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What is the most affordable, sustainable and DIY-Simple way to self build a new home?    We think this is it.

Waterproof concrete base, walls and top. All cast on site in manageable sections with our expert assistance.

Using formwork materials that the self builder can later use in his home or sell to another self builder.

Self builders can self build themselves a basement and / or the whole house very cheaply, super-effectively, and to the Passivhaus Standard. It is so easy.

The Passivhaus Standard can be met with just a solid, airtight concrete box and thin insulation. That means:
Specific Heating Demand ≤ 15 kWh/m2.yr
Specific Cooling Demand ≤ 15 kWh/m2.yr


But all self builders want windows so the self builder will need to increase the wall insulation to compensate. Most self builders have heat recovery ventilation.

The most sustainable self build home has shrink-free, waterproof concrete walls that will remain completely waterproof, vapour proof and air proof, probably for centuries.

Our method is perfect for self builders because it is simple and cheap to self build and it will help the self builder save the maximum energy.
  self build formwork double sided

You will require very special concrete. We supply self builders the additives and the concrete know how they need.

Highly workable, very cohesive concrete requires exceedingly strong formwork that self builders can make easily. And the self-build formwork needs to be cheap and re-usable afterwards. Our method is all these things. You buy very little from us and what you don't want at the end we can buy from you if you don't use it or sell it to another self builder.

The self-build formwork is removed so you can see that you have done a good job and that the concrete is complete throughout. Unlike ICF where you have no idea.


If you are interested in self building a sustainable home then you probably know about the Passivhaus standard.

" The core focus of the Passivhaus standard is to dramatically reduce the requirement for space heating and cooling, whilst also creating excellent indoor air quality and comfort levels. "


British architects seem to be masters at capturing heat from the sun, storing it in walls to be released later, and reducing heating bills through what they call thermal mass.

But it only takes a heat wave for other experts to tell us that architects have got it all wrong, and probably cannot meet the passivhaus standard for Specific Cooling Demand because Thermal mass is a huge mistake. For instance this report (opens in a new window) Uncomfortably hot outside? Blame architects and planners

There is some flexibility in the Passivhaus standard but 4 Basic Principles.

This is how we help.

  1. "good levels of insulation with minimal thermal bridges

  2. passive solar gains and internal heat sources

  3. excellent level of airtightness







  4. good indoor air quality, provided by a whole house mechanical ventilation system with highly efficient heat recovery."
 
  • The self builder chooses his insulation. We help prevent the thermal bridges.

  • The self builder's choice, our method allows anything.

  • Yes, excellent if not 100%. (After all, the same self-build method using waterproof concrete for self built basements is totally waterproof).

    And because this is reinforced, waterproof concrete it will not crack, unlike timber frame and SIPs that can, and do, warp later. Also the self-builder can build it, rather than a specialist sub contractor.

  • The self-builder's choice, our method allows anything.

You can have insulation one side or both sides. As much or as little as you want.

If you believe in thermal mass you might need to create channels in the concrete for wiring and back boxes to be able to leave your concrete exposed internally.

If, like me, you are more convinced by the "heat only the space" argument then you will have insulation inside and you can bury your services in it.

But don't let that stop you having insulation outside to stop over-heating your urban environment (which is what the article above is about).

self build formwork single sided   This formwork is almost all timber that the self builder can use 7 to 10 times then use as a building material. It can cost virtually nothing in materials and save CO2 because self builders can use it so many times.

The concrete is particularly strong and completely waterproof. It quickly becomes inert to everything that exists above ground, including drying out. Self builders will not hear the creaks of drying out timber frame or SIPs.


Cement gets a bad press, mainly because of the huge amount produced not how much CO2 is produced just building a house. A concrete house saves more than the original cost in CO2 annually, compared to how we built all our houses a few years ago. And self builders want these energy savings because the house is for them.


However there has been a lot of work in the Middle East, recently, developing concrete with less embedded energy - and we make that research available to you as a part of our admixture service.

The waterproof concrete we help each self builder use, with the right reinforcement, will last the self builder centuries. Greener concrete will need to be designed according to your requirements.

The self builder strips off the formwork for re-use then the self builder adds the insulation of his choice later. Inside or outside or both inside and outside. Polystyrene, polyurethane board or sprayed-on polyurethane, foil-faced, rockwool, shredded newspaper, straw bales, sheep's wool or whatever the self builder wants. The self-builder's choice. No one is making you pay extra for fabrication or making you compromise on your insulation preferences.

These walls are proof against every kind of weather. You don't need a cavity. Most self builders choose either extruded polystyrene or Kingspan K5 for their external insulation. Extruded polystyrene is waterproof. K5 needs protection such as render. Internally the self builder can choose anything or nothing.

In case you hadn't realised yet, our contribution to your self build is only the waterproof concrete admixtures and some wall formwork accessories. That is because we are civil engineers not builders. But self building your walls to save energy for more years than any other material available today, and showing the self builder how to do that cheaply himself is a very valuable contribution, we think.

We have other websites for self builders about basements and concrete with links at the bottom of the page.

The DIY self build wall formwork promoted and part-sold by us is scaffold boards, which can always be sold on; 4x2, which is usually useful for bedroom stud walls; fibre glass threaded rods (that get cast in the concrete) and nuts that you get from us and 6x3 timbers which we will buy back if you don't want to use them in your new home.
  1. No single item is particularly heavy.

  2. Everything can be screwed together with washered coach screws that come out again just as easily.

  3. There are very few rules so any self builder willing to have a go can self build this.

  4. All the timber, all the coach screws, all the big nuts can be used many times and finally used for something else or sold to us.

  5. It is very strong.

  6. The self builder uncovers and inspects the concrete, unlike ICF.

  7. The self builder buys insulation of his choice and adds it later.
  self build formwork

  The self builder can have any wall thickness with steps, reductions, corbels, columns. tied into floors or whatever he wants.
Here you see 300mm and 100mm thick concrete walls in the same self build project. 300mm for a basement and 100mm for a house above it.

If the self builder bought all this formwork and threw it away, perfectly good scaffold boards, perfectly good 4x2 timber and so on, it would cost him £40 a m².

But of course self builders don't throw much away, and almost never after only one use.

After repeated use and most being used in the self build as a building material or else sold on the rate comes down to less than £7 a m² and much of that is for the original transport costs.


For specific information on our very special, waterproof, vapour proof, air proof and crack proof concrete click on this link at the bottom of each page.

waterproof concrete

The concrete usually costs £8 a m³ more, our additives cost £42 per m³ waterproofed and we insist on attending your concrete pours for £200 a visit. All plus VAT.

What other walls are available to a self builder that will remain maintenance free for centuries? What other walls are available to self builders for anything like this cost?




Return to the self build homepage   self build house formwork   self build manual   self build photos   contact self build

finishing walls insulated concrete formwork   self build insulated concrete formwork   energy argument self build



The Concrete Knowledge Ltd group of companies has two other web sites.

For specific information on waterproofing concrete and waterproof concrete structures go to

waterproof concrete

To see how we construct basements go to

basement expert



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