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new verandah ridge beam and joist hangers

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  1. #1
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    Default new verandah ridge beam and joist hangers

    Hi to all. I am about to start my brothers verandah measuring 5 x 4.4m. Using 115*115 posts and 190*45 side beams and fascia beam. 5 metre house side connected to fascia which has been reinforced in the roof and end of fascia beam extends out onto a post. Gable roof with laserlight on top with 140*45 rafters at 900 centres. Side beam spans 5 metres over 3 posts, while 4.4 side will have 3 posts.

    In previous verandah constructions, I have used simple a-frame trussed preformed on the ground and lifted it up with 2 people and placed in joist hangers from fascia beam to side beam. However have decided this verandah to use a ridge beam instead. Also I have access to a mates nailgun, but have no experience with one, since have used joist hangers all the time for rafter to beam connections.

    My queries are:

    1. As i understand a ridge beam essentially is not load bearing but simply holds everything into place as such, what is the recommended size i should use for this ridge beam since rafters are 140*45 and side beams are 190*45. Ridge beam length is 5 metres?

    2. If ridge beam is not load bearing, I dont necessarily need a longer post holding up the ridge beam on each side, since have seen some people do this but most have avoided this. simple rafter connections to ridge will essentially hold the ridge beam up?

    3. what is a stronger connection - a joist hanger or 3 nail gun hits for the ridge to rafter and rafter to fascia beam connection? (havent used a nailgun before but prefer the clean look of a nail gun)

    4.Planning to put a A-frame on each end of the verandah to support the ridge beam, would joist hangers be suitable here since am worried about holding up the long 5 metre beam high up in the air while attaching the rafters.

    Any advice and help would be appreciated. Thanx

  2. #2
    Old Chippy - 4K Club Member
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    mmm - 'a ridge beam is not load bearing' . . . Perhaps I am misreading, but your level of knowledge of what is involved looks to me like an unhappy experience might be on its way.

    Can I suggest that you should draw up a sketch to scale and a plan and post them to seek advice.

    Nails should not replace hangers and other joint connectors - they might look good, but there is a reason why we use connectors - they work, work well and stay secure over a long time and are required by the building standards too.
    Advice from me on this forum is general and for guidance based on information given by the member posing the question. Not to be used in place of professional advice from people appropriately qualified in the relevant field. All structural work must be approved and constructed to the BCA or other relevant standards by suitably licensed persons. The person doing the work and reading my advice accepts responsibility for ensuring the work done accords with the applicable law.

  3. #3
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  4. #4
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    Think he may be confusing some terms. A ridge beam is load bearing, transferring the load to either posts or wall ends. A ridge board is not load bearing, but generally the roof needs to be coupled
    Nominal Rafter to Ridge connection can be nailed as per AS1684.3
    As suggested post a detail for roof construction

  5. #5
    Love a reno - 1k club member
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    A ridgeboard 19mm thick needs to be supported (e.g. strut, post) every 1800mm, or 35mm thick every 2300mm. Since your ridge will not be supported, it should be designed as a ridge beam per the span tables. My reading indicates 2/240x35 F7 is required for your beam length and RLW, but this seems hefty and so I would also investigate LVL (but I don't have time ).

    7.2.12 Ridgeboards
    7.2.12.1 General
    Ridgeboards shall be provided to locate and stabilize rafter ends. Opposing pairs of rafters
    shall not be staggered by more than their own thickness at either side of their ridge
    junction.
    ...
    Where a ridgeboard is required to be strutted along its length but there are insufficient
    strutting supports, the ridgeboard shall be designed as a ridge beam for a non-coupled roof,
    or alternative provisions shall be made for the full support of the roof loads.

  6. #6
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    You can have a coupled roof with no struts as long as certain design considerations are taken into account, when people start building roof structures with little or no knowledge in design possibilities things can go bad very quickly

  7. #7
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    Just off the top of my head and its been a while but I think if you put a collar tie every second pair of rafters it would be fine to have no struts from the ridge, unless you went for a chunky collar tie and strutted down to it ( seen that before)

  8. #8
    Love a reno - 1k club member
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    cherub65 and ringtail, we are talking the same thing. The subtlety is that this particular ridge timber must be spec'd as a ridge beam (i.e. from span tables)

  9. #9
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    agree

  10. #10
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    Thanks for the swift replies. I am confused as to the difference between a ridge beam and ridge board. My scenario here is the rafters will be connected to the side of the ridge timber, and each pair of rafters will have a collar tie in the top 3rd of the rafter, maybe 600mm below the ridge.

    Sorry to sound stupid, but i am assuming a strut is the vertical piece of timber used to connect the bottom beam to the rafter on a angle i think. This could be done on the end trusses to support better the ridge timber. I can also add a extra side beam at the width in the middle of the verandah, and add struts to it, so the ridge would be supported by 3 truss style frames with struts and rafters in between with collar ties attached. Would this then still be considered a ridge beam or ridge board, and regardless would this be sufficient and safe.

