View Full Version : rafter/ joist hanger alternatives when flush mounting to beam?
11th Apr 2011, 06:58 PM
I hope this is not a stupid question .
I have finally start building my skillion roof alfresco which will have the rafters flush mounted to the side of the beam .But i do not want to use rafter/joist hangers to mount the rafters to the beam as i will be placing the ceiling directly onto the underside of the rafters and using hangers will mean a lot of extra work cutting and trimming each rafter . I have looked through the Pryda website and i'm still unsure of the alternatives .Could somebody tell me ,as i do not just want to skew nail the rafters to the beam .The rafters and beam are both LVL's if that makes any differences .
Any help would be greatly appreciated
12th Apr 2011, 09:45 AM
In years gone bye before the invent if metal hangers (gee I am showing my age) we used to trench the bearer plate on each side at the spacing of the rafter/ceiling joist. The trench would be 15mm deep at the top of the bearer plate and 5mm at the bottom edge creating a angled trench. The rafter/ceiling joist end cuts would then be cut at the angle of the trench. Slip the rafters in from the top and they should lock into position, subject to the trench being accurately cut to the size of the rafter/ceiling joist. Scew nailing can then be used to finish the job
12th Apr 2011, 11:33 AM
Thanks for the reply . interesting way of doing it and something to remember for in the future ,but with 15 rafters at 450 centres this would be even more work and i think the span length of the beam would be effected by all the tenching on it . I just had a closer look at the pryda website and they do have split joist hanger or mini grips which might do the job but i could not find any information on them just a picture .
Thank again for trying to help .They really made things well in the old days ,i love seeing furniture with dove tail joins .
13th Apr 2011, 09:29 AM
...using hangers will mean a lot of extra work cutting and trimming each rafter ....
Not sure you will avoid cutting and trimming rafters in any solution to this. Regardless of how you do it, your rafters should present a full end face to the beam, and joist hangers are the way to go IMHO. Pryda has adjustable hangers for fall and rake, but still, doesn't avoid any cutting
13th Apr 2011, 09:51 AM
Why dont you just use the joist hangers and batten the ceiling out? A few bucks a metre and job done...
13th Apr 2011, 10:00 AM
8421584216All I can say mate is be extremely careful. The method that hoppy suggested is sound and was all the go in years gone by. But, you must combine the trenching with some serious batten screw action through the beam and into the rafter. They must be skewed in so you dont only get end grain of the rafter. Nails are not good enough. The method that hoppy described was responsible for the fatal deck collapse in Brisbane a few years ago. The floor joists fell out of the trench and as they rotated down they pushed the bearer further out and cause them them fall out 1 by 1. Even though yours is a roof, deflection of the bearer could result in the same situation. You could just use standards hangers and run a strip of 20 mm timber on the underside of the rafters. In the scope of things it wont add much to the cost, will add nothing to the time and will give a safe, strong solution. Or batten across the rafters. You would probably want to do something like that anyway so you are not putting multiple nails / screws into the laminates of the LVL.
I just went and had a look at my car port, which is all LVL - excactly as you want. I plumb cut the rafters and then put a seat cut on them so the hanger sits properly. This will work perfectly for you.
13th Apr 2011, 12:04 PM
If jags wants to avoid the seat cuts for the hangers, the adjustable Pryda hangers will suit, but I haven't seen them in stores - probably a special order item.
As suggested, ceiling battens are a solution, and also pretty much halves the amount of rafters required.
13th Apr 2011, 01:30 PM
Agree, battens would be my choice, but if he has already purchased the LVL's the timber yard may not take them back.
14th Apr 2011, 09:37 PM
Half housing the rafters into the beam could be done if the beam was of a thickness which took into account the housings, fasteners could be skewed battens screws of apropriate length & position.
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