How to build pergola ceiling joist and rafters?

https://www.workshop.bunnings.com.au/discussion/comment/43814#Comment_43814

Thanks for your prompt reply Eric.

I want to know if 3500mm span for the ceiling/rafter joist is safe to use 140mmx45mm timber?

Jason

Hi @jasonlee,

For a span of 3500mm you'd need to go for at least 190 x 45mm. However, if you then want to cut it down to achieve that slope, you'd have to step up to 240 x 35/45mm.

Please let me know if you have any questions.

Mitchell

https://www.workshop.bunnings.com.au/discussion/comment/43817#Comment_43817

Hi Mitchell,

In stead of using 240mm beam, can I add another beam on top of all joists in the centre to break 3500mm in half, would that give them more strength ?

https://www.workshop.bunnings.com.au/discussion/comment/84018#Comment_84018

You could certainly add a central support to break up the span to 1750mm @jasonlee. However, since your other dimension is 6000mm, that would have to be a huge support beam to span that distance.

Mitchell

https://www.workshop.bunnings.com.au/discussion/comment/106994#Comment_106994

Can I have 2x3.6m support beam overlap each other around 600mm for the 6m span?

https://www.workshop.bunnings.com.au/discussion/comment/120705#Comment_120705

Would you possibly be able to draw a sketch of what you'd like to achieve, @jasonlee?

Mitchell

https://www.workshop.bunnings.com.au/discussion/comment/120705#Comment_120705

Good Morning @jasonlee

Going throught the posts I am just getting my head around what you want.

So I get you want to shave down one end of the beam so that its level with the ceiling space you are creating.

Having a 5 degree drop is the first part I question, thats not a surface that will help water drain especially if you get dirt and leaves in your area.

Shaving off the the beam will make it weaker. Instead of doubling the height of the beam as I think you are height poor for the space, how about having two beams side by side chamford the way you want them. That way you still get the strength, plus the angle you are after?

Dave

https://www.workshop.bunnings.com.au/discussion/comment/129193#Comment_129193

This is what I’m trying to achieve, support beam and roof joists acting both rafter and ceiling joist.

If I want to separate the roof rafter and ceiling joist which I can, do I need to build a dawrf wall or something at the back so the rafter can fix on to a new walling plate? Because the support beam for the pergola is free standing, there is no structure for me to fix the walling plate onto. That’s why I was trying to use just one beam for two purposes.

Jason

https://www.workshop.bunnings.com.au/discussion/comment/129194#Comment_129194

Hi Dave,

thanks for your input. Can you explain what exactly you mean by having two beams side by side ? I have attached a picture of the structure I’m trying to build. I have no problems in terms of the height, it’s just that the pergola is a free standing one, if I need to raise the height for the rafter to get a pitch what is the best way to frame it on the structure I attached below ?

https://www.workshop.bunnings.com.au/discussion/comment/134580#Comment_134580

As mentioned previously @jasonlee, you can use the same timber to act as the ceiling joist and rafter. However, it needs to be of a suitable calibre to support both the load of the roofing sheets and the internal lining. 140 x 45mm is not of a suitable calibre to span your 3500mm distance, let alone support those loads. As @Dave-1 mentioned, you can have two timbers side-by-side to carry heavier loads but the 140mm is not capable of those spans.

I think what you'll need to two is separate the 6000mm length with a large beam in the middle running the 3500mm direction. From that, you can divide the 3500mm length in two with beams that run perpendicular to it. That way when you use the 140mm timber it only has to span half the 3500mm distance.

Mitchell

https://www.workshop.bunnings.com.au/discussion/comment/138046#Comment_138046

Morning @jasonlee

So next question.

Is this a pre-bought pergola or one you are building from scratch?

If its from scratch, have you drawn up any plans? And do you have a photo of the area you wantto build it in? It may help with a solution to the probelm.

As to the side by side question. I am talking about the rafters across the width of the pergolla you are designing. The ones you wantto champhor down from 140mm to 90mm. I was suggestion that you can bolt/connect two of the lengths together side by side (long flat side to long flat side) to form a stronger beam. Tho after @MitchellMc's suggestion I am starting to think that a 3.6m span may cause some bending even in that.

If you have a plan drawn up we can see what your proposed dimensions are.

Dave

https://www.workshop.bunnings.com.au/discussion/comment/140405#Comment_140405

Hi @Dave-1,

This is a pergola I need to build from scratch.

I don't have a plan for this project but I tried my best to put something together below hope you can understand. There will be some roof extenda brackets on the existing roof and those 3 blue posts to support the main beams. On top of the beams are the ceiling joist/rafters which I want to use one timber for both ideally spanning across 3500mm at 600mm spacing. If I'm going with this option, what's the best size timber for the main beam and rafter to use? I can double them up side by side as you mentioned to make it a stronger rafter.

Another option is to build something like a dwarf wall (picture attached) at the back of the pergola roof above those ceiling joist (running just flat and straight now), then have separate rafters going from the dwarf wall down to the front of the beam where those posts are to create any pitch that is reasonable. I'm not sure if this is the proper way to do it as the pergola has nothing to fix to at the back, only the roof extenda is holding the main beam.

Please advise your thoughts on this.

Jason

Option 1

Option 2

https://www.workshop.bunnings.com.au/discussion/comment/142114#Comment_142114

Morning @jasonlee

I like your sketch and drawing. The drawing would be solid for sure and the beams I would be using 110mm by 45mm ish. I just hesitate impacting the roof for waterproff reasoning. I do like the 600mm spacing as well.

I prefer freestanding pergollas. As in not attached to a roof, mainly becuase a structure should be able to stand on its own and also not to add stresses to an existing structure.

I am not sure if your post that ends up in the middle of the driveway is just an example of the layout or you are planing on covering part of the driveway 🙂 If you are planing on covering part of the driveway I would consider twisting the whole pergolla so there are no legs on the driveway and connect it to the house with a shorter width roof? Or I could be jumping the gun 🙂

Dave

https://www.workshop.bunnings.com.au/discussion/comment/143340#Comment_143340

Hi Dave,

yes that’s just an illustration what I’m planning to do, it’s the same situation at the backyard. The 110mm beam you mentioned, is that for the pergola main beam that supported by posts?