Floor Truss Systems, Span Tables

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PRYDA FLOOR TRUSSES

Pryda Floor Truss Systems are a complete structural system for timber floors made up of flooring material, floor trusses, strong-backs, connections and bracing. They have been proven over many years and provide occupiers with floors that have an excellent and predictably reliable performance.

The timber for these trusses is on the flat, which provides a stable platform during installation and minimizes the overall depth required. All trusses use commonly available timber and most floor trusses in Australia are made from 70 mm or 90 mm dry timber.

Truss Spans and Depth
This table illustrates the significant increase in span capacity by increasing floor truss depth and/or larger chord timber size, and higher timber grade.
Spans for residential floor loads (1.5kPa/1.8kN) at 450mm centres




Reading down the table shows that for a given depth, greater spans or improved stiffness can be achieved as timber grade, thickness or width increases. This performance improvement also results in higher cost timber chords.

Reading across the table shows that for each timber chord selection, greater span or stiffness can be achieved as depth increases. This improvement is at very little extra cost.

The diagonal pattern in the table shows that a cost saving can be achieved by increasing the depth of the truss, thereby reducing chord timber performance requirements, without compromising the span capacity of the truss.

Truss Types

There are two different types of web systems for these trusses. Both have timber chords but Pryda Longreach uses all-timber webs, while Pryda Span uses metal webs for the diagonals and timber webs for the verticals.

Pryda Longreach

Longreach floor trusses are a premium performance product using nail-plated, all-timber trusses of any depth, but typically 300 mm deep for residential floors and 400 mm deep for commercial floors.






Pryda Longreach can be designed for all common floor loads, including commercial loadings up to 5 kPa or point loads up to 6.7 kN. These trusses are slightly heavier than Pryda Span floor trusses and being all-timber generally have a stiffer performance as they can dissipate floor vibrations very well, while the nail-plates connecting the webs and chords are quite substantial.

A major feature of the all timber Longreach product is that low cost increases in depth will significantly increase span capacity or stiffness.

Pryda Span

Pryda Span trusses use galvanised high strength steel diagonal webs for light weight and economy. The webs are available in 250, 300 and 400mm nominal depths. The steel web design has a patented deep V profile incorporating stiffeners for improved performance and resistance to damage during handling on site.





Both systems of Pryda floor trusses are made to order by licensed fabricators. While there are standard end details that allow trusses to be trimmed on site, this practice is not common. This is not only because all trusses are designed for an exact span for economic reasons, but the interaction between the true span of the trusses and the flooring should be considered for proper dynamic performance assessment.

End Support Types

Pryda floor trusses have 18 end support types to choose from. Some are specific to top chord support over steel work; others butt into steel channel, some form integral bracing and support for the upper storey. All are designed in consideration of quick installation and structural performance. Click on the link to view the available selection of end support types.

http://www.pryda.com.au/floor-truss-end-support-details