Author Topic: Joist Replacement/Notches and Building Regulations  (Read 474 times)

Joist Replacement/Notches and Building Regulations
« on: July 31, 2020, 08:27:54 am »
Long story short, due to a slow leak on the hot water feed into the bathroom, we have rotten floor boards and a rotten joist. The joist has a 2.6m span and can be replaced from below by removing and replacing the dining room ceiling.

The joists in the bathroom look like they've been notched for central heating and both hot and cold feeds inside the centre of the span. The two sets of notches are less than 8cm apart and between them a hole has been drilled for the electrics.

The min notch distance from the wall is 0.182m and the max notch distance is 0.652m
The min hole distance is 0.652m and max hole distance is 1.042m

The first notch is 1.073m from the nearest edge of the span. The hole is 1.09m from the nearest edge of the span.

Obviously this is true of the adjacent joists as well as the joist that I'm replacing.
Do I need to rectify this contrarian notching and holing as part of the joist replacement?

Thanks
A Few Apples Short of a Strudel

Aunt Maud

  • Le Flâneur.
Re: Joist Replacement/Notches and Building Regulations
« Reply #1 on: July 31, 2020, 09:08:31 am »
You could apply a 6mm steel flitch plate to the joist from above if the ends of the joist are sound, or you could bury the plate in the wall and stiffen it with noggins. This will save you the hassle of a new ceiling.

Simply take up the floor, slip in the pre notched flitch plate and bolt it to the old joist. The flitch plate will take the load and the old joist/noggins will prevent it from twisting.

Nail the floor back into place and forget about the random plumber/electrician shonky notching. These people have no regard for structural stability and are only interested in running their pipes/cables as easily as possible.

Re: Joist Replacement/Notches and Building Regulations
« Reply #2 on: July 31, 2020, 10:02:33 am »
Electricians are the world's worst.  We just had all our lighting wiring upgraded to include an earth, including some metal wall lights for which they had to cut channels.  First they forgot to connect them and had to be called back.  Next they put back one wall light squint so I removed it to adjust and found they hadn't bothered to connect the earth wire anyway as it was a bit shorter than the other two and putting a longer bit in would clearly have been far too difficult.  We are still awaiting the certificate they promised although the invoice arrived promptly.


Sic transit and all that..

Re: Joist Replacement/Notches and Building Regulations
« Reply #3 on: July 31, 2020, 11:28:18 am »

Do I need to rectify this contrarian notching and holing as part of the joist replacement?

Thanks

Short answer, no.  If the floor has been ok up to now, it'll continue to be so.
We are making a New World (Paul Nash, 1918)

Re: Joist Replacement/Notches and Building Regulations
« Reply #4 on: July 31, 2020, 01:31:16 pm »

Do I need to rectify this contrarian notching and holing as part of the joist replacement?

Thanks

Short answer, no.  If the floor has been ok up to now, it'll continue to be so.

To be honest I think the slight movement in the floor in combination with the use of compression joints instead of soldered joints caused the leak. Turns out we're covered by the home insurers, or at least they are willing to consider a claim. We should be hearing from their assessors in the next 24 hours.
A Few Apples Short of a Strudel

Re: Joist Replacement/Notches and Building Regulations
« Reply #5 on: July 31, 2020, 01:37:59 pm »
Electricians are the world's worst.  We just had all our lighting wiring upgraded to include an earth, including some metal wall lights for which they had to cut channels.  First they forgot to connect them and had to be called back.  Next they put back one wall light squint so I removed it to adjust and found they hadn't bothered to connect the earth wire anyway as it was a bit shorter than the other two and putting a longer bit in would clearly have been far too difficult.  We are still awaiting the certificate they promised although the invoice arrived promptly.
When we built our house the builders electricians did the wiring. A few weeks after moving in we needed some xtra work done so got an electrician we knew to do the work. That then morphed into a several thousand pound piece of work to put right all the problems and give us a legal certificate.

