Cracks in concrete floor

Hi all,

We've been looking at a 'lifestyle' property in the Nelson/Tasman region. On the property is a new house, only a few years old. The house is built on a concrete slab, and the slab has been polished so that floorcoverings are not necessary (and it looks great, actually).

Whilst we were looking we noticed a few cracks in the slab, across the floor in one of the corridors. The cracks do not seem to be "open", and the floor either side does not seem to be uneven. Are cracks in the slab normal? Are they significant? Do they indicate bigger problems for the future, or is it just the house settling?

I am sure there are other things we should be looking for, but this is bothering me a bit.

Thanks in advance for comments and advice.

A

OKay, as a builders wife...it seems that cracks on the slab are quite common.

Hubby specifically gets his slabs cut across stress points to try to prevent 'uncontrolled' cracking, and tries to use water on the slabs for a few days afterwards to help avoid further cracking. Unfortunately in this age of cost cutting, but many builders/building companies don't do this now, so cracks can turn up anywhere and everywhere...

If in doubt, get a reputable builder in to have a look at it.

If it were me, I'd be checking the windows/doors near the cracks if you are worried, make sure they open and shut without any sticking/sagging...and check the walls (if they are brick or plaster) for any cracks up or along them that might be caused by a slab moving...

I know when my barn slab was poured a few years ago, they made cuts across the stress points but some years down the line I note there is one crack that developed. As you described - not open but a crack nevertheless. Go with tiggers advise as it sounds very sensible to me.

I would have thought with polished concrete floors, cracks would not be desirable. Any underfloor heating? Wouldn't concrete be really really cold in Winter in the "deep South"?

My floor has a few hairline cracks like that. They happened as the concrete was drying (despite the builders best efforts to prevent them) and they're not of any significance structurally.

And Didi, concrete floors can be very warm if they're properly insulated underneath because they hold the heat. It's not the same as say a garage floor which would be cold earth next to concrete and would remain cold.

Our slab has polystrene under it which is supposed to increase its heat retention.

We lived on a bare concrete floor in ChCh for many years, it never seemed cold...

I stand corrected. I was thinking of a person I know who has just had her original concrete slab floor polished, in a 1970's house and like mine, it will be sitting on the dirt. Not a good idea? It looks awesome.

We had a few cracks in our concrete pad, despite cuts across the stress points. Watering here wasnt an option, as there wasnt any at the time but it was done late autumn so not so hot. If the place you are looking at is a lifestyle block that could have been the same for them.
We spent our first winter on concrete and it wasnt at all cold, once it warms up it really holds the heat.

we have plenty of cracks in our slab and have lived through the winter on it too :0 not too cold as we have the expol under it too like Tigger and its great at keeping the heat in the floor.
We couldnt get water on it to stop the cracking but everything is fine, no sticking doors or window, just part of the build process i think, it takes a year for the slab to settle...i think...or is that something else...or is that what hubby told me to stop me whining about no carpets

Westermans;219425 wrote: we have plenty of cracks in our slab and have lived through the winter on it too :0 not too cold as we have the expol under it too like Tigger and its great at keeping the heat in the floor.
We couldnt get water on it to stop the cracking but everything is fine, no sticking doors or window, just part of the build process i think, it takes a year for the slab to settle...i think...or is that something else...or is that what hubby told me to stop me whining about no carpets

ditto to Westermans for us

Yep, we are concrete floors for some indefinite time too will have run out of money by the time we are looking at carpet for all but the bedroom...

Nelson is pretty tropical compared to the real deep south

Hi all,

Thanks for all the comments. It would seem there is nothing to worry about apart from the looks (and the cracks don't look bad because they have not shifted). There were lines drawn in the concrete, looks like a blunt stick was drawn across the surface, but the cracks decided to appear elsewhere...

There is carpet in the bedrooms, but nowhere else. The polished concrete looks nice, and there is obviously a cost saving with having no carpet. Not only that, it's easy to clean.

Thanks all.

A

easy to get the spills cleared up in my experience..i dont care who spills what also EXCELLENT for parties

Both my lads are concrete cutters and drillers and what they say should be done are 'expansion cuts' on the stress points, they do new builds all the time even if they are polished after.

We had the polystyrene thingies, steel and then concrete. They made the cuts across it and not one crack appeared. People we know that built a house just before us with the same company had heaps of cracks, I didn't like it at all. I carpeted as I drop too much stuff for polished concrete. Make sure it is finished properly though as daughter cleans a house with it and she can't wash the floors as the concrete soaks it up.

When they come to pour the concrete the truck sat there for ages and nobody got out. We finally come up to have a look and my bloody Highland steer had got in through the electric fence which had broke and was standing right outside the truckies door. He said he was too scared to get out and I fell about laughing. I told him all Clyde wanted was for him to share his lunch. I couldn't see Clyde by that stage and I said, what cow, that one down there he said. Clyde had buggered off down the paddock.