Quick answers
Can a balcony be waterproofed without breaking up the tiles?
Often, yes: if the tiles are firmly stuck, they can be cleaned and covered with a waterproof coating. Any loose ones must come up first, because nothing holds on a crumbling base.
On many balconies and terraces water doesn't get through the tiles themselves but through the grout joints between them, which blacken and open up over the years, and through the corner with the wall. If the tiles are firmly stuck, a waterproof coating can go over them and turn them into one continuous surface.
On this balcony the grout had turned black and the corners were marked by standing water. The tiles were cleaned thoroughly and left to dry, and the white coating went straight over them, running a little way up the wall like a skirting. Not a single tile came up, so there was no dust or rubble in the home. On a slab-paved terrace, the surface was ground first to remove hard residue before the primer went on.
If the tiles have come loose, though, they need to come up first. On one terrace many tiles had worked loose: they were lifted, the joints and cracks were sealed, the holes were filled, and then the waterproofing was sprayed on. On another, where almost every tile had cracked, they all came up and the terrace got a new cement-based layer.
A simple check is to tap the tiles lightly: the ones that sound hollow have usually come loose. Bear in mind too that the coating changes how the floor looks, because it covers tiles and joints in one even colour.
Jobs that show it
Balcony Tiles Sealed with a White Coating
Stained tiles with blackened grout were cleaned and covered with a white waterproof coating, without lifting them, that also runs up the skirting.
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Worn Tiled Terrace Waterproofed by Spraying
On a terrace with loose tiles and peeling old coatings, the joints and holes were sealed and a blue-grey waterproofing was sprayed over the whole surface.
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Terrace Stripped of Old Tiles and Given a New Cement-Based Layer
The broken tiles came up, the joints were cleaned out and sealed, and the terrace and the narrow balcony beside it got a new cement-based coating.
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