Notches over holes?
- Thread starter Starship_Toby
- Start date
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Hence the plates or brackets, he can't undo it now
But he can avoid doing any more.
That looks like a 5" deep joist? If so, maximum notching depth is 0.5" and he's gone a lot deeper than that. If it's a 4" joist it should not be notched at all. The electrician has drilled in the wrong place (not uncommon) but those notches are definitely wrong, drilling or no drilling
I had a similar problem and asked the loft conversion firm to get their structural engineer to provide a calculation showing that what they had done was OK, and withheld £££ until such time as they did (which was never).
The Wiring Regs say that notches should be not deeper than 0.125 joist depth and then only between 0.07 and 0.25 x span, i.e. between 280mm and 1m from the wall for a 4m span. So the position is allowable but the notches look to be far too deep, it's hard to tell from the pic but they also look un-necessarily deep for the pipe dia.
Holes should not be larger than 0.25 joist depth and between 0.25 and 0.4 x span, so although small enough this hole is too near the end of the joist. On its own I would say it would not be a problem, however the plumber has seriously weakened the joist by halving the amount of material over the hole.
From the structural point of view the notches will have a much bigger impact on the bending strength of the joist than holes will. You really need to reinforce it with something like a 5mm steel plate extending as far either side of the notch as the depth of the joist. (The plate will be in compression so if it is too thin it will buckle and not take any of the load.) It would be much better if the pipes were placed at the minimum distance allowed i.e. 280mm from the end of the joist, where there is less stress in the wood at the top. At the very least I would put a dog-leg in the pipe run so that any further notches are not under the same board as the cables.
The Wiring Regs say that notches should be not deeper than 0.125 joist depth and then only between 0.07 and 0.25 x span, i.e. between 280mm and 1m from the wall for a 4m span. So the position is allowable but the notches look to be far too deep, it's hard to tell from the pic but they also look un-necessarily deep for the pipe dia.
Holes should not be larger than 0.25 joist depth and between 0.25 and 0.4 x span, so although small enough this hole is too near the end of the joist. On its own I would say it would not be a problem, however the plumber has seriously weakened the joist by halving the amount of material over the hole.
From the structural point of view the notches will have a much bigger impact on the bending strength of the joist than holes will. You really need to reinforce it with something like a 5mm steel plate extending as far either side of the notch as the depth of the joist. (The plate will be in compression so if it is too thin it will buckle and not take any of the load.) It would be much better if the pipes were placed at the minimum distance allowed i.e. 280mm from the end of the joist, where there is less stress in the wood at the top. At the very least I would put a dog-leg in the pipe run so that any further notches are not under the same board as the cables.
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