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Please can I ask any builders on here if you have any opinion on WAFFLE SLABS


Would you buy a house that was built on a waffle slab?


We have found a beautiful house which is about 12 years old and it is on one of these slabs. I have read some horror stories about them but was wondering if this is the norm. The house in question does not seem to have any issues as yet but obviously we would be concerned about the future.


We would have a builders report done before signing anything but we are going back for a second viewing this week and I don’t want to get too excited if this would be a big NO NO for someone in the know.


thanks all



Flights booked for Sydney 29/09/2015 :cool:

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Waffle slabs work, but generally under very specific conditions - do you have access to the site classification?  If you do and it's and A or S and the site is flat and free-draining, there's no real issues. If you're on H or some M (since 2011 H has been divided into H1 and H2) you may potentially have problems.

I say potentially, because if the house is 12 years old and the slab hasn't cracked you're probably in the clear; we see most structural problems arise in the first year or two as the house settles.  There have been problems in some reactive clay areas where waffles were thrown in (cheap to build) during a prolonged dry spell, then when the rains returned and the soil expanded, they cracked. 

What's the local geology?  if it's sandy or non-reactive fill then you should be alright.  If there's clays around then really go over the walls and see if there's evidence of cracks that have been bogged up.  You can normally expect fine ones around windows but anything a couple of mm wide is cause for concern.

Don't instantly dismiss the place because of the slab - as a geotech we hold engineering liability for 13 years from construction, but make sure that the slab fits the land it's on.


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Thanks so much Eera, I know somebody who does have access to site classification, I will find out which one before we make any offers on the house. I am hoping it will be fine as we love the house.


regards Metoo 

Flights booked for Sydney 29/09/2015 :cool:

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