Saturday 25 October 2014

Roof Drainage

With the good September weather continuing progress was made on the roof waterproofing and drainage system.

In order to give the roof of the house the strength required to support the earth covering the engineers decided that the best option was to have a series if interconnecting reinforced concrete beams running the length and depth of the house. These would be part of the integral structure of the roof and would be on top of the roof so that there would be no intrusion into the living space below. These beams can easily be seen in any photographs of the roof.

In order to prevent a series of pools across the roof as the water drains through through the earth sheltering a system of pipes were installed when the beams were cast. These were positioned to allow for the free flow of water across the roof and drainage pipes were installed to allow the water collected in these pools to drain away on the east, west and northern walls and in due course filter through to the around house drainage system described in earlier posts.

To aid this flow of water sufficient gravel was moved onto the roof to eventually provide a drainage layer across the whole roof. This would allow the water that filtered down  through the earth covering the roof to drain away through the suitably placed interconnecting drains.

 In addition the thermal insulation material that had been laid across the roof prior to laying the waterproofing layer had been carefully graduated to  create gentle slopes to allow the water to flow though the series of drains across the roof and to drain away from the west, north and east facing walls.

Meanwhile the external walls of the lightwell were prepared using the same technique as the roof and the outer walls of the house. i.e. the walls were prepared by removing any protruding sharp edges, sprayed with a sealing cement, covered with a cushioning fibre cloth and then the strong waterproofing layer was set in place and would itself, in turn, be protected by a covering of the egg box like sheeting to protect it when  backfilling.

Gravel is moved to roof for spreading as part of the roof drainage system. Note the drainage pipe that will carry away any accumulation of water.

Looking east across the roof.

Gravel spreading underway.

Sealing the lightwell wall prior to laying the protection and waterproofing layers.

Fixing the waterproofing in place on the lightwell wall. Note the fibre protection layer underneath.