Movement beneath tiles causing cracking grout

[Sc67]

Hi all.

We had some tiling done professionally about a year ago. This involved tiling over an area by the front door which was predominantly a concrete subfloor, however the first row of tiles had to slightly lap over the edge of the adjoining floorboards.

I was concerned about the possibility of movement, and suggested that it may be necessary to install cement board or some other decoupling membrane before tiling, however the tilers said it wouldn’t be necessary given the limited overlap onto floorboards; they just screeded in the end I think.

I wish I had trusted my gut, as now a horizontal crack has developed along the first grout line above where the floorboards meet the concrete. No cracks have developed elsewhere.

I realise the proper solution is likely to be to take up the tiles and have them do it properly with boarding underneath, however that is not really an option at this stage, and so I am wondering about any other possible workarounds that do not involve starting from scratch. The tilers are only suggesting to regrout, which I think is futile as a long-term fix if the issue is movement.

Would raking out the grout and replacing it with some kind of movement/expansion joint be a possible workaround?

Grateful for any suggestions!

 

[Lower]

You could potentially replace the grout either with a flexible grout or silicone.

 

[ree]

OP,
You say you want a "long-term fix" then why not post a pic?

 

[Sc67]

Thanks very much for the helpful replies. It’s little difficult to photograph as it’s more of a hairline crack, but please see below.