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An asphalt roof is one which has been waterproofed by mastic asphalt. Normally it has two 10mm coats of roofing grade asphalt laid upon sheathing felt. The sheathing felt is used to allow for movement between coatings and substrate.
With the installation of an asphalt roof it is very important to prepare the substrate for the application of the mastic asphalt. The substrate must be cleared of all debris and all skirtings must have primer applied.
When this is done, battens must be set out to mark where the asphalt is to be laid. And the separating layer must be put down to allow for movement in the asphalt. This movement can occur from changes in temperature or at joints in the asphalt.
IMPORTANT: If the substrate you are laying on is bituminous it is important to lay building paper between the sheathing felt1 and the substrate. The reason for this is the bitumen can contaminate the mastic asphalt.
The next step is to apply two coats of roofing grade mastic asphalt. Each of these coats should be 10mm thick and give a nominal thickness of 20mm. If the roof is to be used for heavy foot traffic or vehicle use such as a loading bay2 extra hardness will be needed such as a final coating with paving grade asphalt for extra hardness.
Once the roof waterproofing is finished the final step is to apply two coats of solar reflective paint. This is used to reduce the probability of the roof suffering from extreme temperature changes causing thermal movement. Although this does not eliminate thermal movement3 it vastly reduces it due to reducing the roof gap between maximum and minimum temperature throughout the day. This helps extend the roofs lifespan. Depending on the roofs usage and positioning new solar reflective paint should be applied every 3-5 years for the best results.
Click the following link to learn more about how to lay a mastic asphalt roof: How To Lay Mastic Asphalt On A Roof