Meyer Timber OSB and air flow control

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Oriented Strand Board (OSB) is commonly used for structural bracing, cladding backing, and flooring, but now it is also being used to improve air-tightness of the building envelope, as a more robust alternative to specialised membranes.

With rising energy prices hitting homeowners hip pockets, a lack of air-tightness is a problem OSB can fix because it is now proven as an air tight layer. Generally thicker sheets (15mm) of OSB4 are used and with joins between the sheets taped.

According to Thomas Horsfall, Project Engineer at Meyer Timber – supplier to Dahlsens, future developments may result in thinner layers, such as 6mm, having a role to play in air-tightness, with the advantage of thinner layers being that OSB can serve a double purpose as a bracing unit.

At this stage the National Construction Code in Australia does not quantify minimum standards for air-tightness so it is up to the architect, client and builder to agree on thermal performance and the products and materials that will be used. With a CSIRO study finding that new Australian homes can be quite ‘leaky’ with more than 15 air changes each hour, the importance of getting it right will not just save on energy costs, it can also add value to the home when it comes time to sell.

However, it is important that OSB is sourced from reputable suppliers with tested specification, as air permeability can vary dramatically between different grades of OSB and manufacturers.


(Images by Blue Eco Homes)

And before you get set to use OSB, don’t forget that you’ll also need to factor in water vapour because improved air-tightness can lead to increased condensation and the potential for mould or even structural damage.

That’s why it makes sense to talk to your local Dahlsens team first. We can recommend the right products based on your exact needs, as well as install according to the product specifications to minimise risks and costs.

Figure 1 – Common Air Leakage Points (Source:

If you’re interested to know more about OSB, its uses, range of depths and sizes, please speak to the team from Dahlsens.  They can connect you with Thomas and the team of engineers from Meyer Timber for technical advice specific to your projects.