![]() ![]() In my mind, it is the lime equivalent of American Clay Plaster: a convenient, bagged, premeasured plaster with a tested range of pigments that allow you to create a consistent result time after time. It is a bagged lime plaster created by the talented plasterer Ryan Chivers, in partnership with other experts in plaster chemistry. I recently became aware of a product called Limestrong. But these thin veneer plasters leave little room for error or inconsistency, so I have been reluctant to sell them to clients. When finished in the tadelakt tradition, by rubbing oil-based soap into the plaster before it has cured, it can be remarkably waterproof. When applied well and polished, lime plaster can look and feel like marble. On a smaller scale, like a bathroom, lime plasters are a little less daunting. Soaped and polished lime plaster can feel like marble I encourage clients to build wrap-around-porches to take advantage of outdoor living and to allow for clay-plastered exterior walls. So you can see why I gravitate towards clay plaster whenever possible. You could import hydraulic lime from Europe, where the tradition of lime plaster had not been broken, but at a high cost financially and environmentally. It still requires knowledge and skill, but it sets faster and more consistently with less babying. On larger-scale projects, like the exterior of a strawbale home in a climate that gets sideways monsoon rains, we will make our own Type S lime plaster, don our gloves and safety glass, apply the plaster skillfully before it begins to set, and then tend to it patiently until it has cured. Although it is possible to make a good lime plaster from locally-available Type S lime, it requires knowledge, skill, and a fair bit of babying to succeed. Then it became difficult to source lime of high enough quality to produce consistently good lime plaster. Lime plaster used to be very common in the US but was replaced by drywall and gypsum-based plasters in the last century. It is harder and more impact-resistant than clay. If you do it right, lime plaster goes through a chemical change as it cures that effectively turns it back into limestone on the wall. Lime plaster has a slightly lower carbon footprint than cement plaster and is more vapor-permeable than cement (lime plaster is 9 perms per 2″ where straight cement plaster is less than 1 perm per 2″). Exterior Type S lime plaster on a strawbale wall Sometimes you need a plaster that can fulfill different duties. It is also not as hard or impact-resistant as some finishes. This makes it ideal for any building system where you do not want trapped moisture - which should be the goal for every building system but is often ignored in conventional construction.Ĭlay plaster has many benefits, but it does have some limitations. This leads to needing to understand plasters.Ĭlay plaster is one of the most vapor-permeable finishes, coming in at 11 perms per 2″ of plaster. Exterior clay plasterīuilding well with straw bales (and straw-clay, adobe, cob, and other natural building systems) requires an understanding of moisture: vapor permeability, diffusion, wicking, etc. ![]() It is minimally processed, needs no additives, and can be sourced locally. In terms of minimizing environmental impact and carbon footprint, you cannot beat clay plaster. I love clay plaster, it has so much going for it. When I consider what plaster to use, I always think of clay plaster first. ![]()
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