Floor and Rafter 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 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.
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.
Both systems of Pryda floor trusses are generally 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.
Pryda Longreach Trusses:
Longreach 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 trusses are referenced as FT200, FT250, FT300, FT350 and FT400, where “FT’ means Floor Truss, and “200” is the nominal overall depth (mm). The actual depth dimensions are in nominal size steps, or may be individually specified as required for the particular project.
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 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.
Pryda Span Trusses:
Pryda Span trusses have metal diagonal webs for light weight and economy. They are ideal for shallower trusses where there is more clearance room to accommodate the plumbing than with timber webs and for trusses where the chord design has some reserve capacity, as is often the case. In some instances, a few diagonal metal webs may have to be replaced by timber webs in these trusses, as load or geometry considerations dictate.
Webs may be on both faces of the truss or just on alternate faces, and in the latter case this allows for the webs to overlap.
Pryda Span trusses are referenced as PS25, PS30, and PS4O, where “PS” means Pryda Span, and “30” is the nominal overall depth (cm). The overall depths are nominally 250, 300 and 400 mm deep. The actual depth dimensions are in nominal size steps according to the metal web used and if required, the specific depth should be obtained from the Pryda licensed fabricator.
Pryda Span is manufactured using light gauge metal webs and are lighter than Longreach, but this is considered during the design process. The metal web system can be very cost-effective, especially if the truss chords have reserve capacity, as is often the case. The nail plates and Pryda Span metal webs are made to exacting standards from Bluescope© steel with a minimum of Z275 corrosion protective Zinc coating.
Pryda Floor Truss Systems offer many benefits to the designer, the builder and the building owner in providing a reliable high performance system for both domestic and commercial construction. The use of the Pryda Floor Truss System results in a very cost effective, high quality product that is sufficiently flexible to accommodate the most complex of building requirements.
NET INSTALLED COST BENEFIT
The Pryda fully engineered open-web timber floor truss systems with timber webs (Pryda Longreach) or metal webs (Pryda Span) have many advantages that result in a lower net installed cost compared to other systems that are available. In some instances there may be a material cost increase by using Pryda floor trusses over alternative flooring systems. However when it comes to installing the product Pryda floor trusses can provide significant labour savings. In addition, floor trusses have some considerable design advantages that could result in reducing the need for a large amount of costly structural support construction. E.g. Long spans may reduce the need for internal load bearing walls.
Go to the PowerPoint presentation in this section to view the St. Clair Park Village case study. There was a 6% increase in material costs by using Pryda Longreach floor trusses over solid joists. Framing time was reduced by 2 weeks and the labour saving was 2.5 times larger than the material cost increase.
Examples of these advantages are as follows and should be considered in the assessment of the overall cost of the flooring system:
DESIGN COST SAVINGS
- Cost Efficient Design. Each floor truss is customised for the job, including required stiffness, depth, timber grades and span. It will be computer designed for optimal performance and cost and installation efficiency while minimizing waste.
- Significant Design Improvement With Minimal Cost Increases. Span capacity and stiffness can be significantly enhanced by simply increasing the depth of the Pryda Longreach floor truss. Due to the timber web design of the floor trusses, the increase in depth is at a minimal cost.
- Greater Design Flexibility. Extra long spans and large cantilevers can be provided, with the ability to support high loads. Spans up to 7.1 metres at 400mm depth using MGP12 pine can be achieved. This results in the following design and cost benefits:- The long spans can potentially eliminate the need for some interior support walls and beams, giving more scope to architects and designers thus reducing the cost of the support structure.- Large spans within restricted height applications can be achieved. In some cases the use of floor trusses may eliminate the need to use costly steel beams.- Ideal for sloping blocks. In some instances floor trusses could be used to eliminate or reduce the excavation costs associated with sloping blocks.
