Floor joist sizes

[ashdene]

Im having all sorts of problems trying to find the Wooden I-Joist sizes specified on my plans so im now thinking of going for standard timber joists, this will work out slightly cheaper too.

They have to go on 400mm centers to match the roof but what size should I go for, its for a loft conversion and the longest span is 5 meters

cheers

 

[tony1851]

At 5m span for domestic loading, @ 400cs with C16 timber, you are looking at 225x75, which is hefty for a loft conversion.