The range of different natural building techniques out there are many, and all of them are exciting. But when to use which technique? Here’s a starting guide for choosing what to build your walls from.
Though all very different, and used for different reasons, all the natural building methods below have some common aspects.
And the biggest one is: they’re all striving to create comfortable, liveable, non-toxic natural buildings.
Natural building also gives you the chance to build with a much lower energy footprint through using available, more local materials – rather than things like cement, clay brick and treated timber that have huge flow-on effects to both the environments they’re sourced from, and the earth’s atmosphere because of how they’re produced.
But like designing and building anything, your context – which includes your site, climate, resources, location and budget – will define what methods you use to build.
So rather than having your heart set on a particular technique because you love it so, it’s best to have a good hard think about which natural building methods would suit your situation, before you dive in.
This way, you’re more likely to end up with a building that suits your needs, and is a comfortable haven for many decades to come.
A note that there’s many other parts to a building that it’s walls (obviously), but walls seem like a good place to start.
And a note that this information relates to non-tropical environments, which are a whole different story when it comes to working with temperature.
Exterior vs Interior Walls
The first consideration is that not all walls are equal – your exterior and interior walls perform very different functions. We love this quote from Sam Vivas, the master builder who teaches our Natural Building courses, talking about walls of a house:
A livable house should have a good blanket around the outside, and a hot water bottle on the inside.
The ‘good blanket’ is the exterior walls, meaning that they should be as insulative as possible, to protect the inside of the house from outdoor temperature fluctuations of both hot and cold
The ‘hot water bottle’ is the interior walls, and floor if you can manage it, meaning that they should have as much thermal mass as possible.
These thermal mass banks then become an important passive heat sink for the living space, stabilising the inside temperature of the house with a minimum of extra heating or cooling, and making the house super comfortable in both Summer and Winter.
With that in mind, let’s talk wall systems and look at a few different methods in natural building –
Strawbale Walls – infill + load bearing
Strawbales are a favourite exterior wall choice for many natural builders, with good reason. They can be used to build strong walls with a very high insulation value, they’re highly fire resistant when constructed right, and they go up quickly. Bonuses include that the straw is a waste product of agriculture, and it’s possible to source reasonably local material anywhere in Australia (and on some other continents too).
As a product of industrialised agriculture, strawbales come in standard sizes, which allows you to plan ahead when using them. There’s two main ways that they’re used for exterior walls – as a load-bearing arrangement (with no other uprights, just the roof sitting on top) or as infill, with a wooden or steel frame creating the main frame of the structure.
Load-bearing strawbale walls – this technique sees the walls of a structure go up all at once, and is less complex in some ways, as you’re not working around wall frames, so it can be quicker that infill. However, load bearing walls need to all go up at once before any more building can occur, and of course, if it rains before you’ve completed the walls and got a roof on it’s a BIG problem because your bales might get wet (not good). All that said, it’s entirely possible. Here’s a load-bearing strawbale building we made a few years back.
In-fill strawbale walls – this technique is the main way strawbale buildings are constructed, in Australia at least. Far less time-critical and heart stopping than building load bearing strawbale walls, infill sees a building framed up first, the main roof goes on, and only then do you start putting in the exterior wall strawbales. Much less panic inducing if clouds are on the horizon.
The infill technique has the great advantage of giving you a big roof to work under (a much loved aspect of any building site), and also allows other internal building works to proceed while the exterior walls are filled with strawbales. Infill strawbale buildings are also typically easier to get approval for from councils, as the technique is seen as less ‘weird’ than load-bearing strawbale.
Rammed Earth Walls
Rammed earth walls are a popular choice for interior walls because of their high thermal mass. Made up of earth, sand and a bit of cement, the majority of their components can be sourced locally in most places.
Because the earth is literally and mechanically ‘rammed’ into formwork to make rammed earth walls, they do need the building to have very strong foundations in order to be built. And if a second level is going on, the floor level internal rammed earth walls need to be quite wide to bear the weight above, which can lead to large wall footprints in your building.
Light Earth Walls
Light earth is a funky blend between rammed earth and cobb. It comprises of loose straw coated in a small amount of mud, then packed into formwork to make walls, with the formwork being removed once the wall is semi-dry.
Light earth is a good choice for interior walls (not load-bearing ones though, this is an in-fill method) for home builders because it’s an easy technique, cheap to make, extremely effective, and has a higher thermal mass than strawbale (though not as high as rammed earth).
What you save in material costs with light earth you spend in human energy – so while it’s a lot less labour intensive than a technique like cobb, there’s till some hands-on involved. Whack, whack, whack. Make sure you have lots of friends to help, and good food and drinks waiting after the whacking sessions.
Cobb walls are an old, old, old wall building technique hailing from many continents. A mix of mud, loose straw and sand are combined in a vessel, and then handfuls are applied to slowly build a wall, a bit like a sand castle.
This slowly creates a strong wall with great thermal mass. Like light earth, cobb wall building is simple, cheap on materials, and relies on human energy rather than brought-in solutions to make and create the walls.
There’s lots of other wall methods as well which are excellent for certain contexts which we’ll have to leave for another day, but check out
- Cordwood – a mix between cobb and wood – this technique has a high thermal mass and looks gorgeous.
- Super adobe building.
- Earthship style wall construction.
- Constructed straw panels (think fibre board, but made of straw) which are an off-the-shelf solution but can be perfect for some scenarios, like retrofitting exterior mudbrick walls to provide some exterior insulation.
Whichever techniques you choose to use in a build focussing on natural materials, you’ll find yourself working with your surrounding environment, and your wider area’s resources, to create a building in a way that’s totally different from off-the-shelf construction techniques.
A natural building is an opportunity to see the land, resources and environment around you in a different way, and to find ways to make them all a part of your home.
Living in place, quite literally. It’s a beautiful thing.