Floor bracing

[Hello123]

Hi guys, I’m doing some renovation work at moment on my bathroom, and have noticed the joists in the bedroom next to it have no bracing/noggins! The joists are 150x50 3m span and are laying along side the old 4x2 joists which are holding up the ceiling below, the Two different size joist are not fixed together they are independent, I realise noggins couldn’t be used to the full depth of the 150 joist but wondering if a smaller bracing should have been used just above the 4x2, linking the 150s together, this floor was put in by a builder a year ago, should I be worried??

 

[Deleted member 174758]

Independent joists for ceilings and floors were sometimes installed deliberately to help minimise sound transmission between the upper set of joists and the lower ones. You sometimes find this in multiple occupancy buildings (tenaments, flats, etc), nursery room floors, schools, offices etc. If your floor above isn't bouncy you don't need to do anything, so I'd consider the consequences before proceeding

 

[Hello123]

Thanks JAK, I understand totally about the sound transmission situation, I’m now wondering if BC should have picked this up when being built? Or is it acceptable to lay 3m span without any kind of bracing?

 

[Deleted member 174758]

Just how old is the building, and how long ago was this work done? AFAIK Building Control was only really regulated nationally after WWII, when national building and planning standards were enacted. Before that every council had their own rules. But consider this - for a 3m or 10ft span with 150 x 50 (6 × 2in) joists on 16in (c.400mm) centres is more than adequate (go and look it up in the NHBC Standards site - section 6.4.8 joist span tables, I believe). Strutting ( horizontally at the mid point, between joists) is generally only added into floors with a span of over 4 metres. Your BCO (if one existed) would therefore have seen nothing wrong with that. So the builder didn't get it wrong

So I shall reiterate what I said earlier - that the work isn't necessary and that it will potentially increase sound transmission between upstairs to downstairs

 

[Dereekoo]

Strutting recommended at centre for spans between 2.4 to 4m, not obligatory. Not an issue as since there is a 4 x 2 next to joists stopping them moving

 

[Deleted member 174758]

Despite that @Derekoo, solid or herringbone strutting seems rarely to be specified in domestic builds (with presumably average expected loadings) that I've seen and which have sub-4 metre spans. On the other hand some of the commercial floors I've been involved with look like egg boxes before we sheet them off, and feel totally dead, lacking any bounce whatsoever

 

[gemshan1]

Just how old is the building, and how long ago was this work done? AFAIK Building Control was only really regulated nationally after WWII, when national building and planning standards were enacted. Before that every council had their own rules. But consider this - for a 3m or 10ft span with 150 x 50 (6 × 2in) joists on 16in (c.400mm) centres is more than adequate (go and look it up in the NHBC Standards site - section 6.4.8 joist span tables, I believe). Strutting ( horizontally at the mid point, between joists) is generally only added into floors with a span of over 4 metres. Your BCO (if one existed) would therefore have seen nothing wrong with that. So the builder didn't get it wrong

So I shall reiterate what I said earlier - that the work isn't necessary and that it will potentially increase sound transmission between upstairs to downstairs

The building is 1960s, work was done a year ago.

 

[Deleted member 174758]

The building is 1960s, work was done a year ago.

In that case I'd suspect the underlying reason might just be lack of availability of suitable materials (COVID created huge issues for the timber trades) despite the increased labour costs incurred. And the BCO would possibly have seen it, too.