Technical Reference

Treatment Procedures.

Step-by-step waterproofing, structural repair and rehabilitation methods, grouped by the chemistry they use, each mapped to the Armstrong products that carry it out. Select a treatment to view the full procedure and product recommendations.

Choose a treatment

Treatment · Acrylic, rubberised & cool roof

Multi-Layer Waterproofing Systems

2, 3, 4, 5, 6 and 7 layer build-ups, chosen by the condition of the roof

Applications

Sound terraces (2 layers)Cracked or moving roofs (3 layers)Terraces in bad condition or rebuilt (5 layers)Large exposed public roofs (6 layers)Severe heat, wear or heavy damage (7 layers)Metal, GI and AC sheet roofsPodiums, lawns and planter areas

Procedure

Prepare the roof: clean off dirt, dust and old coatings, chip loose mortar and cement lumps, and wire-brush or power-grind. Cut cracks to a 4 to 5 mm V-groove and seal them with ROOFEXSEAL PU 212. Patch debonded areas with polymer mortar over a ROOFBOND SBR 401 bond coat, and form the coving at every wall.
Choose the number of layers from the condition. 2 layers: a sound, draining terrace, two coats with the second at right angles. 3 layers: a cracked or moving roof, a base coat, reinforcement as layer 2, and a top coat. 5 layers: a terrace in bad condition or one that has been repaired, primer, reinforcement as layer 2, two base coats and a top coat. 6 layers: large heat-exposed roofs, a primer, two base coats, an intermediate coat and a reflective top coat in two passes. 7 layers: the most demanding roofs, with reinforcement as layers 2 and 4.
Layer 1, the primer or base coat, is chosen for the surface. RAINSEAL RWC 902 or RAINSEAL BMW 250 diluted with about 50% water on exposed terraces and over old bitumen. ROOFCOAT FLEXI 100 (1 litre to 2 kg cement), ROOFBOND RFX PLUS 210 or ROOFCOAT PU 2K where the slab stays damp, water stands, or a screed, tiles or a roof garden will go on top. ROOFBOND BCS PRIME 501 on porous surfaces.
Lay the reinforcement into the wet coat, 1 m wide with 50 to 100 mm overlaps, pressed in so no air is trapped. Geo-fabric is used mostly on concrete roofs; fibre mesh (40 or 45 GSM) on metal, GI and AC sheet roofs. In a 7-layer build-up a second reinforcement goes in as layer 4.
Cover the reinforcement with the base coats, each after the last has dried. RAINSEAL BMW 250 and RAINSEAL RWC 902 are thinned with about 20% water for these coats.
Where the base is cementitious (ROOFCOAT FLEXI 100, ROOFBOND RFX PLUS 210 or ROOFCOAT PU 2K), sprinkle clean, dry sand over the last base coat while it is still wet. Let it cure, brush off the loose sand, then apply the final layer. The sand gives the top layer a key and adds abrasion resistance.
The top layers can be any Armstrong membrane, chosen by use: RAINSEAL 200 or RAINSEAL FRC 623 for an exposed, heat-reflective finish; SUMMERSHIELD COOL 666 or RAINSEAL CFR 613 for a cool roof; RAINPROOF PU 400 or RAINPROOF FPU 404 where water stands or the roof must last longest; RAINPROOF PWR 690 where there is foot or vehicle traffic. Apply each coat at right angles to the last, with up to 20% water for the water-based coatings.
Carry every layer over the coving and up the parapet. Keep off the roof until the last coat has cured, then flood-test for 24 to 48 hours.

Important Suggestions

The condition sets the minimum number of layers; how the roof is used decides which coating goes in them. Packaged Armstrong systems fix every layer: RAINCARE PRC 5 Layer System (black PU-bitumen primer, mesh, grey, off-white and white coats), RAINPROOF PUF 5 Layer System (polyester fibre mesh 40 GSM as layer 2), RAINSEAL HFC 5 Layer System, RAINPROOF PBR 5 Layer System, RAINPROOF PHC 5 Layer System, CONPROOF FPA 5 Layer System, RAINCARE BRC 6 Layer System, and RAINCARE PUA 7 Layer System (mesh as layers 2 and 4). A crystalline route is also used on lawns and disturbed surfaces: a CONPROOF PFC slurry as layer 1, AFM 40/50 GSM mesh as layer 2, and two-component CONPROOF PFC coats over it, in 4 or 7 layers.

Why This Treatment?

Each extra layer adds thickness and a margin for error, and the reinforcement spreads movement across a wide strip so the film stretches instead of splitting along a crack. A cracked roof with two coats and no reinforcement has nothing holding the cracks together, and they come back through.