joist reinforcing

[bananaspark]

I need to run a 40mm pipe through a couple of joists, and am a bit worried about that.

Is sistering both sides a with 2ft length of equivalent reclaimed joist using 4 coaching bolts acceptable in this situation? Or is another way at all costs to be found to re-route the pipe?

thanks/b.

 

[Deluks]

Do you mean trim? Sistering is when you fix another joists alongside the existing, if you mean to fix noggins to adjacent joists then that's trimming, but you really have to remove the section the pipe will run through and use hangers to support the cut ends on the trimmer.
Probably not the best option anyway, you might need a beefy or steel reinforced trimmer. You could reinforce the drilled joists with a section of steel plate, with a hole drilled through for the pipe. If it's a sensible length (guesstimate 450 - 600mm) and coach bolted through with single sided timber connectors (aka dog washers), then the joists will retain their strength.

Having said that, every floor is different and most people don't think about it and just drill away through the joists. Not best practice IMHO and it's good that you are concerned about the implications of weakening the joist. If they are deep enough to start with then 40mm might not be a big deal.

 

[bananaspark]

thanks,
I usually notch through for 22mm pipe and cable etc without any concern,
but bath waste pipe is new territory

the joists are only 2.5 x8 or thereabouts.
like the idea of steel plate -is there anything in standards /regs that dictates the width of steel plate? also both sides of joist or just one side.
I'll go for 3mm galvanized steel as a default as that seems enough.
b.

 

[Deluks]

-is there anything in standards /regs that dictates the width of steel plate? also both sides of joist or just one side.
I'll go for 3mm galvanized steel as a default as that seems enough.
b.

Dunno

I know that steel plates sometimes get used in cases like these, invent something and get it knocked up at a fabricators, they may have even done a few before. You could use a length of pfc that will incorporate the joist depth in the flange, and drill a hole through it where the pipe will go. A few 2ft offcuts should do it.