How to do footings without concrete
CalBungMelb
| Posted in Green Building Techniques on
We’re looking to build a shed and a workshop in our backyard highlighting sustainable approaches. The buildings will be one-storey, mainly timber, used for some woodworking equipment and general storage so light loadings.
We’re in an area with reactive clay so the common building approach is to use concrete as footings.
Ideally, for site access and other reasons we would prefer to use minimal concrete.
But what else could we use for footings?
Ben Law has used stone.
Are there other alternatives? We’re still at the planning stage re how we do the framing
Regards
David
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Replies
David,
I'm not sure what you mean by "reactive clay"...
Is that the same as "expansive clay" - the clay expands and contracts dramatically between wet and dry cycles?
There is clay in my area which is not-so-expansive.
For out-buildings, pole structures work well.
For my barn, I just sank treated 6x6 into augered holes.
I've also seen details for pressure treated wood foundations that call for a treated 2x "footing" over well drained gravel - I think this was from the Canadian national building code...
David,
Your article doesn't make clear whether you want your foundation to have continuous walls (as for a crawl space or basement) or posts. In either case, you can build with stone if you want, as builders did for thousands of years.
To build a traditional stone cellar, the earth is excavated to below the frost line. On undistrurbed soil, the mason lays a course of large stones and builds up from there.
A modern variation on this method would be to fill the entire excavation with a 4-inch layer of crushed stone, and to build the walls on the crushed stone layer using traditional principles.
If the walls are unmortared, they have to be very large and heavy to resist soil pressure.
It's also possible to build posts out of stacked stones, but you need a good mason for this. Dig your hole and choose your stones carefully. Unless the stones are dressed, they need to be carefully mortared. A friend of mine built an addition to his log house using this type of foundation, and it's doing fine.
My own house has a stone-walled cellar. However, after considering the issue long and hard, I built my stone walls on a concrete footing.
David,
If I'm not mistaken, I think you are somewhere in Australia...
Just curious, but what trees do you have locally that are "rot resistant"?
Is there something similar to cedar, larch or black locust?
In answer to Lucas's question, although rot is a problem, termites and other borers are perhaps a larger concern. We have a bunch of Class 1 durability (inground) timbers that can be used for stumps and which should last for 25+ years. So that is one potential solution.
Thanks for the response, Martin. We would like to have a cellar under the workshop but we're concerned again with the reactive clay. My understanding is that this complicates basements, cellars etc. And we're on a flat block so drainage is also a consideration. We don't really have a frost line - we generally only have a few nights a year when it gets to 0C (32F) so the ground doesn't freeze. So that's one less thing to worry about :)
Your house sounds greatl. Do you have any online articles about your cellar?
Hi Lucas,
I think what you call expansive clay sounds like what we call reactive clay. I've attached a short document that discusses reactive clay.
Complicates some aspects of building construction and maintenance but at least at our place does grow fantastic potatoes :)
Regards
David
David,
The presence of "reactive clay" in your area leads me to recommend that you seek local advice. Someone familiar with your climate, your rainfall, and your soil conditions is in a much better position to provide you advice than I am.
No, I have never written an article about the cellar I built on my hippie house. But here are two photos of my cellar.
David,
Site selection and water management will play important roles in the longevity of whatever foundation type you select.
In parts of Canada that have expansive clay soils, I know that pier foundations are often prefered, but the piers are of concrete and there is still risk of damage if the moisture content of soil adjacent to the piers is not managed properly and/or the pier aren't placed deeply enough.
http://web.mst.edu/~rogersda/expansive_soils/DAMAGE%20TO%20FOUNDATIONS%20FROM%20EXPANSIVE%20SOILS.pdf
http://www.foundationperformance.org/projects/FPA-SC-01-0.pdf
Are there any 100+ year old farm houses or barns in your area?
If so, I'd try to make a field trip out of inspecting their foundations.
A builder here digs a frost depth trench and fills it with 3 inch stone.
For a cellar follow Martin's and lucas' advice.
David,
I like to grow potatoes in my clay soil too.
I find that they are an easy way to start breaking up the clay in anticipation of putting in a new garden bed - easier than using a pick-axe at any rate.
Martin,
Is that the cellar you transplant your winter cabbage into?
Wow, Martin, that looks great. I have a serious case of cellar envy.
David
Lucas, have you tried the no-dig method of preparing a garden bed? We're only on 8000 square feet but we have extensive vegetable beds and around 40 fruit, nut etc trees and bushes, raspberry and boysenberry canes etc.
