What Is Wood Wool Cement Board (Fibrolite)? A Plain Guide for 2026

Fibrolīts (often written "fibrolite" in English) is the Latvian and wider Baltic term for wood wool cement board: rigid acoustic panels made from long strands of spruce wood wool bound in Portland cement. If you searched "fibrolite" hoping to find this material, you are in the right place - but it is worth knowing why the search results for that word are so mixed. In several English-speaking markets, "Fibrolite" was historically a registered brand name for asbestos-cement sheet, and it is also used informally in mineralogy for a variety of the mineral sillimanite. None of that is what this guide, or our Sonablock panels, are about. Wood wool cement board contains no asbestos, no fibre-cement, and no mineral fibre in the sillimanite sense - it is wood, cement and water, full stop. This guide covers the Baltic/EU building-material sense of the word: what wood wool cement board is, how it performs, where it is used, and how it compares to the other brands you will have come across if you are specifying acoustic ceilings or walls in Europe.

The confusion is purely a naming coincidence, not a product relationship. Several unrelated construction and cladding materials have been sold under "fibrolite" or very similar names in different countries over the years, but in the Baltics today the word is used almost exclusively for wood wool cement board. That regional difference is why a search from Latvia and a search from, say, the UK or New Zealand can land on completely different products.

What is wood wool cement board (fibrolite) made of?

The composition is deliberately simple: long strands of spruce wood wool, Portland cement, and water. Nothing else goes into the board. The timber is shredded into fine fibres, coated in cement slurry, and pressed into rigid panels that cure over several days. There is no glue, no added formaldehyde, and no plastic binder, which is one reason the material has stayed popular for schools, healthcare buildings and other public spaces where indoor air quality is scrutinised.

Our Sonablock range is manufactured in Latvia by Stiga RM, using PEFC-certified spruce with full chain-of-custody certification (BMCERT-PEFC-COC-00175) and an Environmental Product Declaration (EPD-IES-0031288). The manufacturing process itself is what gives fibrolite its particular acoustic character: spruce logs are debarked and shredded into long, thin wood wool strands rather than short chips, which is why the surface reads as fibrous rather than granular. Those strands are coated in a cement slurry, laid up into mats at the target thickness, and pressed under controlled pressure so the cement fully wets every fibre without crushing the wool structure that makes the panel absorptive. The pressed boards then cure for several days before being trimmed to size and, for the Sonablock line, quality-checked with AI-assisted inspection on the production line in Tukums to catch density or surface inconsistencies before dispatch. The mineralised wood fibre gives the panel its open, textured surface, which is what does the acoustic work described below.

How well does fibrolite absorb sound?

Sonablock panels reach αw 0.60 to 0.65, Absorption Class C, tested to EN ISO 354 by RISE Research Institutes of Sweden (report O100282), as a bare panel mounted with a 200 mm air gap. Sound absorption is the main reason fibrolite gets specified at all - the open fibre surface absorbs sound energy rather than reflecting it back into the room. That air gap matters more than most buyers expect: absorption rises substantially once mineral wool is added into the cavity behind the panel, and published data across the wood wool category shows Class A build-ups are achievable that way. If you are trying to hit a specific reverberation time rather than just "add some panels," our reverberation time targets by room type guide and our plain explanation of how many acoustic panels you actually need are the next two pages to read.

Two figures come up constantly once you start comparing acoustic panels: NRC and αw. Both describe how much of the sound hitting a surface gets absorbed rather than reflected, but they come from different test standards - NRC is the North American measure, αw is the European one used on our test reports - and a panel's rating changes depending on whether it is tested bare, with an air gap, or with mineral wool added behind it. If a spec sheet just says "high absorption" without a class or a mounting condition, treat it with caution. We break the whole topic down properly in NRC and alpha-w: what sound absorption ratings actually mean.

How fire-resistant is fibrolite?

Because the wood fibre is locked inside a cement matrix, the standard Sonablock board carries a Euroclass B-s1,d0 rating to EN 13501-1: low contribution to fire, low smoke, and no flaming droplets. Where a project specifies non-combustible materials, the Sonablock FireSafe series is classified A2-s1,d0 in accordance with EN 13168:2012+A1:2015. For a wider comparison of what Class A, Class B and the rest actually mean across wall panel materials generally (not just wood wool), see our guide to fire ratings for wall panel materials.

Does fibrolite insulate, and how durable is it?

