This application assumes the following:
House Loading: 0.75kN/m2 Dead Load + 1.5kN/m2 Imposed Load.
Flat Loading: 1.15kN/m2 Dead Load + 1.5kN/m2 Imposed Load.
Deflection Limit: 0.003 x engineering span or 12mm whichever is lesser.
It is assumed that for "Built-In" joists that the masonry is 100mm wide and for joists "On Hangers" the hanger has a 75mm bottom plate.
"Max. Centres" is the maximum centres that this joist can be used for in this application. If a joist's "Max. Centres" is 600mm then the joist can be used at 300mm, 400mm, 480mm and 600mm centres. If it's Max. Centres is 300mm then it can only be used at 300mm centres.
Cost Index is a rough estimate of the order of Joists and Centres, from cheapest to most expensive, based on RRP. 0 is the most cost effective.
These calculations are only to be used as a guide and for any further use including multi-span, multi-ply or non-uniformly loaded joists you should refer to JoistMaster, available from our Downloads section.