Drilling joist for waste pipe

[jon92]

I have to pass a 40mm pipe through a 6" by 4" floor joist (not a regular joist, but at 90 degrees to the main floor joists, I think it is supporting the hearth or chimney in an adjoining room). The hole would be very near one end of the joist and roughly centred top-to-bottom. Do I need to strengthen the drilled joist to compensate, perhaps fixing a noggin alongside?

 

[big-all]

if i have this right you are talking around 2 ft span !!!!

is there anything apart from floor boards/ceiling attached to the joist!!!

 

[dav]

Technically all drilled holes on a joist should be made in the middle or neutral axis, notches etc on top away from the edges. The hole drilled should be no more than .25 diameter of the depth of the joist so your joist is around 144-46mm in depth a quarter of that is maximum diameter of your hole - 36-37mm so close - up to you, depends what it is supporting and whether as Big all has asked if the span is very short.

 

[jon92]

Thanks for the replies, I'll have to bite the bullet I think. Given the short span it should be ok, I'll add some extra support too. Keep an eye out for me in the DIY Disasters forum.

 

[JohnD]

how does this timber relate to the other floor joists? Is it on top/underneath/between?

Is is built into a wall at the end, or what?

Might it be a trimmer or a noggin?