Joists....Have I boobed?

[Dee]

To get enough fall into the waste pipes that 'someone else' laid I've notched out the underside of 5 joists! Sorry!

The joists are 6 x 2 x 8ft and about 60yrs old. The deepest notch is 30mm shallowing on each subsequent joists.

The notches are about 18" from the wall.

Have I done a major boob??

How do I strengthen them?

Panicking!

 

 

[joe90]

Pic please…..

[Redbeard]

Joist depth	Notch depth
150mm	18mm
175mm	21mm
200mm	25mm
225mm	28mm

1 more row

•

5 Oct 2022

 

Notches and holes - Eden District Council

[joe90]

So it’s over the recommended depth of cut, however I would offer this solution., 1/2” ply, glued and screwed both sides of the joist. excuse the CAD (crayon assisted drawing).

 

 

 

[Conor]

Just sister it up with a similar size piece of timber on one side. Or even ply as Joe suggests.

[Dee]

Along the whole length or just around the notch?

[joe90]

Just around the notch ( about 300mm total length will do)

[Mattg4321]

Pretty sure no notches are allowable to the underside of joists. Only to the top

[joe90]

3 minutes ago, Mattg4321 said:

Pretty sure no notches are allowable to the underside of joists. Only to the top

My suggestion above will mitigate that .

[Dee]

So, in what scenario would you notch the top of a joist? Surely you wouldn't run waste pipes over joists?

[Redbeard]

12 minutes ago, Dee said:

Surely you wouldn't run waste pipes over joists?

 

Have I misunderstood? Why not?

[joe90]

Waste pipes are too big to be notched into joists ( normal size ), if at all holes should be in the middle of the joist, the top of a joist is in compression and the bottom in tension so both top and bottom are most important to strength.

[Redbeard]

@joe90, I agree in principle, but @Dee has already put said notches in the wrong bit, a remedy for which you have suggested. 

 

@Dee asked "So, in what scenario would you notch the top of a joist? Surely you wouldn't run waste pipes over joists?"

 

No, I would not seek to notch for that big a pipe, but @Mattg4321 's suggestion was, I think, that it could be less critical at the top (although still requiring strengthening). 

 

I agree re holes in the middle, but I am not sure what max dia hole (at joist ctre) is allowable in what jst depth.

 

Edit: Now I am! I re-read that Eden DC link: 0.25 xx jst depth, so 37.5mm.

 

O.P. What's the waste pipe dia?

Edited December 2, 2023 by Redbeard
Conf re hole size

[Dee]

3 hours ago, Redbeard said:

Have I misunderstood? Why not?

I think I'm confusing everyone as usual. My scenario is there are floor joists, then a void beneath then ceiling joists of the kitchen below. Therefore my pipes run in the void but there is not enough 'space in the void to get fall so I had to notch on the underside of those joists to achthe fall needed.  I now realise I should not have notched!

[Mattg4321]

Just for reference...

 

https://www.labc.co.uk/news/how-get-it-right-notches-holes-solid-timber-joists

[Dee]

This is what I can't undo!

Im such an arse

[markc]

Is it ideal? No. Is it something to worry about? No. Traddies will have seen much worse and it’s been like that for years. Stop worrying, learn from it and carry on.

[joe90]

2 hours ago, Dee said:

This is what I can't undo!

Im such an arse

No, you are learning, as @markc says, we have seen worse. On a practical level this is a bathroom so not liable to see lots of people at the same time so loading will be minimal. If it does worry you then sister it or like I posted above purely fir peace of mind.

[SimonD]

1 hour ago, joe90 said:

loading will be minimal. If it does worry you then sister it or like I posted above purely fir peace of mind.

 

Unless there's a bath to go in there? But as you say, swallow the mistake, have a cup of tea, keep calm and carry on and either cut some plywood or sister with a meter or so of 4 x 2 and job done ☺️

[Redbeard]

How chunky are the kitchen joists. Are they more spindly - just to take a ceiling - or do they look similar to the ones above. If the latter, why not strut between the 2, so the kitchen joists take some of the load?

[joe90]

I maybe wrong but I cant see any supports fir that pipe., if not hot water in it may make it sag over time, if you do the “ply” thing I suggested earlier this will also support the pipe 👍 2 birds with one stone and all that 🤷‍♂️

[saveasteading]

I say that you should take it seriously,  for strength and deflection.

That 20% depth reduction is taking away 1/3 of the strength, and it will be bouncy.

As above, fix a timber or ply to the side, or both sides.

Jump hard on it before and after and note the difference. There's no reason to skimp, so make it 600mm long , or even more. And use plenty of screws.

[Andehh]

Aa said, I've seen worse and you'd be amazed at what plumbers will do butchering their way through these, only to then hide it below some ply and tiles!!

 

Sister joists, glued and screwed well and forget about it!

[Dee]

Thankyou boys for your invaluable advice and encouragement!

I will sister the joists as I had planned to do anyway 

SimonD@ no bath, will be a rarely used ensuite.

[Dee]

The reason I'm so anxious is we've never had the house signed off....after 18 yrs!

I want/need to do this for my darling late Husband Michael....he will not 'rest' until I have that final sign off.

I now have a firm plan....

Had a run in with my plumber about the 'fall'. He insisted there was 4" over 4mtrs of run..I tested it with jug of water down the basin waste snd barely a trickle in the manhole. Anyhoo onwards to sistering

Thankyou all. So grateful