Slab Classification h2 - Acid Sulphate Soils, is it needed?

Hi guys,

We are about to lodge our plans to council and all of a sudden are now up for a variation to our slab as apparently we now need a H2 slab instead of our already upgrade H1 slab. They say this is due to our s149 certificate? which mentions our property is potentially affected by acid sulphate soils.

Whilst I do not disagree with this, my questions is, how does this mean we need to upgrade our slab? From my understanding of acid sulphate soils, these only pose an issue mainly for excavation purposes and if you will be disturbing the soil and have the potential to lower the water table etc. They do not seem to effect the slab classification am I correct?

Whilst I would accept this change if they said oh due to the soil report it was recommended as you have X soil or because X was discovered etc etc but I don't seem to accept the need due to the s149 as no s149 gives guidance on the recommend slab classifications.

Any I being overly dramatic or does the builder has a case here? And can anyone let me know the difference between a H1 and H2 slab and when one would generally be upgrade?

Sorry, does anyone have any insight?

I'm not clued up on this stuff but understand that Acid Sulphite Soils are treated in a similar way to Saline soils in that you need to have a thicker membrane under the slab as well as a layer of sand before the slab goes down. The extra materials are probably reflected in the H2 price. What I'd also be asking is if this affects your brick choice - we had to get an exposure grade brick.

Have you tried to speak to a town planner or engineer from Council as to what is normally expected in this type of slab or maybe people on here like Building Expert, mgilla, StewieD or insider are worth shooting a message to as I think they'd have a better idea.

Best of luck

Hi hillsbuild,

Try Cement and Concrete Association I suggest to get started on this... they should be able to put you onto a top expert on this very subject. Good luck. Might I also add that the underlay when turned up to ground level forms a physical extra barrier if the taping is well done. Also slope the ground away from the house a little more to prevent brackish water lapping the slab edge.

Good luck too.

Leonardo_23