Hill Holt Wood

complex wall shapes made from earth on site


Hill Holt Wood are an exemplary organisation with a slew of awards in both provision of help and training for young people, but also in sustainable building. They have been earth building in different ways on their site for the last 20 years. The project works with youth who aren’t achieving in school or otherwise not fitting into the system well.

They are based in a wood in the east Midlands and the whole site is entirely ‘off grid’ so using things like compost toilets are ‘fitted as standard’. So when they embarked on an ambitious new build to increase their capacity rammed earth was a natural choice. Doing so has allowed bigger visitor and learning groups into the woods and bridged public perceptions of natural building in interesting ways. It was natural for them to look to the materials they have on site for their basic building elements, and to turn the use of those materials into a building course for their young people.

We have dug up many buildings over time but Hill Holt Wood was very interesting because every trial pit we dug produced different material. Mixing the product of each trial pit we managed to find a very useful building material. Bryce the architect and the team did a great job in getting some 250 tonnes mixed thoroughly and dried out in the middle of a wood in the East Midlands, no mean feat.


  The circular rammed earth walls and double reciprocal roof create a comfortable space  

It took us around 10 years to start building elements with the complexity involved in this build. It took us a week to teach the team in the woods. The building has a ten metre internal diameter and a twelve sided polygon outside. Most of the walls are external and are insulated externally, with just a small proportion fully internal and therefore left exposed. This meant that the walls where both circular and facetted, so changed in thickness from a minimum 350mm to a maximum 500mm.

On top of this wall is a double reciprocal roof, cut from logs harvested from the wood. The total calculated weight of the roof is around six tonnes. Initially there was scepticism that earth walls could hold such a load. But in fact each facetted section is about six tonnes so the total roof load was the equivalent to adding 3% to the wall height. This is not the first time that putting the roof on has caused these concerns, and won't be the last. It is hard to equate the density of the walls with other 'heavy' materials like timber. It is only with experience that confidence comes.




    Complex work but built in the first week  




    The geometry of the formwork is the same was the geometry of the wall