Monday, 26 January 2009

More adventures in straw

Since my stories regarding the hippies and the straw bale houses have garnered a larger than usual number of comments and questions, I will write some more on this matter in a Q&A format.

Q. Do they wash away in the rain?

A. Only if you are dumb enough to not allow for a large roof overhang. Given this is Ostralia, and the country is generally flippin' hot, wide verandahs are a great idea anyway. For a single storey house, eaves of 75cm are the minimum. If you get rain that slants in a lot, go wider with the roof.

It's important to remember that the outer layer of render is full of lime, making it similar to cement. Does your cement render wash off your brick house in the rain? If the answer is 'yes', sue your builder.

Many years ago, the Big T's parents decided to build a house out of rammed earth near Margaret River. They had terrible problems with the council, who were also worried about it washing away in the rain (because they heard the word 'earth', and thought the house was just rammed mud). Rammed earth walls contain 10% cement (help me out here Big T - long time since I worked on that cement mixer), so they are very unlikely to wash away.

The only troublesome time with straw bale houses and rain is if it rains before you get a cap on the wall. Before leaving the site each day, you have to put plastic or tarps over the top of the walls and weight them down.

Q. Aren't they full of mice?

A straw bale contains very little oxygen as it is. Once you wrap it in render on all four sides, it is hermetically sealed. The fun thing to watch as you are applying the first coat of render is to watch all the mice come rushing out when there is only a small patch of unrendered bale left. They know the O2 is running low, and they split. Once the wall is sealed, nothing can live in there. If the bales are dry before the render goes in, they won't get mouldy or break down. There are houses in the US (Montana I think) that are 100 years old, and when they've taken off some render to have a look, the bales have been as good as new. Think mummification.

This is also why they won't burn in a bushfire. Fire needs oxygen. Even though the outer wall can get stinking hot, the straw inside will not burn or smoulder without oxygen.

Q. I'm worried about bushfires. What should I do?

A. Move elsewhere.

Or, slap a thicker layer of render on the outside, keep your gutters clear, close the gaps below the roof and clear out all the crap around your house. That's a good start.

Q. Do they look like crap inside?

A. They look 'rustic'. If you like that look, then they look great. If you hate that look, cover the walls in plasterboard and make the inside look like every other suburban rabbit hutch. In fact, if you hate the look, build with brick. As the bale nazi would say, "No straw for you!"

Q. How do you run wiring and plumbing?

A. You run wiring in conduit into the bales before applying any render. You can cut a trench using a chainsaw (chainsaws are the tool to have with straw bale building) and slot the conduit into that. If you need more wiring later, well, you've fucked up.

As for plumbing, fanatics would build wet areas out of bales, but I wouldn't. Build your bathrooms and laundry and maybe even your kitchen out of something else.

Q. Are you better off with an unsupported wall, or using a stud frame and in-filling?

A. I've done both (once). Stud frames are not hard to build (even I can do it, sort of), and they are not that expensive. However, fitting the bales into them can be a pain in the arse.

When it comes to doors and windows, I think the whole design of the house needs to be rethought. Instead of taking a design that works well for a brick and tile house and simply building it out of bales, you should think about what works with bales and what doesn't, and design accordingly.

For instance, I'd build windows right up to the roof. Putting bales on top of a window frame is a pain. Your house will look odd, but be easier to deal with. I'd even recommend doing windows that go floor to ceiling. Same with doors - go for really tall doors, or put a wooden or feature window above the door, rather than bales.

But that's just me. Putting up a straight bale wall without any holes in it is quick and cheap. As soon as you put holes in it (doors and windows), you add complexity, and complexity adds time and money.

Q. Can you paint it?

A. Sure, it's just render. I think you need to be careful about the final coat of render, and that's it. Because you are using dirt, it is darker than normal cement render, so you might need more paint. If the surface isn't treated properly, the paint will peel.

Me, I'd leave it alone and simply hang a lot of artwork.

Q. How do you hang artwork?

A. Picture rails. You can't whack a nail into a bale.

Q. Maintenance. What about maintenance?

A. Dunno. Ask me in 10 years time.

Q. Does it crack?

A. The way we did it was to build up multiple layers of render. The "original" method is to get a whipper snipper and use it to "clean" all the stray, sticky-outy bits of straw off the bales before putting on the first coat. You take all the little bits of straw and cut them into segments an inch or so long (I think) and mix that into the first coat of mud. The little bits of straw act like re-bar does in a concrete floor. You can cheat and put up plastic mesh instead (you staple it into the bales) and apply render to that. The plastic supposedly acts in the same way and stops cracking. You also really work that first layer into the straw (more render ends up on your feet on the first few coats than on the walls - but then it's only mud.)

We were given formula for each coat, but the idea was that you added more lime as you went out. The first coat can be really grainy and lumpy, but you want the last coat to be smooth. Lippy got a professional plasterer to help with the render - you should have seen that bloke flick mud onto a wall - just magic.

Q. What if rain gets into it?

A. If the straw goes mouldy, I think you are screwed - total or partial rebuild required.

Q. Would you build with it?

A. I'll give that a qualified 'yes'. It would depend on the block.

The best idea the hippies introduced me to was this idea of building "pavilions". Let's say you buy a block up the coast somewhere, have limited holidays in which to build but want to do it yourself. The pavilion idea is perfect.

On your first holiday, you build a one roomed pavilion. Take your pick as to which function it will have - I'd do the lounge/dining room first - a big open room that you can also sleep in until a bedroom is built. [You cook on a BBQ and wash under a portable shower strung over a tree.]

Next holidays, you build another pavilion - say a bedroom. By keeping them as separate buildings, you don't have complications with joining walls or rooflines. You can build square, rectangular or round buildings - take your pick. Yes, round rooms are very easy with straw bales.

If the kids want to stay, get them to build another pavilion as their bedroom. If more guests come to stay, they can put up another pavilion for sleeping. You link the pavilions with boardwalks if required (covered if it rains a lot).

You build as time (and money) permits, and depending on need. Expansion is easy (if you have the room).

If I was in a hot climate, the cooking area would be an open walled tin shed with a concrete floor and flyscreens all around. But that's just me.

Councils and building inspectors would probably freak at all those ideas, but that's life.

Funnily enough, BundyMan (who lived in the Territory for 20-odd years) thought that was the answer to a lot of Aboriginal housing. Forget building 3 bedroom, 2 bathroom brick and tile bungalows like we have in Sydney or Melbourne, where all the materials have to be shipped in (at enormous expense) and where all the labour has to be flown in (at enormous expense).

If I can put up a straw bale building using a reasonable amount of local materials with simple tools, then the blackfellas should be able to do the same.

I will post more on that idea later.

1 comment:

Anonymous said...

Straw is mostly cellulose. A good dry bale won't rot.

Also, have you read any of Ron Edward's Bushcraft books?