Load-bearing structure made of CLT

What is CLT?

Joeri: "CLT stands for Cross Laminated Timber. This is 3 or 5 layers of timber on top of each other, each time changing the thread direction of the timber so that they become stronger together to form a complete panel. From this we can then make walls and floors to make the construction of laminated beams stronger. The building system we use in 't Centrum is a hybrid building system because we connect different building types. We have the columns and beams in laminated timber, beam-to-beam floor slabs in CLT and exterior walls in Timber Frame Construction (HSB). In two directions, we use a grid of 5 by 5 metres. This is the standardisation that our consortium, after much research, wants to put forward as the ideal for office buildings. We create the rigidity by also making part of the walls, stair cores and the lift in CLT. The insulated outer walls are prefabricated modular timber frame construction suspended from the building, 23 cm wide SLS pegs, Fermacell boards on the inside and an Exie board on the outside, and cellulose is blown in between."

What are the advantages of building with CLT?

Joeri: "We initially chose timber construction because timber is CO2 capturing. If we look at the variants in traditional construction, such as stone, concrete or steel, these materials consume a lot of CO2.For this project, new connectors were developed to achieve higher demountability. The connectors connecting the beams and columns are easy to assemble and disassemble by just 2 locking screws. The CLT floors running from beam to beam are a standard panel 125 cm wide and have the length of 1 or 2 grids to be screwed to the beams with 4 strong screws. This is easily dismantled by loosening a few screws

We prepared this entirely in BIM. This is an intermediate step to then convert to production to control all the CNC machines and production. This does the machining accurately to the millimetre so that the 'puzzle' fits on site."

Why was CLT chosen at 't Centrum?

Joeri: "Demountability played a big role so we can give a second or third life to these building materials."

Does this construction method require more preparation than another construction system?

Joeri: "Yes, because many things have to be calculated at the beginning: the stability, ventilation flow rates, all BIM drawings have to be worked out along with it; this is because making recesses, cut-outs, ... is done best and most efficiently in the workshop. The engineers, stability and techniques have to work well together from the beginning, this together with the architect and the contractor and the construction team so that all those knots are solved. We need a longer preparation time to have a more efficient execution period afterwards."

Does Beneens also work with CLT in other projects? Is it an increasing demand?

Joeri: "We have been working with CLT in projects for 10 years and we do several projects in CLT every year. Now there are four running simultaneously. Yes, there is an increasing demand."

Circular, warm and healthy indoor climate

What about the cost of a CLT building compared to a traditional brick and concrete building?

Joeri: "Unfortunately, the price per square metre of a CLT wall is already more expensive than a fast track building installed on site. We can't compete against fast track construction. Despite the recent price increases, a masonry building is still cheaper. With concrete construction and steel construction, we observe the same thing because the construction method itself is more expensive. But you can't recoup it in efficiency. At 't Centrum, we deliberately choose to capture CO2, the dismantleability and the nicer look of the building and the more pleasant feel."

Which customers choose CLT?

Joeri: "Both private individuals and companies. It is applied to shops and office buildings. In the last year, it has mainly been office buildings. The customers consciously choose the view you get from CLT, which is the warm and healthy indoor climate, and the circular approach, of course."