Sister joists in bathroom

danrv

Hi
The heavily notched joists in my bathroom have been commented on here before but have just realized that extra ones have been added.
The notches are on the ends and the joist at bottom of pic has a smaller sister one secured to it. 
Then there’s an extra one in between that joins to a ‘T’ piece on the wall.

The middle joist has a split most of the way along this section and the top has buckled over a bit. I’m thinking of reinforcing and straightening this with some 3/4” ply. 
Maybe just on one side as the sink waste pipe would obstruct a drill.
Just wondering if this is all that’s needed.
Any help appreciated.

GDB2222

You can do both sides if you drill right through an use bolts.

 The sister joists are holding up the ceiling, not supporting the floor?

grumbler

Personally, I don't think that they are notched too heavily.  Joists are mostly stressed in the middle, not at the sides.

And I don't think that these extra pieces really 'reinforce' anything.  The strength of a joist is directly proportional to it's cubed height. Even if the height is 1/2, it's just 1/8 added, but it looks rather like 1/3 or 1/4, not 1/2.

That said, yes, good plywood screwed to the sides of the split joist will reinforce it.

danrv

grumbler said:

Personally, I don't think that they are notched too heavily.  Joists are mostly stressed in the middle, not at the sides.

And I don't think that these extra pieces really 'reinforce' anything.  The strength of a joist is directly proportional to it's cubed height. Even if the height is 1/2, it's just 1/8 added, but it looks rather like 1/3 or 1/4, not 1/2.

That said, yes, good plywood screwed to the sides of the split joist will reinforce it.

Thanks.
Extra joist is just under 1/2 height.
Largest cutout is 65-70mm out of 195mm height.

danrv

GDB2222 said:

You can do both sides if you drill right through an use bolts.

 The sister joists are holding up the ceiling, not supporting the floor?

Good idea to bolt through 👍
They could be for the ceiling. There’s only these two though.

grumbler

danrv said:

grumbler said:

Personally, I don't think that they are notched too heavily.  Joists are mostly stressed in the middle, not at the sides.

And I don't think that these extra pieces really 'reinforce' anything.  The strength of a joist is directly proportional to it's cubed height. Even if the height is 1/2, it's just 1/8 added, but it looks rather like 1/3 or 1/4, not 1/2.

That said, yes, good plywood screwed to the sides of the split joist will reinforce it.

Largest cutout is 65-70mm out of 195mm height.

As I said,  it's the position of a cutout that matters as well, not just the size. However, to make things simpler, rules usually stipulate the same max cutout for any position - based on the max cutout in the middle.

From the top of my head it's 1/3 for rafters. I guess, it's the same for joists.

grumbler

GDB2222 said:

You can do both sides if you drill right through an use bolts.

You can do both sides with screws. IMO, bolts is overkill for plywood.

FreeBear

grumbler said:

danrv said:

grumbler said:

Personally, I don't think that they are notched too heavily.  Joists are mostly stressed in the middle, not at the sides.

And I don't think that these extra pieces really 'reinforce' anything.  The strength of a joist is directly proportional to it's cubed height. Even if the height is 1/2, it's just 1/8 added, but it looks rather like 1/3 or 1/4, not 1/2.

That said, yes, good plywood screwed to the sides of the split joist will reinforce it.

Largest cutout is 65-70mm out of 195mm height.

As I said,  it's the position of a cutout that matters as well, not just the size. However, to make things simpler, rules usually stipulate the same max cutout for any position - based on the max cutout in the middle.

From the top of my head it's 1/3 for rafters. I guess, it's the same for joists.

Quite a bit less than a third for joists, and you should never be notching in the middle of a span. From - https://nhbc-standards.co.uk/6-superstructure-excluding-roofs/6-4-timber-and-concrete-upper-floors/6-4-18-notching-and-drilling/ So for a 195mm deep joist, maximum recommended notch depth is ~30mm.

Another source - https://www.labc.co.uk/news/how-get-it-right-notches-holes-solid-timber-joists says ~25mm..

Just to add - If I were to strengthen the OP's joists, I'd use lengths of odd-leg angle (100x50x6 min) and use coach screws or even bolts. One length either side of each joist, and there would be minimal chance of it failing.

danrv

FreeBear said:

grumbler said:

danrv said:

grumbler said:

Personally, I don't think that they are notched too heavily.  Joists are mostly stressed in the middle, not at the sides.

And I don't think that these extra pieces really 'reinforce' anything.  The strength of a joist is directly proportional to it's cubed height. Even if the height is 1/2, it's just 1/8 added, but it looks rather like 1/3 or 1/4, not 1/2.

That said, yes, good plywood screwed to the sides of the split joist will reinforce it.

Largest cutout is 65-70mm out of 195mm height.

As I said,  it's the position of a cutout that matters as well, not just the size. However, to make things simpler, rules usually stipulate the same max cutout for any position - based on the max cutout in the middle.

From the top of my head it's 1/3 for rafters. I guess, it's the same for joists.

I'd use lengths of odd-leg angle (100x50x6 min) 

Haven’t heard of that. Presume it’s a steel bracket.

FreeBear

danrv said:

FreeBear said:

grumbler said:

danrv said:

grumbler said:

Personally, I don't think that they are notched too heavily.  Joists are mostly stressed in the middle, not at the sides.

And I don't think that these extra pieces really 'reinforce' anything.  The strength of a joist is directly proportional to it's cubed height. Even if the height is 1/2, it's just 1/8 added, but it looks rather like 1/3 or 1/4, not 1/2.

That said, yes, good plywood screwed to the sides of the split joist will reinforce it.

Largest cutout is 65-70mm out of 195mm height.

As I said,  it's the position of a cutout that matters as well, not just the size. However, to make things simpler, rules usually stipulate the same max cutout for any position - based on the max cutout in the middle.

From the top of my head it's 1/3 for rafters. I guess, it's the same for joists.

I'd use lengths of odd-leg angle (100x50x6 min) 

Haven’t heard of that. Presume it’s a steel bracket.

A selection available here (picked at random) - https://www.parkersteel.co.uk/Matrix/8/Unequal-Angles

danrv

FreeBear said:

danrv said:

FreeBear said:

grumbler said:

danrv said:

grumbler said:

Personally, I don't think that they are notched too heavily.  Joists are mostly stressed in the middle, not at the sides.

And I don't think that these extra pieces really 'reinforce' anything.  The strength of a joist is directly proportional to it's cubed height. Even if the height is 1/2, it's just 1/8 added, but it looks rather like 1/3 or 1/4, not 1/2.

That said, yes, good plywood screwed to the sides of the split joist will reinforce it.

Largest cutout is 65-70mm out of 195mm height.

As I said,  it's the position of a cutout that matters as well, not just the size. However, to make things simpler, rules usually stipulate the same max cutout for any position - based on the max cutout in the middle.

From the top of my head it's 1/3 for rafters. I guess, it's the same for joists.

I'd use lengths of odd-leg angle (100x50x6 min) 

Haven’t heard of that. Presume it’s a steel bracket.

A selection available here (picked at random) - https://www.parkersteel.co.uk/Matrix/8/Unequal-Angles

Thanks.
Angle for strength I assume rather than shape for fitting.