clay:clay_plasters

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clay:clay_plasters [2025/12/03 14:57] – Dave Darbyclay:clay_plasters [2026/03/26 18:33] (current) – external edit 127.0.0.1
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-# Clay & earth plasters+This topic is part of [[gt:buildings|Buildings & construction]]. 
 +====== Clay & earth plasters ======
  
  
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-## What are clay plasters?+===== What are clay plasters? =====
  
-Clay or earth plasters are blends of unfired clays mixed with fine sand to provide a natural, breathable finish for internal walls. They have been used all over the world for thousands of years, and still exist in lots of traditional vernacular buildings. Clay plasters were often used in old buildings in the UK as a base coat, with a top coat of [lime](http://lowimpactorg.onyx-sites.io/lowimpact-topic/lime/), as clay is cheaper than lime.+Clay or earth plasters are blends of unfired clays mixed with fine sand to provide a natural, breathable finish for internal walls. They have been used all over the world for thousands of years, and still exist in lots of traditional vernacular buildings. Clay plasters were often used in old buildings in the UK as a base coat, with a top coat of [lime](/lime/lime), as clay is cheaper than lime.
  
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 <caption> <caption>
-Clay plasters add an extra dimension to living areas. +_Clay plasters add an extra dimension to living areas._
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-Clay plasterers at work.+_Clay plasterers at work._
  
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-## What are the benefits of clay plasters?+===== What are the benefits of clay plasters? =====
  
 **Environmental benefits** **Environmental benefits**
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 <caption> <caption>
-Demonstration of how to make and apply your own earth plaster.+_Demonstration of how to make and apply your own earth plaster._
  
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-Making clay plaster from on-site clay.+_Making clay plaster from on-site clay._
  
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 - Clay plasters maintain a consistent relative humidity of around 50-60%, which is beneficial for people with asthma or other respiratory problems, but detrimental to dust mites - which reduces problems associated with allergies. - Clay plasters maintain a consistent relative humidity of around 50-60%, which is beneficial for people with asthma or other respiratory problems, but detrimental to dust mites - which reduces problems associated with allergies.
  
-- Clays contain no nasty chemicals, and are able to absorb toxins and thus improve indoor air quality. Even if you avoid toxic [cleaning](http://lowimpactorg.onyx-sites.io/categories/natural-cleaning) / househould products, in this day and age, it's difficult to avoid toxins completely, and so clay plasters can help.+- Clays contain no nasty chemicals, and are able to absorb toxins and thus improve indoor air quality. Even if you avoid toxic [cleaning](/ntcl/natural_cleaning) / househould products, in this day and age, it's difficult to avoid toxins completely, and so clay plasters can help.
  
 - You have to be in a room with a clay plaster to understand how beautiful, sensuous, natural, earthy (add your own epithet here) they are. They just make you feel good. - You have to be in a room with a clay plaster to understand how beautiful, sensuous, natural, earthy (add your own epithet here) they are. They just make you feel good.
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 <caption> <caption>
-Clayworks pigmented top coat plaster with colour chart.+_Clayworks pigmented top coat plaster with colour chart._
  
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-## What can I do?+===== What can I do? =====
  
-Learn as much as you can first. See our [further info section](http://lowimpactorg.onyx-sites.io/categories/clay-earth-plasters/further-info) for more details on application and maintenance of clay plasters.+Learn as much as you can first. See our [further info section](https://www.lowimpact.org/categories/clay-earth-plasters/further-info) for more details on application and maintenance of clay plasters.
  
 You can buy base coat and top coat plasters, or you can have a go at making a base coat (bought plaster will be much finer, so it may be better to buy the top coat). First test whether you have clay. The field test is that clay is sticky and can be rolled into a sausage shape. See _Using Natural Finishes_ and other books for more detailed tests, plus lots more information on making and applying clay plasters. You can buy base coat and top coat plasters, or you can have a go at making a base coat (bought plaster will be much finer, so it may be better to buy the top coat). First test whether you have clay. The field test is that clay is sticky and can be rolled into a sausage shape. See _Using Natural Finishes_ and other books for more detailed tests, plus lots more information on making and applying clay plasters.
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 The clayey earth is dug out of the ground and then soaked and sieved to remove aggregates. What's left is clay. Let that stand and keep taking water off the top until it dries. Clays are not uniform, so they will differ in composition depending on locality. This may take a little experience. The clayey earth is dug out of the ground and then soaked and sieved to remove aggregates. What's left is clay. Let that stand and keep taking water off the top until it dries. Clays are not uniform, so they will differ in composition depending on locality. This may take a little experience.
  
