Cable Runs

[Stoobydale]

Hi, could anyone tell me if it is ok to drill through roof joists on a single storey extension to run lighting cables through? The joists are 150mm and the hole is 50mm plus in from the underside with a 13mm hole.

 

[haj]

Hi i think you will find drilling roof joists is a BIG NO NO check out building regs book. If i am wrong someone will soon correct me !! ok as i said someone would correct me i knew you could not drill one of them ; Rafters i stand corrected

 

[pushrod]

Ii thought that you can drill them as long as they are not within 50mm of the top or bottom. I think there is also a limit as to how close to the wall they can be - something like 0.4 M or 0.25M but not certain.


edit : just checked red book 522 .6.5(1) 50mm thing is correct but couldn't find anything about closeness to wall.

 

[saveloy]

Max size of hole is 0.25 x 150mm= 37.5mm so 13mm hole is fine.


You will need to know the free span of the joists. So say for example the free span is 10' or 3.0m.
Safe area for drilling is BETWEEN

0.25 x 3.0 M = 750mm AND
0.4 x 3.0 M = 1200mm from either end.

These holes must be drilled on the CENTRE LINE of the joist. Ie @ 75mm from top and bottom on a 150mm joist.

Just multiply the 0.25 and 0.4 factors, by the given free span measurement of the joists you are drilling, to find the safe zones from either end

Hope this helps.

 

[Spudnik]

You are permitted to drill roof joists within limits set out above, but you are NOT permitted to drill rafters at all.

 

[daniel hill]

all these drilling out regulations saying 50 mm deep and all that but how many plumbers do u see thet just notch the joist haha

 

[pushrod]

Isn't notching allowed if you put a steel plate across the top? - I know plumbers never do!

 

[Stoobydale]

What options do you have if it is a vaulted roof? The only woodwork is actually rafters, would it be ok to drill in this situation?

 

[Spudnik]

What options do you have if it is a vaulted roof? The only woodwork is actually rafters, would it be ok to drill in this situation?

No it wouldnt.

 

[Had8Lives]

One solution is to fix a plank across the joists and clip the cable to it. That way you don't have to feed the cables through and you can comply with the maximum spacing for clips (OSG P.113) even if the joists are further apart.