DPMs are sheet or liquid membranes designed to resist damp
caused by capillary action. They do not have to perform as
well as tanking membranes, which must resist water pressure.
DPMs may be positioned under site slabs providing the hardcore
is smoothed with 25 mm minimum rolled sand or preferably
25 mm smooth blinding concrete. This position is more
vulnerable to damage than placing them over smooth finished
site slabs. In this position the membrane can prevent
satisfactory bonding between slab and screed, so a thick
screed is needed, ideally at least 63 mm.
DPMs must be carried up to lap or join DPCs in walls. Brushapplied
membranes are better than sheets in this respect.
Care must be taken not to penetrate membranes when laying.
Any pipe ducts must be in position before screeds are poured,
as any subsequent chasing could well damage the DPM.

kg/m3

Blue 2405
Engineering 2165
Sand cement 2085
Fire brick 1890
London stock 1845
Sand lime 1845
Flettons 1795
Red facings 1765
Diatomaceous 480

Standard windows listed below are manufactured in softwood,
hardwood and in PVC in a wide range of sizes and
types and are the most commonly available. The sizes are
approximate.

This is by far the most common type of standard window.
They are available as single sashes or in twos, threes and fours.
There are numerous combinations of fully-opening side hung
sashes, one or more fixed lights and smaller top hung vents,
with or without glazing bars. Side hung sashes can be fitted
with concealed friction stays fixed over the top and under the
bottom of sashes, in lieu of conventional hinges, for easier
cleaning from inside.
Widths : 630, 915, 1200, 1770 and 2340 mm.
Heights : 750, 900, 1050, 1200 and 1350 mm.

Square, splayed at 45°, semi-circular and shallow curved bay
windows are available using combinations of fixed lights, side
and top hung casements and double hung sashes to suit
structural opening widths of approximately 1200 to 3500 mm
with projections as little as 130 mm for shallow curved bays
and up to 1000 mm for semi-circular bays.

OPEN RISERS
are allowed except for stairs for the disabled where
no lift is available.
Stairs used by children under 5 must have treads overlapping
a minimum of 16mm and be constructed so that a 100mm ø sphere
cannot pass through.