herringbone straps instead of noggins

[Chris Styles]

I'm about to put floor joists in my loft so I can board it for storage. These herringbone straps look like a pretty convenient way of avoiding timber noggins.

Question is, how many should I use on a 4.2m span?

One either end and one in the middle? One every 900mm ?

Any sugegstions welcome.

Cheers Chris

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[Christian McArdle]

According to BM Trada, that is acceptable, although it says this is a minimum requirement and recommends you have more if possible.

Above 4.5m span, you should have 2 intermediate struts, so you are getting into marginal territory for 1 intermediate with your 4.2m span.

[The Natural Philosopher]

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These really do stiffen up a floor/ceiling..better than noggins IMHO.

cut lots on a circular or handsaw and whack em in everywhere. The more the better.

The great advantage is they can be a little bit inaccurate unlike noggins, which really need to be mm perfect to work.

[dom]

I had assumed soild noggins were the better choice? Aren't noggins convenient to position the joints between plasterboard sheets under?

[<me9]

Any suggestions as to fit herringbone strutting to an existing ceiling? Our upstairs floor is about 4.3m span, and has no strutting (national builder of the 70s with green hekicopter), and is springy enough to creak when walked on. Will the 'no more nails' type adhesives do an adequate job, as it is impossible to nail without removing the ceiling.

[Staffbull]

?_dyncharset=UTF-8&howMany=15&searchText=herringOn mine (same span) I had one run of them down the middle, this was fine for BCO, :-) 22mm chip floor on the top and all is well :-)

[Chris Styles]

?_dyncharset=UTF-8&howMany=15&searchText=herring> These really do stiffen up a floor/ceiling..better than noggins IMHO.

I thought they'd be fitted by nailing the flat ends to the tops of adjacent joists so that the strap is 90 degrees to the direction of the joist, i.e. to replace a noggin... in which case why the circular/hand saw?

Have I totally missed how these are fitted?

Cheers, Chris

[Christian McArdle]

I presume he means wooden herringbone strutting. This a couple of advantages over the metal sort. Firstly, it is cheaper. You just cut up battenning for it. Secondly, you can attach to the face of the joist, rather than the top and bottom, which might not be accessible in a retofit context.

Christian.

[dom]

They're there to prevent racking, so bottom edge of one face of one joist connected to the top the next face of the next joist - and vice versa - giving a diagonal/herringbone pattern.

No point in connecting tops to tops or bottoms to bottoms as the floorboards and plasterboards do that already

I'm less clear on which is superior, herringbone struts or noggins, and why - in these days of mitre saws, cutting solid noggins to an exact fit is no hassle.

[Christian McArdle]

Herringbone is superior in every respect:

1. Lighter (less dead load)
2. Cheaper (less wood)
3. Easier to install (less cutting, less precision required)
4. Easier to run cables/pipework.
5. Less susceptible to expansion/contraction.

Christian.

[adder1969]

I want to remove a wall under some joists and it'll mean the span will go up to 4.5m. The joists are 2*7.5 (or 47mm*190mm) and I cant find any table to tell me if this is acceptable. For 400mm spacing this is just over th elimit but on mine the gap to the first joist is 400mm then there are two close together like 150mm then another 400mm. Would strutting these joists make them comply do you think?

[Chris Styles]

Thanks for ther TRADA link, it makes good reading.

are a few constraint in what I am doing :

1) I dont have access to the underside of the joists, beacause I have a ceiling there already, which rules out the metal straps 2) The new joists are going on on 400mm centres between the 600mm centred trusses, which means 2 out of three of the gaps will have a 3) The regs say that noggins need to be 3/4 of the depth of the joist

I am fitting 9" joists, which means i'd need 6.75" noggins. However, a 6" noggin would almost be resting on the tops of the truss joists, which means I cant use to-the-spec noggins, and the metal straps are basically out of the question...

Now, given that I dont plan to live in my loft i'm only flooring for storage, and that i'm not after BCO approval, and by the sound of it some people in older houses have hardly any strutting anyway, can anyone venture a guess at what I would safely get away with, regardless of BCO regs etc? For instance, if I used 100mm noggins and 22mm T7G floorboards, would that be good enough to use occassionally and store, even though it wouldnt meet the regs?

Cheers Chris

[Christian McArdle]

You need to strut them anyway, at each end and each third distance intermediate.

Replacing the floorboards with plywood and gluing and screwing it down will comply in spades, but is impractical for future maintenance. Seek advice from your BCO.

Christian.

[Chris Styles]

I used this as a guide...

sure if houses in Worthing are particularly safe or dangerous, but it seemed likea good guide

It is also consisent with my builder friends rule of where you halve the span (in feet) add 2, and that is the depth of the rquired joist in inches (for a 2" wide joist)

[Christian McArdle]

Just use wooden herringbone, as discussed elsewhere. Cut up battenning material for it, particularly easy if you have a compound mitre saw. The

6.75" requirement is just the distance between the top and bottom mounting, as it were, it doesn't all have to be wood.

It is much easier to fit than noggings, as any slight error in length is accommodated by adjusting the angle of fitment.

Christian.

[adder1969]

Where is the strutting requirement? I've looked in document A and couldn't see anything in there about it. Is it all up to BCO's discretion or are there actual guidance documents out there somewhere?

[Chris Styles]

of page #4

For domesic floors > 4.5m span, 2 struts at 1/3 spacing...

[Chris Styles]

Ahh... okay, that makes sense

But the length, andgle and distance between the joists are all related, so if I cut slightly too long, the angle will no longer be correct for the

400mm...spacing. Fitting it at an arbitrary angle will mean the strut wont butt nicely onto the joist. It probably doesnt matter, just seems like shoddyness...

[Christian McArdle]

Obviously you should try your best to be accurate. However, 2mm won't make the slightest difference with herringbone. With a nogging, 2mm inaccuracy is as wide as an ocean.

Christian.

[Weatherlawyer]

The herringboning is to stop the joists twisting, as long spans will tend to do so. Noggings are generally applied to stiffen floors and support overlapping boards. They are used in walls to support radiators/shelves etc and if filling the full width of the stud have the same effect as herringboned strut or strapping.

Since the studwork in walls is generally the same material as the noggings, they also stop the studs moving sideways. I can't for the life of me understand how steel studding manages to stay up without it's equivalent.