Are dome homes a housing crisis solution?

With the housing crisis steadily getting worse, and state and local governments tinkering at its edges, all options need to be considered. Lance Turner looks at one housing system that has barely rated a mention.

The average home in Australia is a box, or various derivations of a box, such as multiple interconnected boxes, boxes with extra bits, boxes with bits missing, and numerous other variations. They all have one thing in common—they all have at least four flat sides and a roof.

But homes don’t have to be that way; they can be more interesting and look more natural, and one way of doing that is with curves.

Some homes might have a curved feature wall that offsets the straightness of the rest of the home, but you can go further than that. The ultimate curved home is a dome home, but these are very rare in Australia, despite having some considerable advantages (and a few disadvantages too, of course).

What are dome homes?
The most obvious thing that distinguishes a dome home from a typical home is the shape. Dome homes consist of one or more dome-shaped construction units. They can be as simple as a single large dome which is internally divided into various rooms, or even left mostly open plan, or they can have two or more domes that are either directly joined through a shared wall section, or in other ways, such as with hallway tunnels.

Dome homes can even combine the nice flowing curves of a dome structure with more standard box-style construction—this can particularly be the case if there is an existing structure and the dome is a new extension or addition.

Dome homes can be hemispherical, with the dome reaching right down to the ground, or they may consist of a round home with vertical or near-vertical walls and a dome roof structure on top, such as an oblate ellipsoid. There are several different dome shapes that can be used for homes—which one you choose depends on the materials used, the construction method, and the building forms the builder has available.

Domes also don’t necessarily have to have a circular footprint—they can also be ellipsoids if desired or if the block requires.

How are dome homes constructed?
Construction falls into two broad categories—geodesic and monolithic.

Geodesic domes
Geodesic domes are constructed from multiple geometric panels fixed together, usually overlaid onto a geodesic frame made from materials such as timber or steel. The lead photo is an example of a hybrid geodesic dome and stone structure.

The join between each dome panel needs to be sealed, and those joins are one of the most problematic areas for geodesic domes. Panel materials can be timber, aluminium, steel or composite materials such as SIPs (structural insulated panels) cut to size and sealed along the cut edges. Any lightweight, rigid, weatherproof panel can be used so long as it can be fully sealed. Indeed, if done correctly, an internal frame structure is not needed—the panels, once connected, are self-supporting.

Some geodesics use the internal frame and cover it in a fabric or similar flexible material. While such coverings eliminate the sealing and subsequent water leakage issues, and can last up to 20 years, they are really better suited to zones with stable climates that need minimal heating and cooling, or for temporary or semi-permanent applications, although there are companies that promote these types of geodesic buildings as potential homes. Certainly, given their low cost and rapid assembly, they can make excellent emergency shelters as they are highly resistant to high winds, earthquakes and similar environmental issues.

Monolithic domes
Monolithic domes, on the other hand, are created as one solid piece. Usually, a formwork is created to support the dome as it is being constructed, and the formwork also produces the smooth inside surface of the dome. With the formwork in place, reinforcing is installed over it and concrete or a similar material is laid over the whole structure, covering the reinforcing and forming a single solid structure.

Materials used can include concrete (usually sprayed over the formwork) or aircrete, which is an aerated form of concrete, making it light but strong. Aircrete can be sprayed or poured into formwork, or even cast into appropriately shaped blocks for building the dome by hand from the ground up (see the article Dome-stic Bliss in Renew 159).

You might be wondering how steel reinforcing can be shaped to fit dome-shaped forms. The answer is, not easily, and so alternative materials are used. The most common is basalt-based reinforcing, which takes the shape of rebar, mesh and net materials made from basalt fibres. Basalt is a natural rock that is melted and extruded into thin fibres, much like fibreglass. The fibres are bound together, often with a plastic resin such as epoxy, to form rebar and similar reinforcing materials. Basalt rebar is stronger than steel (for the same weight), has the same expansion coefficient as concrete, and is not electrically conductive. It is also immune to salt attack, making it ideal for structures in proximity to the sea.

But arguably its best feature is that of flexibility. It can simply be flexed and tied into place to form any shape required, and hence is ideal for reinforcing in concrete dome structures.

Monolithic domes usually use internal forms, and these are often fibreglass or similar materials. The forms are bolted or clipped together, the reinforcing laid over the top, electrical conduit and plumbing fitted inside the walls, and the concrete or other material is then laid over the whole structure. When the concrete is set, the forms can be disassembled and removed through a door or window opening. Because the forms are smooth on the concrete side, the internal walls are pretty much prefinished and need very little work.

The outside of the dome is usually smoothed over while the concrete is still wet, and may also have an additional finishing render applied. The exterior surface is often painted to make it look less like concrete, and an insulating layer such as aircrete can be applied as well.

One of the nice advantages of monolithic domes is that, being self-supporting structures, window and door openings generally don’t need support such as lintels, and indeed don’t need to be square at all. As a result, dome homes often end up with arched doorways and arched or round windows, which are more in keeping with the house’s shape, although such doors can cost a lot more than standard rectangular doors and windows, especially when opting for double glazing.

