large notch in joist

[warriorgal]

Plasterer wanted to screw down floorboards in bathroom and he cut a a large notch in joist to enable fitting of shower waste, as he wanted to do that too. I am guessing its ok otherwise he wouldnt have done it.
Im a bit uncomfortable about the size of the notch. the joist is about 9 inches deep by 3 inches wide and the notch goes down 3 inches and is 4 inches wide. I guess about a third of the depth.
I have not called in the buldings regs to pass the plumbing pipework yet so now I have go them to come next week and I will show them the joist and I dont want anythng else done yet until I know all ok so far.
My question is, suppose the building regs are not happy with the hole in the joist, what would need be done to remedy this, is this costly or would some form of bracing be ok. And what do i say to the plasterer as he cut this hole behind my back without me knowing.

 

[AronSearle]

Maximum notch depth is 1/8 of the depth of the beam, he has bodged it.

You will have to strengthen it, normally means doubling up the joists if you can't replace it. or bolting on another piece to the side.

I am guessing its ok otherwise he wouldnt have done it.

F*ck no, UK tradesmen do stupid stuff all the time, can't turn your back on em.

 

[noseall]

The plasterer is a twonk and the guy who ordered the shower base is an even bigger twonk.

Why oh why!

 

[big-all]

what is the unsupported span and what centres are they at

they may be over specked to keep the floor level

 

[cajar]

What was a plasterer doing notching joists?

 

[warriorgal]

Thankyou for all of your replies.
In response, the joists are 40 cm centres, and they span 12 ft from girder to outside wall. The notch is nigh on in the middle of the span (6ft along)
It was me who `ahem` bought the shower tray, but I beleived that the waste would have fitted without a notch at all with a slight adjustment of the shower tray. Maybe I was wrong.
I shall ask the plasterer on monday for his comments, and see what regs say on tuesday.

 

[warriorgal]

What was a plasterer doing notching joists?

he wanted to screw down and secure floorboards, he knew i had someone lined up to do plumbing but he said he would do it. Next thing I see the notch through the shower waste hole which was cut out of the plywood floor.
BTW the shower waste hole was prev cut out by plumber and was not over the notch but next to it.

 

[warriorgal]

View media item 92346

 

[tony1851]

Maximum notch depth is 1/8 of the depth of the beam, he has bodged it.
.

Not necessarily true. If the notch is near the end of the span, there's no problem.

PS just noticed it's near the middle - there is a problem.

 

[AronSearle]

Not necessarily true. If the notch is near the end of the span, there's no problem./quote]

Not in C24, not ever, grading rules for timber that size never allow more than 1/5 knot ratio area, A cut that size invalidates the strength grade no matter where it is. Even in C16 it would be very dubious.

 

[tony1851]

[A cut that size invalidates the strength grade no matter where it is.

No it doesn't.

In the BS 5268 code there are equations for calculating the allowable stress at notches near the end, for any grade of timber. As this is a permissible stress code, allowances are built-in to ensure that the timber is not over-stressed at the notch, whatever the grade.

The EC 5 code has similar provisions, but is more complicated than the BS code.

But I agree that if the notch is in the middle, it has compromised the strength of the beam. But if the span is 12 ft, the question arises as to why the joists are 9 x 3s??

 

[warriorgal]

the beams support a wooden supporting wall which supports part of the roof structure. i.e. the bathroom wall, which is about 3ft away from the notch. This doesn't sound good does it ?

 

[tony1851]

Highly unlikely to collapse because timber can take a greater stress than is usually allowed for in the codes.
But long term it should be strengthened, if only to stop excessive deflection and bounce.

 

[noseall]

I beleived that the waste would have fitted without a notch at all with a slight adjustment of the shower tray.

So, why wasn't there a conversation about the orientation of the waste regarding joist position?

If there is one overriding factor regarding shower tray installation it is what one does with the waste. This includes the pipe as well as the trap. Did no one talk about this?

 

[warriorgal]

he took over matters without consultation. And I never expected this. He said he wanted to fit shower tray, but this was never discussed about. He was there to do plastering. After the notch was done he said the shower waste was not central. I didn't know what to say. But I was uncomfortable when I saw the notch. Maybe he beleived I would have stopped him if he told me his intentions ?