Re: Joist Replacement/Notches and Building Regulations
« Reply #6 on: July 31, 2020, 06:16:07 pm »

Do I need to rectify this contrarian notching and holing as part of the joist replacement?

Thanks

Short answer, no.  If the floor has been ok up to now, it'll continue to be so.

To be honest I think the slight movement in the floor in combination with the use of compression joints instead of soldered joints caused the leak. Turns out we're covered by the home insurers, or at least they are willing to consider a claim. We should be hearing from their assessors in the next 24 hours.

The flexing is very unlikely to be a result of the notching though. Even if that locally weakens the joist the applied load through the floorboards is pretty well distributed.
We are making a New World (Paul Nash, 1918)

Re: Joist Replacement/Notches and Building Regulations
« Reply #7 on: July 31, 2020, 09:56:46 pm »
As upthead flinching will do the reinforcement job. Pipes and cables are supposed to run through the centre of the joist not just to avoid weakness but to prevent screwing and nailing through them. But when you come to replace the floor you will remember where they are, won't you!

Feanor

  • It's mostly downhill from here.
Re: Joist Replacement/Notches and Building Regulations
« Reply #8 on: July 31, 2020, 10:16:00 pm »
Another variable is what is the depth of the notches, and what is the depth of the joists?

Aunt Maud

  • Le Flâneur.
Re: Joist Replacement/Notches and Building Regulations
« Reply #9 on: August 01, 2020, 08:36:09 pm »


As a fully paid up member of the ligneous mass appreciation society, the correct positioning of the holes for pipes and whatnot ,as mentioned above, is on the neutral axis of the joist. Holes in this position minimise the structural weakening caused by the severing of the wood fibres which are in either compression or tension either side of said axis.

Re: Joist Replacement/Notches and Building Regulations
« Reply #10 on: August 02, 2020, 10:30:04 am »
Electricians are the world's worst.  We just had all our lighting wiring upgraded to include an earth, including some metal wall lights for which they had to cut channels.  First they forgot to connect them and had to be called back.  Next they put back one wall light squint so I removed it to adjust and found they hadn't bothered to connect the earth wire anyway as it was a bit shorter than the other two and putting a longer bit in would clearly have been far too difficult.  We are still awaiting the certificate they promised although the invoice arrived promptly.

To be fair to electricians, some are shite perhaps but equally, just as in any trade or profession, some are really good.

Re: Joist Replacement/Notches and Building Regulations
« Reply #11 on: Yesterday at 06:35:25 pm »
Thanks for all the help and suggestions. Since posting, we've taken the dining room ceiling down and done a lot of reading.

We've got two joists with rot issues. Further examination of the joists shows lots of knots in them. I counted 11 in one of them, most quite sizeable. There's varying numbers of notches in the joists, a good number in each and in the worst case 7. Notches of varying shapes and sizes.

The span is 2.660m and the worst deflection I've measured at 13mm with no live load (bath water, people) on top of the superimposed load (bathroom suite etc.).
According to current regs, the max deflection should be just under 8mm.

At the far end of the intermediate supporting wall, 2 of the joists are almost 10 mm higher than they are at the other end where seated in the exterior wall. In fact, it's quite a sharp rise and you can see the flex in the floor boards, one of which has started to split.

Temptation is to replace the joists with rot issues and replace the ceiling. But I'm seriously considering getting a structural engineer to take a look first.
A Few Apples Short of a Strudel

Re: Joist Replacement/Notches and Building Regulations
« Reply #12 on: Yesterday at 07:32:23 pm »
Rot and poor installation aside, don’t get too hung up on the regs, they’re constantly evolving. Our upstairs ceiling is nailed to “joists” that are 1/4 of 8” diameter trees, with the bark still on. Deflection of the bedroom floor is such we have a 2” thick length of wood under the foot legs to level it out. It’s been around 180 years. Not ideal admittedly but not likely to fail anytime soon.

You don’t need a structural engineer, a decent builder will sort it if you decide to go that route. 
We are making a New World (Paul Nash, 1918)