Cross Laminated Timber – a.k.a. Brettsperrholz or Kreuzlagenholz – is made of small wooden boards, cross-wise glued together to form large sheets, reaching dimensions up to 22 x 3,5 meter and some 40 cm thick.
Main producers are Germany, Austria and Scandinavia, using pine from sustainable FSC® and PEFC forestry, a CO2-neutral, renewable resource.
It has a number of characteristics that make it an interesting alternative for brick, concrete or even timber-frame :
- Being a massive product, once it is finished with plaster it is hardly distinctable from the average stone-based wall.
Such a plaster-finish however isn’t mandatory, the material can be used without it and as than provides a warm, natural interior atmosphere.
- Like pre-cast concrete elements, CLT-elements introduce stiffness and rigidity in your building, no matter if it is used to form walls, façades or floors.
- Weighing only about 450 kg/m³ CLT is some 80% lighter than concrete, allowing for lighter foundations and thinner floor-slabs.
Large elements make multiple-span floors possible, thus further reducing floor-slab thickness, giving more interior height and/or allowing more space for integrating installations and ducts.
- CLT in many cases will be produced on order and is CNC machined within a tollerance of only ± 1 mm, making the pieces fit snugly to form an airtight structure.
A CLT structure can be erected in very short time – often it will take less than a day – using the on-board crane of the delivery truck.
Only a few temporary supports are needed during erection; once the structure stands, they can be removed and of course there is no waiting for hardening and drying, so workers can commence their work applying installations and finishings right after completion of the structure.
Being all-wood, CLT makes the life of installers a lot easier too; no need to drill holes, just screw it on… that saves a lot of time and dust !
- Believe it or not, CLT is fire-safe !
It may sound strange, but it is a known fact that a well-designed wooden structure preserves its strenght longer in case of fire, because during the fire a layer of charcoal forms on its surface that strongly reduces the impact of the fire on the wood.
- A CLT structure is safer in case of an earthquake.
The flexibility of the basic material in combination with its use in a large sheet-structure makes it better resilient in case of an earthquake than any stone-based construction.
In the Netherlands this has never been very important, yet, since we see earthquakes more often these days, this certainly is something to take into consideration, especially when building in Groningen.
- CLT raises interior comfort and helps saving energy.
Wood has a high thermal accumulation capacity; a façade of CLT and wood-fiber insulation will retain warmth up to 10-12 hours, thus making day-time solar energy available at night and minimizing heat-loss during the day… this is the ideal setup for using “passive” energy in winter and providing a comfortable low interior temperature during a hot summer day without the need of (expensive) active cooling.
There even are elements of 364 mm thickness that are compliant with current Bouwbesluit insulation-rules without adding extra insulation !
- Acoustically CLT provides shorter reverberation time than most stone materials, thus lowering the overall sound-pressure in rooms; this advantage will be felt especially with the currently popular “hard” finishings of walls, ceilings and floors in our homes.
Also, due to its flexibility, outside traffic-sound is dampened significantly.
- Not measurable, but not less important, a wooden environment has a soothing, comforting effect on people; many will favor the interior climate in a CLT building over the interior climate in a stone building.
- CLT is re-usable.
Once it reaches the end of its lifespan, a CLT building can be dismantled into the original sheets again; openings van easily be patched and new openings easily created using a circular saw, preparing the sheets for a new function in a new CLT building without any significant loss of material.
In short : CLT shows us how to optimally use a renewable resource; it combines CO2-neutrality with circular use, super-quick building and a human-friendly built environment.
Does that make CLT the answer to all our building-challenges ?
Of course not ! Every building demands its own set of custom solutions, but it most certainly deserves more attention than it has gotten so far…
Want to know more about the possibilies of this eco-friendly material ?Just give me a call or fill out the contact-form.