Preparation is always key to laying mastic asphalt from sweeping clean the roof to priming skirting and setting out the sheathing felt and appropriate battens, mastic asphalt is transported to the roof via metal buckets. From the time the lorry arrives on site with the mastic asphalt in blocks it is unloaded by hand and stacked by the asphalt mixer or pot, using a sledgehammer or club the blocks are broken into quarters and placed into the mixer.
Gas is situated at least 3 metres away from the burners with 2 fire extinguishers placed near to the gas bottles as a matter of heath and safety once lit the blocks melt and form large mass which then ha to be agitated as to break up and allow to flow thus not burning the mastic asphalt heated to 220° and fully agitated continuously the mastic asphalt then becomes ready for laying, then controlled by temperature gauges as to keep consistency.
The metal buckets that transport the mastic asphalt are dusted with cement this helps the asphalt to flow out evenly, not sticking to the sides. Once transported to the roof or wherever the mastic is being laid it is tipped by an experienced labourer who pours out along a 2 metre wide lap.
The asphalt spreader uses his float with immense skill to lay evenly 10mm thick to a wooden batten until he reaches the end of the bay he has set out. The mixer man will then take the opportunity to refill the asphalt machine with new blocks, when ready the topcoat will be applied. A new batten will be placed 100mm inside the 1st coat.
The same procedure occurs on the top coat laying 10mm but this time coarse rubbing sand will be thrown evenly on to the mastic asphalt and then smoothly rubbed with the laying float, this is to stop the bitumen in the asphalt from coming to the surface, if rubbing sand is not applied to the top layer, rainwater will lay in large bobble and within weeks the bitumen that has raised to the surface will create crazing giving the appearance of continuous cracking.
This procedure applies to all mastic asphalt surfaces including roofing, flooring, carparks, paving and balconies, the only exception is tanking where no coarse sand is used. Thickness laying levels vary according to which particular specification is put in place i.e. flooring laid with mastic asphalt is often laid at a minimum of 25mm in thickness and one coat only. A carpark will have a thickness and one coat only.
You can find more information on mastic asphalt roofing here: https://masticasphaltcontractor.co.uk/asphalt-roofing/
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