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Acoustic problems and solutions within CLT joists

Interest in building in wood has increased significantly in recent years, and a contributing factor is the need to reduce CO2 emissions in construction, which of course are usually represented by various concrete structures. However, concrete suffers from a relatively large CO2 impact and the need to find alternative solutions has therefore grown extremely quickly and in very large volumes. This trend does not only apply in the Scandinavian countries, but the need also has a large international spread. Read more about Aprobo’s solutions in combination with CLT joists!

The construction that has received the most attention is the CLT beam (Cross Laminated Timber) also called KL-Trä, KLT, X-Lam, BSP etc., which can be briefly explained as a wood-based building product that is made up of an uneven number of layers consisting of planed wood. Normally three, five, seven or nine layers are used. Each layer consists of finger-jointed lamellas laid side by side. Each layer is laid at right angles to each other, for increased stability and strength.

Read more about Decibel Concept here.

Environmentally, wooden floors are completely superior to concrete, but acoustically speaking, it is often a challenge to find solutions that meet the sound requirements for homes, offices, schools and hotels.
This led to experimenting in various ways over a long period of time in projects with designs that may not have always been the most efficient or even qualitatively particularly good.

We have seen product combinations with casts on top of insulation materials that may not be designed for the weight and fatigue it is subjected to over an extremely long period of time. Another example is coating a sound-insulating material with crushed stone/gravel, which certainly leaves a lot to be desired in terms of building height, efficiency and agility at the workplace. However, this has changed recently and most CLT producers are now working intensively to solve these problems.

A company that is involved in this issue and that cooperates with manufacturers of CLT is Aprobo AB, which recently presented an extensive study with their Decibel Concept, where around 40 full-scale test objects with CLT were evaluated in the lab combined with a number of field measurements.

The information has then been collected, and concentrated on selected construction solutions to clearly show how to build to achieve sound class B and C for homes, schools, offices and hotels, in an efficient way.

The information clearly shows construction layouts as well as acoustic graphs and third-band values so that acousticians can then perform their own calculations in projects based on given dimensions and volumes.

In the main, they have started from Aprobo AB’s SoundSeal construction, which means that their Decibel acoustic mats are integrated into the joist via a leveling compound applied above, but they also present “dry solutions” where board material is used instead of the leveling compound.

If you read this compilation, it also shows Aprobo AB’s environmental policy for their Decibel Concept, which is positive, as one of the main arguments for CLT is precisely to reduce the environmental impact in construction.

This information is now adapted for different markets and their different sound requirements, an extensive work that will certainly continue for many years to come in the company’s international goals.

CLT and other wooden structures are certainly not the only solutions available in the future, and from Aprobo AB’s side you also see interesting combination solutions with their Decibel acoustic mats in combination with concrete, as an increased weight is needed for stability and the CLT construction now rises higher and higher towards the sky.

Clearly, CLT is here to stay and the future will show who creates the best solutions for our environment, regardless of whether we speak in general terms or as an acoustic environment.

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Read more about Aprobo’s solutions in combination with CLT joists!