Is wood wool slab fire resistant? And other advantages and disadvantage


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If you’ve ever wondered whether wood wool slabs are fire-resistant, then you are not alone. I too have wondered. That then caused me to do some digging. So here are my results.

What are Woodwool Slabs?

Wood wool slabs have become an eco-friendly way of insulating buildings because the material comes from sustainably managed forests. Before we talk about the fire-resistant quality of wood wool slabs, it would be best to know what it is.

A wood wool slab is an artificial slab with a thickness of about 50mm to 75mm. They are composed of other materials like wood shavings, other wood fibers, gypsum, etc., bound by a cement paste.

wood wool slab fire resistance

This material has been used for mostly the insulation of roof ceilings as far back as the 19th Century. Back in 1908, Heraklith invented the wood wool slab recipe, which was wood wool, water, and a mix of cement and lime. Since then, there have been improvements made.

As already established that they are building boards that are made up of mineralized wood thus, making them durable, breathable, and rot-resistant. They are also suitable for carrying lime or clay renders and plasters.

The primary use of wood wool slabs is for thermally and acoustically insulating not just the ceilings of a building but the inside walls too, which has dramatically been employed by architects and for the interior decorators, its rough appearance can also be very decorative. Wood wool slabs exist in several forms that give them great versatility in application and incredible durability in various climatic conditions.

Is wood wool slab fire resistant?

Wood wool slabs are very fire-resistant. It is made in such a way that it doesn’t burn easily. wood wool, in case you are not yet aware, is made up of wood chips and other materials held together by cement paste.

According to fire resistance research carried out by the fire research station, there is no immediate risk to fire safety in buildings where wood wool materials are used.

Composition and Properties of Woodwool Slabs

Wood wool slabs have become a known household name for buildings. And there have been many product variants made up of species of conifers in the form of fine threads. These Northern European spruce woods are predominantly used to manufacture wood wool.

These wood fibers are mixed with cement as the main mineral element. At the same time, rock wool, polyethylene, gypsum or lime and other additives (such as a water-repellant substance) can be combined depending on its use.

After which, the wood pulp is then compressed into a wood wool board and put in an oven to be dehydrated. The finished product is usually a whitish surface, but with advancement in production processes, the coarseness can be easily removed. All these give the wood wool slab its composite board. And now, with the application of pigments (colors), wood wool can be found in various colors.

Wood wool slabs can be found in low, medium, and high densities, depending on the amount of material per cubic meter or the pressure.  It is a material used in wall and ceiling cladding, as earlier said, and its significant characteristics include fire resistance, acoustic and thermal insulation properties.

Another valuable property of wood wool is that it can regain its initial volume when the pressure has been removed from its compressed form. This property helps in easy transportation and moving of the material.

Also, because of its large surface area and high volume, wood wool slabs can be deployed where water retention and absorption is required.

is wood wool slab fire resistant

Types of Woodwool slabs Suitable for Insulation

There are so many manufactured insulation options out there, but when in need of a better choice for your building, wood wool slabs are always the most preferred.

Research has it that there are stable(rigid) wood wool slabs, semi-stable wood wool slabs, and flexible wood wool slabs. The stable wood wool slabs are often used as a roof underlay or as a finishing and insulation material for floors, walls, and flat roofs. At the same time, the flexible wood wool slabs are easy to cut to size and use between the rafters of a roof. There is, of course, a weatherproof wood wool slab that is mainly deployed for roof sarking and external house cladding.

There are wood wool slabs available for whatever artificial modification suits the client’s needs.

Advantages of Wood Wool Insulation

For something to be present as far back as the 19th century and is still in use now, it can only mean one that, which is, wood wool slabs have proven their worth when it comes to building and construction in general. Hence, as all things are with their advantages and disadvantages, so do wood wool slabs.

1. Good fire performance:

irrespective of the high wood content, wood wool slabs have excellent resistance to fire. This is because of its thickness, as earlier mentioned, its coarseness, and the binder. Wood wool slabs are fire-resistant.

This does not mean they do not go up in flames compared to their other insulation counterparts like fiberglass and the rest, and it just takes a much longer time for wood wool slabs to burn, which will be in a highly intense fire. For instance, a 50mm thick wood wool slab will resist fire for about an hour. This begs the question, are wood wool slabs fire-resistant? Yes, they are.

2. Durability:

wood wool slabs are very durable because of their high moisture absorption. Especially in high humidity, wood wool slabs are preferred to other insulation materials. This property, in turn, makes it a perfect mold and rot-resistant material, which is required for a healthy building.

3. Good acoustic performance:

In terms of acoustic, which of course deals with sound, they have an excellent sound absorption property due to their concave surface structure, which allows a high level of sound absorption.

This makes them suitable for installation in all kinds of public gathering places like churches, auditoriums, and the likes, industries, etc. This sound absorption increases as the thickness of the wood wool slab increases. Hence, being used as sound insulators in these buildings.

Disadvantages of Wood wool Slabs.

As earlier stated, wood wool slabs are not without disadvantages, even though their advantages outweigh the later

Most wood wool slabs deployed in buildings are always imported from another country. Hence the cost of transportation is a problem because it is pretty absurd.

Not only is transportation high,  but it can also be fragile.

It’s no news that wood wool slabs are expensive, though worth it.


Just as every building needs a good design, every insulation material needs excellent properties and composition before deployment, as seen in wood wool slabs. They are also energy-efficient, eco-friendly, sustainable, compostable, recyclable, etc. With all these qualities, they are just the best insulation materials. And yes, they are also fire-resistant.

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