Thats my point the granular layer under the waffle allows moisture ingress undrer the slab but that is not the situation with the convential raft slab.
“Soil should always fall away from the slab, if the building pad needs to be raised to achieve this then so be it. Engineers specify this as a requirement as part of the design and the builder needs to ensure this happens.”
Unfortunately builders don’t slope the ground away from the house.
You can see this fact at any new housing estate.I would like to see anybody post halve a dozen examples of a properly drained house underconstruction to AS2870 standards.
“Waffle pod systems also utilise footings, edge beams and drilled piers, a perfect chance to confirm the soil test is accurate. If tree roots are encountered during the soil test the site would be reclassified as P which is also taken into account when the engineer specifies their Design Range.”
The majority of waffle slabs don’t have piers or deepened edge beams
so that doesn’t apply in most cases.
*"E" reactive sites are often called "H2" because once it is an "E" you can't use a waffle.If you constantly call sites "E" you will lose volume builders because they only want waffles.You may say well to bad the site is what it is and I agree with this but the fact is it influences what geotech's are prepared to say so waffles are put on "E" sites.
“I find it hard to believe that an engineering firm would do this, not worth risking their licence and credibility. However I've seen some stranger things happen in the building industry. “
I know this for a fact and it is a major problem in the industry
The biggest problem with waffles is site prepartion.Cut flat, granular bedding, no temporary downpipes and artificial slopes built up against the slab.
Everything has to be done correctly with waffles and unfortuntely with no enforcment of the standards this isn’t happening.
I would built with a waffle only on class “M” or less soil reativity.
With the recent rain we may see further slab heave cases occuring but maybe not the same magnitude as the previous two slab heave waves.
Engineering company always referenced the slab as E.
It used 375mm waffle pods with 100mm concrete on top, thicker steel, beams within etc.
During the build, the ground was built up against the slab with clay and sloped away to storm water drains our builder constructed. The down pipes were always connected.
It's not illegal to build an E class waffle slab , it just has to be "engineered".
We also used Darbecca for every stage of the build.
The house was built on level 1 construction fill so at least we know what's in it.
There may be issues one day, who knows.
The reality is, we saved a huge amount of money with our volume builder and we were as diligent as we could be.
It's not cool to constantly critique waffle pods and try to make average home owners worry and stress. Things might happen regardless of the type of slab used, nothing is fool proof.