Hemp, Lime & Clay

Louise mixing hemp and limeIn the developed world, how we construct and live in our buildings accounts for almost half of our overall carbon emissions. But we could significantly reduce our domestic carbon footprint if all our housing stock were adequately insulated and efficiently heated.

Of course it is not as simple as that if you happen to live in sub-standard council housing or rent an unmodernised Victorian terrace from a private landlord whose main interest is maximising the profits from their buy-to-let portfolio.

And even if you do own your home – or that part of it not covered by a mortgage – the cost of ground source heat pumps, solar electric panels and roof-top wind generators might not be within your income range – and in any case may not seem to justify their expense in terms of energy bill savings or carbon emissions averted.

But there are simple things that we can all do to substantially reduce our utility bills and make our houses less Thermal imaging of heat-loss from a 1960's housewasteful of energy. And since it is anticipated that 80% of current housing stock will still be in use in 2050, it is crucial that we make our existing homes – and how we live in them – much more energy-efficient.

It has recently been estimated in the UK that it will cost an average of £15,000 per house to achieve national carbon reduction targets. This is of course well beyond most people’s budgets but most of us have barely yet begun even to think about the cheap and easy measures that we can achieve.

The first thing is to stop giving our houses TV inspired cosmetic makeovers and throwing out the black granite worktops because they are so 1990’s now. We need to regard our homes as the assets that they really are – not commodities from which to make an annual gain, but the places where we make our lives – the basic source of our shelter and wellbeing among an interacting community of neighbours.

My own eco-building work is mainly in traditional and vernacular buildings. So the less familiar renewable materials like hemp that I highlight here are not suitable for every application. But it is worth exploring the range of natural building and insulation materials and methods that are increasingly available as alternatives to the carbon-heavy concrete, brick and breezeblock that we automatically tend to use to ‘improve’ our homes. I particularly like hemp because it is a fast growing renewable crop with many versatile uses other than as a building material and lime because it absorbs carbon dioxide as it re-carbonates into limestone. By contrast, cement gives off a tonne of carbon dioxide for each tonne manufactured and used.


(Links to some useful eco-retrofitting websites follow the pictures below)




Digging out old floor

Digging out old floor

Expanded clay balls for hardcore and insulation

Expanded clay balls as hardcore and insulation

Lightweight hemp-lime floorslab

Lightweight hemp-lime floorslab

Laying reclaimed terracotta tiles in lime mortar on top of sand/lime screeded floor slab

Reclaimed terracotta tiles in lime mortar on top of sand/lime screeded floor slab


Throwing hemp/lime plaster first coat onto walls

First coat of insulating hemp/lime plaster applied by hand on interior walls


Stud partitions awaiting hemp/lime infill

Stud partitions awaiting hemp/lime infill

Packing hemp/lime wall mix behind temporary shuttering

Packing hemp/lime wall mix behind temporary shuttering

'Green' hemp/lime walls awaiting top coat

‘Green’ hemp/lime walls awaiting top coat

Clay plastered walls

Clay plastered walls

Finished bathroom with hemp/lime insulation and clay plaster walls

Bathroom with hemp/lime insulation and clay plaster walls prior to painting with natural clay based paints



Eco Retrofitting

The Yellow House – http://www.theyellowhouse.org.uk/

Donnachadh McCarthy – http://www.cix.co.uk/~dmccarthy/mygreenhouse.html

Ecovation (Eco-Renovating) – http://ecovation.org.uk/

Penney Poyser – http://www.youtube.com/watch?v=8ATpxabVmvc

Green Building Forum – http://www.newbuilder.co.uk/forum/welcome.asp

Energy Saving Trust – http://www.energysavingtrust.org.uk/

Natural Paints – http://www.guardian.co.uk/lifeandstyle/2009/feb/09/eco-natural-paints-guide-best

Hemp, Lime & Clay

Steve Allin – http://www.hempbuilding.com/

Hemplime Construction Products Association – http://www.hemplime.org.uk/

Studio MGM Architects (Ralph Carpenter) – http://www.studiomgm.co.uk/hemp.htm

Sustain and Build Video – http://www.youtube.com/watch?v=FcctSvVFheA&feature=related

Building Limes Forum – http://www.buildinglimesforum.org.uk/

Sustainable Build UK – http://www.sustainablebuild.co.uk/UsingLime.html

Becky Little and Alison Davie – http://www.littleanddavie.co.uk/about.htm

Devon Earth Building Association – http://www.devonearthbuilding.com/

Katy Bryce & Adam Weissman – http://www.cobincornwall.com/

Kevin McCabe Cob Building – http://www.buildsomethingbeautiful.com/

Making Cob video – http://www.youtube.com/watch?v=2i1cHHJAguA&feature=related


  1. I have been restoring a 15th century timber framed building in shropshire, i first came across hemp 5 years ago and can recommend it to anyone who is restoring a timber framed building.. im now moving into this field working for myself.. its a wonderful eco friendly material thats breathable and will move with the building where as standard plasters crack…

  2. Have just finished putting 150mm of Hemp/lime plaster on solid log (Larch) house. Initial objective was to eliminate rodents but closing all air gaps, additional insulation and cosy looking finish has made project very worthwhile. Mostly DIY with help from experienced builder.

  3. Hi Jonty, we came across your website looking for information about how to lay terracotta tiles without using cement. We would like to ask you how you laid your tiles, how thick was the layer of sand/lime screed underneath the tiles. What was your ratio of sand/lime in your screed? Did you lay the tiles with no gaps in between? Did you use sand afterwards to sweep it in the existing gaps between tiles once they were laid? What lime did you use? We came across St Astier limes site but sadly there are no stockists in Slovakia where we live. We would be very happy for any information about the screed. We also love the throwing of the hemp/lime plaster on the wall. Did you have to repair the wall first? Was the wall built with lime or cob? We are renovating a house that was built with stone and cob.
    We are looking forward to reading the rest of your blog.

    Jana and David

    • Hi Jana and David,
      The lime mortar to bed the tiles was about a half an inch thick, made up of a three to one mix of fine sand (O-2 grade in France) and St Astier NHL 3.5. This went on top of a two inch sand-lime screed – 4:1 with a sharper sand (0-4). There were no gaps between tiles – apart from irregularities in reclaimed handmade tiles – and I pointed in (and cleaned up) gaps and irregularities as I went along to get an even lay out.
      For hemp-lime plaster, the walls do need to be repaired first. Traditional buildings in Finistere are granite bedded in clay and they are usually full of mouse runs, etc. The worst of these need to be filled in/repaired with lime mortar and then the hemp-lime mix applied over that. I usually apply hemp-lime in two coats on consecutive days – the first to get a couple of inches on the wall, then built out by another inch or so – this depth to get maximum insulation benefit. I tend to finish with a thin lime and sand render though others leave a hemp-lime finish. Btw, it is imperative that the wall is not subject to damp as with constant humidity the hemp can rot and develop an unhealthy black mould.
      Hemp-lime can also be projected onto the walls with a large hose and an air compressor – this is evolving as a technology in Brittany where hemp is becoming more common as an agricultural crop.
      Best of luck with your renovation!

  4. Hi,
    wonder if straw could be used together with lime as insulating material, as in hemp/lime insulation.

    • Worth experimenting, but bear in mind that it is the oils in hemp (and flax) plus the small size of shive that makes these very suitable for using with lime. Be difficult to shred straw to a suitable size in order to be thoroughly coated with lime.

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