Is this floor ok?

[InvictusBob]

I'm removing some ceramic floor tiles prior to laying some new ones. The old tiles are coming up without too much damage to the surface below but some cracks have been exposed. The concrete seems sound apart from the cracks, and they don't seem to extend further than shown here. Should I do anything in the way of repair before laying the new tiles?

Bob

 

[shaggy]

My guess is it looks like shrinkage cracking. If the concrete dries too quickly at the surface you will get that, which is why a concrete slab is covered to reduce water loss while it's curing. I wouldn't do anything.

 

[Thermo]

how old is the floor?

 

[masona]

how old is the floor?

I was wondering that, doesn't look like floor screed to me unless it's glue on top.

 

[InvictusBob]

I think the floor was put down around 1976. Removing the tiles has generally only removed a small amount of the surface so I guess there wasn't anything different on top. What is now the surface is not loose or crumbly although you can loosen it with your heal.

Bob

 

[InvictusBob]

OK, so I'll assume Shaggy's assessment is correct. But the surface is quite rough even though it's fairly level and I've only laid tiles on a smooth surface before. Would you add a thin layer of levelling compound just to make it easier to apply the adhesive or whack it straight down?

 

[masona]

OK, so I'll assume Shaggy's assessment is correct.

Yes I think so, you could put some cement grout (cement + water) to pour into the cracks before tiling.