A Fine Finish: Natural Wall Finishes, Nontoxic Paints and Clay Plasters

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Textured walls add warmth.
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American Clay offers a wide variety of color pigment options.
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Well-graded coarse aggregate

A new wall finish can transform your home. Finishes protect walls from the elements and from daily wear, and they play an important role in regulating indoor temperature and humidity. Natural finishes, which undergo minimal processing and are generally nontoxic, can be made from clay, lime, chalk, casein, rock dusts, earth pigments, and natural plant extracts such as oils and waxes. These naturally beautiful materials bathe walls in color and texture while balancing relative humidity, creating a more comfortable indoor environment.

Natural finishes are essential for buildings made of straw bales, cob and non-stabilized adobe because these materials must “breathe” to remain healthy. However, their use is hardly limited to those types of homes. They’re compatible with all wall types, though some walls require a nontoxic primer.

• Don’t use conventional paints, which often are petroleum-based and contain poisonous chemicals and volatile organic compounds (VOCs).

• Do consider making your own clay plaster using local soils.

DIY or buy?

You can buy pre-manufactured natural finishes such as clay-based paints and plasters at specialty building supply stores. You can also make handmade finishes such as clay plaster and limewash using simple ingredients. Homemade finishes are less predictable than those out of a can or a packet, so it’s essential to assess performance, texture and appearance by testing wall patches before application.

Homemade clay plaster or paint

Pro:  Inexpensive; very low carbon footprint if sourcing materials onsite
Con:  Labor-intensive and time-consuming; requires extensive testing; ess reliable than a pre-made product

Pre-manufactured clay plaster or paint

Pro:  Less labor-intensive; consistent and durable if applied correctly; wider variety of colors available
Con:  More expensive than homemade finish; processed materials have higher carbon footprint

Why should I use natural finishes?

1. They’re good for humans. Nontoxic natural finishes are essential for people with chemical sensitivities and respiratory problems. By balancing relative humidity in the atmosphere,
they reduce dampness and mold.

2. They’re good for the planet. Natural finishes require less extraction and processing than synthetic finishes and have fewer disposal issues. Most of their ingredients biodegrade easily and safely and are recyclable.

3. They’re good for buildings. Natural finishes’ high vapor permeability (ability to let moisture pass in and out) allows buildings to “breathe,” which helps increase the durability of the walls, roof and foundation.

Katy Bryce and Adam Weismann are the authors of Using Natural Finishes: Lime & Earth Based Plasters, Renders & Paints–A Step-by-Step Guide and Building with Cob: A Step-by-Step Guide. They work with lime and clay on a daily basis through their company, Cob in Cornwall/Clayworks, based in England.

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