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An asphalt flat roof should last at least 25 years if laid by an accredited mastic asphalt contractor. This can be extended even further if the roof is cared for correctly with regular maintenance and the re-application of solar reflective paint.
Below we will look at areas to pay close attention to ensure you get the maximum lifespan out of your mastic asphalt roof. A few of these areas are no actually to do with asphalt waterproofing. These are structural issues which often wrongly get blamed on the asphalt waterproofing.
1. Coping Stones
This is a common problem across all flat roofs where coping stones have not had any damp course placed underneath them. The problem with this is the mortar between the asphalt roof waterproofing can break down and get underneath the asphalt. Your roof’s longevity can be preserved by putting a damp proof course underneath and coping stones around the perimeter of the roof.
2. Cracked Rendering
A lot of roofs fail not because of the roof but because the rendering of the wall the roof joins to is faulty. What happens here is water hits the wall and travels through cracks in the rendering and underneath the asphalt roof. The way to prevent this is to contact a rendering specialist and take fast action when any rendering cracks occur.
3. Lead Flashings
Failing lead flashing can also cause problems with asphalt roofing. A common problem with lead flashing is the mortar joint between the flashing and the wall. What happens here is water gets through the failing joint and underneath the roofing system. This can often cause leaks. Although the roofing system has failed, it is not because of the asphalt. The way to stop this happening and giving your asphalt roof the best lifetime possible is to get a professional roofing contractor to inspect your roof periodically and carry out any necessary roof repair work.
4. Air Handling Units
A lot of modern flat roof systems have air handling unit1 and other types of plant machinery housed on them. For roof systems in mastic asphalt this can be problematic due to the maintenance of this plant equipment. This is due to oil damaging mastic asphalt. This is usually accidental as the tradesman carrying out the repair work has no idea that oil is harmful to asphalt. And they unknowingly damage the asphalt surface by laying their tools on it. The solution here is to always inform tradesman not to let oil come into asphalt before any repair work commences. Doing this will prevent any roof failures due to an easily preventable accident due to a lack of awareness.
5. Impact Damage
Asphalt roofs can fail due to impact damage. This is due to heavy objects being dropped on the asphalt causing an indentation or a split in the surface. If this is done in cold conditions the asphalt is more likely to suffer damage as there is less movement in it. If you do discover the asphalt roof covering has suffered impact damage, the best thing you can do to ensure the longevity of the roof is to contact a profession to carry out the necessary asphalt roof repair work.
6. Sun Damage
Asphalt is vulnerable to the sun and the heating effect it has. Prolonged exposure to the sun leads to the bitumen being pulled out of the asphalt. You often see asphalt roofs change colour to a worn grey over time.
The exposure to the sun can cause the asphalt to slump. Or start to develop cracks as it goes through the cycle of expanding in the heat and contracting in colder conditions.
The best way to prevent sun exposure problems for an asphalt roof is to finish any asphalt roofing with a solar reflective paint. This paint is a light grey colour and vastly reduces the effect the sun has on the asphalt. Effectively it is like sun cream for the roof.
For the maximum longevity for the roof it is best to renew the paint every 3 to 5 years depending on the sun exposure it must endure. It is also important to paint lead flashing on an asphalt roof, and the asphalt it covers. This is because lead is a conductor of heat and can cause an amplification effect on the heat endured by the asphalt it covers.