Basin Waste over joist!

[Peter Hemmings]

Hi,

I am about to buy one of those bowls that stand on a wooden base with the waste being concealed inside a wooden upright square pillar.

I have just found that I have a 7x2 inch joist that's just where the pipe will go into the floor. It runs parallel with the wall but its not far enough away from it to get the waste in between the wall and joist.

I do not want the waste boxed in (it would then go into a shower), so can I slot the top of the joist (1 1/4inch or metric equivalent) in order for it to run it under the floorboards and out under a shower tray?

Thanks

[meow2222]

Since you've got 7" and thats far more than is actually needed, losing so little really would make no noticeable or relevant diference. It would be a different story if you had 4" joists.

NT

[Frank Erskine]

Oo-err missus.

[John Rumm]

You might be right, but I would say that is a tough call not knowing either the span of the joist, what load it is carrying, and where along it he wants to notch it.

[Matty F]

I agree. Assuming that you are usiing plastic waste pipe, how about getting a large diameter pipe, put it in boiling water and squash it to the thickness of the floorboard for the part that goes over the joist.

[Roger]

The message from Peter Hemmings contains these words:

There are rules to follow for notching joists. A quick google brought up the following quote"

"Notches should only be made in the top edge of the joist. Notches should be no deeper than 0.125 times the depth of the joist. Notches should be no closer to the structure supporting them than 0.07 times the span of the joist and no further away than 0.25 (¼) times the span. This is to avoid the area of maximum shear force, and the area of maximum bending in the joist."

On that basis you shouldn't be able to put a 1 1/4" notch in your floor joist and if your basin is in or near the middle of the wall you shouldn't notch at all. However these rules may be unnecessarily restrictive for your situation. A 7" x 2" joist can span 12' at 16" centres so if the supports are less than 12' apart the joist will have some spare meat. Also the beams are sized to take the maximum permitted floor load which back in the dim and distant past used to be 5 cwt per linear foot of joist, 10 cwt concentrated load and an average uniform load of 0.75 cwt per square foot. If the load was truly uniform the joist close to the wall would only be carrying about two thirds of the load that the other joists carry so there again there is the possibility of spare meat but only someone with detailed knowledge of your setup can advise whether or not you have sufficient room for manoeuvre.

[meow2222]

I figured its going to be pretty hard to find a 7" joist that has so little margin it cant run as 5.75" for a tiny fraction of its length. If th OP tells us the joist details we could eliminate that remote possibility.

Would create a blockage point though. Its extremely unlikely there is going to be any problem at all with notching the joist. If due to some odd situation it would be a problem, I'd be more inclined to use up a bit of the flooring height, thereby reducing the joist notching. Or, depending on construction details, see if its poss to run the pipe along the joist then go through the centre of it, where any hole will have relatively little effect.

Really though, I think this is only complicating whats simple.

NT

[John Rumm]

You can get away with less notch still if you use the thickness of the floorboard as well (i.e. have the pipe top level with the finished floor level)

[Christian McArdle]

Is a new floor going down?

You could trim out the problem joist. Just cut out the problem section and trim to the joists either side (or to a neighbouring joist one side and a loadbearing wall the other). Check it is OK first (i.e. no baths supported) in case it needs further strengthening.

Christian.

[Peter Hemmings]

The total length of the joist is 4 metres and it has 6 3/4 inch T&G flooring on top, in a main bedroom. A friendly structural engineer said this floor would fail todays specifications, but I guessed they would! Distance between joists is 14 inches.

Yep, but I ALWAYS prefer a margin of safety for when I hammer nails into the floor!

>

[John Rumm]

And where along that 4m do you want to notch it?

Would the pipe turn not be covered by the wooden pedestal though?

[meow2222]

time to stop worrying.

NT

[Christian McArdle]

Personally, I wouldn't notch a 4m 7" joist.

Christian.

[Peter Hemmings]

I did post the details but I cannot see it on my mail client!

Just as a final update, the joists are 4 metres long and will have the shower tray at the corner of the bedroom with a small basin in the middle of the wall. I have now found a basin that will be mounted on top of a vanity unit (which are an absolutely ridiculous price) and I no longer need to go across the joist. The BS called to check my noggins last week and I asked if I could channel out the joist for a 1 and quarter inch pipe, the answer was no! He said max depth of channel was 1/10 of height ie .7inches. So one could in fact cut slot in floorboard, put metal plate across it and it would be legal! (that is if you have to get it inspected in my area!)