Signs your balcony is letting water through
Brown stains, bubbling paint or sagging plaster on the ceiling under the balcony. White, powdery crust along grout lines or the balcony edge, called efflorescence, which is salt left behind as water moves through the tile bed.
Tiles that sound hollow when tapped, cracked or missing grout, water pooling after rain, rust stains from balustrade posts, or swelling and rot in the door frame and skirting inside the balcony door.
Why balconies leak
The membrane has failed. It's the waterproof layer under the tile bed, and it can crack with movement, break down with age or have been thin or patchy from day one.
Water can't get to the drain. A balcony needs a fall (a slight slope) towards the drain or edge. Flat spots and back-falls leave water sitting on the membrane's weakest points.
The edges weren't detailed. The membrane should turn up the walls and under the door sill, and seal into the drain. Most leaks show up at these joins rather than in the middle.
Something punched through it. Balustrade posts, screws and plumbing fixed through the membrane without proper sealing are a common culprit.
How a proper re-waterproof is done
Find the cause
A moisture meter, a look at the ceiling below and sometimes a flood test (blocking the drain and holding water on the balcony for a set time) show where water is getting through.
Strip back
Tiles, tile bed and old membrane come up, down to the concrete or substrate underneath.
Fix the falls and drain
Low spots are built up so water runs to the outlet, and the drain gets a fitting the new membrane can seal into.
Membrane and cure
The new membrane goes on in coats, turned up the walls and under the door sill, with each coat left to cure as the product's maker specifies.
Test, then tile
A good contractor flood tests before tiling. Then the tile bed and tiles go back down, with flexible joints at the edges.
Questions to ask before anyone lifts a tile
- What do you think is causing the leak, and how did you confirm it?
- Which membrane system will you use, and is it made to go under tiles?
- Will you fix the falls and replace the drain fitting?
- How will the membrane finish at the door sill and walls?
- Will you flood test before tiling, and can I see it?
- What licence do you hold for waterproofing here, and what warranty do you give?
What you can do, and what needs a professional
You can
- Keep the balcony drain and any edge outlet clear of leaves and grit
- Photograph stains on the ceiling below and note when they appear
- Avoid fixing pots, screens or hooks through the tiles
- In an apartment, report it to your strata manager or owners corporation first
Leave to a roofer
- Finding where the water gets through
- Lifting tiles and removing the old membrane
- Correcting falls and drains, and laying the new membrane
- Flood testing and re-tiling
What we'd do
We'd pay for a proper diagnosis before anything else, because a leak at the door sill and a failed membrane across the whole balcony are very different jobs. If water is reaching the ceiling below, we wouldn't spend money on a clear sealer over the tiles. We'd strip it back, fix the falls and re-membrane once, properly, with a flood test before the tiles go back down.
Want a roofer to take a look?
Tell us the job and your postcode. We match it with a Find My Roofer certified roofer who specialises in that kind of work, and they call you to quote. Your number goes to them alone.