Solution for some slight tile movement and grout cracking?

6 Nov 2009
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United Kingdom
We are in a 7 year old property with suspended chipboard flooring. The shower room is overlaid with plywood and screwed down onto the chipboard with really close spacing. The tiles are porcelain and the floor area is 2.6 sq metres.

We can feel slight movement of about half of the tiles underfoot and there is cracking along the grout lines, with some grout breaking up.

I am not sure why this is happening but we may have caused this by using a steam mop to clean the floor.

1. Is this floor salvageable or is a complete lifting and re-tiling necessary? I ask because I believe there is an adhesive that can be injected down the joints.

2. If a re-do is necessary, excluding materials, what would the approximate cost be to lift and re tile 2.6 sq metres of floor? The tiles run under the toilet, but not the sink.

3. In view of the nature of the floor ie chipboard with screwed ply over, what would be the best adhesive to use?

4. Due to the flooring type can this tile loosening and grout cracking be avoided again?

5. Is it the case that a steam mop must not be used on this type of floor? I would add that we have a tiled kitchen floor on which we use a steam mop with no problems.

6. Should we stop using the steam mop on the porcelain tiled kitchen floor.

7. The shower room
shower floor.jpg
floor looks ok. Could we just re=grout with a flexible grout from time to time.

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when did it start?
some possibilities are, has there been any leaks? is there any floor movement in any other surroundingroom, does the ply have expansion gaps at all edges? is the ply screwed through the chipboard into the joists? is the ply glued to the chipboard? did you leave an expansion gap around the room and at all abutments for the tile? was first class tile adhesive and grout mixed and used according to mfrs directionss? Your grout lines look very ttight andthin.
As a bathroom job it looks great.

injecting adheasive wont work, regrouting is not the answer, i dont know anything aboutthe steam mops.
Thanks to both for your replies.

The only question I can answer is that I began to notice a few tiles lifting in 2019. It has slowly spread to others.
It was a new build and an apparently highly skilled tiler laid the floor. Having said that I subsequently discovered that for the walls he was dabber rather than a screeder when he did the walls. The only thing I noticed was that it was ply (thickness unknown) over chipboard, which was screwed at a very close spacing.
I asked for narrow grout lines. Perhaps that was a mistake.
That door on the right is now binding on the floor. The floor seems to be rising in a slight V down the centre. I have checked for leakage but can't identify anything. There is no surface water around the pan and no musty damp smell within the concealed cistern housing.
I gather from your replies it requires a complete re-do?
Any tips to avoid a recurrence are welcome. I would also appreciate an estimate to lift and lay 2.6 sq m of a similar porcelain tile.
I take it I should ensure that chipboard is screwed well into the joists. It is a timber-frame construction so the joists are not that thick. They are laid over the ply kit frame.
Which brand of flexible adhesive and screed notch would you recommend?
Which brand of flexible grout?
Anything else?
Thanks again
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The grout lines make it look like the tiles could be touching. such a narrow/shallow groutline might allow moisture to get below the tiles and cause swelling.A slight V means the tile or the ply is tentingbecause of lackof expansionor moisture getting will have toslowly lift all the tilesand after cleaning they can be reused. maybe the ply will also have to come up.look for edge expansion gaps as you lift materials.
Timber frame has nothing to do with joist sections or spans.
find out whats the cause before anythingelse or you will soon be doing it all agagin.
If there's any bounce in the floor then a tiled solution is doomed. The problem will just manifest itself again. If it's a typical developer house the joists will be set to the minimum and they'll be some bounce and as mentioned you need to understand why it failed before trying to fix it. If it is an issue with the floor flexing then adding additional joists could sort it but obviously that's a very invasive solution. Personally I'd lift the tiles, screw some thin ply down and stick vinyl down.
Thanks a lot for taking the time to provide a considered reply to our problem.

Weighing up your information and advice, as much as we like the tiled look, it seems that we may have to go in a completely different direction, so we don't want a repeat of the problem. In any case it is difficult to get a tiler never mind a highly skilled one, in this area. We will therefore have to go with rubber, vinyl or water-resistant laminate. When you read the cons the first 2 tend to give off toxic volatiles so we are currently favouring the latter at the moment. Underlay and the laminate thickness should take the floor back to its original height to merge with the engineered wood floor in the hall.

In the shower room, the wall tiles come right down to floor level without any skirting. I assume sealant can be used at the floor/wall junction?

Any recommendations or advice on the above 3 alternative flooring types?

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