Floor joist obstruction

[Tom JE]

Hi,

I'm finally ready to fit my shower tray (see previous thread) but now have a huge problem. The tray arrived today and i marked out where the waste pipe needs to go under the floor. The problem is its right on top of my floor joist. I have no idea how to tackle this at all. Obviously i dont want to hack away at the joist to accomodate the waste pipe. I could relocate the shower as a very last resort or build a box for the tray to stand on as a very very last resort. Any suggestions?

Cheers

Tom

 

[noseall]

obviously you've tried re orientating the tray?

 

[peca27]

Why can't you cut out a section for the shower waste?

that's what i did when i fitted my tray approx 18 mths ago. Because of the fall i needed, the waste could only go in one position, so I ended up cutting out an approx 13 cm chunk out of my floor joist. As long as your not weakening a set of 4 or 5 joists in the same area it's a fairly common thing to do & doesn't compromise your joist structurally, ring a floor joist manufacturer if your still unsure.

 

[Tom JE]

The tray is a quadrant tray unfortunately so cant be repositioned in that area.

It looks like a may have to cut away some of the joist. Is there a limit as to how much i can cut away without weakening the floor at all?

 

[noseall]

modern buildings tend to be overengineered and allow for 25mm knock out for pipe runs etc. to acommodate a shower trap you will be removing too much material weakening the joist. definately a no no. raise the tray by a minimum amount, after all you have 25mm plus floor thickness to play with

 

[JohnD]

Have you got a shallow trap?

 

[Tom JE]

TBH i havent even bought the trap yet as i was going to wait until i got a rsponse here. I'll have to size it up and see what i have to play with. I have the thickness of the floor boards, plus 6mm ply, tile adhesive and tiles so there may well be enough....

 

[noseall]

best to use a specific shower trap as these have a detachable insert that can be removed for cleaning purposes, long after the tray has been irreversibly fixed/sealed/tiled in/sealed again!

 

[Tom JE]

Thanks again for the help mate.

Well apreciated chaps! I'll wonder around B&Q this weekend and see whats what

 

[Nige F]

You could go lower and drill a hole for the waste thru the 1 joist with a good holesaw I did @ my last house.used a cheap one and it just made the hole before burning out..but 1 was all I needed

 

[Tom JE]

How do you mean Nige? My waste is coming out directly on top of the waste. Do you mean drill a hole on the top side of the joist?

 

[Nige F]

Sorry , Didn`t read original post carefully BUT there may be an option to limit the distance the waste runs below the tray.......Got it right now ........You could use a Hep waste valve, with a 90 degree converter elbow .this takes the place of a trap and will not hang down more than a shallow trap would .But give total protection against vaccuum and pressure in the pipework.......They`re stocked @ all good plumbers merchants.Hope this helps Noseall`s idea is probably the best/cheapest.

 

[BOB NUTS]

if your putting in a hole regs says that -

- the hole should not be any larger than 25% of the floor joist depth (e,g 150mm deep joists allow a 37.5mm diameter hole)

-the hole should be drilled through the neutral axis (so if 150mm deep joists the centre point would be at 75mm)

- the hole should be located between 25% - 40% the span of the joist (e,g if you have a 4m span this would be between 1.0m - 1.6m from the support)

- if you need more than one hole they must be spaced at least 3 diameters apart (eg if 25mm dia holes the chunck of timber between them should be 3x25 = 75mm minimum

Notches - they are a hole different story

from what ive experienced modern floor joists tend to be less over the top than earlier construction

 

[PatrickD]

As a last resort: you could cut out the offending section and trim it to the joists on either side!

Patrick

 

[noseall]

that would mean doubling up the joists on either side too. big job!