    So, in summarising i have a 5m by 4.4m wide verandah supported by 3 190*45 width beams truss style with struts and 140*45 rafters nailed to the side of the ridge and side beams with collar ties at every pair of rafter. Would this be now sufficient and upto scratch.

    I dont want to support the ridge timber with posts.

    hoping my technical lingo is upto scratch.

    thanx
    Attached Thumbnails Attached Thumbnails pergola.png  

  11. #11
    Love a reno - 1k club member
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    What size ridge timber are you planning on?
    What size battens are you planning on to span 2.5m between rafters?
    Can you attach an elevation view of an a-frame showing all rafters, collar tie, struts and posts, and the cross-section (e.g. ends) of all beams and battens.

    EDIT: If you stick with your 2.5m rafter spacing, you would design purlins rather than battens. Purlins are like battens but installed on their edge rather than on their side), and depending on the angle of your rafters the purlins may need to be supported by blocking or brackets to stop their tendency to 'fall over'.

  12. #12
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    Quote Originally Posted by r3nov8or View Post
    What size ridge timber are you planning on?
    What size battens are you planning on to span 2.5m between rafters?
    Can you attach an elevation view of an a-frame showing all rafters, collar tie, struts and posts, and the cross-section (e.g. ends) of all beams and battens.

    EDIT: If you stick with your 2.5m rafter spacing, you would design purlins rather than battens. Purlins are like battens but installed on their edge rather than on their side), and depending on the angle of your rafters the purlins may need to be supported by blocking or brackets to stop their tendency to 'fall over'.

    Ridge timber was going to be 190*45, same as my bearers. Battens were going to be 70*45 and be 5metres long and can be placed either flat or its side. I think purlins you mentioned are placed under the rafter for extra support. Wasnt planning to do that, however I have seen verandahs with battens placed on its side, but not above the rafters but inbetween (takes much longer to install with seperate cuts). I can do this if this will provide extra support.

  13. #13
    Love a reno - 1k club member
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    The purlins I mentioned are indeed purlins. You are thinking of underpurlins that, on struts, support rafters. (Think about C or Z purlins in steel - on their edge and on top of the rafters - get the picture?)

    Check your span tables. I have a feeling 70x45 is too small for 2.5m span. The limit for batten spans is 1200. Purlins then take over and the 'Rafters and Purlins' span table (table 29) is used for them. If you place them between the rafters remember they are then single span, not continuous span.

    Have any of those verandahs you've seen got their rafters spaced at 2.5m?

    EDIT Also, what stress grades are you using, and what is you planned batten spacing?

  14. #14
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    Quote Originally Posted by r3nov8or View Post
    The purlins I mentioned are indeed purlins. You are thinking of underpurlins that, on struts, support rafters. (Think about C or Z purlins in steel - on their edge and on top of the rafters - get the picture?)

    Check your span tables. I have a feeling 70x45 is too small for 2.5m span. The limit for batten spans is 1200. Purlins then take over and the 'Rafters and Purlins' span table (table 29) is used for them. If you place them between the rafters remember they are then single span, not continuous span.

    Have any of those verandahs you've seen got their rafters spaced at 2.5m?

    EDIT Also, what stress grades are you using, and what is you planned batten spacing?
    I think there is some confusion in regards to the spans. Verandah will have 3 truss style supports at ends and one extra one in the middle in the 5m length. rafters will be added in between connected to the ridge spaced at roughly 850mm gap between each rafter pair. So effectively there will 7 rafter pairs along the whole length of 5metres roughly 850 spacing between each. Battens will be most likely placed on top of rafters on its side, nailed into top of every rafter. Can increase batten size to 90*45 if need be. Batten length will be same as ridge length ie. 5 metres.

    When you say those verandahs got their rafters spaced at 2.5m, they dont. their rafter spacing is also at every 850 or 900. Hope i made sense.

    Also, since verandah width is 4.4, maths tells me that the rafter length on 22.5degrees will be roughly 2.5metres also. So i plan to use 4 battens on top of the rafter with batten gaps of about 800.

  15. #15
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    Making sense of it now. I would ditch the truss type arrangement and go with straight out rafters with collar ties. I wouldnt lie the battens on edge, put them flat and run a 100 mm batten screw into the rafter. Dont forget the speed brace or strapping.

  16. #16
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    Agree with Ringtail, also ridge should be next size up as angle cut will be longer. What pitch are you using?

  17. #17
    Love a reno - 1k club member
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    Why oh Why oh Why didn't you draw all the rafters on your diagram????????????

    now it's standard battens, standard everything...

    what ringtail and cherub says...

