Waterproof Flat Roofs
Flat roofs using concrete, FC and plywood, have become very popular for houses with a view as it enables them to go higher than a pitched tile or metal roof. They also provide an excellent surface for air conditioning, solar panels and possibly recreational areas if permitted by the local council.
From the waterproofing point of view, the key question is whether the roof is insulated on top or below the concrete as FC and plywood are normally membrane roofs. If insulating on top, called IRMA (Inverted Roof Membrane Assembly), then Wrimco SBS plain is used, but if exposed, then torch apply Wrimco SBS Granules.
New Flat Roof Construction
For roofs with stepped sections and parapets, it is normal to run the membrane up and over, but if the height exceeds say 1 m, then best to terminate with pressure seal and continue with an external acrylic. Metal
is not recommended as screws through the membrane should be avoided where possible, even though they can be effectively sealed with brush applied Wrimco Flashing and Polyroof SBS caulking mastic.
Where toppings or reinforced screeds are applied over the membrane to create good falls, the membrane should be protected with Protection board.
For large commercial buildings, pavers are often supported on adjustable Polypads and laser levelled while the concrete is laid to falls. To guard against fire from accumulated flammable debris that may fall through the openings between the pavers, self protected Wrimco SBS Granules should be used instead of protection boards.
Repair leaking roofs
Roofs are fairly easy to repair provided the substrate can be viewed from below and high risk loose laid Plasticised (Polyester) PVC or APP bitumen membrane have not been used, as the source of the water penetration can be fairly easy located with fully bonded system having elastic properties.
If the old membrane has lost its properties due to plasticiser migration, UV degradation, water ponding (latter especially with acrylics) or movement in the structure, then it is always preferable to replace it with Wrimco SBS rather than go over it. For liquid applied membranes then cannot be readily stripped like sheet membranes and still adhere strongly, then simply torch over with Wrimco SBS as the molten SBS is an excellent adhesive.
Gutters and sheet metal ducts often should be replaced but may be very difficult to do so in practice. For metal gutters, self adhesive tapes (SBS or butyl rubber) over the joints followed by a liquid applied membrane such as Wrimco supplied latex/bitumen provide an economical answer.
It is difficult but not impossible to torch apply SBS onto metal because of its high expansion or Rigid PVC because of its low decomposition temperature. Applying a first layer of SBS self stick such as Self-adhesive SBS Membrane will greatly facilitate subsequent torch application, or a second layer of Self-adhesive Granules can be used.
Where torch on membrane has lost adhesion to a wall, but is still sound, re-torch and apply a pressure seal. If there is a problem with vent pipes, clamp a SS jubilee clip to ensure water does not penetrate at such points.