Browse Forums Building Standards; Getting It Right! 1 Nov 09, 2016 10:17 pm Hi everyone, our slab has been poured for 3 weeks and now we spotted some thin and long cracks on the slab. They locate across the centre of the slab, from one side to the other, even extend to the edge of slab. Is that normal? Should we ask the builder to repair it? Will it cause any structural issue? Please assist? Thank you TF Build thread - viewtopic.php?f=31&t=83484 Our Glendale 39, SA Re: Thin and long Cracks on slab 2Nov 09, 2016 11:00 pm I think I read somewhere saying it's common for cracks appearing in newly poured concrete because it's still curing but I would definitely be concerned and would want to question my SM about it. Re: Thin and long Cracks on slab 3Nov 10, 2016 5:25 am That looks like a normal shrinkage crack and nothing to worry about. if you want to finf out more check out this link: https://anewhouse.com.au/2012/02/concrete-cracking/ The Harder You Try - the Luckier You Get ! Web site http://www.anewhouse.com.au Informative, Amusing, and Opinionated Blog - Over 600 posts on all aspects of building a new house. Re: Thin and long Cracks on slab 4Nov 10, 2016 1:17 pm The reason why i am worry is because the cracks extend from one edge to the other,so feel like the whole slab has been broken into half eventhough they are very thin. Build thread - viewtopic.php?f=31&t=83484 Our Glendale 39, SA Re: Thin and long Cracks on slab 5Nov 10, 2016 4:34 pm Once a crack starts it tends to run until it either reaches an edge or another crack. They look to be less than 1mm which is fine. The slab uses the reinforcing steel, plus the interlocking effect of the irregular crack surface, to maintain the structural strength. The Harder You Try - the Luckier You Get ! Web site http://www.anewhouse.com.au Informative, Amusing, and Opinionated Blog - Over 600 posts on all aspects of building a new house. Re: Thin and long Cracks on slab 6Nov 10, 2016 6:34 pm bashworth Once a crack starts it tends to run until it either reaches an edge or another crack. They look to be less than 1mm which is fine. The slab uses the reinforcing steel, plus the interlocking effect of the irregular crack surface, to maintain the structural strength. Thank you for clearing our minds!! Seem we worried too much:) Build thread - viewtopic.php?f=31&t=83484 Our Glendale 39, SA Re: Thin and long Cracks on slab 7Nov 13, 2016 1:12 am tungfai bashworth Once a crack starts it tends to run until it either reaches an edge or another crack. They look to be less than 1mm which is fine. The slab uses the reinforcing steel, plus the interlocking effect of the irregular crack surface, to maintain the structural strength. Thank you for clearing our minds!! Seem we worried too much:) Re: Thin and long Cracks on slab 8Nov 13, 2016 1:20 am Hi, I tend to disagree with the recommendation when saying the cracks at 3 months are 1mm and no cause for concern. Firstly - do you have a soil report and who did the soil sample? Secondly - what is the slab classification based on that soil report? These are two very critical factors that you need to ensure are accurate due to potential issues that can occur if it has been classified incorrectly. The classification determines the appropriate thickness and depth of footings. If they are not correct, the potential of slab heave is very possible. Re: Thin and long Cracks on slab 9Nov 13, 2016 4:16 am Bashworth has given a good answer. Concrete shrinks, they are the physical properties of concrete. Shrinkage is controlled with reinforcing steel to ensure that instead of large cracks there are thousands of small cracks mostly invisible to the eye. Presently there is no evidence pointing to defects requiring further attention. Foremost Building Expert in Australia,assisting with building problems/disputes, building stage inspections,pre-contract review advice for peace of mind 200 blogs http://www.buildingexpert.net.au/blog Re: Thin and long Cracks on slab 10Nov 13, 2016 5:25 pm It's not that the answer is invalid, the response I have provided is based on my own experience where hairline cracks where visible and I was given the same answer 12 years ago. Yes, I have slab heave and yes the soil report incorrectly classified the site resulting in more than just cracks to the slab. There is no harm in checking and questioning to ensure that the foundations are sound. It's also good to understand what each classification means. My property had large trees and an existing premises which was torn down and the property sub divided. The site has a "H classification and 3 structural engineers agreed it should have been "P" at a minimum "E". Therefore the slab was undersized for its purpose. 7 5746 The CSIRO BTF18 explains differnt types of cracks and what "normal" is Google this and the top result is actually the latest version. You normally have to buy this from… 9 9270 The spacing of the studs looks pretty large especially for a load bearing wall. 3 11103 |