Cracks in concrete floor

[dustyrivergardens]

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 floor coverings 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 on 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.

 

[dustyrivergardens]

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 floor coverings 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 on 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. https://www.epoxyflooringboston.co/

Thanks in advance for comments and advice.

 

[Markit]

Earthquakes are a thing here. My foundations go down 2+ meters. If you're talking about a "floating" foundation then good luck. What happens during a real earthquake is that the ground literally turns to liquid. Not wet but if you've ever seen a sand bed cleaner you'll understand when you shake something hard enough that's what happens. Your floating foundation will possible sink. Lived in California where they're illegal.

 

[Balifrog]

A few pictures would help, preferably with something (pack of cig) positionned near the crack to have an idea of size.
Agreed with @Markit concerning the floating slab, but it seems to be the "standard" here.

On the other hand a superficial crack could simply be due to inadequate curing of the concrete / cement after pouring. It should be kept wet during curing to avoid it to dry to fast.

Google for more technical details and pics.

 

[AuroraB]

I'm not familiar with "Nelson/Tasman" region. Sounds like not Bali?

Anyway, suggest having a look at the blueprints to identify possible issues.

 

[Mark]

I think minor cracking in polished concrete floors is pretty common. Remember seeing this in an episode of Grand Designs Australia.

 

[mugwump]

This topic seemingly concerns New Zealand rather than Bali, but if I may deviate to concern the cracking of cement in Bali may contribute a source of the cause. All too frequently in recent years sand in the project has its source ocean beaches which contain sea salt which subsequently dries, shrinks and vanishes leaving cracks and a weakened project.
This problem my be directed to member Populaire who may have a suggestion as to how to determine if sand can be tested to learn if it contains salt?