Cutting holes in joists

[neilma]

Hi,

I am in the process of moving my (electricity) consumer unit and need to move some of the wiring. The route that I want (or can only) take is through 2 joists. Basically, is it safe to drill a hole using a 50-60mm flat bit through a joist? Will the joist still be strong enough after? (The joist is about 6.5 inches in height). Is it better to drill the hole near the top of the joist or through the middle? I'm working from underneath if that helps as I already have the ceiling removed.

Thanks for any advice.

 

[IanDB]

60mm sounds a bit big for a hole, would suggest two smaller ones. The location should be in the middle rather than nearer the top - avoids nails coming down from above!

 

[neilma]

Yeah, I should have clarified that a bit - 60mm in width. But I take your point. I'll do it in two or three holes along the middle. Thanks!

 

[dingbat]

Holes in joists should not be greater than 0.25 x joist depth. They should be on the centre line between 0.25 and 0.4 x span, measured from either end. Multiple holes should be at least three diameters apart.