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How to manage different pitch of roof for pergola build

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  1. #1
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    Default How to manage different pitch of roof for pergola build

    Hello All,

    I am new to the forum but have read and taken advice many times from other posts, which has been invaluable.

    This time I need help that Google or forums such as this can't seem to help me with..........

    I want to build a pergola and have got most of the 'easy' stuff down pat. What I haven't got figured is how to deal with what will be different pitch for different parts of my pergola.

    My house has several rooms jutting out from each other, creating a staggered appearance to the area that I want to cover with a pergola. This means that if I build the pergola as pictured on the attached plan (the pergola area is already concreted) I will have a different length run from the 'front pergola beam to where it connects at different areas along the length of the house. For example, the shortest run will be approximately 2.8m while the longest run will be 6.6m. The other is about 4.0m.

    I have the rafter brackets attached through the house fascia so the idea is to attach a beam along each of the three different areas of the pergola (all will be the same height above ground) to the beam at the front of the pergola area that will be at the same height across its entire length. This will, of course, mean that there will be a different slope for the three different areas of the pergola. Or, as I think of it - three separate pergolas built next to and attached to each other.

    So, questions..........

    How do you suggest I do this?

    How do I roof it and keep water/rain leaks out from between the different roof pitches?

    I want to have the roof pitch running back to the house (front of pergola higher than where it joins the house to take advantage of views) and use existing gutters to manage water run-off (maybe an extra downpipe to send water to tank nearby). Top of beam at house will be about 2550mm to front of pergola must be about 2.8-3.0m to get decent roof pitch. Is this a good idea?

    I plan on using design pine or TP for the pergola and the longest run between posts for the support beam and rafters will be the 6.6m for the largest pergola area. I assume that I will need to use 270-280mm X 45mm for both beams and rafters for this section to get the necessary strength for the roof load, which I intend to be Colorbond and clear/tinted panels to allow light (pergola faces about 5 degrees east of north, so misses the late afternoon summer sun but does get the afternoon winter sun.

    If using the larger design pine for the longer runs I will likely use it for the other runs as well to maintain consistency of look, even though it will cost more.

    Don't know at this stage if I will insulate and put a ceiling on it, but would like to have that option.

    Because of the many different roof lines to the house it makes it very difficult, if not impossible, to use extenda brackets to build a flyover pergola, so looking for any help or advice I can get.

    Cheers,
    Lionel66

    Proposed pergola.pdf

  2. #2
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    I know what your saying, but having a hard time visualising the finished look without drawing it up in CAD.
    Sounds like your going to have 3 distinct roof lines and perhaps vertical flashing (tin or semi clear laserlite/corflute type look/feel)

    Without seeing the current roof line, measurements of how far each jut out and the width of each, hard to suggest look at possible options.
    So I'II throw out some ideas:

    1. If you drew a line from the top right corner to the bottom left corner (of the house gutter points), can you achieve rafter spacing at the same height so you effectivily have a gradual rafter angle change with the roof "rolling" even if the extenda brks were slightly varying heights? ....maybe something like the attached photos but in your situation as a single flat roof....but without measurements its hard to picture the finished look.
    2. Can you consider roof design changes such as say a pitch roof in the middle with 2 flat roofs either side. Depending on your roof design, potentially you could use sandwich roof panels as this can span 8m from memory


    In all cases need to be sure on what other aditional requirements are with engineering on the existing house roof (additional tiedowns, rafter reinforcement etc)
    From memory most roof cladding require 5 degree fall. This would be you min requirement outside of other design considerations.

    Sandwich panel has the insulation and lining all one piece.
    If using just tin, Perhaps consider sarking as a minium?


    Anyway, food for thought!!

    house_photos_005.jpg

    house_photos_001.jpg

    house_photos_015.jpg

  3. #3
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    I think your best bet might be to do it in three vaulted type rooves with six gable ends.

  4. #4
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    Since a pergola is an unrooved structure, just build it flat

    But of course you mean a covered/rooved structure. Eg verandah

    Maybe, in tune with Bob's suggestion, 3 overlapping flyovers is a workable option?

    Complexity adds cost, but also adds value when done right

    Photos?

    An arrangement of solid sails may be feasible (engineer required)

  5. #5
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    Default More info from original post

    Since it'll only be me and my inexperienced 18 year old son doing the work I'd like to keep the job as simple as possible and avoid gables. I also think the look of a flat roofed verandah would better suit the house. A fall from front of verandah to house would better enhance the view.

    The main problem I have is that the walls of the house jut out (or back, depending on your perspective). In the diagram where each wall corner is, there is also a ridge line in the roof above. See the attached photo of the house also to get the idea of what I'm dealing with.

    So, with so many ridges in the roof, I can't get a level roofline for the verandah at the house unless I use the existing fascia brackets. Extenda brackets attached to rafters through the roof tiles would end up giving an uneven level at the house end as all the runs and falls are different and the ridge lines get in the way.


