Drilling through joists regs?

On the john guest site they say this:

Traditional joists

Instructions on the drilling of joists is given in the Building Regulations Approved Document A, and summarised as follows:

1. Holes should be no greater than 0.25 of the depth of the joist.

2. Holes should be drilled at the neutral axis.

3. Holes should not be less than 3 diameters (centre to centre) apart.

4. Holes should be located between 0.25 and 0.4 times the span from the support.

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I have looked at Doucument A and just can't find refference to this. Any help anyone? Jono

I don't have a copy but A refers to structure so that is where you should find it.

there are British Standards laying out what is allowed. The corgi manual is just a rehash of these and what you quoted is correct.

Joists must be minimum 100mm.

notching otoh is in different part of span, 1/14th to 1/4 in from each supporting wall, notch depth up to 1/8th.

There are also now some special machined joists like I beams with either knockouts or you can drill them, but not notch them. They are a piece of sterling board with some 2 by 2 top and bottom. The floors are glued to these and the whole structure is very strong.

BUT good luck in future years when you ask someone to rewire or replumb or fit heating for first time. Only safe way will be to deconstruct the whole structure and start again, as it has to be one structure to be to spec. So book your plasterer to redo the ceiling at the same time.

My advice is buy a quality house built around 1880 or earlier.

I have found that our LABC will not allow any notching of joists, drilling holes is the only accepted method for them(new build and planned extension).
The I beams with knock out holes dont half save some time.

Thanks Paul,

I am a little confused over number 4.

4. Holes should be located between 0.25 and 0.4 times the span from the support.

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Does this mean a 4 metre long joist should have holes located between 1m and 1.6m from each end?

or for a 1m long joist it should be between 25cm and 40cm from each end????

lcgs, I have put in new timber joists and will be drilling only.

Jono_UK said:

Does this mean a 4 metre long joist should have holes located between 1m and 1.6m from each end?

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Yes.

As for LA not allowing notching, jumped up little twa t.

Hope thats the LABC and not me Paul.