Hair line crack on cement tile

[John Horne]

The attached image shows a hair line crack on some cement floor tiles about 4 ft in length that starts at the wall and runs to the middle of the room. The tiles were laid by a professional about 14 months ago in my upstair bathroom - regular 1960 's timber frame house. There was also some structural work done down stairs at the same time. This crack has only just appeared. What checks do I now need to undertake to attempt to identify the cause of this material failure so that it can be put right. Thanks

 

[One Day]

That crack is quite clearly passing through ALL the tiles.
Has to be movement beneath the tiles.
Could be just below the tiles, could be the room below if there is a supporting wall directly below the crack?
Without further investigation it could be many causes of movement.

 

[jobdone]

What was laid under the tiles? Backer board or any decoupling membrane.

 

[Time's Ran Out]

As above - what was the substrate - how did he strengthen the timber floor?
If it’s 4feet in length it’s most likely a plywood underlay he’s tiled onto!

 

[John Horne]

We don't see any cracking elsewhere so I'm not thinking its structural movement but just flexing of the sub floor. Would it be acceptable to assume that we could replace just the cracked tiles or would these just crack again....

 

[John Horne]

Had the builder round today. There was no talk of backer board or decoupling membrane so I'm suspicious that whilst some movement was always a possibilty, in light of the structural work carried out below, there was little or no effort made to mitigate for that.... Would decoupling membrane be considered essential for tiling an upstair bathroom or does it depend on the particular circumstances...? Any words of wisdom much appreciated.

 

[Time's Ran Out]

An earlier post asked for the preparation of the subfloor!

 

[CJ]

What structural work was done below??

Could be after that work, it has settled/dropped very slightly.......enough to crack the tiles. Also the weight of them???

 

[John Horne]

Basically a supporting wall was taken out and RSJ put in directly below the problem. All to Engineers spec. Closer inspection has now revealed a possible slipped joist which I think we need second opinion on. Builder saying joist movement is nothing to do with him as all work was inspected approved and to spec....would a stronger sub floor have accommodated some structural movement? Or is that just wishful thinking...

Respect of sub floor I have not been able to get any detailed info. There is electric underfloor heating and that may or may not be on backer board but I seriously doubt that decoupling membrane was used. I need to lift a few things for a look see.

I have noticed that the floor is most certainly not flat. 2 - 3 mm gaps under a straight edge when laid across the floor. Although it is fairly level. Is this a cause for concern?

Thanks to all for your input so far.

 

[Dumbo]

Even if it was all put back in place correctly I think you would be extremely lucky to not get any cracking in something as rigid as a tiled floor when carrying out that level of structural work directly beneath it .

 

[John Horne]

Yes my thoughts also. It probably needed 6 months with just something temporary for things to bed in before laying costly tiles, just disappointed that the builder didn't anticipate that.

 

[CJ]

So builder has passed the buck.............as Tom Jones would say “It’s not unusual”.