| 摘要 |
The efficient drainage of flat roofs is facilitated by the inclusion in the construction of a flat roof of a drainage board, preferably of a bead material. The drainage board is provided above a water barrier layer and below a thermal insulation layer. Water falling on a flat roof passes readily through a protective layer of gravel or like material, through the abutting joints of the thermal insulation layer and through the drainage board. The water then flows on the water barrier layer to conventional water gulleys and downpipes.
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