A landed house in Singapore has four surfaces that take rain directly and sit over something that must stay dry: the car porch roof, the roof terrace, the balconies and the planters. Each is a small flat concrete slab with the same physics as a commercial roof — falls, outlets, upstands, movement — but with less attention paid at the design stage and a surface that is usually finished with tiles, so the waterproofing is hidden and the first sign of failure is a stain on a ceiling. This guide takes the four surfaces in turn, sets out what fails in each and how each is waterproofed, and ends with what an applicator needs to quote the work.
The car porch roof
The car porch is the surface most often forgotten and most often leaking. It is a flat slab, sometimes cantilevered, with a low parapet and a single outlet. Under URA’s landed housing guidelines the car porch roof may serve as an open terrace but not be enclosed, so it stays exposed for the life of the house. It is frequently tiled, and the tile grout is mistaken for the waterproofing.
What fails. The outlet, because it is the only one and it blocks; the parapet upstand, because the membrane — if there was one — stopped short of it; and ponding, because a small slab with a single outlet at one corner holds water at the other. The signal is a stained or dripping car porch ceiling, and the wrong response is a re-grout.
How it is waterproofed. Where the porch is tiled and the membrane has failed, the tiles come up. The slab is prepared, the falls checked to the outlet, cracks reinstated with a non-sag repair such as PatchBond TX80, and a seamless liquid membrane installed and dressed into the outlet and up the parapet. SealForce RC30 — a roller-applied polyurea membrane used beneath tiling and in car-park deck systems, with elongation above 500% and adhesion to concrete above 2.5 N/mm² — is the usual choice under a re-tiled porch. Where the porch is to be left exposed, a UV-stable aliphatic membrane such as SealForce RC40 is applied in two layers and left as the finish, walkable for cleaning.
The car park guide covers the porch as the same job as a traffic deck, in miniature.
The roof terrace
The roof terrace is a larger slab that people use — furnished, planted, sometimes with a pergola or a tank on it — and almost always finished with tiles or pavers.
What fails. Thresholds, where the terrace meets a door and the membrane has to rise behind the frame; outlets under pavers that nobody has seen for years; upstands at the parapet and at the base of any structure standing on the slab; and ponding under pavers on pedestals where the falls beneath were never right.
How it is waterproofed. As a concealed membrane under the finish — RC30 for a terrace that will be tiled or paved — with the details done first: the threshold detailed to the specified height behind the frame, every outlet dressed and clamped, every upstand reinforced and terminated. Where a terrace is to be left as an exposed finish for maintenance access rather than furnished, RC40 is applied as the surface. The RC roof guide sets out the assessment that comes before any of this.
The balconies
A balcony is a terrace in miniature, cantilevered over the room below or over the garden, with a door threshold, a single outlet, a parapet or a railing base, and usually a tiled finish.
What fails. The threshold and the railing posts. The threshold because the membrane stops at the door frame instead of rising behind it; the posts because they were fixed through the slab after the membrane went on, or the membrane was never dressed around them. The signal is a stain on the ceiling of the room below, or damp at the top of the wall inside.
How it is waterproofed. As the terrace: tiles up, slab prepared, falls to the outlet confirmed, membrane installed with the threshold carried up behind the frame and every post base detailed as a penetration, then re-tiled. On a balcony used for washing and drying, the same membrane that serves wet areas beneath tiles does the job — RC30 is published for waterproofing beneath tiling and in bathrooms and wet areas.
The planters
A planter is a tank. It is permanently wet, it holds soil and roots against its walls, and the fertiliser salts and organic acids in the soil sit against the membrane for years.
What fails. The membrane that was never there, or was a cementitious slurry that cracked when the planter moved; the top edge, where the membrane did not turn over the rim and water ran down behind it; and root penetration into any film that was not protected.
How it is waterproofed. Emptied, cleaned to sound concrete, and lined with one continuous seamless membrane that covers the floor, the walls and the outlet, turns over the top edge, and is protected from roots by a drainage layer and a root barrier before the soil goes back. RC30 lines the planter; the drainage and root barrier above it are what keep it lined.
What is common to all four
Every one of these surfaces fails at the details, not in the field, and every one is repaired by the same sequence: assess, correct the falls, reinstate the cracks, detail the outlets, upstands and thresholds, install the membrane as one continuous film, and protect it with the finish. None of them is fixed by re-grouting, by a sealer brushed over the tiles, or by a thicker coat over a pond. The membrane types guide explains why a liquid-applied membrane is the usual choice on all four.
What the applicator needs to quote
Photographs of each surface from above, close-ups of the outlet, the parapet or railing base, the door threshold and any cracks; a photograph of the stain or leak inside; the approximate area of each surface; whether it is tiled, paved or exposed; and where water stands after rain. Send that to Rayson and we will specify the system for each surface, send the technical data sheets, and — where you need one — introduce an applicator in the Rayson network who inspects the house, issues the quotation and carries out the work under its own workmanship warranty.