Waffle pod slabs

Hi just wanted some info on these slabs. They concern me a bit but hey I'm no engineer. I can see how the foam won't break down or could even be that strong compared to a conventional style of slab. To me it just seems like a cheaper way to construct a foundation. Rather then a better way. And yet they don't pass the cost savings on. Any way just wondering people's thoughts

I'm no engineer and you may be right up to a point. However we had to have a raft slab. One thing that puts you behind the 8 ball straight away is it grossly affects your 6 star energy rating.

We had to have double glazed windows to the east/west walls and upgraded insulation. This added extra along with the increased slab cost.

So if you site is straight forward enough I believe you can add a waffle pod with great confidence. However there's still plenty of applications where raft is required. As we found out.

The whole styro block thing affects thermal mass in a good way I believe.

I'm always happy to weigh-in with an uninformed opinion ... and it's my belief that there's no structural downside to a waffle-pod slab over something like a solid concrete one, at least in the circumstances where one is used; the styrofoam doesn't support anything, it's just there as a form of insulation.

With respect to "them" not passing the savings on; well, theoretically the market & competition takes care of that. Everyone uses waffle-pods, and everyone competes with each other. If you want to use anything unusual for a slab, you'll pay more.

Our builder, beechwood doesn't believe in waffle pods either. Not sure why, and I don't know for sure either way, but the only important point to make is that the piers you do get put in the ground have to line up with your slab edges, unlike a raft, where they don't have to line up as much.

Am also wondering about the fact that foam is flexible. Also I'd be curious as I use to be a volunteer fire fighter how safe this would be in a fire. As I know that in fires concrete that has air pockets tends to explode due to the heated air expanding

I have built with both Waffle pod and conventional raft slab and would be happy to use whichever my builder preferred.

See http://www.anewhouse.com.au/?p=3294 for more info on waffle slabs.

Shouldn't matter, it's only filling space (maybe it gets used for an hour or two to hold the wet concrete in place while it dries?). It doesn't have any structural purpose.


You may have a point there; but don't forget it's under the heat & under a layer of concrete. Having said that, it'd also be a bit odd if it's never been considered with respect to the BAL-x requirements for bushfire-prone areas.

My parents built two houses in the 90's. Both had waffle-slab construction. This type of slab has been in use for years.