The slab-on-ground disaster

The high-set house, often called a Queenslander, evolved in an era abundant with timber resources and less mechanisation, reinforced concrete was then a labour-intensive and expensive activity that was only used when necessary.

Nowadays, a load of 27 tonne trucks are slurped up and spewed out by concrete pumps to almost make wheelbarrows an archaeological contraption.

Abetting easy concrete placement are excavation machines of ferocious ability, the profile of any land modifiable to human want and whim. Dump the unwanted spoil anywhere allowed, import the fill wanted.

There’s an old riddle, “Why do dogs lick themselves? Because they can!”

Dogs are living within abilities gifted by the gods — man no longer is. The destructive means available to man, and such power’s consequences must be queried with why, where and when it should happen. 

The slab-on-ground house requires a flat platform. Minor groundwork on relatively flat sites, massive work on sloping sites demanding excavation and dumping of spoil, or the compaction of soil, or both. Costly retaining walls become essential unless on solid rock. 

Adding to the expense of retaining walls are the needs for tanking, back filling with aggregate, installation of subsoil drains, wrapping the lot in geo fabric to avoid siltation build up and the delusion that all will never leak—dream on.

Compare the above to the abundant examples of old Queenslanders on flat and sloping sites.

Dig the stump holes, install the stumps, spread the small amount of excavated dirt on the site and get on with the construction, free of groundwater. Steep sites: tall stumps on the low ground, short on the high.

On the precipitous older suburbs of Brisbane — and many other places in Australia – houses exist where some stumps are higher than the present City Plan’s maximum allowable building height above natural ground.

From the top of the stumps the house starts: 3.6 metre floor to ceiling plus about 2.1 metres for the sensible pitched roofs of the time. The result: a minimum encroachment of 5.7 metres above today’s allowable!

The era’s builders, unconstrained by ethereal City Plans with a view that all topography is flatter than the Nullarbor could be pragmatists rather than by-lawed idiots. 

Owners of steep sites should not have to suffer the financial brutality of Local Authorities’ development application costs to build on sites because of no option but to exceed maximum heights. It is as logical as the authority saying, “This is the only size of undies allowed to be worn in our shire”.

There are zero advantages for slab-on-ground houses during rain — they are disastrous in floods. The Queenslander gave some freeboard when low set and substantial when high.

Repeatedly flooded towns produce images ad nauseum of high set residents looking down from verandas on inundated low sets, and sometimes low set houses looking down on inundated slab-on-ground houses. All wonder: “Why aren’t they all high set?” 

The advantage for the low set house by not being slab-on-ground is it can be raised to be above flood levels and provide double the available space with no consumption of the site’s green space.

The floodable under-croft is still useful space. Brick veneered low set houses require the outer skin brickwork to be demolished as is usually a stud framed structure. Cavity brick, forget it – it’s doomed, unliftable.

The slab-on-ground’s cheapest increase in habitable area is expansion of the slab at ground level at the cost of green space. Not to be forgotten is that this extension exterminates the natural light and ventilation of the former external wall which becomes internal. 

 If green space is to be preserved, additional space must be added above the existing slab-on-ground residence. This requires the removal of the roof and ceiling, strengthening of the studwork and maybe also the foundations, and then reinstallation of a new roof and ceiling. 

The Queenslander lifts all above the bearers in place — the roof still on, so no threat of water damage, all electricals are in place. The common solution for expansion of a slab-on-ground and keeping the backyard is to demolish all and start again. Great! A truly net zero green answer in this enlightened age.

It is ironic when denser uses are required of land, the solid cavity brick house built to last a millennia is demolished and dumped. While  the Queenslander, looking fragile and delicate, is trucked to be re-erected on a new site to continue life as a home.

Many large footprint slab-on-ground houses designed by renowned architects are illustrated in magazines on huge acreage sites. The houses could be extended to the size of the Melbourne Cricket Ground and still have surrounding vegetation and space.

Compare those with the often-portrayed drone images on the evening news of low-cost housing on 300 square metre block subdivisions: single level as cheapest, the gutters  almost touch the side boundaries, and the back yard… what backyard? There’s not a tree to be seen, no park land, just roads and immense site cover with the resultant huge water runoff.

At street level the disaster continues. Cars must be accommodated, usually two. That’s six metres of the frontage gone. If to the best orientation (north), that’s an abject tragedy.  

North to the side boundary is no saviour either, as the neighbouring house is so close the winter sun is occluded. Best is north-facing over the minute backyard as the total elevation is available for the sun. Still a dud answer.

A high setting immensely improves the house on small area low-cost sites. The minimum height above any useful slab installation under must be 2.7 metres to the underside of the bearers to ensure any future enclosure is habitable room height.

The advantages of high setting are:

1. site cover is reduced, giving greater green space
2. car parking is undercover, enabling the full street elevation to be available for habitable rooms
3. the 36 square metres not occupied by cars enables plan flexibility to orient the house to take advantage of the sun. If north to the side boundary, the house can be narrower gaining greater spaces between houses. If north to the front or rear, the full elevation is available for the sun
4. under-the-house can be used for activities desired by the owners: workshop, shaded extension of the yard, more cars, whatever
5. any expansion under will be massively cheaper
6. the house can be removed from the site to continue as a useful dwelling on another site
7. the house can be lifted to add a mid-level keeping the under-croft ground level for its existing uses

After the 2011 flood in Brisbane, the council enabled owners of low-set houses to raise them to above flood height. Many did so. They avoided the floods in 2022. 

Can’t do that with an S on G! 

Meanwhile, slab-on-ground houses got fixed up only to get flooded again in 2022. Fix them up again and wait for the next flood.

Lismore has many houses on stumps. Should owners wish to stay where they are, the council should allow them to raise the house above flood height even if this is on six metres or higher stumps. There is nothing uglier and costlier than something that doesn’t work.  

Unfortunately, there is no gutsy experimental housing attempted in Australia. When did a Buckminster-Fuller Dymaxion house get attempted here? Governments don’t do it, academia doesn’t do it, the private sector doesn’t do it. Developers are obscenely weaponised by governments to insist their fetishes are your built fetish, so purchasers are disallowed from experimenting. They condition you to a slab-on-ground house to ensure you are flooded.

The only solution for this doomed-at-concept house is its demolition with 90 per cent waste of materials, energy and human effort used in its construction and demolition.  We are pseudo environmentalists.

These impractical splats of slab-on-ground houses on small sites will continue with the occasional visual quirk of difference fulfilling what a butcher once said to me: “Beauty is only skin deep, but ugliness goes to the bone.”