Wood wool cement board is sometimes assumed to be a thermal insulator because of the timber content - it is not, at least not on its own. We cover this properly, including where it does help and where you need a separate insulation layer, in do wood wool panels insulate? Thermal performance explained. Where fibrolite does perform reliably is durability: the cement matrix tolerates up to 90% relative humidity without warping, which is why you still see original wood wool ceilings from decades ago in reasonable condition in damp plant rooms, pool halls and unheated stores. It is also dimensionally stable across normal temperature swings, resists pests and rot in the way an untreated timber product would not, and does not support mould growth the way a paper-faced board can in a humid room. None of that makes it a substitute for a proper vapour barrier or insulation layer where the building physics calls for one - it simply means the panel itself is not the weak point in most installations.

What does fibrolite look like, and what finishes are available?

Fibrolite has an honest, tactile surface rather than a flat manufactured one. Fibre width sets the character: a fine 1.0 mm fibre reads clean and precise, a coarse 2.0 mm fibre gives a bold, raw texture, and 1.5 mm sits between the two. Panels can be left natural (a warm cement grey) or supplied in white, light grey, dark grey or black, and they need no filling, sanding or painting after installation. If you do want a custom RAL colour, or need to touch up cut edges on site, our guide to painting wood wool acoustic panels without killing the acoustics covers exactly what to use and what to avoid. Edge detailing also matters more than people expect for the finished look of a ceiling grid - see wood wool panel edge profiles explained for the B0, B5, B11, A24, E24 and C options.

What are fibrolite's technical specifications?

• Composition: mineralised spruce wood wool bonded with Portland cement. No adhesives, no binders, no off-gassing.
• Thickness: 25 mm standard, also available in 15 mm and 35 mm.
• Panel sizes: 600×600 mm, 1200×600 mm and 2400×600 mm, ordered per panel.
• Fibre sizes: 1.0 mm (fine, higher acoustic density), 1.5 mm (balanced, the most popular option) and 2.0 mm (coarse, industrial texture).
• Colours: natural cement grey, white, light grey, dark grey and black, with custom RAL/NCS and printed panels available on request.
• Weight: approximately 11 kg/m² at 25 mm (around 6.8 kg/m² at 15 mm) - factor this into fixing selection for ceiling installations.
• Minimum order: one pallet, roughly 31 m² at 25 mm or 50 m² at 15 mm.

How does fibrolite compare to Troldtekt, Heraklith and Cewood?

If you have specified acoustic ceilings in Europe before, you have almost certainly come across Troldtekt (Denmark) and Heraklith (Austria/Knauf) - both are wood wool cement board manufacturers, and both are the products people usually mean when they say "fibrolite" as a generic category rather than a specific brand. Cewood (Estonia) is a third well-known Baltic manufacturer in the same category. All four brands sit within the same performance envelope on paper - fire class, general absorption range and panel format are broadly comparable - so the practical differences that actually decide a specification tend to be lead time, minimum order size and where the freight is coming from. Sonablock is manufactured in Latvia rather than imported from Denmark or Austria, which typically means shorter lead times and lower freight cost for Baltic and Central European projects, plus a lower minimum order than most manufacturer-direct routes for Troldtekt or Heraklith. We have written detailed head-to-head comparisons if you are actively choosing between brands: looking for a Troldtekt alternative, Troldtekt vs Sonablock, and looking for a Heraklith alternative. If you are still deciding whether wood wool is the right material category at all, rather than which brand, fibrolite vs other acoustic panels and our comparisons against mineral fibre ceiling tiles and perforated plasterboard lay out the trade-offs directly.

How is fibrolite installed, and why does the air gap matter?

Fibrolite panels are typically fixed directly to a batten grid or suspended ceiling system, with the air gap behind them (rather than the panel itself) doing much of the acoustic heavy lifting once mineral wool is added. Our full walkthrough, how to install wood wool acoustic panels, covers wall and ceiling fixing, air gap depth, and the tools you actually need. If you are inheriting an existing wood wool ceiling rather than specifying a new one, renovating old wood wool ceilings and cleaning and maintaining acoustic panels cover repair, repaint and replace decisions, and routine upkeep. Coordinating a wood wool ceiling with lighting, sprinklers and ventilation penetrations is its own small discipline - see coordinating an acoustic ceiling with services. And if you have already installed panels and the room still sounds bad, why your room still echoes after installing acoustic panels is worth reading before you assume the product is at fault.

Where is fibrolite used?

