What is this joist doing?

[Dereekoo]

Thank you all for your comments, they've been helpful! I'm going to get rid of it, add some noggins to actually reduce bounce, and eventually replace the kitchen units, placing them in such a way as to eliminate that silly gap.

Noggins to reduce bounce, how does that work?

 

[noseall]

Noggins to reduce bounce, how does that work?

Solid, midspan bridging, reduces bounce (deflection).

(edited for clarity)

 

[robinbanks]

The fact it has a bearing in the walls on either end also made me hesitate.

How big of a bearing?

What size is it, compared to the joists?

Noggins to reduce bounce, how does that work?

By transferring part of point loads above one joist to its neighbours more effectively than the floorboarding can. Needs something that runs from the bottom of any given joist to the tops of its neighbours, either a full fill rectangle or some kind of X arrangement

we tested the theory by stomping about in the bathroom above - and there was indeed quite a lot of bounce in the joists

Can you add some numbers to this? The size of your joists, their spacing, the weight of the person stomping about, what stomping entailed (full on jumping with both feet? How high?) and the amount of midspan deflection you observed during the process?

 

[Koolpc]

If it were me, i would get a Structural Engineer to look at it just to be on the safe side...

 

[Dereekoo]

Solid, midspan bridging, reduces bounce.

How

 

[Munroast]

Noggins to reduce bounce, how does that work?

if they are in tight they will spread the load across the florr and it will feel more solid, not as good as a separate larger joist underneath the middle bit - but good tight noggins make a better more solid floor

 

[noseall]

How

Preventing torsion movement and locking them together thus improving load distribution.

 

[Dereekoo]

if they are in tight they will spread the load across the florr and it will feel more solid, not as good as a separate larger joist underneath the middle bit - but good tight noggins make a better more solid floor

 

[Dereekoo]

Preventing torsion movement and locking them together thus improving load distribution.

if they are in tight they will spread the load across the florr and it will feel more solid, not as good as a separate larger joist underneath the middle bit - but good tight noggins make a better more solid floor

Interesting, what spacing of the rows of struts do you suggest to accomplish this phenomenon

 

[noseall]

Interesting, what spacing of the rows of struts do you suggest

Midspan on shorter floor joist lengths up to 1/3rd spans on longer.
It's not best kept secret.

 

[Dereekoo]

Midspan on shorter floor joist lengths up to 1/3rd spans on longer.
It's not best kept secret.

It certainly isn't a secret but don't know what your definition of short and long lengths are, TRADA gives struts (not noggins) at mid span for 2.5 - 4.5 m. I thought from your post that you were advocating struts or noggins at lesser centres to give give credence to your theory of transferring loads between joists which is what the floorboards do. Taking a 4.5m span, there would be 1 row of struts in the centre which would not do very much, if anything, re load transference and the subsequent eradication of bounce but as you rightly say they stop joists twisting which in the worst case would reduce a 6 x 2 to a 2x6 resulting in greater deflection (not likely in practice but it gives the gist) So right size joist and correct strutting to TRADA spec should suffice to prevent bounce and extra struts not required? Would be interesting to know what the OP joists size/span are which may reveal the cause of the bounce.

 

[Munroast]

the more you put in the more solid the floor would feel

if I was doing a 4m span in my own house I would put 2 in (1.33m apart) in someone elses house I would just do one in the muddle

same with stud walls, noggins make them feel much stronger and sold - they spread the load and stop warping

 

[Ivor Windybottom]

It certainly isn't a secret but don't know what your definition of short and long lengths are, TRADA gives struts (not noggins) at mid span for 2.5 - 4.5 m. I thought from your post that you were advocating struts or noggins at lesser centres to give give credence to your theory of transferring loads between joists which is what the floorboards do. Taking a 4.5m span, there would be 1 row of struts in the centre which would not do very much, if anything, re load transference and the subsequent eradication of bounce but as you rightly say they stop joists twisting which in the worst case would reduce a 6 x 2 to a 2x6 resulting in greater deflection (not likely in practice but it gives the gist) So right size joist and correct strutting to TRADA spec should suffice to prevent bounce and extra struts not required? Would be interesting to know what the OP joists size/span are which may reveal the cause of the bounce.

Jesus, I bet you're the life and soul of the party.

Put down the textbook, get out of your chair and do some proper work, find things out in the real world.

Obviously putting more structure into anything makes it more rigid.

 

[Ivor Windybottom]

If it were me, i would get a Structural Engineer to look at it just to be on the safe side...

No need, just stick a drill into the wall diagonally at its end. I'm betting there's no wood behind the surface of the plaster, in which case it's definitely not supporting anything, as it isn't supported itself and is just dangling from the ceiling.

If it is actually sitting on the bricks behind the plaster then things are different. But I'm thinking that's very unlikely, so not worth thinking about unless that unlikely scenario actually is the case.

 

[Koolpc]

Dont take any chances...