What Is Mycelium? A Plain-English Guide
Mycelium is the living network that sits beneath the visible part of a fungus. It is often described as being “like the roots of a mushroom”, although the comparison is not exact. Mycelium is not a root, and a mushroom is not the whole fungus. The mushroom is the fruiting body. Mycelium is the larger, branching network that grows through soil, wood and other organic matter.
This network is now being explored as a basis for new bio-based interior materials. It can grow through agricultural by-products, bind loose fibres together and form lightweight shapes with useful acoustic and thermal properties.
The material is promising, but it is not a universal replacement for every conventional material. To use it responsibly, you need to understand both its strengths and its limitations.
Mycelium In Simple Terms
A fungus grows through very fine threads called hyphae. When many of these threads join together, they form mycelium.
You can picture it as a three-dimensional web. It spreads through its food source, looking for nutrients and breaking down organic matter as it grows. In a forest, mycelium may run through soil, fallen leaves and decaying wood. It can connect plants, transport nutrients and help organic matter return to the soil.
The visible mushroom is only one stage of the fungal life cycle. It is the part that produces spores. Most of the fungus may remain hidden inside the material where it is growing.
For material development, the mycelium is especially useful because its thread-like structure can grow around loose particles and hold them together. In this sense, it acts as a natural binder.
Mycelium And Mushrooms: What Is The Difference?
The terms are often used interchangeably, but they describe different things.
- Mycelium is the network of fungal threads.
- Hyphae are the individual threads that make up the network.
- A mushroom is the visible fruiting body produced by some fungi.
- A mycelium material is usually made by growing mycelium through a chosen feedstock, then drying or heat-treating it.
A mycelium-based material does not need to contain a mushroom. In fact, material processes are generally designed to encourage the mycelium to grow through the feedstock rather than produce fruiting bodies.
Once the material has reached the required density and shape, it is dried. This stops the biological growth and creates a stable, non-living material for use in interiors or other applications.
How Is Mycelium Grown?
The process begins with a suitable fungal culture and an organic feedstock. The feedstock provides the structure and nutrients that allow the mycelium to grow.
Common feedstocks include:
- Hemp fibres and hemp hurd
- Straw
- Sawdust
- Wood by-products
- Agricultural waste
- Plant fibres and other processed organic residues
The feedstock is prepared, cleaned and placed into a controlled growing environment. The mycelium is then introduced and allowed to spread through the material.
As it grows, the network moves around the particles and binds them together. The final density, texture and strength depend on several factors, including:
- The type of fungus
- The feedstock used
- Particle size
- Moisture levels
- Temperature
- Growing time
- The pressure or mould used
- The drying and finishing process
The material can be grown inside a mould, allowing the shape to be formed during the biological process rather than cut from a larger block. This is one reason mycelium is relevant to mycelium design. It offers a way to develop forms, textures and surfaces around a specific spatial requirement.
The process is deliberate rather than instant. Time is part of the material system.
What Properties Does Mycelium Have?
Mycelium-based materials are not all the same. A soft, low-density panel will behave differently from a dense moulded element. Always ask for information about the specific formulation and tested product.
However, several properties are commonly associated with mycelium composites.
Lightweight But Rigid
Mycelium materials are generally light when compared with dense construction materials. Their structure is often closer to a rigid foam, cork or fibrous board than to concrete, metal or structural timber.
This can make them useful where weight needs to be limited. Lightweight components may be easier to transport, handle and install. They can also be suitable for suspended elements, acoustic features and non-structural interior applications.
Lightweight does not mean weak in every situation. A well-formed material can feel firm and rigid, particularly when it has been grown at a higher density. However, it should not automatically be treated as load-bearing.
For a project, check:
- Compressive strength
- Tensile strength
- Flexural strength
- Fixing performance
- Impact resistance
- Long-term dimensional stability
Acoustic Absorption
The open, fibrous structure of mycelium materials can help absorb sound. Instead of allowing sound energy to reflect directly from a hard surface, a porous material can reduce some of that energy and help control reverberation.
This makes mycelium relevant to acoustic panels, ceiling elements, wall treatments and other interior features where sound quality matters.
Performance will depend on the material’s thickness, density, surface finish, shape and position in the room. A thin decorative layer will not necessarily perform in the same way as a deeper acoustic panel.
Before specifying it, request tested acoustic data, such as sound absorption coefficients or the relevant rating for the intended application.
Thermal Behaviour
Mycelium composites can have relatively low thermal conductivity. Reported values are often in the region of 0.05–0.07 W/m·K, although results vary according to density, feedstock and manufacturing method.
In simple terms, lower thermal conductivity means that the material slows the movement of heat. This can make mycelium useful for certain insulation, infill or interior lining applications.
