Span of floor joists.

[igge99]

I will be doing an extension on our summer cottage. The extension will be 4x5 m. In the joist system, I will use 45x220mm K24 timber. The joists will be placed with 60 c/c. The joist system will rest on cast pillars at the edges. The extension will be in one level. My question is: can I have a span of 4 meters between the supports, or do I need to have a support in the middle as well?

 

[Johan Gunverth]

If you screw-glue floor particle board to these floor joists, it works. I have a 4.80 span with 45x220, c/c 600mm, but then floor particle board was a requirement. Otherwise, c/c 400mm would have been needed. I don't know where the limit is, but I assume it's around 3.7-3.8 meters span without reinforcing floor particle board.

In any case, a structural engineer always knows what you should do.

 

[igge99]

okay, I was planning to screw a massive tongue-and-groove pine floor 25X136 directly onto the beams. Should work just like the chipboard, right?

 

[Johan Gunverth]

ok, I was thinking of screwing a solid tongue and groove pine floor 25X136 directly onto the beams. Should work just like the chipboard?

No, it's the actual gluing of the chipboard that reinforces the structure.

 

[nimhed]

I have just laid floor joists 4.5 m out. I have laid 190mm c/c 400, Shortlat every meter or so. Then I have laid 2''3 crossed on top. It feels extremely rigid.