Hybrid Natural Building Materials

Photo left: wattle & daub wall: woven bamboo lattice with clay/straw mixture

Photo right: completed wall with clay plaster finish

The thing is...most natural building methods are actually a combination of materials. Like a stew. Each chosen from what is available locally and used for its particular characteristics.

Materials that trap air pockets where insulation is required. Sticky materials where a binding glue is needed. Sand to control shrinking or increase compressive strength. Fibrous ingredients when you need to knit materials together.

Most hybrid natural materials are made up one of two or more of the following (hence the term "hybrid"):

Clay - super sticky binder used in a variety of natural materials

Sand - aggregate added to increase strength and reduce shrinkage & cracking

Fiber - such as straw or hemp, provides insulation & knits materials together

Wood/Bamboo - ideal for structural supports, woven elements, or cordwood

Lime - binder used for wear-resistant plasters & paints

The idea is to look at what is available locally in nature in abundance. Then understand the performance qualities you need. Do you need insulation to stay warm in winter? Do you need mass to absorb heat? Do you just need a partition to separate spaces? Then select those local materials that will best accomplish those needs. Scroll below to see a breakdown of some of the most common hybrid natural materials and where to use them.

Best Use

Use hybrid walls where you need thinner, non-structural walls or to maximize the use of your local materials.

Cheat Sheet

HYBRID MATERIALS COMBINE TWO OR MORE OF THE FOLLOWING:

Clay - super sticky binder that creates internal structure for a variety of applications

Sand - aggregate added to increase strength and reduce shrinkage & cracking

Fiber - such as straw or hemp, provides insulation & knits clay materials together

Wood/Bamboo - ideal for structural supports

Lime - binder used for wear-resistant plasters & paints

AT A GLANCE

most hybrid materials combine fibrous ingredients (such as straw or hemp) with a natural binder (such as clay or lime)most hybrids are non-structural (except cordwood)

BEST USE

when you need to maximize the performance of various local materials

LINK TO GLOSSARY

Read the glossary description here.

Comparison of Hybrid Natural Wall Materials

quick look at various methods that use a hybrid of materials from nature

MATERIAL	DESCRIPTION	BEST USE	BENEFITS	CHALLENGES
LIGHT CLAY	Light clay straw is made by coating straw fibers with liquid clay and tamping the mixture into a wall cavity. The clay glues the straw fibers together. tocreate a solid infill material.	Use where modest insulation or good sound absorption is a benefit	•excellent acoustic performance •simple installation •very inexpensive •prevents air leakage	•requires ample airflow during drying •requires cavity wall system (such as stud framing) •labor intensive •limited testing data
HEMPCRETE	Hempcrete is a combination of hemp hurds (from woody hemp stalks) glued together with sticky lime. The mixture is tamped into a wall cavity and then plasteredon both sides.	Use as insulation to save energy for heating or cooling. especially where walls need resilience from occasional wetting.	•high insulation •can handle some dampness •sequesters CO2 •regulates humidity •prevents air leakage	•lime binder is caustic during installation •requires cavity wall system (such as stud framing) •labor intensive •currently costly in USA
CORDWOOD	Cordwood features logs, round or split, all cut to the same length. The logs are mortared together, with their length creating. the wall-width.	Use if you have wood in abundance and benefit from modest insulation	•modest insulation •nofinish plastering required •uses short pieces of wood •logs create the wall surface aesthetic	•slow construction •logs must be cured (dried) to prevent shrinking in place •wood-intensive •pointing between logs can be tricky
WATTLE & DAUB	Wattle is woven material, shap. Daub is a wet mixture of clay soil and plant fivers (such as straw).	Use as non-structural partitions where insulation is not required	•nearly free interior wall system •thin walls simple, low-tech •intuitive	•non-structural •usually requires finish plaster •low thermal mass •non-insulating