A man with a geotechnical survey machine

For better or worse, a soil study

With things progressing and our hopes elevated, we decided to go ahead with a soil study before signing. We’ve seen so many plots since this journey began, including:

  • plots that had already been terraced, badly, meaning drainage would cost a bomb.
  • inaccessible plots necessitating two or three pumps to get concrete to the site for a foundation.
  • sites so far removed from services we’d have to blow half our budget just to get water and electric to the site.
  • stunningly beautiful sites in summer, freezing cold in winter.
  • and so on…

This one, the one we want to build on, seemed to be ticking all the boxes. We were optimistic about the soil study and did it really as a formality and for peace of mind, hence waiting until the 11th hour. What we didn’t expect was a result to come back saying we’d need a footing that goes down to 1.8m.

Why? Well, no-one goes down to 1.8m here! The builders we’ve spoken to think it’s mad. The locals we’ve spoken to think it’s mad! Our neighbour (now sadly deceased) built his house himself on a 60cm foundation. Okay, maybe that’s not enough – it is clay after all – but to his credit the house, built with brick ~20 years ago, is still standing and I can say with certainty there aren’t any cracks in it because he never bothered to render it, so there’s nothing to hide.

But you can’t unknow the known. One the one hand we’re thinking, damn, why did we have this done? We could just have ploughed on with a (relatively) shallow foundation and worry about it later – but we wanted peace of mind with respect to the ground beneath. We were hoping for rock a relatively short distance below the clay. What we’ve got is not that at all.

In a future post I’ll write something about the etude de sol process. It was quick and looked pretty simple. The company we used, Sole Terre, work across France and we really helpful and sent out an engineer so we could get our report back before the August holiday, when all of France typically shuts down. He arrived with his van at 6.30am (it was a good job we’d decided to camp on site!) and just got on with it. Then, just 24 hours later, we had our report. Now the journey begins.

As far as next steps go we’re busy trying to get advice on a suitable foundation – suitable being both for the soil conditions and for our budget. This isn’t somewhere we wanted to be with this build – worrying about finishing before we’ve even started – but it is what it is!

This morning I’ve mailed a couple of UK-trained structural engineers who are based in France, so hopefully they’ll be able to offer some practical suggestions and put us at ease. We’ll see.

A 3D image of a house superimposed on a green field, with a line of small trees to the right

Here it is.

Up until now we’ve been using this blog as a “bucket” – to capture information, share it between us, and enable us to find it quickly when we need it. Things have been quietly moving on behind the scenes, so I think we’re at the point where we finally have something to blog about. Let’s begin!

We started this as the planning stage. When we found the land and discussed the purchase with the owner, the CU had six months left to run. We wanted to put a clause suspensive in the compromis de vente to say that the sale would be null and void in the event that we weren’t able to get planning permission. The owner checked with the notaire, who suggested we apply for planning permission in advance of progressing the purchase, so that’s what we did.

Now, almost a year on, we’re almost at the signing – and paying stage. Planning permission was obtained in February and (due to unforeseen Brexit-related events causing a two-month delay in our plans) the compromis was finally signed in June.

This means we’re in the last stages and we should at last be able to use the land, to progress our build.

There are two things going on. First, the sale is going through the usual administrative process, which means consultation with SAFER for the agricultural portion. Second, the etude du sol will be conducted in July and the results hopefully sent in August. This means we can plan (and cost) our foundation. We have a budget of 10,000 euros for this. Will it be enough!? We know that the land is clay and our DIY evaluation (involving a jam jar and some water) suggests it’s up to 90% clay, which is great news if we decide to go ahead with a “traditional” mud render.

And that’s the biggest decision we’re in the midst of. The big question that hovers over us now, is to GREB or not to GREB? More on that soon.

Find out about Seismic Risk

In France, there is a useful database that you can search to find out about the level of seismic risk for your commune.

First choose your region(click the map or select from the list) and then drill down to find your commune.
http://www.planseisme.fr/spip.php?page=didacticiel1

This is the info that comes up for our commune:
http://www.planseisme.fr/spip.php?page=didacticiel4&code_insee=11303&zone_id=3&classe_bati_id=II_MI&nature=N

There are some FAQs on
http://www.planseisme.fr/-FAQ-162- and also a bunch of other info there related to construction – though of course no detail!

