below the roof.

Are You Experiencing Problems With Your Asphalt Roof?

Hopefully this page has given you some insight into the different problems that mastic asphalt roofs can experience. Should you find any faults in your asphalt roofing and neither further support and advice with how to address these issues please do get in touch with our friendly team today on email us at or call us on 07739207726 we would be delighted to assist you on how to maximise the durability of rooff.