  18. #18
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    Sorry, i should of made it clear in the diagram there were rafters, even though I mentioned it continously in the old threads. So, since everything now with the battens is fine, can I reasonably assume that my timber sizes and particulars are all ok for this gable style verandah

    side and fascia beams 190*45
    rafters 140*45 every 850-900mm
    ridge 190*45
    collar tie in top 1/3rd of rafter pairs 140*45
    Battens flat 70*45
    laserlite sheeting on top
    beam to rafter to ridge connections - joist hanger
    collar tie connection - 12mm bolt and nut into rafter
    beam connection to post - 12mm bolt and nut

    Thanx for the input guys.

  19. #19
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    What do the plans say ? I'm sure you need approval for what you want to do and therefore need plans ?

  20. #20
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    I don't know about others, but leaving out the real intended rafter spacing, along with a drawing of 3 rafters @ 2.5 spacing made me focus on things that otherwise would not have been a concern. But while on a wild goose chase I did do detailed reading of certain parts of the Standard and I learnt more and more. So I got something out of the 'omission' even if you didn't (I need a reason to do things, and this forums gives me many reasons!) Anyway...

    Goes without saying that the structure needs a permit.

    If you have the AS, or load up Hyne Design 7 and/or Timber Solutions I think you'll find you can save money on your beams and rafters (unless you want a 'chunkier' look). The jury is still out on the ridge beam - are you supporting the ridge in the centre (e.g. via a strut)?

  21. #21
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    Quote Originally Posted by r3nov8or View Post
    I don't know about others, but leaving out the real intended rafter spacing, along with a drawing of 3 rafters @ 2.5 spacing made me focus on things that otherwise would not have been a concern. But while on a wild goose chase I did do detailed reading of certain parts of the Standard and I learnt more and more. So I got something out of the 'omission' even if you didn't (I need a reason to do things, and this forums gives me many reasons!) Anyway...

    Goes without saying that the structure needs a permit.

    If you have the AS, or load up Hyne Design 7 and/or Timber Solutions I think you'll find you can save money on your beams and rafters (unless you want a 'chunkier' look). The jury is still out on the ridge beam - are you supporting the ridge in the centre (e.g. via a strut)?
    Im aware i need a permit, but i usually do my research first and have a grasp at things first, then ill offer it to council.


    As for the spans, yes i am aware that i can go lower in the rafter to 90*45, but i am happy with 140*45.

    For the ridge, im hoping having collar ties for each 7 pairs of rafters, and having a extra 190*45 beam in the centre of the ridge with similar supports to the end rafters will be adequate. That way 3 of the 7 rafters will have truss style supports, and all will have collar ties.

    I can add extra underpurlins but am unsure on that yet. I think the struts that have been mentioned are used between the bottom beam and the rafter (same as a truss style form).

  22. #22
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    Quote Originally Posted by ozizu View Post
    That way 3 of the 7 rafters will have truss style supports,
    I'm little lost here, can you post a pic of what you plan to do? also what pitch and will it have a ceiling?

  23. #23
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    Yes it will have a ceiling, most likely lightweight laserlight. Definitely not concrete tiles etc. The pitch will be roughly 22.5 degrees.

    The truss style frame i mention are simple A-frames that will be on the ends, and one in the middle of the 5 metre long side of the verandah. the other 4 rafter pairs will have collar ties for extra support. See diagaram for details.

    Rafter spacing will be about 830mm, battens spaced at 900.
    truss.png

  24. #24
    Love a reno - 1k club member
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    Quote Originally Posted by ozizu View Post
    Yes it will have a ceiling, most likely lightweight laserlight. Definitely not concrete tiles etc. ...
    When you say ceiling, I think you mean roof.

  25. #25
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    Back to the ridge beam/ridge board debate, since I will placing collar ties on essentially all the rafters except for the gable ends which will have truss style a-frames, can someone help me with the size of the ridge timber. I have used HyneDesign7 I assume the ridge timber is found from going to spantables/bearers and beam/roof beam.

    For a 5 metre long span, it says a 200*45 LVL will span 4.9mtr with conditions (lightsheet, no ceiling, 22.5deg, RLW of 2.4 and rafter spacing of 1.0m). However is this assuming the ridge is desgined as a ridge beam, or a coupled roof with a proped ridge (i think my verandah will be the latter).

    Will a 190*45 f7 treated pine be sufficient for a ridge board for a coupled roof with a 5mtre span and a RLW of 2.4m.
    Thanx

  26. #26
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    Please read and understand post #5 above.

    So you need to know whether your design meets the definition of a compliant coupled roof

    The "coupled, unstrutted roof" seen here http://www.tilling.com.au/sites/defa.../Determination of roof load width_0.pdf is similar to yours in that there are no strutts, but a standard coupled roof requires ceiling joists by definition.

    Also, in HyneDesign7 I find it easier to use its Simple Design tool for this sort of thing. You'll find ridge beam specifically in there.

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