Balcony waterproofing in Sydney

A balcony is a roof with tiles on it, and most balcony leaks start at the details rather than the open floor: a membrane that stops short of the door sill, an outlet sitting higher than the bed around it, no upturn behind the skirting tiles, or a balustrade post fixed straight through the membrane.

Whatever gets through the tiles has to be stopped by a membrane and carried to an outlet, and when the space below is a bedroom or someone else’s apartment, a failure shows up there first. For balconies over rooms in a house, and for balconies on apartment buildings, the NCC requires the membrane to meet AS 4654.1 and the system to be designed and installed to AS 4654.2.

The fix depends on what has failed and on the tiles. A new or stripped balcony gets a full membrane under a new tile bed. Where the tiles are well bonded and the balcony drains properly, some leaks can be repaired over the existing tiles, which is covered on our remedial waterproofing page.

A leaking balcony is repaired from the top. Sealing or painting the ceiling underneath can hide the stain for a while, but water keeps coming in through the balcony, and the concrete and steel in between stay wet.

What the repair involves depends on what has failed. A missing upturn at the door or a badly set outlet can sometimes be fixed by lifting a strip of tiles. Where the membrane has failed across the floor, or there never was one, the tiles and bed come up and the balcony is waterproofed again from the slab.

A terrace over a garage or living area is waterproofed the same way as a balcony, but it’s bigger, so falls, outlet positions and movement joints matter more.

Many terraces are finished with pavers on adjustable pedestals instead of a tile bed. Water drains freely under the pavers, and a few can be lifted later to look at the membrane, which a tiled finish doesn’t allow.

A planter box is permanently wet, full of soil, and often built over a room, a garage or a neighbour’s balcony. The membrane goes across the base and up every inside face to the top, a protection board covers it so soil and roots can’t damage it, and a drainage layer with filter fabric keeps the outlet from silting up.

On apartment buildings the NCC says exposed construction and movement joints in a balcony or roof slab must not sit beneath or run through a planter box (NCC 2022 Volume One, F1D4). If a leak shows under an older planter, a slab joint running under it is one of the first things to check.

Sometimes. If the leak is at one detail, such as the door sill, an outlet or a balustrade post, it can be repaired locally. Clear sealers over the tiles slow water through the grout for a while, but they don’t fix a membrane that has failed underneath.

Because the bed under the tiles has been wet for a long time, or the falls are wrong. A local repair works only when the rest of the membrane is sound and the balcony drains.

Yes. We flood test the membrane before it’s covered and give you a waterproofing certificate when the job is finished. Keep it: strata managers and buyers often ask for it.

Water travels along the slab and through the tile bed before it finds a way down, so a stain under the balcony can be metres from where water is getting in. That’s why we look at the whole balcony, not only the patch above the stain.

They need a membrane suited to being permanently wet and buried, with a protection board over it. Roots and sharp fill damage an unprotected membrane, and once a planter is filled and planted, the membrane can’t be inspected.