    Basically, it all comes down to the rise or fall over the three different runs for the three distinct and different areas to erect the structure - and how I manage that.

    The smallest area is approx. 4100mm wide X 2400 long, the second is 3500 wide X 4850 long, and the third is 4700 wide and 6600 long.

    So, with a starting height at the top of the fascia brackets of 2450 right along the house, I have runs of 2400, 4850, and 6600mm.

    By my calculations, (2.450 X 1.76 X run in m), this means a rise or fall, respectively, of 100mm, 195mm and 285mm to get the 5 degree slope required.

    As I'd like the verandah rafters to fall back towards the house, this would mean having different beam heights to attach the rafters to at the front of the house. And visible to anyone that comes up the drive or sits under the verandah. With a starting height of 2550 for the first beam/post, the second would be 2745 and the third 2835.

    Having the fall towards the front and away from the house allows for a level beam across the entire front of the verandah, and so better to the eye, but leaves me unsure how to raise the beams enough on the fascia brackets and still maintain structural integrity.

    Using 320mm beams at the fascia brackets and 280mm rafters, I have about 80mm flexibility for raising/lowering rafter attachment height using different placements of the rafters on the beam using universal brackets, which might be a subtle way of doing it, but I can't get the entire height flexibility I need. With a need to raise levels a total of 185mm from first to third verandah area, it just can't happen.

    So, what to do.............

    Any further advice considering the new information?
    Attached Thumbnails Attached Thumbnails house-photo.jpg  

  6. #6
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    Verandah design.pdf

    Here is another diagram of the verandah design, with the fall going back to the house. Note the different elevations of the rafters on the beams, which is due to the different runs of the verandah areas and the consistent 5 degree slope back to the house.

    Please excuse the dodgy perspective/angles, etc. I don't have CAD or similar to plan such things, just a pencil and some graph paper or drawing lines and rectangles with Microsoft Word!

    As mentioned in my previous post, with the beam at house being a consistent 2450, the lowest beam section at front needs to be at about 2550, the middle section at about 2650 and the larger section about 2750mm high to get the 5 degree slope.

    My idea is to overlap the roof sections and then install some sort of flashing, likely clear laserlite or similar, between sections to prevent rain entering the covered area.

    Where sections of the verandah rafters join the beam at the posts I can simply cut posts to hold beams at different levels and attach. However, since two of the three beams at the house will meet the next section of the verandah rafters at about the mid point, thebottom of the rafters will be slightly higher than the bottom of the beam. Do I just attach the beams with universal brackets to the rafters wherever they meet or should I shave/cut the beams down to ensure the bottoms of each piece are at the same level?

    Overall, am I on the right track with my thinking and planning or am I missing something that makes my ideas a potential disaster/failure/danger?

    The plan is to over-engineer the design and use Design Pine 320 X 65 beams at house and front of verandah, 4 x 135 x 135mm posts and likely, 320 x 65mm rafters (necessary for the larger section) across the entire structure for aesthetic purposes. I could use smaller sized rafters for other sections but unsure if I should do that to save money or just stick to the same look across the entire structure. If I end up insulating and putting a ceiling on the structure, the size of rafters won't matter as much obviously. I'm using a 30kg/m2 loading for the roof in my calculations just in case. Initially the plan is to just go colorbond with some clear laserlite.

  7. #7
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    Hmm. If they are all 5 degree fall, they are parallel, and won't meet at any stage, regardless of length

  8. #8
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    Quote Originally Posted by r3nov8or View Post
    Hmm. If they are all 5 degree fall, they are parallel, and won't meet at any stage, regardless of length
    The rafters will all have a fall of 5 degrees on all three sections and will of course run parallel and never meet. I was talking about running the beams at the house to meet the rafters coming at 90 degrees.

    The fascia brackets are not placed at the edges of each section of the house that juts out so I'll have to attach the beams with overhang to have them run the length of the house section I need to cover. I can therefore run the beam overhang to meet the rafter or let it float.

    If I let it float (maximum float is about 450mm past the fascia bracket) then I worry about lack of stability. If I run the beam a few more centimetres further, to meet and attach to the first rafter from the next verandah section along, it would provide more stability.

    The only trouble i see is that the first rafter from the next section, because it starts at a higher point than the last rafter of the first section, won't meet exactly level, i.e., there will be a few centimetres of the beam showing below the rafter rather than a neat level finish. Therefore, I could join as is and have it look disjointed, or shave/cut the beam down on an angle along its bottom to finish off level with the bottom of the rafter. A few heavy duty timber screws through the rafter into the end of the beam and job done.

    I am just seeking some guidance from experienced persons on here to help me decide what I'm going to do, or spot any problems I may not have realised.

