Hi, I've bought a 500 year old house in croatia that needs 2 new floors. The interior measures 6m x 6m. The original joists are really small and rotten. What size of joists would I need to have to span the room without support posts ? I don't think I will be able to get I-beams but could get timber in the following dimensions: 100mm x
200mm or 140mm x 200mm. Would this be sufficient ? Cheers.
These sites should tell you all about it:
I'm sure that some of the experts will quote chapter and verse from the loading tables - but 6 metres seems a hell of a span to do in one go. From the top of my head, I reckon you would need something with a vertical dimension considerably in excess of 200mm.
Are you *sure * you can't get an I-section RSJ? With a 200mm high RSJ across the middle of the room, you could cut 200x50 joists into it - so the RSJ would be within the ceiling depth and would be hidden. The joist span would then only be 3 metres - which is fine.
It depends on what you would consider to be an allowable maximum deflection for the floor. In the UK you are limited by building regs to about 0.003 * the length of the beam (or 14mm for beams over ~5m IIRC). Assuming there is no Croatian BCO standing over your shoulder and you can tollerate say 30mm deflection then you have a much simpler task.
I would have thought that 140x200 would do a credible job at that length even if they did not reach UK standards for deflection.
The other possibility is a flitch beam - that would need a metal plate down the middle and wood either side all bolted together - but that may be more accessable than a full on I beam.
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