-Mix the clay with coarse sharp sand for a base coat - roughly 3 parts sand: 1 clay (and chop in straw or [hemp](http://lowimpactorg.onyx-sites.io/lowimpact-topic/hemp-building/) for binder, which helps with shrinkage and stops it cracking when it dries). Then add water until you have the right consistency for a plaster. For a top coat, use the same ratio of sand and clay, but use a finer grade sand, like silver sand.+Mix the clay with coarse sharp sand for a base coat - roughly 3 parts sand: 1 clay (and chop in straw or [hemp](/hemp/hemp_building) for binder, which helps with shrinkage and stops it cracking when it dries). Then add water until you have the right consistency for a plaster. For a top coat, use the same ratio of sand and clay, but use a finer grade sand, like silver sand.
  
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-Clay plasters can deal with humidity and add beauty to kitchens.+_Clay plasters can deal with humidity and add beauty to kitchens._
  
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-Apply 10-15mm of base coat, and 3mm of top coat. Apply the top coat in thin layers, and don't over-trowel, as it brings the moisture to the surface, with makes it liable to crack as it dries. Lay the base coat on with a steel float, then scour with a wooden / plastic float, which compresses the surface and gives a good hard surface for the top coat. Apply the top coat with a metal float, then burnish with a plastic trowel - steel might mark the pigment, but plastic doesn't (and it doesn't bring water to the surface as much either). If you're plastering over 2 different surfaces, e.g. brick and [cob](http://lowimpactorg.onyx-sites.io/lowimpact-topic/cob-building/), to prevent cracking, it may be a good idea to use hessian or glass fibre mesh. Apply the base coat, then push the mesh in, and trowel over it.+Apply 10-15mm of base coat, and 3mm of top coat. Apply the top coat in thin layers, and don't over-trowel, as it brings the moisture to the surface, with makes it liable to crack as it dries. Lay the base coat on with a steel float, then scour with a wooden / plastic float, which compresses the surface and gives a good hard surface for the top coat. Apply the top coat with a metal float, then burnish with a plastic trowel - steel might mark the pigment, but plastic doesn't (and it doesn't bring water to the surface as much either). If you're plastering over 2 different surfaces, e.g. brick and [cob](/cobb/cob_building), to prevent cracking, it may be a good idea to use hessian or glass fibre mesh. Apply the base coat, then push the mesh in, and trowel over it.
  
-Clay plasters can be painted with [breathable paints](http://lowimpactorg.onyx-sites.io/lowimpact-topic/natural-paints/), but nowadays you can also buy more refined top coats that will provide a finer finish and can be bought already containing coloured natural pigments, saving time and money.+Clay plasters can be painted with [breathable paints](/ntpa/natural_paints), but nowadays you can also buy more refined top coats that will provide a finer finish and can be bought already containing coloured natural pigments, saving time and money.
  
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 <caption> <caption>
-Clays, pigments, tools & binder.+_Clays, pigments, tools & binder._
  
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-## Specialist(s)+===== Forum ===== 
 + 
 +This topic belongs to the section [[gt:buildings|Buildings & construction]]. You can ask questions or add information on the corresponding [Forum section](https://forum.growingthecommons.org/t/buildings). 
 + 
 +===== Further resources =====
  
-**Thanks to Paul Fitzpatrick of [Strawhaus](http://www.strawhaus.co.uk/) for information and [Clayworks](http://www.clay-works.com/) for photographs.**+- [Tips & tutorials](https://www.lowimpact.org/categories/shelter/clay-earth-plasters/further-info/) - including preparation, application and recipes 
 +- [Clay plaster pros & cons, and where to use it](https://www.homebuilding.co.uk/advice/clay-plaster) 
 +- [How to make earthen plaster](https://www.themudhome.com/earth-plaster.html)
  
  
-![](https://lowimpactorg.onyx-sites.io/wp-content/uploads/phil-christopher.jpeg) 
  
-Phil Christopher is an environmentalist, builder and trainer and he believes in making a low-impact lifestyle an attractive possibility for everyone. Phil runs [Huff and Puff Construction](http://www.huffpuff.me), specialising in straw bale and sustainable building, training and design. He's a passionate advocate of earthen and lime plasters, stating “It’s the part everyone loves doing, even if they didn’t think they would!”+===== Related topics =====
  
 +- [Low-impact building](buil:building)
 +- [Natural paints](ntpa:natural_paints)
 +- [Retrofitting & refurbishment](retf:retrofitting)
 +- [Wattle & daub](watd:wattle_and_daub)
 +- [Straw-bale building](strw:straw-bale_building)
 +- [Cob building](cobb:cob_building)
 +- [Lime](lime:lime)
 +- [Earthen floors](eafl:earthen_floors)
  
 +===== Specialist curators of this topic =====
  
-_Date on Lowimpact:2013-01-06_ 
  
  • clay/clay_plasters.1764773874.txt.gz
  • Last modified: 2025/12/03 14:57
  • by Dave Darby