    Cheers,

  9. #9
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    I was mainly referring to your diagram, which shows a universe where overlapping 5 degree rafters can meet

    If you think you will add a ceiling soon, I wouldn't bother with the chamfer at the end of the beam, but if that's a long ways down the track, the cut area could always be replaced to take the ceiling. Depends how much you are planning to take away I guess. Personal choice. You could even decide when framing up once you see how it looks

  10. #10
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    Quote Originally Posted by r3nov8or View Post
    I was mainly referring to your diagram, which shows a universe where overlapping 5 degree rafters can meet
    Yeah, the diagram is a bit dodgy, although not as dodgy as you'd think. There was SOME method to my madness in the drawing.....I just mucked it up a bit.

    Since I'm doing three separate verandahs and joining them up to create one, there will be two rafters attached to the beam at the front (non-house) of the verandah, one either side of both the two middle posts to ensure a level slope on each separate roof, i.e., each of the two middle posts is the finish of one verandah and start of the next.

    So, if the rafters for each separate section start their run on beams at different heights at the front and end up at the same height on the back, and over a run that is different by a couple of metres, there will an ever-decreasing angle (relative to each other) between the rafters on either side of the posts. It is this decreasing gap that I was trying to convery, which is the gap between rafters and roofs that will need to be waterproofed or flashed in some way. Any ideas on that?

    So yes, the drawing was crap, but I hope I've explained my thinking a bit better. Its so complicated and hard to explain things when you know less than half of what you think you should know!

  11. #11
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    What roofing material are you using and what pitch ?
    You could look at a change in pitch at each step, but that would depend on the minimum allowed for the sheet you are using.

  12. #12
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    To achieve a consistent 5 degree fall and visualise it all correctly, make a model of it.

    (and consistency is what you really want, and 5 degrees is minimum for corri)

    Find yourself 3 rectangles of a similar scale to the difference in your 3 rooves. Be it pieces of wood, books, plastic sheets, whatever.

    Place them on the table with the front (non house) side straight (as is your plan). Place a matchbox (or similar) under the front edge of the smallest 'roof'. Pretend that fall is 5 degrees, back to the house.

    Raise the next roof until the roof is parallel to the first and prop it up. It's also '5 degrees'. Do the same with the third 'roof'

    All 3 rooves are at the same level on the house side, all are 5 degrees, each has a different height at the front, and there is no convergence

  13. #13
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    Re droog's post, yes, totally doable.

    But don't be half pregnant. If using different falls for each roof, have the front beam at the same height across the full length

    Put a ruler under the full front edge of your model roof to see what happens to the levels

  14. #14
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    Haven't decided on roof material just yet, but most likely will use sheet metal, but not corro.

    I'll have to do some modelling now as suggested and think about the different pitch for each section using the same height beam at front. That's probably the most pleasing look aesthetically considering the options.

  15. #15
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    All good ideas and 3 roof lines/frames is the way to go but don't be afraid to use custom orb/corro because if you run your battens at about 700 centres the roof will not leak even down to 1 or 2 degrees, unless of course it is laid by elephants
    I would strongly suggest you install a 45 degree flashing off the top of the gutter batten dropping down into the gutter to stop water tracking back under the roof sheet EVEN if you use trimdeck.
    Corro, due to the profile, is about the strongest you can get.
    eg I have a pergola roofed with corro at about 1 degree (i did not build it) but with battens at 700 centres it does not leak even in the 300 mm/hour dump that occurred around 2012.
    Trimdeck on the other hand can easily be damaged during install.

    As to using the existing gutter it most likely will not take the extra (30 square metres at a guess) and it will overflow as Cecile asked about in the last week.
    https://www.renovateforum.com/f232/g...2/#post1134745

    You say the slab is already poured so no idea how you will add more downpipes to what may already be an overtaxed storm drain, but you will need a larger gutter maybe twice the existing, to cope with the extra water especially considering you have valleys feeding it.

    Any good roofer will flash each section but you will need a roofer who knows what he is doing otherwise it will be a silicone nightmare of which I have seen plenty.

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    Quote Originally Posted by cyclic View Post
    ... don't be afraid to use custom orb/corro because if you run your battens at about 700 centres the roof will not leak even down to 1 or 2 degrees, unless of course it is laid by elephants
    ....
    Although OP has mentioned some Laserlite sections, which in my experience means all bets are off

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    It would be good to see photos towards the house from the furthest corner, and also from the house towards the views

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    Quote Originally Posted by r3nov8or View Post
    It would be good to see photos towards the house from the furthest corner, and also from the house towards the views
    Here are some more photos as requested. I hope they help. FYI, the family room exit is the door near the window where my granddaughter is standing.