LABOUR COST SAVINGS
- Set-down or Recess sections. The ability to design and manufacture set down sections into the floor trusses provides significant labour savings in the following situations:- In cantilever and balcony areas where the provision of adequate flashing and accommodation of different floor covering material thicknesses is critical.- Bathrooms, toilets and other wet areas may also require the floor surface to be set-down. This will provide significant labour savings when other trades start installing bathroom fixtures, fittings and tiling.
- No Cutting, Drilling or Notching.The open webs allow easy fixing of electrical, plumbing, ducts and energy services. There is no need for drilling or notching, saving time on site.
- Quick Installation. A large selection of end support types for quick and easy installation. Pryda floor trusses arrive on site Mmanufactured to size and ready to install, eliminating the need to trim on site. There is no material or labour wastage. Pryda floor trusses are designed and manufactured with end types for fast, secure fixing to steel, concrete, masonry or timber. Go to the product drawing library to view the available options.
In addition to providing net installed cost savings there are numerous design and construction benefits of Pryda floor truss systems, they are as follows:
- Assured Performance. Pryda floor and rafter truss systems have been used with outstanding results for over 15 years by designers and builders.
- Design Versatility. The long span capacity – up to 8 metres or more – offers functional design freedom and can eliminate the need for interior support walls and beams.
- Depths to Suit. Wide range of standard depths available – from 200 to 450mm – or can be manufactured specifically for a particular project.
- Limited Space. Designs can accommodate large spans in restricted height applications.
- Cost Effective. Timber grade in chords is selected to suit the design requirements of each individual project to provide the most cost effective system.
- Larger Spans at Low Cost. With all-timber trusses (Pryda Longreach) the span capacity increases significantly as the truss depth increases – at little extra cost.
- Commercial Applications. Pryda floor trusses not only accommodate domestic loads but may also be designed for commercial applications including offices, schools, hospitals and function areas.
- Designed to Order. Stiffness required, depth, timber grades and sizes can be varied to suit any
Individual job requirements. Computer designed for optimal performance efficiency and lowest material cost.
- Wide Range of End Supports. Standard end support types suit structural connections to steel, concrete, masonry or timber.
- Extra Stiffness in Floors. Stiffer than other floor systems with established dynamic limits to ensure rigidity and to overcome springiness and bounce. Designed to provide a floor that feels and acts “rock-solid”.
- Accommodates Large Ducts. Large rectangular ducts to 500mm wide can fit within the standard design and special duct routing within rows of trusses can be incorporated.
- Dimensionally Stable. Fully kiln-dried timber ensures stability, free from movement due to shrinkage.
- Efficient Use of Timber. More efficient use of natural resources than solid timber joists.
- CAD Compatible. Standard data and design details available on CAD.
- Easy to Install. Truss end support connections are pre-manufactured to fit. No cutting or notching will minimise the possibility of mistakes.
- Ease of Access. Flexible ducting, electrical wiring and electronic data cabling can be easily run between the truss webs.
- No Cutting Holes. Simplifies the work of following trades. Plumbing, ventilation ducts and conduits can be simply attached to the webs or chords without any cutting or drilling holes.
- Faster Installation. Quicker installation times provide the opportunity to reduce construction costs.
- Stable Platform During Construction. The wide chord flanges are more stable for tradesmen moving around the elevated areas on a job.
- Lightweight. Trusses are much lighter than solid timber sections. Much easier to handle and lift on site.
- Floor Set-Down Feature. A section of Longreach floor trusses can be manufactured with a reduced depth to accommodate tiled wet areas and other floor coverings in bathorooms and on balconies.
- Consistent Depth. Longreach floor trusses can be manufactured to the same depth for the entire project to eliminate uneven ceiling levels at little extra cost – regardless of the variations in spans.
- Robust Construction. More robust than other prefabricated systems, and more able to resist the effects of mishandling. Pryda Span metal web design has a patented deep V profile incorporating stiffeners for improved performance and resistance to damage during handling on site.