Substrates & Preparation
Preparing Old Quarry Tiles for a Liquid Screed
Old quarry tiles are dense, low-absorption and often uneven, so they're usually treated as a base for a floating build-up rather than something a screed bonds to directly.
Got old quarry tiles you want to build over rather than rip out?
We'll assess the tile bed's condition and design a floating screed build-up that works around it.
Or call our landline on 01392 237700
Quarry tiles turn up frequently in older properties, particularly in kitchens, pantries and hallways, and they're often still firmly bedded to the slab decades after being laid. Because they're vitrified and dense, they don't offer the kind of porous, mechanically keyed surface that a bonded screed needs, so trying to bond directly onto them is rarely the sensible route.
The more common approach is to treat the tiled surface as a stable but non-bonding base, and build a floating screed over insulation or a separating layer above it. That sidesteps the adhesion question entirely and lets the new floor absorb any minor unevenness in the old tiling.
Where quarry tiles are cracked, loose in places, or laid on a bed that's itself lifting from the slab, the condition of that whole build-up needs checking before anything goes on top, since a floating screed still needs a stable platform beneath it even if it isn't bonding to it. Many quarry-tiled floors were laid straight onto a lean concrete or ash sub-base long before modern damp-proofing became routine, so the moisture condition of what's under the tiles is worth considering alongside the tiles themselves.
Overlaying Old Quarry Tiles — the points that decide it
- Vitrified quarry tiles have very low porosity, so a bonded screed has little to key into and adhesion can't be relied upon
- A floating screed over rigid insulation or a separating membrane is the usual solution, since it doesn't depend on bonding to the tile surface
- Any loose, cracked or hollow-sounding tiles should be identified by sounding the floor before covering it, as a floating layer over an unstable tile bed can still crack
- Old quarry tile beds are sometimes proud or uneven at doorways and thresholds, which affects the achievable screed depth locally
- Original bedding mortar under quarry tiles can be significantly thicker than modern screeds, so overall floor buildup and finished levels need checking against door clearances
- Skirting and wall junctions around old tiled floors often need re-checking, since perimeter insulation and edge strip need a genuinely sound edge to sit against
- A moisture check on the sub-base beneath the tiles is worth carrying out where the original construction predates any damp-proof membrane
- Grout lines and slightly uneven tile faces can be levelled with a smoothing compound before insulation goes down, giving a truer surface for the boards to sit on
Why bonding directly is avoided
Quarry tiles are fired at high temperatures and have minimal surface porosity, which means a bonded cementitious screed has almost nothing to grip. Even where a primer is used, the risk of delamination under load is higher than on a more open, absorbent substrate, so most specifications move straight to a floating design rather than attempting a direct bond.
This isn't a judgement on the tiles themselves — they're often perfectly sound and structurally stable — it's simply that their surface characteristics don't suit the adhesion mechanism a bonded screed relies on. Treating them as a base rather than a substrate to key into sidesteps the problem entirely.
Assessing what's underneath the tiles
Before covering the tiles with insulation, it's worth sounding the floor for hollow patches that indicate the tile bed has separated from the slab beneath. A floating screed will transfer point loads down through the insulation onto whatever is underneath it, so a delaminated tile bed can still cause problems even though the new screed isn't bonded to it.
Where a significant area sounds hollow, it may be more practical to lift the tiles in that section and level with sand or a levelling compound before insulation goes down, rather than floating over a known weak spot. A methodical tap test across the whole floor, rather than a few spot checks, gives a more reliable picture of where problems are concentrated.
Levelling minor unevenness before insulation
Quarry tiles laid decades ago rarely sit perfectly flat, and grout lines, chipped edges and slight dishing across the floor can all leave a surface that's sound but not truly level. A self-smoothing compound applied over the tiles, once any loose sections have been addressed, gives the insulation boards a flatter base to sit on and reduces the risk of point loading on individual boards.
This levelling step also helps close the grout lines themselves, which can otherwise act as small channels that let a fluid liquid screed migrate sideways if the insulation joints above aren't perfectly sealed.
Finished levels and doorway clearances
Quarry tile bedding was often laid noticeably thicker than a modern floor build-up requires, so once insulation and a new liquid screed are added on top, the overall floor height can rise more than expected. Checking this against door clearances, staircase nosings and skirting lines early avoids awkward surprises once the new floor is in.
Where the rise is a genuine problem, options include reducing insulation thickness locally, adjusting door undercuts, or in some cases lifting the tiles in affected areas to recover extra depth, but each of these needs deciding before the pour rather than after.
Got old quarry tiles you want to build over rather than rip out?
We'll assess the tile bed's condition and design a floating screed build-up that works around it.
Or call our landline on 01392 237700
Overlaying Old Quarry Tiles — your questions
In short
Old quarry tiles are dense, low-absorption and often uneven, so they're usually treated as a base for a floating build-up rather than something a screed bonds to directly.
Where to look next
Got old quarry tiles you want to build over rather than rip out?
We'll assess the tile bed's condition and design a floating screed build-up that works around it.