Roof on structure

Discussion in 'Builders' Talk' started by Ajaz, Jun 8, 2020.

  1. jonathanc

    jonathanc Screwfix Select

  2. Jord86

    Jord86 Screwfix Select


    Looking at your photos and giving and taking a few mm I work it out at roughly 17.8 degree pitch, almost a 4 in 12 pitch. It doesn't really matter though as you'll soon find out once you place a length of timber up there.

    C24 grade 6x2 Timber at 400mm centres, you'll need to "cut the roof on" by hand, yours couldn't be simpler provided you own a new handsaw, two foot spirit level, a piece of string a few metres long and a tape measure. Are you going to be doing this yourself ?
     
  3. Abrickie

    Abrickie Screwfix Select

    Er I have a feeling you’re a little higher than the 2.5m rule, about 615mm at the moment. Just saying ;)
     
  4. Ajaz

    Ajaz New Member

    I'm not great at this kind of stuff but I've had enough. I'm having no luck with builders. So might as well have a go.. I do have the tools you've mentioned. Not sure if it's going to be simple for me though. Appreciate the reply. Thanks
     
  5. Ajaz

    Ajaz New Member

    Also where shall I place the wall plate. On top or on the inside. Thanks
     
  6. Jord86

    Jord86 Screwfix Select


    Aren't those 4x3 timber wallplates on top of both outer span walls?
     
  7. jonathanc

    jonathanc Screwfix Select

    On top. Looks like it is already there? Remember to strap the wall plate down
     
  8. Ajaz

    Ajaz New Member

    The builder actually bought 3x3. Which even seemed weird to me. But yes they are sitting on top at both ends but the back one is just sitting there not yet secured down. The front one is secured down but I was going to remove it because its a 3x3 and replace it with 4x2. Thanks
     
  9. Ajaz

    Ajaz New Member

    Yes I have bought the straps. 1.2m ones
     
  10. Ajaz

    Ajaz New Member

    can the timber be put on the inside flush with the last course so that the rafters are flush. Thanks
     
  11. Jord86

    Jord86 Screwfix Select

    Keep the 3x3, fix it flush to the outermost edge of the outside blocks so from inside the building there's an inch step, that way when you scribe your rafters to sit on them you won't have to double notch the birdsmouth in order for it to sit down tight over the wall.
     
  12. Severntrent

    Severntrent Screwfix Select

    Just a general query how are you going to marry the new tiles in with your existing to make a water proof joint, whatever you do with your joists they need to be set for roofing battens to be in right place. Minimum pitch for slate tiles is 20 degrees which you just about have. I assume you are felting the underside of the tiles.
     
  13. Jord86

    Jord86 Screwfix Select


    Looking at the second of his photographs the new roof height is lower than the old.
     
  14. Severntrent

    Severntrent Screwfix Select

    Of course it is, daft me, to busy looking at 4th photo and making wrong assumption.
     
  15. Jord86

    Jord86 Screwfix Select


    I wouldn't worry, I must have looked at them half a dozen times when trying to work his pitch out for fear of being pulled up by a saddo like me :p
     
    Severntrent likes this.
  16. Severntrent

    Severntrent Screwfix Select

    75 x 75 lintel just about OK for 1.2m opening but that's based on building regs snow loading, and ignoring dead load of roof structure, but as its only a shed they don't apply and lower factor of safety acceptable?
     
  17. Ajaz

    Ajaz New Member

    You couldn't draw a rough sketch of how it should look please. Thanks
     
  18. Jord86

    Jord86 Screwfix Select

    I can't at the moment as my ipads knackered and I'm doing this on a kindle, but Google 'monopitch roof detail' and look at several plans, sketches and side elevations to gain an understanding of what you need to do. You need to be careful as you only have a single skin structure, it will be unstable until the rafters are birdsmouthed and fixed to sit over both wallplates and strapped into the existing house via plugs and screws. Unless you're opting for a vaulted ceiling which will bring you new issues as you really need a structural engineer to specify what's suitable, you would be better off building the joist structure first to tie the two opposing walls together.
     
  19. Ajaz

    Ajaz New Member

    Right OK.. What do you think of this. Will it be suitable? IMG-20200609-WA0007.jpg
     
  20. Jord86

    Jord86 Screwfix Select

    No.

    Position a length of 6x2 over both of your wallplates and let it run long once you've fixed them down with straps so they don't move, come parallel off the outside of your new wall six inches so the timber is inside the wall by two inches (as its a four inch wide block), then using a small offcut of 4x2 flush with the wallplate run it into the rafter and mark around it so you're left with a V shaped notch marked to be cut out. Do this at both wallplate locations. Remove the rafter, cut out the notches then drop the rafter back in the position you marked it out on. It should fit well.

    Try this rafter at the middle and other end of the building and if it fits accurately cut all your rafters the same, Mark the wallplates every 400mm and fix a rafter at these points. It's a lot easier to do than describe.
     

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