Thoughts on begrudgingly coming to love lime plaster

Tile set into clay plaster

When I consider what plaster to use, I always think of clay plaster first. I love clay plaster, it has so much going for it.

In terms of minimizing environmental impact and carbon footprint, you cannot beat clay plaster. It is minimally processed, needs no additives, and can be sourced locally.

Exterior clay plaster

Building well with straw bales (and straw-clay, adobe, cob, and other natural building systems) requires an understanding of moisture: vapor permeability, diffusion, wicking, etc. This leads to needing to understand plasters.

Clay plaster is one of the most vapor-permeable finishes, coming in at 11 perms per 2″ of plaster. 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.

Clay plaster has many benefits, but it does have some limitations. Once it gets wet enough, it will erode. It is also not as hard or impact-resistant as some finishes. Sometimes you need a plaster that can fulfill different duties. This is when I turn to lime plaster.

Exterior Type S lime plaster on a strawbale 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″).

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. It will not erode. It is harder and more impact-resistant than clay.

Lime plaster used to be very common in the US but was replaced by drywall and gypsum-based plasters in the last century. Then it became difficult to source lime of high enough quality to produce consistently good lime plaster. 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.

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.

Hydraulic lime is another option. It still requires knowledge and skill, but it sets faster and more consistently with less babying. 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.

So you can see why I gravitate towards clay plaster whenever possible. I encourage clients to build wrap-around-porches to take advantage of outdoor living and to allow for clay-plastered exterior walls.

Soaped and polished lime plaster can feel like marble

On a smaller scale, like a bathroom, lime plasters are a little less daunting. When applied well and polished, lime plaster can look and feel like marble. When finished in the tadelakt tradition, by rubbing oil-based soap into the plaster before it has cured, it can be remarkably waterproof. But these thin veneer plasters leave little room for error or inconsistency, so I have been reluctant to sell them to clients.

I recently became aware of a product called Limestrong. It is a bagged lime plaster created by the talented plasterer Ryan Chivers, in partnership with other experts in plaster chemistry. 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. And, like American Clay, you do pay more for this convenience.

Professional plasterer and founder of Limestrong, Ryan Chivers

At the 2020 Natural Plasterers’ Guild Retreat in January in Jacksonville, Oregon, I had a chance to learn more about Limestrong and see Ryan demonstrate the line of products.

Most importantly to me, Limestrong sources all of its ingredients from the US. Since lime itself has a larger carbon footprint due to the amount of heat needed to process it, keeping the embodied carbon involved in shipping as low as possible is important.

Limestrong uses pumice as the aggregate. This not only makes it lighter to ship (and carry around the job site), the pumice creates a mild pozzolanic effect, making the plaster slightly hydraulic. Although this means a faster set time, it also ensures a more even cure.

The only additive in Limestrong is cellulose, which is a non-toxic material that helps retard the set and acts as an adhesive to help it stick to difficult substrates like painted drywall.

So it is with great excitement that we have decided to host a professional plasterers’ training for Limestrong plasters at our current job site in Valley Center, CA, in March. We will learn directly from Ryan Chivers and his co-teacher Liz Johndrow about applying Limestrong over drywall. If time and interest permit, we may also install Limestrong over a clay plaster base coat on a straw bale wall. Attendees will also be able to observe two tadelakt shower surrounds being installed by our crew. Exciting stuff!

If you are an experienced plasterer who is interested in attending this training, join us to learn about this great product. Here is a link to the registration.

Limestrong lime plaster training March 14-15

We are excited to announce that we are hosting a training in Limestrong lime plasters at our current job site! These natural, durable plasters are perfect for existing homes as well as new construction.

Join Ryan Chivers, owner and formulator of Limestrong Mineral Finishes, for a hands-on lime plaster weekend training at our current project in Valley Center, CA. Discover each of Limestrong’s beautiful finish plasters: Sand, Stone, Marble, Tadelakt and Limewash as we plaster inside a local residence. Instruction and lunch provided on Saturday and Sunday, 10 am – 4 pm.

Soaped and polished lime plaster can feel and shine like marble

What is Limestrong?

Limestrong is a dry, bagged lime plaster mix created by the talented plasterer Ryan Chivers, in partnership with other experts in plaster chemistry. 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.

Meet Ryan Chivers, Limestrong founder, who saw there were no plaster companies offering US sourced materials + easy application + affordability, so he decided to change that. A life-long plasterer and lime geek/mad scientist, if it’s about lime, he’s read it or learned it the hard way.

Limestrong sources all of its ingredients from the US. Since lime itself has a relatively large carbon footprint due to the amount of heat needed to process it, keeping the embodied carbon involved in shipping as low as possible is important.

The aggregate in Limestrong is pumice. This not only makes it lighter to ship (and carry around the job site), the pumice creates a mild pozzolanic effect, making the plaster slightly hydraulic. Although this means a faster set time, it also ensures a more even cure. The only additive in Limestrong is cellulose, which is a non-toxic material that helps retard the set and acts as an adhesive to help it stick to difficult substrates like painted drywall.

Co-teacher Liz Johndorw works on building projects large and small, teaches natural material-based building skills in workshops and apprenticeships throughout the US and Central America.  Liz met Ryan learning tadelakt on a project of his in 2011 and has been assisting and co-teaching with him when the opportunity arises ever since!

If you would like to expand your range of plastering skills to include this beautiful, non-toxic, eco-friendly lime plaster system, join us for this informative and fun workshop.

Space is limited so register soon! 

* Some people have reported having issues with the registration page on Limestrong’s website. Make sure the number of tickets is set to at least 1 before clicking the registration button. If you are unable to sign up, please email limestrongartisan@gmail.com

Simple Construct is now a Benefit Corporation

We are proud to announce that we have restructured our business to reflect and embed our values: we have become a Benefit Corporation. This means that, although we are a for-profit company, maximizing profits is not our only consideration. We have written into our articles of incorporation that:

“The specific public benefit of this corporation is to preserve the environment and improve human health by reducing the embodied-energy, consumption, toxicity, and carbon footprint of construction through the use of local, natural, and carbon-sequestering building materials.”

As part of this process, we also defined our mission:

Our mission is to create high-performance natural homes from local, carbon-sequestering materials; to preserve the environment by reducing embodied-carbon; and to educate about, advocate for, and provide healthy, high-quality shelter for as many people as possible.

We hope you share our vision for a way of building that not only does less harm, but can actively do good for the environment and human health.

Plaster Party & Booktalk 10/5/19

Join us at Terra Corazon Farm in Valley Center for a fun, free day of learning!

This event is free but you must register in advance

Applications for our Natural Building Training + Certificate Program are due May 18

Interested in part-time on-the-job training and focused classwork centered on natural, high-performance building? Check out our new Training + Certificate Program!

We are pleased to offer this unique opportunity in partnership with the San Diego Sustainable Living Institute. Only four places will be offered per 3 month semester, applications are due May 18, 2019. Here’s a link to more info: https://www.sdsustainable.org/natural-building-pre-apprenti….