It is important not to confuse thermal insulation with thermal mass. Mycelium is generally a lightweight material. It may slow heat transfer, but it will not behave like a dense masonry wall that stores and releases large amounts of heat.
Ask for tested thermal performance for the exact material, thickness and installation build-up.
Mouldable And Growable Into Forms
Mycelium can grow inside a mould, allowing the material to take on a planned shape. This may reduce the need for extensive cutting and create forms that would be difficult to produce through standard sheet fabrication.
Design possibilities can include:
- Curved or irregular panels
- Textured surfaces
- Acoustic baffles
- Bespoke screens
- Lightweight sculptural elements
- Integrated forms grown for a particular space
The growth process also leaves room for natural variation. Surface texture, colour and density may not be completely uniform. For some projects, this is part of the material’s character. For others, a more consistent finish or coating may be required.
What About Fire?
Mycelium-based materials contain organic matter. They should not be treated as naturally fireproof.
Fire behaviour depends on the fungal material, feedstock, density, coatings, thickness and overall assembly. Some materials may char or slow the movement of heat at the surface, but this does not remove the need for testing.
For commercial or public interiors, check:
- Reaction-to-fire classification
- Smoke production
- Flame spread
- Performance of any coating or treatment
- Performance of the complete wall, ceiling or panel assembly
- Local building regulation requirements
Do not rely on general statements about mycelium when a project requires a specific fire rating. The tested system is what matters.
Moisture And Humidity
Moisture is one of the most important considerations.
Mycelium materials can absorb water from the air or from direct contact. If they remain damp, they may lose strength, change shape or become more vulnerable to biological degradation.
This does not mean they cannot be used indoors. It means the environment needs to be appropriate.
Use particular care in:
- Bathrooms
- Kitchens
- Basements
- Spa environments
- Unheated spaces
- Areas with condensation
- Locations exposed to leaks or splash water
The material should be properly dried and protected. Depending on the application, this may involve a coating, a sealed edge, a ventilated build-up or protection from direct contact with water.
For every project, confirm the acceptable humidity range, water absorption, dimensional movement and cleaning requirements.
Is Mycelium Durable?
Mycelium can be durable when it is correctly grown, dried, finished and used in a suitable environment. It is not durable in the same way in every condition.
Its service life will depend on:
- Moisture exposure
- Physical impact
- Ultraviolet exposure
- Temperature changes
- Cleaning methods
- Fixings and support
- Coatings and surface treatments
- The quality of the installation
Most current applications are better suited to controlled interior environments than to exposed external conditions. A material designed for a dry wall panel should not automatically be used as an outdoor façade element.
Durability claims should be supported by testing and a clear maintenance plan.
Is Mycelium Sustainable?
Mycelium materials are bio-based, meaning that they are made partly or wholly from biological sources. They may also use agricultural or wood by-products that would otherwise have limited value.
Bio-based does not automatically mean sustainable.
A responsible assessment should consider:
- Where the feedstock comes from
- How it is processed
- Energy used during growing and drying
- Transport distances
- Any resins, coatings or additives
- Expected service life
- Repair and replacement options
- What happens at end of life
Mycelium may biodegrade under suitable conditions, but a finished interior component may also contain coatings, fixings or composite layers that affect its disposal route.
End-of-life planning should therefore be part of the design from the beginning. A material is easier to recover when it can be separated, repaired, reused or processed without contamination from incompatible layers.
What Should You Check Before Specifying It?
If you are considering mycelium for an interior project, ask for clear information about the exact material rather than relying on broad descriptions.
Check:
- Composition: What fungus and feedstock are used?
- Density: How does the density affect strength and acoustic performance?
- Moisture: What humidity and water exposure can it tolerate?
- Fire: What testing has been completed?
- Acoustics: What results apply to your proposed thickness and installation?
- Thermal performance: What is the tested conductivity or resistance?
- Durability: How does it behave under impact, cleaning and long-term use?
- Finishing: Are coatings or sealants required?
- Installation: How should it be cut, fixed and supported?
- End of life: Can it be separated, reused or biodegraded?
These questions help move mycelium from an interesting concept to a properly considered material choice.
Mycelium As A Design Material
Mycelium sits between biology, material science and interior design. It offers a different way to think about making: instead of only cutting, pressing or moulding a material, we can also grow it.
That approach can support lighter, more tactile and more responsive interior elements. It can also encourage designers to think about feedstocks, time, moisture, maintenance and end of life as part of the design brief.
At Osmose Studio, we explore mycelium through material development, biophilic interior design and professional learning. You can learn more about our approach through our materials work and CPD and training courses.
Mycelium is not a magic material. It is a living system that becomes a useful material through careful growing, drying, testing and design. The better we understand its properties, the more thoughtfully we can use it.