difference of opinion, floor joists

[chirpychippy]

Currently I am doubling up exisitng floor joists in a very old house, the exisitng are 5x2 and I am doubling up with new 5x2 timber effectively making them 5x4. We have knocked down the divinding wall and are making two rooms into one large one and appose to putting a steel in at the point of the once dividing wall(mid point) we are putting in a large Oak Beam, now my grievance is this, I reckon the new 5x2 should extend 3-400mm past the mid point of the new Oak beam, however my boss reckons it will be ok for them to sit and finish on the beam and not extend beyond. What do you reckon?

 

[Softus]

Currently I am doubling up exisitng floor joists in a very old house, the exisitng are 5x2 and I am doubling up with new 5x2 timber effectively making them 5x4.

To be picky, this doesn't double the effective timber width, it reduces the average distance between joists.

We have knocked down the divinding wall and are making two rooms into one large one and appose to putting a steel in at the point of the once dividing wall(mid point) we are putting in a large Oak Beam, now my grievance is this, I reckon the new 5x2 should extend 3-400mm past the mid point of the new Oak beam, however my boss reckons it will be ok for them to sit and finish on the beam and not extend beyond. What do you reckon?

I can't see any benefit in extending a joist beyond the edge of the supporting beam or wall. However, the joist should go the full width of the support.

Also, don't forget to use the correct method of protection at the other end of the joists, where they sit in the wall. I have a feeling that the BRs have changed in this respect recently, and you can no longer just treat the ends and smother with silicone.

If you're in any doubt about the size of the beam, or about the depth or width of the joists, or the manner of laying them, then you should consult the LABC, since they will be overseeing this alteration anyway.