TILING OVER TILES – YES OR NO?

Picture this – Your partner has finally ‘persuaded’ you to re-vamp your bathroom, including all the tiling, a job you’ve been promising faithfully to do for six months (and the rest).

So, you’re thinking

“This is going to be LOT of work and those big tiles will take some fixing so I could do with making my life easier somehow. I know, I reckon I can save myself a load of hassle and put them on top of the existing tiles. And that’ll get the job done quicker which will keep the ‘other half’ quiet. It’s OK to fix tiles on tiles, isn’t it? Yes, ‘course it is – sounds like a plan”

Well, just hold your horses because it just isn’t as straightforward as that – there are some important questions to answer before you do anything;

What’s the substrate (wall) made of?

Is it plastered brickwork or block work? Or maybe plasterboard or plywood on a timber frame (stud wall) or something else. Whatever it is, you need to find out because this will determine the strength of the wall and whether it’s capable of carrying the very heavy extra load of the additional tiles.

For example, a plastered brick or block wall will, potentially, be stronger than a hollow stud wall. However, this assumes that the plaster is in good condition, hasn’t blown or been water damaged which will weaken it. If it’s old plaster or there’s evidence of possible leaking, the chances are it simply won’t be strong enough.

How solidly are the existing tiles fixed?

Tap the tiles all over and if there’s even a hint of a hollow sound then the fixing is compromised and weak. Affected tiles will need to be removed and replaced with plaster. Any cracked or broken tiles will also need to be removed. The problem is, even if your tiles sound solid, you don’t know what condition the substrate is in. You’re not just relying on the bond between the tiles and the plaster/plasterboard etc., but also the bond between the plaster and the wall – that’s two unknowns.

How will I make sure that the new tiles stick to the old ones properly?

There’s actually no real problem making sure the new tiles will stick, provided the old ones are properly prepared. So, if you’re absolutely determined to go ahead, the old tiles need to be very clean. Use sugar soap to thoroughly clean the tiles and remove all dust, grit, grease and any contamination. Scoring or scratching the surface of the old tiles will also help adhesion.

You should never use PVA which is designed to seal porous surfaces and because tiles aren’t porous, it will only make matters worse. It’s very important to use the correct adhesive, so check carefully with the manufacturers to make sure it’s suitable.

New tiles + old tiles = a lot of weight, will the wall take it?

There are limits to the weight a wall material can carry. For example, the maximum recommended loading on plaster is 20kg/m2 and on plasterboard it’s 32kg/m2. This might sound like a lot, but tiles are very heavy things, especially today’s popular large format tiles. If the wall materials are overloaded, then a potential failure is highly likely and some of them could fall off (hopefully not while someone’s in the bath). So it doesn’t matter how well the new tiles are fixed to the old tiles if they’re all fixed to a poor surface.

Tiling over tiles will double the thickness – is this OK?

Tiling over tiles has implications regarding both appearance and use. A double tile thickness will be particularly noticeable if a room is only part tiled because the extra thickness will be very prominent at the edge. It will also be very obvious where the tiles meet architraves and door/window frames and the aesthetics of the room can be thrown off balance.

The double tile thickness may also have practical implications where there are fittings like taps, radiators, shower fittings etc. For example a narrower gap between the bath taps and the tiled wall may make turning the taps awkward. And shower fittings/pipes that have been specifically cut to size may need altering. All this can add extra cost and work.

What about tiling over floor tiles, surely that’s not a problem?

Generally no, it’s not a problem because there are no potential issues of structural/bonding failures. The only thing you have to be sure of is that the existing tiles are fixed firmly. Any hollow sounding or cracked tiles will need removing and the existing tiles will need thoroughly cleaning. Again, use an appropriate adhesive. The double thickness of tiles on floors is unlikely to have any appearance or practical implications.

Should I cut corners and tile over tilesy?

A significant part of the success or failure of any job lies in the preparation and tiling is no exception. Although it is, of course, possible to tile over tiles, by far the best thing to do is tackle the job properly because a bit more work and attention to detail in the short term will definitely have longer term benefits.

Although you might think you’re cutting down on the amount of work required now, you can easily end up having to do even more work and spend more money to put things right.