Tiling over existing bathroom tiles is one of the most common questions we get asked in Edinburgh homes, and the honest answer is: sometimes it's a smart shortcut, and sometimes it stores up expensive problems. This guide explains how to tell the difference before you commit either way.
Yes, in principle. Modern flexible tile adhesives are designed to bond to well-prepared glazed surfaces, so tiling over tiles is a recognised method rather than a bodge. It saves the mess, skip hire and labour of stripping back to the wall, which matters in tenement flats where getting rubble down three flights of a shared stair is a job in itself.
The catch is that everything depends on what's underneath. New tiles are only as solid as the old ones they're stuck to. If the existing tiles are hollow, cracked or fixed to crumbling plaster, you're bonding new work to a failing surface, and the whole lot can come away later. That's why the first job is always a proper survey, not a trip to the tile shop.
The existing tiles need to be firmly bonded, flat and dry. We tap every tile: a solid sound means good adhesion, a hollow ring means a debonded tile that has to come off or the area has to be stripped. As a rough rule, if more than around 10 to 15 percent of tiles sound hollow, overlaying stops making sense.
You also need to think about weight. Old plaster walls in Victorian and Edwardian properties, common across Edinburgh and the Lothians, have limits on how much tile they can carry. Two layers of ceramic plus adhesive can exceed 30 kg per square metre, and standard gypsum plaster is only rated for about 20 kg per square metre. Large-format porcelain over existing tiles on old plaster is usually asking for trouble.
Any sign of water damage means strip it out. Staining, spongy plaster, drummy patches around the bath or shower, or mouldy grout that keeps coming back all point to moisture behind the tiles. Covering that up doesn't fix it, and in a shower area it will fail again, only now there are two layers to remove.
Shower enclosures deserve special caution. We'd generally strip these back and re-board with a cement-based or waterproof backer board, then tank the wet area before retiling. It costs more up front, but a properly tanked shower is the difference between a bathroom that lasts twenty years and one that leaks into the flat below, which in a tenement is a conversation nobody wants with their downstairs neighbour.
Preparation is most of the work. The old tiles get degreased and washed down, any loose ones are removed and the voids filled, and the glazed surface is either scored or primed with a suitable bonding primer. New joints should be offset from the old ones so grout lines don't sit on top of each other, and a flexible cement-based adhesive is essential; ready-mixed tub adhesive isn't suitable over existing tiles.
Edges need thought too. The doubled-up thickness shows at window reveals, around the bath rim and at doorways, so trims and careful detailing keep it looking intentional rather than layered. Sockets, shaver points and pipe penetrations may need extending, which is where having a builder who also handles the joinery and electrical side saves coordinating three separate trades.
For a typical Edinburgh bathroom, tiling over existing tiles usually saves somewhere in the region of £300 to £700 compared with stripping back, mainly on labour, skip hire and re-plastering or re-boarding. On a small splashback the saving is modest; on a fully tiled bathroom it's more meaningful.
Against that, weigh the downsides: you lose a little room space, resale surveys sometimes flag doubled-up tiling, and if anything goes wrong behind the wall later, there are two layers to get through. Our honest steer is that overlaying suits sound, dry walls outside the shower zone, while wet areas and anything with a history of damp are worth doing properly from the wall out. A quick look at the room is usually enough to tell you which side of that line your bathroom sits on.
Tap each tile with a coin or knuckle: a solid sound means it's well bonded, a hollow ring means it's loose. If more than roughly one tile in ten sounds hollow, or grout lines are cracking in patches, stripping back is usually the better call.
It's possible but we'd rarely recommend it. Showers take the most water and movement, so we'd normally strip back, fit waterproof backer board and tank the area before retiling, which is far more reliable long term.
You lose roughly 10 to 15 mm per tiled wall, which you won't notice in the room itself. Where it does show is at window reveals, door frames and around the bath edge, so those details need trims and proper finishing to look right.