A-DT-504 · v0.1 · Draft

Roof waterproofing (inverted roof)

A 3D section of a concrete roof with a parapet: screed to falls, a fillet, two 4 mm bitumen membranes turned up the parapet with a termination bar and counter-flashing, then 50 mm XPS, geotextile and gravel ballast, and a drain with a clamping ring. Every part has a name and a function.

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Parts of the detail

01
Concrete roof slab
The structure under every layer.
02
Screed to falls, about 1.5%
About 70 mm at the parapet, thinning towards the drain.
03
50×50 fillet
Removes the sharp corner under the membrane at the parapet.
04
Primer
Prepares the surface so the membrane bonds.
05
Two 4 mm bitumen membranes
Torch-applied with offset laps, turned up the parapet more than 150 mm above the finished surface.
06
Termination bar and sealant
Hold the top of the membrane on the parapet and seal it.
07
Counter-flashing in a chase
Covers the membrane top and sheds water clear.
08
Drain with clamping ring
The membrane is clamped onto the drain flange, with a gravel guard on top.
09
Protection layer
Between the membrane and everything above it.
10
50 mm XPS insulation
In an inverted roof it sits above the membrane and shields it from heat.
11
Geotextile
Filter layer between insulation and gravel.
12
50 mm gravel
Ballast that holds the insulation down and shades it.
13
Coping
Caps the parapet, sloped towards the roof, with drips.