Notching joists
Discussion
Well yes, but if you're going to build to the current regs then it needs to come out and be replaced anyway if that's the case.
If you 'notch' the full width of the beam, so it's a 6 x 3 then it's fine for a span of just under 4m. The 8 x 3 would be just under 5m, with a notch the span will still be much closer to the later than the former. If the floor is down properly then the adjacent beams will bring the strength up further.
The top of the beam is in compression, so a properly fixed floor will take the compressive load that the notched wood would have taken, as well as distributing the load to the other joists. The compressive load is higher at the centre of the beam, so a notch near the end is less problematic.
I can't honestly see any circumstances where, assuming the beams are in good order, notching isn't a perfectly decent solution for the problem as described. The regs are worked to so many worse-case scenarios that aren't going to be a problem in this situation.
If you 'notch' the full width of the beam, so it's a 6 x 3 then it's fine for a span of just under 4m. The 8 x 3 would be just under 5m, with a notch the span will still be much closer to the later than the former. If the floor is down properly then the adjacent beams will bring the strength up further.
The top of the beam is in compression, so a properly fixed floor will take the compressive load that the notched wood would have taken, as well as distributing the load to the other joists. The compressive load is higher at the centre of the beam, so a notch near the end is less problematic.
I can't honestly see any circumstances where, assuming the beams are in good order, notching isn't a perfectly decent solution for the problem as described. The regs are worked to so many worse-case scenarios that aren't going to be a problem in this situation.
paulrockliffe said:
The 8 x 3 would be just under 5m, with a notch the span will
be less. The actual span is 5.8m.Like you I tend to think that a reduction in capacity near (300mm) from the support should usually be OK but you do get exceptions and as A mentions:
Ahbefive said:
So its notching 2 joists that are side by side. I should imagine there is a good reason that there are 2 there, it must be quite structural. Also 3" wide would indicate they are there for quite heavy loading.
I'd be wary without knowing what purpose it fulfils in the building.
I should point out that this is not my house, but a friend's who I'm helping out. His neighbour is a retired architect who has now had a look too. We've seen there is a steel, which these two sit in, making them about 3.5m long, So we have 2 3x8in joists that have a stud wall around mid way over them. We can't see anything else tied in, so he says notch them! I'm tempted and thought I could replace the floor over them with 18mm ply. What do you think?
It won't make any appreciable difference using ply or chipboard, over the notch they would be loaded in compression and either is fine. The failure mode would be buckling, so the most important factor is how well the flooring is screwed down, especially immediately around the notch. I would use 22mm chipboard too.
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