Tiles moving and holes appearing in grout

Hi, Tiles are moving due to the following reasons: 1. Tile over plywood installed over engineered wooden flooring. If this is the case, the installer was very bad. You now have 2 floating floors with tiles on top. Cracks appear ASAP. 2. Tile over plywood installed over concrete floor. If this is the case plywood should never be installed over a concrete subfloor. The correct way to do it is the following. Remove engineered wooden flooring. Level subfloor. Check for cracks in the concrete subfloor and if you have cracks dura base or ditra mat needs to be installed. I would install it anyway because it's such a good product because it absorbs the movement of the subfloor. Install tiles, job done. Regards, Lucian

Engineered floor is a floating floor and should not be tiled on its design is to expand and contract. This is why the tiles are cracking.

The plywood has not been put properly it probably has slight movement thats why tiles move. The only reason that tiles can move is when the base under the tile is also moving.

There might be few reasons 1: your original floor was moving before 2: your builder didn’t screw the plywood properly 3: might be he didn’t use the primer PVA Before the tiles on top of plywood Right way is to take off original floor level the area and use primer before laying the tiles

Because they shouldn’t of laid them on engineered flooring, this should have been removed and tiles should have been fitted straight on to the concrete screed!!

Sub-base movement isn’t the only possible cause, though solid and sound base is a vital requirement. Assuming it’s 15mm ply fixed at 300mm centres also consider: 1) preparation - was the background clean and sealed (I use an acrylic primer in two applications) 2) Type of adhesive used - I would use an S2 rapid set flexible adhesive. I would recommend the use of a decoupling membrane, either fixed or floating. My guess if you lifted a few tiles is that they have delaminated with the adhesive from the ply completely....... although direct fixing onto plywood on floors is still acceptable under British Standards I would use caution. I’d rip the whole lot up down to the concrete and start again!!! There are other factors I’ve not covered....UFH? Coverage? Size of your tiled areas? Not sure what you mean with the threshold question: do you mean an expansion joint or door bar has been fitted?

Lift up the old floor to do proper job, then you won’t have problems in first place. Regards Norm

Firstly the idea of laying tiles over numerous floating substrates does not resound as best practice. There are also a number of other variables to consider including: Was the adhesive used a suitably flexible adhesive? Was the plywood properly sealed withe the correct sealant prior to laying the tiles? Was the adhesive properly mixed? Was the grout properly mixed with the possible addition of a flex agent? How thin was the plywood and was it properly secured throughout. The statement that the grout is “crumbling” might indicate that it was incorrectly prepared. Presumably there is a d@mp proof membrane under the engineered flooring? If not ant rising damp would be potentially trapped and unable to breathe. In short lots of potential causes. How good / professional was your tiler - a real professional would be straight back to advise.