Re: cutting holes on joists
Posted by dick on June 14, 19100 at 09:17:23:
In response to Re: cutting holes on joists
: Dear Terry, I am looking to relocate my toilet in my 1st floor flat. In its new location, i will need to pass the waste pipe over 1, possobly 2 joists to reach the soil stack on the outside of the house. The joists are 8" by 2" and the waste pipe is 4" diameter. Can you tell me whether it is safe to remove half of the joist. Should i drill a 4" hole in the centre of the joist? Should the hole be in the centre of the joist span or towards the end i.e by the exterior wall.Please help, your advice would be very appreciated.

wETHER IT IS SAFE TO REMOVE HALF THE JOIST depends on the span, but probably it is not safe.
What I would do (not necessarily right or acording to any code) is mark a location 3' out from the wall or 1/4 of the span whichever is greater. Then nail a 2x8x6' to the existing joist centered on this mark. Nail with 16d nails , two rows near the top edge and bottom edge 3" apart. (that comes to 48 nails). Then drill the holes through the center of the doubled joist.

The object is to make the joist as stiff as it was originaly so your floor doesn't feel like your walking on a trampoline. Floor joists are designed for strength first and then stiffness. Stiffness generaly requires much more and heavier joists than the strength requirement.

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