Sometimes, but it is rarely the right answer. An overlay bonds to what it lands on, so a tiled surface transfers every problem the tiles have — hollow tiles, failed adhesive, movement at grout lines — straight into the new surface. Where tiles are fully bonded, sound and outdoors, an overlay can work over a mechanically abraded surface. Where any are drummy, they come up.
The test that decides it
Tap every tile with something hard. A solidly bonded tile sounds dead. A drummy tile sounds hollow, which means the adhesive has released and the tile is being held in place by its neighbours and the grout.
If any meaningful proportion sound hollow, the tiles come up. An overlay over a drummy tile has nothing to hold it — the tile moves under load, and the new surface cracks along the tile edge within a season. Covering it changes nothing except how long it takes to become visible.
If they are all solid, the conversation continues. Solid does not mean suitable, but it means the question is now about preparation rather than removal.
Why grout lines telegraph
Grout joints are lines of weakness and lines of differential movement. Tiles expand and contract; grout does not do it identically. Lay a thin overlay across that and the joint pattern eventually appears through the new surface as fine cracking in a grid — the tiles you were trying to hide, drawn faintly on top.
Where an overlay over tiles does work, it is because the surface has been mechanically abraded to a profile, the joints have been addressed, and the overlay is thick enough to move as one piece rather than following the substrate.
Indoors and outdoors are different problems
Outdoors, tiles over a concrete slab with no movement joints and no water underneath is the best case. Grind the glaze off, prepare properly, and a cement overlay can go over the top.
Indoors is usually worse, not better. Tiles inside are often laid over a bed on a slab without a membrane, or over sheeting rather than concrete, and neither gives an overlay anything reliable to bond to. Height is the other constraint — an overlay raises the floor, and doors, thresholds and cabinetry rarely have that clearance to give.
Wet areas are a straight no. Any overlay over tiles in a shower or on a balcony sits over a waterproofing membrane that has been penetrated by the tile adhesive, and that is a waterproofing job rather than a resurfacing one.
What we usually recommend
On an outdoor tiled patio or pool surround where every tile is solid, we will quote an overlay and be honest about the risk of joint telegraphing.
Everywhere else, removing the tiles and resurfacing the slab underneath costs more up front and is the cheaper of the two options over any real timeframe. We would rather quote the removal than sell you a surface that is going to map out the tiles beneath it.
The questions we get asked
Can a concrete overlay go over tiles?
Sometimes — outdoors, on a concrete slab, where every tile is solidly bonded and the surface is mechanically abraded first. It is not the usual answer.
How do I know if my tiles are suitable?
Tap them. Hollow-sounding tiles have lost their adhesive and must come up. If any meaningful number are drummy, the whole lot goes.
Will the grout lines show through?
They can, as fine grid cracking, because grout and tile move differently. A thicker overlay and proper joint treatment reduce the risk but do not eliminate it.
Can you resurface over tiles in a bathroom?
No. Tiles in a wet area sit over a waterproofing membrane that the tile adhesive has already penetrated. That is a waterproofing job, not a resurfacing one.
Is removing the tiles expensive?
It costs more up front and less over any real timeframe than an overlay that telegraphs the tiles. We quote both so you can see the difference.
Send a photo of the slab.
We will tell you whether it can be resurfaced, what finish suits it, and what it costs — before anyone turns up with a grinder.