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Timber structures Panel products

• removal of option to fix panels parallel to joists • clarifying expansion gaps, both intermediate and at the perimeter where the floor runs under the wall • changes to resilient floor underlayment specifications (BS 82031 changes) • new panel products, that is ‘glue-only’ floor systems and weather-resistant panel products.

Noggings The Panel Guide mentions that noggings should be present for square-edge panels used in flooring, but it does not specify dimensions or what is considered suitable. Current practice has been reviewed and, together with recommendations from respected bodies in the industry, a nogging minimum size has been specified that will give the minimum bearing and support required.

the figures in Panel Guide shows panels running parallel to the joists over single spans. These two pieces of guidance were in conflict and the decision was made to remove the figure.

Expansion gaps Panel Guide states that there should be expansion gaps around the perimeter of a room between the floor and the wall. This guidance is applicable for a floor that is laid after the joists have been put down, but is not practical where the floor deck is already laid to the edges of a cassette floor and the wall is to be built on top of the floor. In addition, the guidance (or lack of it) was putting the Panel Guide in conflict with other well-respected industry guidance. So current guidance and common practice have been reviewed, the implications have been considered and the Panel Guide now includes guidance on how this situation should be addressed. The amount of expansion needed in intermediate expansion gaps where there are large or long runs of flooring has also been clarified.

Square-edge structural decking laid across the joists and supported by noggings. Source: Panel Guide V4.1, p22

Mid-span finishes One issue raised by industry feedback was what should be done when a panel finishes mid-span rather than on a joist. Although this situation is not ideal, one solution is to use an ‘H’ nogging. Allowable overhang Industry feedback also requested guidance on the amount a panel can overhang the first or last joist running parallel to a wall. This was reviewed and, with the long history of use of this practice, it was decided that the Panel Guide should align with the guidance of the National House Building Council standard, clause 6.4.10, which states: construction of timber floors must ‘have a clearance of 25-75mm between the first joist and the wall face to aid the installation of services and the fixing of floor decking’. Fixing panels parallel to joists The guidance in Panel Guide, and most testing on flooring grade panels, is conducted with panels over two spans because this will produce the strongest deck. However, one of

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Timber 2019 Industry Yearbook

Resilient floor underlayment specifications BS 82031 was revised in 2017, with the involvement of the wood-based panel industry, and resulted in the tightening of the specification for ‘fabricated underlays’. A fabricated underlay is a panel product that overlays an existing wooden floor, but is the underlay to a resilient floor covering. The Panel Guide has therefore been brought into line with BS 82031 and modified to clarify the terminology around the difference between fabricated underlays and floating floor overlays. This could cause confusion as they both overlay, but the fabricated underlay terminology is born from the floor covering sector so it is considered an underlay in that sector. Guidance for the installation of resilient floor coverings has also been aligned with that of BS 82031. New panel products The final change to the flooring section was necessary due to the prevalence in the market of not just raw uncoated panel products but variants and systems developed as a response to customer requirements. These requirements were for weather resistance during construction, cleaning up floors following completion of the building, plus so called ‘glueonly’ floor systems, which are flooring systems with reduced mechanical fixing requirements that can not only speed up installation but primarily aim to reduce noises that can be present in timber floors. While the Panel Guide recognises that these products are available, it doesn’t give detailed information as each system is particular to a manufacturer. It does, however, serve as a good signpost to those products being available to help the users of panel products choose the most appropriate product for their job.

Profile for BM TRADA

Timber 2019 Industry Yearbook  

The annual publication of the Timber Research and Development Association (TRADA) includes topical and technical features on all aspects of...

Timber 2019 Industry Yearbook  

The annual publication of the Timber Research and Development Association (TRADA) includes topical and technical features on all aspects of...

Profile for trada