No-dig is a great way to get beds going; at least in our temperate conditions. Just put some paper on the ground where you want to have a garden bed. (We've made low retaining walls around our beds with a few levels of loose laid recycled bricks and we're about to make some more permanent beds using wooden frames.) Then add layers of compost, manure, green mulch and so on topping it all off with a nice high carbon mulch (arborist chipped wood is good). Leave for a few months after which the earthworms, assorted arthropods and other invertebrates and the thundering micro-herd of soil biota will be in full swing. They do excellent work in building a soil bed for you.
Lot easier than digging or using a rotary hoe for bed preparation
Cheers
David
David,
If you have cellar envy, then I might have fruit tree envy.
All my fruit trees are 5 years or less.
But there are nuts and berries in the forest.
I have never tried the "no-dig garden".
Sounds interesting.
I have been experimenting a little with "hugelkultur".
I'm thinking of expanding our garden into a type of "forest garden" using this approach.
I'd be interested to hear how you go with the hugelkultur. Probably particularly useful as a way to use softwood slash/windthrow etc in a damp climate or if you have other sources of water available.
The mountain ash (hardwood) forest we have in Victoria is to some extent one big hugelkultur with lots of fallen trees and litter. Decent sized logs can last 100+ years on the ground.
Strongly recommend reading Edible Forest Gardens if you're setting off on the Forest Garden journey. Some interesting material.
And for an entertaining and interesting read I can recommend:
Tree Crops: A permanent agriculture, by J. Russell Smith
Influenced the development of Permaculture and 100 years on still raises relevant questions on how we coudl approach some agriculture differently
Regards
David
David,
Thanks for the book titles.
Most of the books I have read on permaculture have been by Bill Mollison.
Of course the internet is full of stuff too - although I do prefer a good book.
Something else I've become quite interested in lately that seems to dovetail is "pattern language".
My understanding is still very rudimentary but I am eager to see how I can apply it in the garden.
Should be fun.
Here's a couple of widely used methods:
http://www.abchance.com/resources/literature/01-0505.pdf
http://www.pinfoundations.com/commercial.htm
The diamond pier pin foundations are "greener".
Lucas,
Q. "Is that the cellar you transplant your winter cabbage into?"
A. Yes. Here's a photo looking down at the cabbages (taken from halfway up the cellar stairs).
David,
Back in the 1950s and 1960s, the "no dig" method was usually referred to as Ruth Stout's no-till method. Like hugelkultur, the only problem with these easy methods of gardening is that they are a lot more work than the older methods that are supposed to be so complicated.
Who's got the time to haul mulch to cover the entire vegetable garden to a depth of one foot? And who has the time to make all those beautiful German hugelkultur mounds, so beautifully sculpted and layered?
Ah, but these methods are so much easier than conventional gardening...
Martin,
Your cabbages look delicious.
I think I might also have cellar envy too.
You're right that hugelkultur is not an easy way to start a garden.
What I am most curious to find out is whether the extra up-front labour will result in a long-term payoff.
In particular whether the hugelkultur beds would require less watering - the idea being that the composted logs act like big sponges, keeping the subsoil damp during hot dry weather.
David,
Sorry for taking your thread so far off your original topic.
Hopefully I'm not out of line carrying on here.
As I mentioned in my last comment to Martin, I am mainly interested in the low water maintenance feature of hugelkultur beds (although they are aesthetically pleasing too once they've grown in).
I only have rain water for irrigation so if this pans out, it could be a big advantage.
I built the beds with a swale along one side which allows rainwater to infiltrate the bottom of the bed where the logs can soak it up...
I think it is best to start a bed using logs that are already somewhat rotted since they are more sponge-like.
Also, I think if the logs are already partially rotted they take up less nitrogen from the soil during decomposition.
So far I have only constructed two small hugelkultur herb beds but neither has required any watering at all - apparently getting by on what rain we received despite some very long, hot, dry stretches.
Sounds like an interesting project, Lucas. I would be interested to hear how it's going down the track.
So I guess to wrap up this thread for the moment there are several alternatives that can reduce the amount of concrete required for footings if they are appropriate for the conditions. Thanks for all the suggestions from everyone.
This sustainable shed project continues. I've just had a guy around with a camera and locator to tell us where the various drains are. That's an interesting piece of technology.
David
David - Is this still an active question? You may find interest in http://surefootfootings.com.au. Proven technology in your backyard.