283757893275

150 Barry’s Advanced Construction of Buildings
Concrete wall cast
against membrane
Waterstop bonded
to membrane at
construction joint
Reinforcing
strip
Concrete floor
cast on
membrane
Waterstop
bonded to
membrane
below joint
Figure 3.71 Bituminous sheet membrane tanking.
film, or sheet bonded to a self-adhesive rubber/bitumen compound or a polymer modified
bitumen. The heavier grades of these membranes are reinforced with a meshed fabric
sandwiched in the self-adhesive bitumen. The membrane is supplied in rolls about 1 m wide
and 12–18 m long, with the self-adhesive surface protected with a release paper backing.
The particular advantage of these membranes is that their flexibility can accommodate
small shrinkage, structural, thermal and moisture movements without damage to the
membrane. Used in conjunction with waterstops to concrete substructures, these membranes
may be used as tanking (see Figure 3.60, Figure 3.61 and Figure 3.71).
The surface to which the membrane is applied by adhesion of the bitumen coating must
be dry, clean and free from any visible projections that would puncture the membrane. The
membrane is applied to a dry, clean float finished screed for floors and to level concrete
wall surfaces on which all projecting nibs from formwork have been removed and cavities
filled. The vertical surface to which the membrane is to be applied is first primed. The rolls
of sheet are laid out, the paper backing removed and the membrane laid with the adhesive
bitumen face down or against walls and spread out and firmly pressed on to the surface
with a roller. Joints between long edges of the membrane are overlapped 75 mm and end
joints 150 mm, and the overlap joints are firmly rolled in to compact the join. Laps on