Holes in timber joists

[spiidey]

We've stripped off the ceiling in our downstairs kitchen to expose the joists between the ceiling and the floor above.

These joists have varying circular holes cut through them to allow hot water / central heating pipes to run through them.

We want to lag the pipes with pipe wrap, but this would necessitate making the holes slightly larger in diameter.

What is the rule of thumb regarding how big a hole can be in a joist before the joist weakens too much?

 

[rjm2k]

We want to lag the pipes with pipe wrap, but this would necessitate making the holes slightly larger in diameter.

Why do you want to lag them?

Easier just lag upto either side of the existing holes

 

[spiidey]

We want to lag the pipes with pipe wrap, but this would necessitate making the holes slightly larger in diameter.

Why do you want to lag them?

Easier just lag upto either side of the existing holes

Where the pipes go through the joists, they rub against the timber when they expand (I.e. when central heating / hot water is on)

 

[foxhole]

Just cut short sections of plastic pipe in half and pass above and below pipes then tape together, will prevent friction noise, which Is what I assume you are trying to do.?

 

[spiidey]

Just cut short sections of plastic pipe in half and pass above and below pipes then tape together, will prevent friction noise, which Is what I assume you are trying to do.?

We're trying to lag the area of the pipe around where it actually goes through the timber joist (i.e. in the joist itself).

Using a product such as this:-

http://www.diy.com/nav/build/insula...flex-Pipe-Insulation-22mm-x-13mm-x-1m-9273771

Doesn't work as the hole in the joist is not big enough to take the foam pipe wrap.

Is there another product that would lag/wrap the pipe enough to stop any friction/vibration against the timber, but would be small enough to fit into the joist?

The hole in the joist has about 5mm additional radius in total over and above the pipe itself.

 

[foxhole]

Pointless to lag thru timber the timber provide insulation.If you have 5mm spare then pipes do not expand enough to touch the timber.

 

[WalksWithTurkeys]

There are regulations on the cutting of holes through joists for obvious reasons. I'd not both, and lag either side.

the timber provide insulation.

Yes. Very good insulation.