Large Rooftop Terrace — Heat-Welded Sheet Membrane Under Tiles (ARDEX WPM 1000 WeldTec)

Completed — ARDEX WPM 1000 WeldTec membrane across the full terrace, laps welded, outlets detailed, Sydney skyline beyond

The object

The same new residential building in Potts Point where we completed the level 4 planter box in welded PVC. This stage is the large rooftop terrace — an open, tiled outdoor area over habitable space, with parapet walls, floor outlets and multiple wall junctions along the facade.

The problem we solved

The terrace is to be finished in tiles, so the waterproofing must be a fully bonded tile-over system — one that the tile adhesive bonds to directly and that stays watertight beneath a rigid, trafficked finish. Every outlet, upstand, door threshold and wall junction has to be sealed before the tilers start.

Our scope of works

Substrate preparation and installation of the ARDEX WPM 1000 WeldTec system across the full terrace: a polypropylene-fleece-lined synthetic-rubber (butynol-type) sheet membrane, factory-made at a consistent 1.2 mm, fully bonded to the primed deck with the ARDEX-specified adhesive and hot-air welded at every lap and seam. Wall junctions, upstands, outlets, thresholds and penetrations are formed from sheet cut on site and welded by hand. The fleece face is the direct substrate for the tile adhesive — flood testing and tiling can follow 60 minutes after installation.

Special features / difficulty

A large open area with a long facade line — many wall junctions, thresholds and penetrations that must be detailed consistently, and every weld probe-tested so the tile-over system performs as specified. Work is carried out on an active construction site with other trades following directly behind us.

The result

Completed — the full terrace, parapet walls, dividing upstands, outlets and facade junctions are covered in a continuous, hot-air-welded ARDEX WPM 1000 WeldTec membrane and handed over ready for the tilers. The works were delivered together with our partner Lion Seal Waterproofing, a professional membrane contractor we work alongside on larger installations.