Farm building conversion using Hempcrete

We started investigating the use of hemp in the renovation of brick and lime buildings in 2008 and contacted Ralph Carpenter, who probably has the most experience of hemp building in England. This gave us the confidence to go ahead and renovate our own redundant brick and lime farm buildings using our home-grown hemp. Ralph suggested that we add hempcrete to the exterior of the building to preserve the internal space and also construct a solid hempcrete wall for the new build element. We then began the ten month battle to get planning approval for the change of materials. 

Members of the Planning Committee were aware that more planning applications would specify the use of sustainable and renewable materials and they needed to act positively. 

At last we were able to make a start using hempcrete. We have worked closely with Mike Turner, a local builder, and together we researched lime in all its various forms to enable us decide on our formulas. We then prepared the buildings to enable us to apply 200mm of hempcrete insulation to the exterior of the brick walls. We fixed wooden pegs into the wall to act as a key for the hempcrete and also to attach the shuttering, using adjusting screws. We were now ready to mix HemShiv-Build and lime binder in a pan mixer. 

Part of the project required replacing walls and here we used shuttering to build a new 450mm thick hempcrete wall around a light timber frame. All exterior walls have been rendered with a plaster consisting of HemShiv-Fine, lime and sand. No pigments have been added to the final plaster coat leaving a completely natural colour. Roof joists were filled with 300mm of dry hempcrete mix to make a “warm roof”. This was covered by a breathable membrane and finished with local pantiles. An overhanging roof gives protection to the walls from the weather. 

All floors have been laid on top of 40mm gravel. We have used three different methods of floor construction. In the lounge we made a suspended floor, the joists are in- filled with dry-mix hempcrete and finished with an engineered hardwood floor. For the kitchen floor we used pre-made 150mm thick hempcrete blocks in-filled with hempcrete to speed the drying time and in the hall the floor is 150mm deep hempcrete laid in-situ. Both these floors were topped with a screed of sand, lime and HemShiv-Fine, with tiles as the final finish. 

We built a circular shower cubicle, within a bathroom/wetroom, using the shuttered hempcrete system we formed the wall with flexible plywood curved round a light wooden frame. This method could easily be employed to make any curved wall. The walls of the shower area have been plastered with Tadelakt – a Moroccan plaster. The surface was polished using a special ceramic stone and waterproofed by applying olive oil soap. A sunpipe increases the natural light inside the shower room. 

In one corner of the kitchen we have built a small room - 1 metre square - also fully insulated with hemp. We have added an air conditioning unit and shelving to create a cool food store/fridge. 

Partition walls and ceilings have been formed using Celenit breathable wood wool boards. All the joists between the floors and the cavities in the internal walls have been filled with dry hempcrete insulation /roof mix, which also helps sound insulation in upstairs rooms.