CLT construction: cross-laminated timber in Finland in 2026

CLT (cross-laminated timber) is a solid wood panel made of 3, 5 or 7 crosswise lamella layers. Panels are manufactured in sizes up to 3.2 × 12 metres and 60–300 mm thick, and they weigh only about a fifth of an equivalent concrete structure. In Finland, CLT is manufactured by CrossLam in Kuhmo, Hoisko in Alajärvi and Stora Enso, among others.

How is a CLT house built?

The elements are machined to size at the factory, window and door openings included, and craned into place on site. For professionals, erecting a detached-house frame typically takes 1–4 days. The saving is in the whole chain: dimensionally exact elements mean no sawing or fettling on site, and interior works can start early.

The frame is dry from day one: the structure involves no wet pours. An 80 mm ground-bearing concrete slab, by contrast, typically takes 2–4 months to dry ready for floor coverings, and the decision to cover always rests on a moisture measurement. Mass timber involves no such wait. Weather protection still has to be managed: elements are stored off the ground, covered but ventilated, and the roof goes on quickly. On demanding timber projects the whole frame is increasingly built under a tent-like weather shelter.

Where is CLT used in Finland in 2026?

Mass timber panel is the staple of timber apartment blocks and public timber buildings. Over 30 years Finland has seen around 200 timber apartment buildings of more than two storeys, with over 6,000 flats. Keep the scale in perspective: timber-block flats still account for only around one per cent of new apartment builds – CLT is a growth story, not yet mainstream. In the public sector, indoor-air and climate arguments drive timber's popularity: schools, nurseries and service buildings are increasingly built of wood.

On the detached-house side the picture is different: about 90 per cent of new detached houses in Finland are timber-framed, and roughly a third of self-builders choose log. CLT competes alongside these especially on projects where the architecture demands complete freedom.

CLT, log or stud frame?

• Log: the solid wood shows both inside and out, with a traditional or modern look. Solid wood walls have their own energy rules: for a wall at least 180 mm thick, the U-value reference is 0.40 W/(m²K) and the E-value limit for a detached house is 20% more lenient.
• CLT: a mass timber panel that is usually clad inside and out. The architecture is unconstrained, the structure does not settle, and the panels' stiffness allows open-plan spaces.
• Stud frame: the cheapest and most common method; thermal insulation is provided by mineral wool, and the structure lacks solid wood's moisture buffering. The majority of self-builders working with sawn timber choose a stud frame with board cladding.

The shared advantage of mass timber structures is the wood's capacity to even out indoor humidity. In a log house the wood is in direct contact with the room air; in a CLT house it usually sits behind the surface finishes.

A timber building is a carbon store

A cubic metre of wood binds about 750 kilograms of carbon dioxide – the "tonne per cubic metre" seen in older texts is an exaggeration. A timber building acts as a carbon store throughout its life, and in researchers' scenarios, increasing timber construction could cut the built environment's annual emissions by as much as 11 per cent by 2035. Regulation is moving the same way: since the start of 2026, most new buildings in Finland – including apartment and terraced buildings and halls over 1,000 m², though not detached houses – must produce a climate assessment calculating the whole-life carbon footprint, where a timber frame's carbon store is a clear advantage. This applies to all timber frames – log, CLT and stud – but mass timber stores the most wood.

What does CLT construction need in order to succeed?

CLT is not a DIY material. The designer needs specialist expertise in mass timber panels, and the site needs crane capacity and precise logistics. Moisture management is planned in advance: the permit stage requires a moisture-management report, from which a site plan is drawn up. A widely accepted route is the Kuivaketju10 model maintained by RALA, covering the ten most significant moisture risks. Well managed, the frame stage shrinks from weeks to days.

Who is CLT for?

CLT is strongest when you want a timber structure's ecological credentials and a fast, dry frame stage, but free-form architecture without the log-house look. If you want the solid wood to show as it is, log is the more direct route. Both act as carbon stores and both are made in Finland – the choice is one of architecture and taste, not ideology. For a realistic comparison, request quotes for both a CLT and a log build and compare total price, not just frame material.

• CLT is a 3-, 5- or 7-layer cross-laminated solid wood panel; panel sizes up to 3.2 × 12 m, thickness 60–300 mm.
• CLT weighs about a fifth of concrete, and professionals erect a detached-house frame in 1–4 days.
• In Finland, CLT is manufactured by CrossLam Kuhmo, Hoisko and Stora Enso, among others.
• A cubic metre of wood binds about 750 kg of carbon dioxide – a timber building stores carbon for its whole life.
• Timber-block flats are still only about 1% of new apartment builds – CLT is a growth story, not the mainstream.
• CLT is usually clad; in a log house the solid wood stays visible inside and out.