Thread: Tying down roof trusses/joists
11th Mar 2006, 12:59 PM #1
Tying down roof trusses/joists
OK in the hope that someone can help me so I can get some work done this weekend (people that manufactured the trusses are not open on the weekend). I had a quick question in relation to what to use to tie down the roof trusses and intermediate ceiling joists to the top plate. I have been given both cyclone ties and some strapping that goes over the truss/joist and under the top plate etc. (multigrip???) so what exactly should I use to tie the truss/joist to the top plate? The way I understand it either could be used to do the job. To add to the confusion I have some binders there but they don’t get used on external walls, or do they? The guide I have doesn’t really explain it well and what it does show is fixing for jack/creeper trusses where as all I have is the jack/creeper rafters so??
Anyway thanks in advance
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11th Mar 2006, 01:44 PM #2
What is usually used in Canberra is triple grips on the external wall plates and truss brackets on the internal walls. You're likely in a higher wind category up there so the requirements may be different to here.
Have a look at Pryda's guide, it may help out.
11th Mar 2006, 01:49 PM #3
we used to use a device called a triple grip which was nailed to the joist and top plate with 2 " gal clouts. I have also used plain old hoop iron. Thi idea is to strengthen against wind gusts. You know the type i mean.
You can see siomilar here on the right:
Most hardware shops will have them. but it sounds like you might already have what you need.
good luckray c
dunno what's more fun, buyin' the tools or usin' em'
11th Mar 2006, 02:58 PM #4
Well thats wierd. The Truss guide (which is Multinail) lists a cyclone tie what the Pryda site lists as a multigrip, and the multigrip in the truss guide (which is shaped strapping) is listed as a cyclpne strap on the Pryda site.
Maybe I will go cyclone straps (as per the Pryda site) on the trusses and the multigrips (as per the Pryda site) on the intermediate joists.
11th Mar 2006, 03:08 PM #5
LOL...buggers don't make it easy eh
by "intermediate joists" do you mean the trusses bottom chord ?
if you do you usually use truss brackets (pryda hitch) on the internal walls, don't use triple grips.
11th Mar 2006, 05:03 PM #6
Yeah could have been easier but as the +1 said if I had done yesterday what I did today, instead of having a late start , then I could have called the truss crew and asked.
Truss's are at 900 centers so the intermediate joists are just straight timber spanning from from one top plate to the other between 2 trusses. I am actually not going to worry about the internal walls for ages so they aren't a problem.
12th Mar 2006, 10:42 AM #7
can you post a pic of your trusses / roof framing when you get them up, be interested in seeing exactly what the layout is.
12th Mar 2006, 09:29 PM #8
Judging by some of the questions you have been asking you may find it useful to get a copy of the australian standard for timber framing - AS 1684.
Tie down, bracing, spans, and joint type etc can vary considerably from area to area depending on wind loading etc. The answers you get on this site may only be relevent to the location of member who posted the answer.
12th Mar 2006, 09:51 PM #9
Spent Sat mostly doing something else so today put up the hip section (excluding hanging beams) so here are a couple of low res pics (whats with the 100K limit?). Will look at doing the other trusses and intermediate joists tomorrow.
Have AS1684 julianx along with other material and it is a great help but sometimes I get hung up on details that the reference stuff isn't clear about. Like this thread, the truss folks gave me cyclyone straps and multigrips which both would do the same job in relation to tying down the intermediate joists and trusses but which to use where (numbers supplied of each didn't help clear things up either)?
Guess I will find out tomorrow if I made the right choice
Heaps of info and helpful people on the site which is great so thanks.
13th Mar 2006, 05:37 PM #10
ah ok, now I see what you're doing there.
was wondering why you were talking about ceiling joists on a trussed roof but I see you've got a mix of old and new happening there.
those door/window openings are certainly well supported too
14th Mar 2006, 08:52 AM #11
Check the truss layout and also the fixings summary, cyclone straps are usually only for the larger trusses and the girder trusses, the other will only usually require one multigrip. You should use hoop iron to tie down your plates to your studs. Also triple grip the top chord of your creeper and hip truss to the girder.
hope this helps. otherwise call the truss mob.
14th Mar 2006, 09:18 AM #12
I think what you are referring to as 'intermediate ceiling joists' are what I would call hanging beams. They're there to hold up the ceiling. I'm pretty sure that they don't need any tie-down, just skew nailing. Anyway, a triple grip at each end wont hurt. We used cyclone straps on all of our trusses because it gets a bit windy where we are building. Triple grips would have been enough to satisfy local regs though.
Hope you're going to put lintels over the openings in the back wall. I think I would have preferred to have a ribbon plate on that wall too."I don't practice what I preach because I'm not the kind of person I'm preaching to."
14th Mar 2006, 11:34 AM #13
Rang the truss crew yesterday and would you beleive it the engineering report included with the trusses included the tie down detal....DOH!!!! (it was hard to spot but......)
Cyclone straps for the hip rafters only and the saddle/valley rafters and aside from 1 truss 1 grip each side and nothing about the intermediate joists (so I assume nominal fixing - skew nail is OK). Guess I have overdone it a bit but that can't be a bad thing yeah..
silentC - The main opening in the back wall isn't framed up yet because I had it as a window on the plans but I might put french doors there (provided the certifier gets back to me that the change isn't going to be a hassle) so when I no for sure I will frame it properly with lintel etc. What did you mean by ribbon plate?
Thanks agin for all your help and included a couple of pics with all the trusses/joists up.
14th Mar 2006, 11:42 AM #14
The ribbon plate is the extra bit of 4x2 on the top plate. You've got it under the trusses. I suppose structurally you only need it if the trusses or rafters are going to fall more than 100mm (or whatever the actual limit is, can't recall) either side of a stud. However, it also gives you fixing at the top of the wall for your plaster. By the time you put up ceiling battens and hang the plaster, there's not much top plate left to take the top of the wall sheets. Saves having to put in noggings. We just cut all the wall frames the same height and then run a 50mm ribbon plate around all external walls.
The doorway on the right will need a lintel too - but you already knew that"I don't practice what I preach because I'm not the kind of person I'm preaching to."
29th Oct 2007, 03:31 PM #15
The intermediate joists should be nominal if the design was for the trusses only otherwise they should probably be triple grips also.
Just another tip the Multigrips and Triple Grips are interchangeable if installed correctly.
And the ribbon plate is the upper top plate. Depending on the frame company they will probably have a lower top plate that makes the frame non load bearing then the ribbon plate is added on site to make it load bearing. You must ensure that the two top plates are tied together well enough to transfer wind loads.
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