Herringbone Strap 400 mm or noggins, for mid span on flat roof decking?
Herringbone Strap 400mm ?
- Thread starter ANGLER
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Noggins will be fine
unless you really want to go herringbone
unless you really want to go herringbone
herringbone would save a lot of time and hassle, only if this is a correct suitable method.
Sorry I missunderstood I thought you were talking herringbone noggins rather than standard noggins
I see you actually ment strapping
Use noggins as they will give better support and stop twisting
I see you actually ment strapping
Use noggins as they will give better support and stop twisting
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Herringbone strutting is better for stopping joists twisting than solid blocking, though it is of course more difficult to fix.
But why bother with any strutting if it's a roof?
But why bother with any strutting if it's a roof?
In my experience you are correct but only if used on I beams
Otherwise Simple noggins are better
@Roger;
With respect, one humbly begs to differ. For an explanation, may one draw your attention to the attached sketch?
Assume we have 7x2 floor joists at 16" centres, with 2x2 strutting nailed tightly between. Over time, the joists will inevitably shrink as the moisture content falls. They will shrink more in the vertical dimension than in the width, as shown by the broken line.
This vertical shrinkage will tend to reduce slightly the angle 'a' between the strut and the horizontal. However, the distance between the centres of the joists - 'x' - remains the same.
This means that the angled strut is being forced into a slightly smaller space. Obviously this will put pressure on the side of the joist, both at the tops and the bottoms. It is this compressive force which tightens up all the joists and enhances their load-sharing capacity.
To achieve the full potential of the strutting, the angled pieces have to be cut accurately to fit flush with the face of the joists.
Conversely, with solid strutting, the joists shrink away slightly from the cut ends of the blocking, meaning that any restraint is only provided by the nails.
With respect, one humbly begs to differ. For an explanation, may one draw your attention to the attached sketch?
Assume we have 7x2 floor joists at 16" centres, with 2x2 strutting nailed tightly between. Over time, the joists will inevitably shrink as the moisture content falls. They will shrink more in the vertical dimension than in the width, as shown by the broken line.
This vertical shrinkage will tend to reduce slightly the angle 'a' between the strut and the horizontal. However, the distance between the centres of the joists - 'x' - remains the same.
This means that the angled strut is being forced into a slightly smaller space. Obviously this will put pressure on the side of the joist, both at the tops and the bottoms. It is this compressive force which tightens up all the joists and enhances their load-sharing capacity.
To achieve the full potential of the strutting, the angled pieces have to be cut accurately to fit flush with the face of the joists.
Conversely, with solid strutting, the joists shrink away slightly from the cut ends of the blocking, meaning that any restraint is only provided by the nails.
LOL
My experience from using the the stuff differs from what you are saying
Theary is all well and good but if it was as good as they try to make it out to be then it would be made common practise to use it rather than noggins.
My experience from using the the stuff differs from what you are saying
Theary is all well and good but if it was as good as they try to make it out to be then it would be made common practise to use it rather than noggins.
Nowadays it's quicker and cheaper to use offcuts as blocking pieces, that's why - just not as effective. The tin things from builder's merchants are not much better.
I would think the reason that herringbone strutting is not common practice these days is that it is far more time consuming to cut and fit timber herringbone strutting than steel struts or noggins.
Timber struts have to be cut perfectly to do the job correctly, and this means the builder / chippy either has to cut each individually to the correct size, or ensure that the joist spacing is exactly the same every time.
If the cut size of the strut isn't quite right then the ends wont fit flush against the side of the joist so there will still be a risk of twisting.
Noggins are not a requirement for I-beams or any engineered joist. Nor is any form of herringbone strutting.
That's from my experience as a I-beam/open web joist & Roof designer.
Well aware of that LOL and in general i agree but you still use noggins with open web joists.... Hell if you look at the Alpine open web manual it states it in there and even has Pictures
(here is a link if you cant be bothered to look http://www.nrtl.co.uk/assets/nrtl_1.pdf)
Several years ago a lot of building control officials and Architects insisted that the Herringbone was used on I beams since then open web has been developed much further and is my preferred method on a new build
And lets not forget about all the times noggins have to be used to catch plaster boards etc etc
Back to the OP
Simple noggins is as good as anything else LOL
Well aware of that LOL and in general i agree but you still use noggins with open web joists.... Hell if you look at the Alpine open web manual it states it in there and even has Pictures
(here is a link if you cant be bothered to look http://www.nrtl.co.uk/assets/nrtl_1.pdf)
Several years ago a lot of building control officials and Architects insisted that the Herringbone was used on I beams since then open web has been developed much further and is my preferred method on a new build
And lets not forget about all the times noggins have to be used to catch plaster boards etc etc
Back to the OP
Simple noggins is as good as anything else LOL
That link isnt working for me.
Surprisingly though I am quite familiar with ITW's spacejoists. The only details in their technical guides are for perimeter/partition details.
They are noggins, although not for stopping the twist.
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