    Please excuse the mess, and the horse's @@@@.
    Attached Thumbnails Attached Thumbnails house-north.jpg   views-family-room-exit.jpg   view-house-north-east.jpg  

  19. #19
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    Were those facia brackets for a previous verandah? Do you know how big it was? Do you plan on (re)using them? (Assuming this is to be a much larger heavier structure...)

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    Quote Originally Posted by r3nov8or View Post
    Although OP has mentioned some Laserlite sections, which in my experience means all bets are off
    I agree as to Laserlite but I have never liked it for the simple reason it buckles in heat and lets too much heat in.
    In fact I had to remove some off a job and use fibreglass at the owners expense as I had written in the quote I was using Laserlite at the direction of the owner and was not responsible if the owner was not happy.

    I would suggest opaque fibreglass available in heavy corro pattern which I have used many times.
    I used to get it from Qld Roofing Materials in Bris and here on the coast.

    Another suggestion is if the OP is going to fit a ceiling then look seriously at using insulated panel which can span the required length with only a beam each end.

  21. #21
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    The fascia brackets were included with the original house build in about 2004 but have never been used. And yes, I do intend on using them for this build. Is that a likely problem?

    As for roofing material I am torn between trimdek and corro but didn't want to go corro if there were concerns over leaks at joins with pitch of less than 5 degrees. However, after learning much from advice so far, and likely having three different pitched structures all from the same height beam at front, I am now looking at pitches if 3.5 degrees, 5.1 degrees and 7.2 degrees, all approx. So corro sounds like it'll do ok. As for laserlite, I only used that name because I couldn't think of any other product to describe a clear panel to allow indirect sunlight to the structure and, hopefully, direct winter sunlight into the house. I will, of course, suss this out when I come to decide what to use the steel sheeting.

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    Not sure about the brackets... You need to know how they are fixed back into the house framing. If they are just part of the facia or simply screwed into the rafter ends, I'd be concerned. Just two/three per section... You mentioned over-engineering, but at first glance these don't seem to match that intention...

  23. #23
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    The fascia brackets go through the fascia and are bolted to the house rafters with M10 high tensile bolts.

  24. #24
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    Quote Originally Posted by cyclic View Post
    I agree as to Laserlite but I have never liked it for the simple reason it buckles in heat and lets too much heat in.
    I have Laserlite and it has never buckled in about 30 years old now, is it more of a problem up north? Yes it lets too much heat through though you can get Suntuff designed to reduce that.

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    The insulated roof panels might be an option, but they seem very costly at $170 square metre through Stratco. Sure, they eliminate rafters and reduce costs in other areas, particularly if going to put a ceiling in later, but does anyone know a cheaper place to purchase?

  26. #26
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    Quote Originally Posted by Lionel66 View Post
    The fascia brackets go through the fascia and are bolted to the house rafters with M10 high tensile bolts.
    Like this? Steel, back past the top plate, would provide peace of mind... Lots of big timbers take a lot of holding up!

    https://www.bowens.com.au/p/maxi-met...7C1&size=650mm

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    Quote Originally Posted by r3nov8or View Post
    Like this? Steel, back past the top plate, would provide peace of mind... Lots of big timbers take a lot of holding up!

    https://www.bowens.com.au/p/maxi-met...7C1&size=650mm
    Yes, just like that.

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    Quote Originally Posted by Lionel66 View Post
    Yes, just like that.
    Good to hear! Knowing the structure they were designed to support would give final confidence...

    Looking at your place, I agree that one level front beam and different falls will work best.

    For corro, take note of cyclic's 700 mm batten spacings for the <5 degree section. Never heard that, but he's confident

    You have 2 down pipes for that whole section, and both of them also serve the gutters beyond the verandah area. The 'system' could already be close to its limits...

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    Quote Originally Posted by r3nov8or View Post
    You have 2 down pipes for that whole section, and both of them also serve the gutters beyond the verandah area. The 'system' could already be close to its limits...
    Yeah. Not enough. Think I'll have to get wider gutters and a couple of extra downpipes to funnel water to new drainage areas. Existing downpipes lead to water tank pipes under concrete and they are pretty small - typical residential size - so extra water coming off the new roof will likely cause problems. Any other suggestions on managing this anyone?

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    I'm not too sure that Extenda brackets onto your top plates should be discounted so quickly, and then you should be able to get enough height to fall the water away from the house and still keep your view.

    From personal experience (I've done a carport falling to the house gutter), at first you convince yourself that some water under the roof is "ok" because, hey, it's still "outside". But I rue every bl0ddy drop of water that shouldn't be there!

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    With all the advice on here I'm slowly getting it straighter in my mind. Extenda brackets are coming back to me the more I think about the water dispersal challenge. Will have to look at them more closely now.

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    Why not incorporate a mix of pitch angles? Use Extenda brackets for the centre section and just go with the flow on the sides? It's then a design feature
    "A big boy did it and ran away"

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