Cracked floor

tonyenglish

Hi,

A long while ago, we had our kitchen renovated.  Part of the renovation was to widen the archway between the original part of the kitchen and the part added in the extension which was built before we bought the house.  Fast forward 15 years and we decided to have a polished concrete floor installed.  I pulled up the tiles and an absolute ton of tile adhesive.  It seems that the floors in both rooms were not level and the difference filled with a huge amount of tile adhesive!  The guy installing the floor didn't raise any concerns about this.  The floor got put in and was ground down.  Then it started cracking.  He's saying it is cracking because the join between the slab in the old part of the house and the 20 year old extension was never joined to each other.  I was told that a chunk will need to be cut out between the two and and concrete and metal bars added to link the 2 slabs to stop them moving.

My question is, if the change to the extension wasn't correctly done, can the movement be something that would come under the home insurance?  The original extension was done before we moved here 25 years ago and the change we made to it was about 15 years ago.  Is there anybody who we could/should get in to properly assess what's going on?

Over time we did have some tiles in the kitchen crack, but that was over the course of 15 years, not to couple of days the concrete was in.

stuart45

Have you got some photos of the issue?

casper_gutman

It will be very difficult to tie two concrete slabs rigidly together if they were not designed and constructed to achieve this in the first place. Even if you tie the areas close to the junction together (where the metal bars would be put in) you would most likely just see cracking elsewhere. The slabs will not have been reinforced to withstand bending, and any differential movement of the ground supporting them will almost certainly cause significant cracking* somewhere if they are tied together.

A polished concrete floor is about the worst possible finish for showing any cracks that do form. On projects I've been involved with (as a client not an engineer), the recommended solution to similar issues has been to provide a movement joint where the movement can be accommodated without damaging the finishes. This is essentially the opposite of what the floor installer seems to be recommending: rather than trying to hold the slabs together, you accept there will be movement, and use the fact that it will occur at a predictable position to build in a means of tolerating it without damage.

*Any slab will crack, if only due to shrinkage of the concrete. Reinforcement in ground-bearing slabs is usually designed to limit the size of cracks (by ensuring there are lots of little ones) rather than to stop cracking completely. But if you bend an unreinforced slab (or otherwise apply tension to it) then it will crack and the crack will keep opening up as long as the movement continues.