What is burlapcrete?

2012/09/20 deej 1

One of the joys of setting up Gallifrey is getting to try a lot of the things I’ve been interested in for a long time but haven’t had the opportunity to implement. Things like putting in swales and designing a food forest, like large scale outdoor sculptures (I haven’t done any of that yet, but I’m thinking about it), like building a straw bale house, and putting in a big vegetable garden in a good location where I can grow tasty things. Gardens give me so much joy, I’ve wanted to build one of my own for as long as I can remember.

The vegetable garden is, relative to the whole Gallifrey forest project, a small bit of work. It’s also something which can be set up before we’ve got the house built and are living up there, because vegetables don’t need daily attention as long as there’s some kind of automatic watering system and they’re protected from pests. So I designed a vegetable garden.

The design is a mandala pattern, based on a flower mandala I found on the internet. It is centred on a circular open space, with benches for people to sit and rest and admire the garden. This area is surrounded by six stone fruit trees (two cherries, a peach, an apricot, a plum and an almond) which will provide some light shade in the summer for both the people and the garden beds. The trees should all flower at much the same time, providing a springtime display like the Japanese and Korean cherry blossom festivals, but in miniature.

Surrounding this central area are six raised garden beds, for annual vegetables, and siz in-ground beds for perennial vegetables and more spreading annuals. Both the raised and in-ground beds will be hugelkultur beds, to improve the water-retention of the soil without affecting the drainage. This has the added benefit of using some of the dead wood which is currently lying around on the property acting as a fire hazard.

The raised beds we decided to build using earthbags. Partly this was because I wanted to try building something with earthbags, and partly it was because the misprinted grain sacks are cheap and the gravel and dirt to fill them is free, since it’s dug from the site. We have to dig the area out anyway, because the in-ground beds have to start out as holes in the ground which can be filled with dead wood and then topped up with topsoil and compost. The alternatives (building raised beds with bricks, or buying corrugated iron to make them with, or similar) are expensive and/or much more time-consuming.

Earthbags, though, have to be rendered. The bags are made of polypropylene, which is almost indestructible in the dark, but degrades in UV light. Immediately I thought of trying burlapcrete. What is burlapcrete, you may ask. That’s a good question. The short version of the answer is pretty simple – it’s concrete laid using hessian fabric (otherwise known as burlap, or sack cloth) as a substrate and support. Basically the same idea as ferrocement, but instead of using chicken wire or rebar to strengthen the concrete.

There’s a bit of information available online about this idea, mostly in forum posts. Notably, John Annesly’s 2004 blog post on the subject is very thorough, and suggests various concrete mixes as well as offering some very useful general advice.

What we did was mix up a standard rich cement mix (1 part portland cement to 3 parts plasterers’ sand), but mixed it to a much wetter slurry than normal. The consistency was more like runny yoghurt than thick, creamy cement. Then we dipped lengths of wet hessian into the mix, and draped them over the filled and placed earthbag walls. It worked remarkably well, even with just one layer. The raised beds are solid enough to walk on without the cement shell cracking, and they look pretty good, I think. Especially considering we didn’t really know what we were doing until after we’d done it.

Permie Porn!

2012/06/18 kai 0

It’s finally the rainy season here in Perth! We’ve been waiting for this for a while now and the first serious rains started up about a month ago. I meant to post this earlier but life has conspired to keep me busy. We were eagerly waiting the first big rains as it would be the first big test of the swales we spent so much time working on over the last few months. Our first visit up after the major storm was actually for our house warming night up on the land with the bonfire (We made up for the lack of house with extra warm).

We arrived fairly early in the day to set things up and get some work done. As we pulled up I found myself quite anxious with worry that the swales might not have held, or they hadn’t worked somehow or washed away. D often says I’m a nervous parent and I suspect she’s right. When we pulled into the property I noticed a strange black line about half way up the swales. My head went into panic mode. Was it a slip? Were they separating? Was it erosion? What was it!?!

Then it suddenly occurred to me.. it was a high water mark! They worked! They captured the run off, held it and then let it soak into the land where they were. SUCCESS! I will admit to dancing a small jig when I saw them and you can see the wonder for yourself. There was much rejoicing. They are performing their required duty perfectly. They are capturing the water and just as importantly the silt in the bottom is rich and soil-y and dark. Things are already growing merrily in them and the broad beans and lupens and nitrogen fixers are growing all over them like mad. We couldn’t be more pleased.

Our Permaculture teacher arrived on site later in the evening and exclaimed with glee when she saw them. She declared it “Permaculture porn” and seductively stuck her finger in it before declaring. “It’s wet!” Clearly we hang out with crazy permies.

The bonfire night was amazing fun and I was so full of happy and joy to be surrounded by family and friends on our land and with the growth of winter starting around us. I can’t think of a happier place to be and people I’d rather be with.

Next time, we might even be able to lay on some food from the property.

Swales

2012/05/08 deej 0

There are a million or more places to start any story – and a garden (or a forest) is just a story which is planted rather than told – but you have to pick one. So while I could start with the search for a location, or with the process of falling in love with this block of land and choosing it and buying it, or with the first trees we planted, I am instead going to start with the swales.

Swales are a logical place to start. For those who don’t grok the concept, a “swale” in this context means a level ditch on contour. They form part of the permanent bone structure of the design, along with any other earthworks. Council regulations don’t allow us to have a dam, so the swales are really the only major earthworks we’ll be doing aside from levelling the building site when we build our house.

According to my research, for the rainfall we’ll be expecting (600 – 700 mm pa average), the swales should be about 12 m apart. As a general rule, swales should be 1 – 1.5m wide at the top (the width at the base is less due to the sloping sides of the swale), 40 – 50 cm deep, and long enough to hold the maximum runoff for a 24 hour period for your catchment area.

Gallifrey is on a sloping site, and along the Western side of the property there are a lot of big chunks of soft stone just under the surface of the laterite gravel and sand that passes for soil in those sections. It’s just too rocky to dig regular swales, even with a rockbreaker. The stone is too soft for the rockbreaker to do more than dig a small hole in the surface, but too hard to dig through. So, we’re going to have two types of swales – the regular sort, dug on contour to about 1m wide and 40cm deep, with a mound on the downhill side, and “Polish” swales. Polish swales are a variation for ground which is too rocky to dig regular swales, based on the gambions which are often used to stop gully formation.

Instead of being dug into the soil, a Polish swale is built up on top of it along the contour lines with small branches, compost, discarded greenery, stones, and other debris. This forms berms that trap soil, leaf litter, bird poo, and anything else sluicing down the slopes. The berms of these inverted swales slow down water and force it to percolate down into the root zone of the garden or food forest. I got the name from ‘Gaia’s Garden: A Guide to Home-Scale Permaculture’, by Toby Hemenway, but I’ve been thinking about similar ideas since I read about hugelkultur. Our Polish swales are going to be built up using dead wood, rocks, gravel, and whatever other appropriate materials we can find. It should work. We haven’t tried it yet, but we will.

Our first experiment with swales involved hiring a dingo for a day to try digging them ourselves. It worked brilliantly, and (who knew?) dingoes are a lot of fun to drive. We tidied the swales up afterwards with a shovel, since our dingo driving skills weren’t quite up to digging a level ditch, but even so. Then we planted the swale mounds by hand with broad beans and lentils, hoping for rain to sprout them and give us some winter groundcover.