Pipe under joists

I think I'll go with gut feel :)

PoP

With Liberty ships the key problem was the previously unknown problem of brittle fracture: normal steel becomes brittle about freezing point and then if overstressed will fracture rather than yield.

To get back on topic, good practice for notching joists is to drill and cut, though of course it depends how much one is taking out the joist.

with the Liberty ships was design/welded construction. The problem with the Titanic was sloppy procedure.

Try an experiment. Get two nails, and two pairs of pliers. Take a nail at room temperature in the pliers, and bend it. Put the other nail and the pliers in the freezer for 1/2 an hour, then put on gloves, pick up the pliers, and bend the nail. It won't snap. --

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Gut feel is OK if like many many craftsmen, you have been using the materials for years and have experienced failures in them.

Otherwise, stick to someone esses rules, or do the (very complex) calculations, or take the engineering route, and put the structures in a machine and stress them till they break.

:-)

It fatigues much quicker tho.

I should expand on that previous statement a bit.....

By "gut feel" I think I'd be swayed towards "I ain't gonna drill that size hole in that size joist!", even if it looked as though it ought to be okay.

Some things aren't worth taking chances with.

PoP

Cheers All... So basically I can drill up to a 25mm hole in a 100mm joist. But not necessarily the 35 mm I require for a kitchen waste output. Is there a regulation minimum for a kitchen waste pipe, thanx again. Will this run and run ??? :-)

I wonder if how you fix the floorboard above a notched joist makes a difference? I've a gut feeling it does...

According to my Onsite Guide (for Electricians) the maximum hole diameter should be 0.25 * joist depth. The maximum depth of a notch should be 0.125 * joist depth.

Holes should b on a centre line in a zone between 0.25 and 0.4 * span of joist. (This requirement is usually ignored) Notches on top in a zone between 0.1 and 0.25 * span of joist.(This requirement is usually ignored)

"Dave D" wrote | Cheers All... | So basically I can drill up to a 25mm hole in a 100mm joist. | But not necessarily the 35 mm I require for a kitchen waste output. | Is there a regulation minimum for a kitchen waste pipe, thanx again. | Will this run and run ??? | :-)

If you get the fall on the pipe wrong it won't run at all :-)

Owain

Not if it gets blocked! (sorry, couldn't resist!)

Barley Twist (Please put out the cats to reply direct)

IIRc the hole must not be more than 20% of the joist depth which means that the joist must be at least a 7x2. The hole edges should be at least

Boring the hole between joists that are square to the joist requires some seriously good tools which I'm going to have to buy for a current job. I need to get a 22mm gas pipe through - the pipe will be fed in from the outside.

I've been looking at those side-on drilling tools as well. There don't seem to be any bargain-basement versions unfortunately.

Bit of a pity really because if there was a Ferm or Nutool version of such a beast then I imagine it might do reasonably well in terms of sales. It's the sort of tool you need in the back of the wagon for the odd occasion when you need it, but the cost most likely doesn't lend itself to acquiring one for most people.

PoP

HI Dave,

Sorry to pee on your parade but if it's a kitchen sink waste I believe you'll find it's 40mm not 32mm

yes.

I'm still curious as to how Dave gets his 40mm waste through a 35mm hole.

Not quite. 30% of the strength when unloaded maybe. But when the joist is in place and loaded then the stresses are carried in the top and bottom of the joist leaving the centre zone with little load. So you can make bigger holes - and that's why notches in the top and bottom have to be much smaller.