Why don’t builders build on stumps?

We are planning a knockdown rebuild and are considering lots of environmental impacts. the biggest of which seems to be that volume builders use concrete slabs. Why is this? It seems terribly bad for the environment. Is it really that much cheaper for them? Are slabs more effective foundations with active soils, root systems or water?

The sales reps just say better thermal properties or it’s faster but it’s not very informative.

if properly insulated becomes a large thermal bank which will stabilize internal temperature
i believe it is cheaper in labour costs

Thanks for that. Could the same thermal properties be achieved with insulation under timber floor?

I agree, cement production is a major greenhouse gas contributor. If the industry was a country, it would be the third biggest polluter behind China and North America. Covering virgin ground with concrete is an environmental disaster yet scant consideration is given to the environmental impact of each new house. At least a house built on wooden beams stores carbon.

Focus is on energy efficiency yet houses are allowed to be built with dark rooves that give off heat signatures greater than the harshest deserts and contribute to the Urban Heat Island Effect, something that substantually contributes to increased energy use during summer in those areas affected.

https://www.abc.net.au/news/2018-03-01/ ... ct/9361156

We have falling water tables due to the high percentage of widespread impermeable urban areas yet no consideration is given to ground water recharge fron suburban stormwater.

The time needed for changes to make a difference is past, Russian naval logs have confirmed this for several years now.

Not exactly, timber doesn't have much of a thermal mass.

Timber is also not very good with handling of excessive moisture (except marine plywood or teak) and can rot/get mould and is also an attractive food source for the insects/termites.

If building on stumps, I would better go with MgO boards instead of OSB and even plywood any day.
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I would rather say "Portland cement". There are many other cements out there, e.g.

https://en.wikipedia.org/wiki/Sorel_cement

Requires much less energy to be produced, cures in hours to much higher MpAs, but crazily expensive.

They use it for dam construction in Asia.

Concrete also retains heat making it hot despite cooling down outside,so can and does work against it as well.

Yes, thermal mass to be properly shaded with longer eaves, etc.
But heat is good for the winter though.

Before large scale introduction of concrete slabs houses were built as brick veneer on stumps and timber floors. I have built many for Housing Commission of Victoria in the seventies and they are still well performing. So there is nothing inherently wrong with building houses with timber floors, so why do builders go for slabs? Its not cheaper for the consumer but definitely it is more profitable for the builders. Once you factor in site costs and slab upgrades (almost a pure cream for the builders) slabs are definitely not cheaper.
In fact I have written before that slabs are a con of the century. Unless you have a flat site and s or m soil classification, forget about slab
It's all about profit.
I read on this forum from other members, site costs and slab upgrades >50k , absolute madness. Strip footings, stumps and base brickwork does not cost all that much, How much timber could you buy for $50k

One of my homes(I did not build it) is a seventies BV on stumps, nothing fancy but a delight to live in, off the ground, dry and healthy.

Interesting I have only a raft slab for garage and laundry off garage,then have all house above right to back off block single storey,all on strip footings and huge brick pylons,tongue floor with mostly timber and tiles to bathrooms, performing magnificently, very happy with it.

Yes , what happened about re foresting the planet and reducing co2 emissions. Timber is co2 bank

Yeah I get what you mean. I’d love to use recycled cladding and floorboards but I feel the framing may have to be new timber. I guess I could go recycled for noggins and such

It's all sequested carbon, new or old, it makes no difference.

Was looking, only last week, at a lovely little bed 'n breakfast build coming up in my SA town. Floor frame is supported on a grid of square metal tube stumps. It's, maybe, a metre up off the ground. The amount of earthworks is absolutely minimal. Very tempting approach to building. Not sure, yet, if the owners are going to use recycled timber for the floor but what an economical way to get a cost effective, aesthetically pleasing solution to the house base. Going to be a doddle to pop in the plumbing, and stuff, too.

*bump*

Interestingly, i have a sloping sandy site which i am being told will cost me ‘$100,000 to get out of the ground’. Being an enviro, I am keen for a light construction, enviro friendly etc. so keen on stumps. That will also help maximise my views... But most project builder are all about the concrete slab!

I always knew that sloping sites would be pricey, but didnt quite expect $100,000k before i’ve even got one room...

Anyone have costs to build on poles / stumps / stilts??

Thanks
V

Worth checking out Cupolex (www.cupolex.com.au), you may use their Rialto system is a good alternative to pier-and-beam foundation at a fraction of the cost - they can go up to 2.5 m

Some concrete will still be needed, however, you would need it for your stumps too.

Thanks alexp79
That doesnt look like something that would work for my situation...