Aside from being very strong structures, monolithic domes, being mostly concrete, usually have very good fire resistance, with no gutters, gaps or crevices to allow embers into the structure, and so can easily attain BAL FZ rating, provided suitable windows and doors are used.

Build speed is also another advantage, with domes taking just a few weeks to construct, due to the simple construction method.

Why are domes not more popular?
So, dome homes have some distinct advantages, but how about disadvantages? There are several issues that have helped keep dome homes from becoming popular, or even remotely common, at least in Australia.

One of the most obvious is the curved walls. While they have a very organic look about them, they are not conducive to space efficiency, especially when it comes to regular furniture. Domes that curve inward from the ground upwards, rather than having a section of vertical wall, don’t fit regular furniture well at all. Any standard box-like furnishing with any sort of height will be closest to the wall along its top edge, while the gap between the furniture and the wall will increase as you go towards the floor. This means that, for example, a cupboard 1800mm high and 450mm deep will actually sit out much further than that at the base, and so will take more room than expected.

The solution to this is custom inbuilt storage, where units with curved backs that are designed to fit the walls without gaps are made for each specific location in the home. Of course, this means considerable expense compared to off-the-shelf furniture and storage solutions.

Another reason for the dearth of dome homes is simply the lack of experience amongst most builders (and indeed architects and designers) in creating this sort of home. Dome homes need a somewhat different skillset to creating the regular cookie-cutter boxes that pass for a typical home in Australia, and so the requisite skills are just not generally available in most areas.

Councils are also inexperienced with such unusual homes, and so it can take quite a bit of extra effort to get them to accept a dome home as a suitable Class 1a building. This will vary from council to council, but most tend to prefer that you keep things simple and typical, rather than unusual and complex. The added work to get a dome home approved can increase pre-build costs quite a bit.

Another issue is water collection. Some councils require homes to have at least one small water tank, but dome homes have no gutters, with water flowing off at ground level. One solution is to have a trench-type gutter system with underground rainwater storage (or a pump to push collected water to an above-ground tank). Or, you might include a more conventional section in the house plan that can accommodate regular gutters. In this case, a standard free-standing shed or garage may meet the requirements for rainwater collection.

Builder or DIY?
So, what if you have decided that you really want a dome home, but don’t know where to start? The first step is to talk to your council and see if they will even accept such a dwelling. They may have no guidelines at all and tell you to “come back with a set of plans”. If that’s the case, you must then seek out a suitable set of pre-drawn plans, or a building designer or architect who has dome home experience. Or, if you are really lucky (and regularly stumble upon hens’ teeth), you might find a builder who has built a dome before and has all the required contacts and knowledge.

Whether you are going to use suitably knowledgeable people to help in the project, or are going to go the owner-builder route and do the whole thing yourself, is up to you. The latter option is certainly possible, but the learning curve is steep and long and the council may make things less than easy.

If you find a suitable builder or architect to take you on your journey, then the next decisions include the type and size of home you can fit within your budget and requirements, and then work with those professionals to get the end result you need. That process is too complex to go into here, but if you go the DIY route, there is a fair bit of useful information around to get you started on your dome home journey.

For monolithic domes or block domes, aircrete is a much easier material to DIY with than regular concrete, as it is much lighter and provides a reasonable degree of insulation into the structure itself. One place to start is Aircrete Domes (aircretedomesaustralia.com), who run workshops that teach you all aspects of building an aircrete dome, from building forms, making the ideal aircrete mixture, how to create and cut aircrete blocks, making arch supports for doors and windows, and how to fit them into the structure, applying internal and external wall finishes, and all other skills and knowledge needed to build a dome structure from scratch.

One builder that does specialise in dome homes is Domeshells, based Murwillumbah NSW, although they have built domes in NSW and Victoria. See the case study at the end of this article for more information on this company, how they got started, and their dome home design service.

Non-dome round homes
So, what if a dome is too radical for you, but the thought of living in a flat-sided box is not your preferred option? In this case, you should consider a round house. These are exactly as they sound, circular or oval homes with either curved walls or made from many flat sides—effectively a many-sided polygon. The flat sides fit regular furniture, but the overall look and feel of the house is that of a circular home. A good example of these homes is the kits and homes designs from Australian Roundhouses (australianroundhouses.com.au).

Because these sorts of buildings are closer to regular constructions, some more conventional builders offer polygonal homes in their range, or homes with some polygonal sections.

Non-dwelling dome structures
Of course, domes are suitable for more than just living in, and in fact can be ideal for smaller and temporary structures such as secondary dwellings (granny flats), studios, sheds and similar structures. The simplest forms of such domes are geodesic domes, which can be made from basic materials using free plans, or you can buy them in kit form.

There are also smaller buildings available in kit form, such as the octagonal Steel Framed Yurts from Modular Steel Kit Homes (modularsteelkithomes.com.au/our-range/steel-framed-yurts), which are just one example.