There is some more general info about seismic and other environmental risks on this http://www.prim.net/seismes/

Green Energy Suppliers in France

One of the requirements of RT2012 is that all new builds must include a solar-power element. This can mean investing in micro-generation system for your own land or property, choosing a low-carbon, low-energy heat source as your main form or energy. But there is also a third option, which is great for those of us who are on tight budgets. That option is to commit to using an energy supplier that obtains at least 50% of their energy from green sources (solar, wind, water, etc.)

So how to find these? 

There’s quite a list in this article here but also this recent article which gives an overview of Greenpeace’s assessment of the main suppliers in France. Looking at the two lists I would think that you could pass RT2012 by signing up for EDF’s green tariff but according to Greenpeace you’re probably being greenwashed and unlikely to be actually buying energy generated from renewable and non-polluting sources.

One of the companies I lik the look of is https://www.ilek.fr. There’s also https://www.enercoop.fr, which also has non-capitalist credentials. Enercoop has a similar feel to Green Energy, which is the company we used in the UK and is also a cooperative. 

You might be thinking well, how green is it really to be buying energy from a company, but this recent article from the Centre for Alternative Technology suggests that connecting to the grid is a better solution than going off grid. It’s worth remembering that all technology has an environmental cost. Also, if you are generating energy that you are contributing to the total amount of green energy that is available for sale to others who perhaps don’t have the means to invest in solutions themselves. If green electricity is flowing in, the demand that needs to be met by dirty energy (and in that I include nuclear) is reduced. Which also feeds into this article about how being green has become something we do (and get to feel smug about) on an individual level when really collective action is needed.

There’s more info on packages with suppliers for auto-consommation (self-generation) here

Ilek seem to have a comprehensive calculator on their site, giving info on expected payback times and also taking government grants into account.

RT2012 Recommended Boilers (Thermo Dynamic)

For RT2012 one of the ways around having to have expensive solar solutions is to fit a thermodynamic boiler.

This one on Mano Mano is 1.5k euros and may be what we need. 

According to one green energy site they reduce the annual cost of heating water from 350 to 80 euros for a 4-person house.

https://www.manomano.fr/chauffe-eau-thermodynamique/aeromax-4-vs-270-l-thermor-296061-519359?model_id=519359


This comes on the list under ventilation…

This might be one? https://www.atlantic-climatisation-ventilation.fr/ventilation/chauffe-eau-thermodynamique-sur-air-extrait/aquacosy-av/aquacosy-av-100l-et-200l
2035 euro


How thermodynamic water heaters work

Messages Sent

24/10/18 – Message sent to http://mmu34.eklablog.com via their contact form.

I am planning a GREB house and considering how do to the foundations. I am interested in the method you chose and also the products you used. What is the make of the polystyrene blocks? I have tried to find them using the internet but no luck. Do you find the floor is well insulated?

A Simple Woodburner or a Boiler Stove?

Someone in a self-build group suggested a boiler stove instead of just a burner requiring separate water heating. The oone they linked to had a heat output of 2kW with 8kW going to the water. That seems low given we’ve been told we need a 10kW stove for m2.

Cost wise they’re not much difference though. Something to consider?

This one, the Stratford EBW12, has a total output for 24kW, of which 6kW goes into the room and 11.8kW into the water.

It has a direct air supply (required by RT2012).

£1,912.00

Stratford EBW12 wood boiler stove

Trying to find out why you’d choose a water heating stove and the Centre for Alternative Technology have an article suggesting that it’s not worth it unless you have a super-duper stove such as the Broseley eVolution 26 boiler. With this you get 10kW for heating and 15.8kW for hot water heating. I can’t find a price for it though!

Choosing the Right Type of Foundation

Slab vs. vide sanitaire? Discussion here along with info on how to layer with the moisture barrier and insulation.

https://www.ecohome.net/guides/2370/slab-on-grade-or-foundation-and-basement/

Some other useful articles here:

Tips from these pages:

  • Dig out the earth and then pack it tightly before pouring any concrete.
  • You can – if you’re crazy enough – do this without using any rebar (as if!)
  • You can literally make it up as you go along. These guys used rockwool under the slab and EPS under the footings. How does that not compress when under concrete and with the weight of the house on it. 
  • It IS important to use a Radon/vapour barrier before pour cement.
  • Remember to put the rebar over the vapour barrier!
  • Polished concrete is a good idea – but who is capable of doing this here in France?