Joist Hangers both ends of rafters for pergola

[steve&da'boys]

Hi,
I am building a 9mx4.8m pergola. 9m length along the double brick house will have a 190x45 beam attached and will support 4.8m 190x35 (standard treated pine from bunnings) rafters using joist hangers (spacing approx 1050mm).

At the other end I will have 4 90x90 posts (3m spacing) again with a 190x45 beam. As it is along the fence line (and I want to put up fibre cement cladding on the vertical to screen the fence) I was considering using joist hangers at the other end instead of hanging them over the beam (cantilever??) - that would stick into the neighbours yard.

I have looked over the net and I could not locate much info on this. The bunnings/softwoods people seem to think it would be ok however I am not confident with their responses.

Has anyone used joist hangers both ends - if so have you had any problems?

If the common consensus is that hangers at both ends are not good, what cantilever (I hope this is the correct terminology) length should I use?

Thanks.

[derekh]

I used joist hangers at both ends that also allowed me to hang my gutter off the end beam. My pergola was 9m * 3.6m and I used 900mm spacing between the rafters. I used a 90 * 45 ledger bolted to noggins behind the facia, a 190 * 45 end beam and 145 * 45 rafters.

hth
Derek

[DvdHntr]

You have confused me. So the joists aren't going to continue past the beam near the neighbours?

[steve&da'boys]

Thats correct. I am planning 4 poles along the neighbouring fence line. I will attach a beam to these poles. I will then place joist ('rafter') hangers on the inside of the beam the same as I will at the other end of the rafter where it meets the house wall beam. The rafter will then sit inside the hanger (ie not sitting on top of the beam as they generally seem to do). That any clearer? haha prob not. cheers.

[derekh]

Steve, as I indicated earlier my pergola is the same design and it worked and looks a treat. I housed out the rafters to take the battens so the colourbond sheeting sits flat on the rafters and battens. I also used 25mm strapping across each diagonal for strength.

The only thing I should of done was to cut the end of the rafters at an equivalent angle to the slope so the rafter end butted up against the beam without leaving a gap at the bottom. If required, give me a day or two and I could post a photo.

derek

[steve&da'boys]

If you could get a photo up that would be great as I have been struggling to find anything the same as what I am imagining in my head! either posted or to [email protected]. Thanks again.

[derekh]

Here are the plans submitted to council.

[derekh]

Some variations between the design and the actual build:

1. The posts are all on the same side of a rafter so they were evenly spaced.
2. This allowed the adjoining rafter to be bolted to the post
3. The front beam was joined using a halving joint at a post rather than between posts (looks better and probably stronger).

You will have a fourth post where one end of my pergola front beam actually had to be fixed to a noggin behind the facia. It took ages to ponder over but I was very pleased with my final solution.

[Dirty Doogie]

I think your 190 x 35 x 4800 span rafters are going to sag something horrible even if you dont put roof sheeting on. You need to go to 290 x 35 for that sort of span and spacing.

[steve&da'boys]

Thanks re the span of rafters. It's amazing how many different opinions you get on span, the wood suppliers recommend 190x35 for that span to carry colourbond - I even said I would get 190x45 just to be safe and they said it wasnt needed! Can anyone say whether they have spanned 190x35 over 4.8 with metal sheeting and if so how it is looking these days? I don't mind spending the extra cash but its just knowing who's advice to follow. No point building it if it is going to pull the joist hangers out of the beams from sagging. Thanks.

[Dirty Doogie]

If you have already bought the wood, clamp each end to a sawhorse or just few blocks 4.8 metres apart, so the timber stands like it will when fixed. Run a stringline along the top and leave it there a few days.

I would expect the center of the timber to sag very quickly.

[DvdHntr]

Thats correct. I am planning 4 poles along the neighbouring fence line. I will attach a beam to these poles. I will then place joist ('rafter') hangers on the inside of the beam the same as I will at the other end of the rafter where it meets the house wall beam. The rafter will then sit inside the hanger (ie not sitting on top of the beam as they generally seem to do). That any clearer? haha prob not. cheers.

That is exactly how you are supposed to use joist hangers. I will not comment any further on the size of the rafters except to say that you should check them out and verify they are large enough.

[Bloss]

If you do a search and look for span tables you will see that you are light over 4.8m.

If you notch in the battens as the drawings indicate on derekh's plans then you reduce the effective depth of the rafter to the amount remaining under the notch - and the overall depth of the rafter has to be increased to counter that (or house the battens or use triple grips or mini hangers to have them un-notched, but remain flush.