Wood wool's combination of fire performance, low-VOC composition and genuine sound absorption keeps it in the specification for a consistent set of building types. We have written a dedicated guide for most of them: schools, offices, restaurants and hospitality, sports halls, healthcare settings, music and recording rooms, meeting rooms, pools, spas and wellness rooms, and residential use in living rooms, bedrooms and home cinemas.

How sustainable is fibrolite, and what happens at end of life?

Because the material is only wood, cement and water, fibrolite has a genuinely straightforward sustainability story compared with composite acoustic products that mix plastics, foams and mineral fibres. We go through the fibre sourcing, the cement's carbon footprint, and what actually happens to the board at end of life in how sustainable is wood wool cement board.

How do I choose and buy the right fibrolite panel?

Fibre size, thickness, colour, edge profile and fire class all interact when you are choosing a Sonablock panel, and getting one wrong (an edge profile that does not suit your ceiling grid, or a fibre size that reads too coarse for the room) is an easy way to end a project unhappy with the visual result even though the acoustics are fine. Our guide to choosing wood wool acoustic panels walks through the decision in order.

Sonablock is manufactured by Stiga RM in Tukums, Latvia; Wall Panels Pro is the direct distributor for standard-size orders, project quantities and samples, without the industrial-quote back-and-forth. See where to buy wood wool cement board in Europe for sizes, prices and delivery, or if you are specifying at pallet or container scale, Sonablock for large projects and how much Sonablock fits in a container cover B2B pricing and freight planning directly.

Fibrolite FAQ

Is fibrolite the same as asbestos cement sheet? No. Modern wood wool cement board contains no asbestos. The "Fibrolite" brand name was historically used for asbestos cement sheet in some markets (notably New Zealand and parts of the UK), which is an unrelated product from an unrelated manufacturer. Wood wool cement board is wood, cement and water, fully REACH compliant, and backed by an Environmental Product Declaration.

What is fibrolite's fire rating? Standard Sonablock panels are Euroclass B-s1,d0 to EN 13501-1. The FireSafe series is A2-s1,d0. Always check which class a specific project requires before ordering, since the two series are not interchangeable on a compliance drawing.

What sound absorption class does fibrolite achieve? Sonablock reaches αw 0.60-0.65 (Absorption Class C) as a bare panel with a 200 mm air gap, tested to EN ISO 354. Adding mineral wool in the cavity behind the panel raises this to Class A build-ups.

Can fibrolite be used outdoors or in humid rooms? Yes - the cement matrix tolerates up to 90% relative humidity and does not warp in cold or damp conditions, which is why it is common in pool halls, plant rooms and unheated spaces.

How is fibrolite different from Troldtekt or Heraklith? They are the same category of material (wood wool cement board) from different manufacturers. Sonablock is manufactured in Latvia, which typically means shorter lead times and lower freight costs than importing Troldtekt (Denmark) or Heraklith (Austria) into Baltic or Central European projects. See the comparison guides linked above for a direct spec-by-spec look.

Can fibrolite panels be cut on site? Yes. Standard tools are an angle grinder with a diamond blade, a circular saw with a masonry blade, or a jigsaw with a carbide blade. Wear a dust mask, since cutting produces cement fibre dust. Cut edges can be painted to match the panel or left as a contrast detail.

Is fibrolite the same as mineral wool acoustic panels? No - mineral wool panels are a spun mineral fibre product, usually faced with fabric or a perforated facing, while fibrolite is a solid wood-and-cement board that is acoustically active on its own textured surface. Both can hit similar absorption classes with the right build-up, but they look, weigh and install differently. Our wood wool vs mineral fibre ceiling tiles comparison goes through the practical differences.

In this guide

This page is the pillar for our full wood wool / Sonablock content series. Related reading, grouped by topic:

Performance and testing: Thermal performance · Sustainability and end of life · Edge profiles explained · Reverberation time targets by room type

Comparisons: Troldtekt alternative · Troldtekt vs Sonablock · Heraklith alternative · Fibrolite vs other acoustic panels · vs mineral fibre ceiling tiles · vs perforated plasterboard

Applications by room: Schools · Offices · Restaurants & hospitality · Sports halls · Healthcare · Music & recording rooms · Meeting rooms · Pools, spas & wellness · Home & living rooms

Installation, care and buying: Installation and the air gap · Painting · Cleaning and maintenance · Renovating old ceilings · Coordinating with services · How to choose a panel · Where to buy in Europe · Large projects & B2B pricing · Container freight guide

Ready to see the panels themselves? Browse the full Sonablock range, or contact us about the FireSafe A2 series and cavity build-ups for higher absorption classes.