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The Interspan flooring system consists of 170mm-215mm wide precast prestressed concrete ribs spaced generally at 900mm centres with timber infills placed between them . The ribs have variable depth to suit the projects load/span requirements.
This system has the benefit of being suitable for those tricky sites where access is a problem or poor foundation conditions dictate the use of a comparatively lightweight floor.
This multi piece system is tied together with a 75mm in-situ concrete topping and mesh reinforcing.
Interspan is easily adapted to circular floor plans, where the use of other suspended flooring systems is difficult . Large floor openings of up to 700mm between ribs are easily accommodated.
Timber infill planks are typically merchant grade rough sawn timber. The infill plank depth is typically 25mm although this does vary depending on availability. Timber infills should be dampened prior to placing the concrete topping. Alternative timber types can be left with an exposed underside finish to create an architectural feature, e.g. polyurethaned macrocarpa or rimu.
One of the major features of a concrete floor is the low sound transmission. The table below shows sound transmission ratings achieved by Interspan.
Rib strength = 45 mpa at 28 days
Topping strength = 25 mpa minimum at 28 days (as required by nZs 3101:2006)
Topping thickness = 75mm
Propping = from 1-4 props rib centres = 900mm typically, may vary fire rating 60 minutes
Interspan ribs must be handled and stacked at two points, at, or directly beside the lifting eyes.
It is recommended that Interspan ribs be seated 75mm onto the supporting walls/beams, and bedded on wet mortar, vinyl or plastic bearing strips to ensure an even bearing at the correct level. Less than 75mm seating may be used in consultation with Stresscrete.
Fire resistance rating
Standard interspan provides a 1 hour fire resistance rating . an increased fire rating can be achieved with specific design.
Alternative flooring systems
Hollowcore and Double Tees are available for longer spans, and/or heavier loads.
Further technical information
Specifications for the manufacture, transport and erection of Interspan, and standard details for typical situations, are available from your nearest Stresscrete branch. experienced and qualified staff will be pleased to discuss design and fixing details.