[Thaddeus]

Background: Previous owner installed tile over a floor repair he made when he installed gas and electric to an island. Tile cracked when he installed over voids he left in patched concrete and uneven concrete. Piping was not below slab either but in the concrete. Concrete was definitely different mixtures. I will be installing luxury vinyl planks when repair is done. I removed and no longer need gas and electric that was to island. This is a house slab in north Texas built in the 1970s.. Sawcut slab is about 1 foot wide and 10 foot long, all interior to the house.

Questions:
1. Should I jackhammer out all the patched concrete or just fill in and level holes?
2. If I jackhammer out, do I need dowels in existing concrete to keep concrete from settling or just use a bonding agent on existing concrete on each side of trench or just pour new concrete in trench?
3. I do not think vapor barrier was installed under rest of slab, should I install for sawcut portion?

 

[SW Dweller]

Concrete is not water proof, vapor barrier for such a tiny area, not needed.

Dowels have nothing to do with the concrete settling. The soil/concrete under the pour does.

Jack hammer if you wish, level/smooth is more important

 

[huesmann]

Well, the dowels do help keep the new and old concrete settling together.