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    • CommentAuthorgoodevans
    • CommentTimeFeb 2nd 2018 edited
     
    Posted By: davidfreeboroughThe membrane only needs to lap about 150mm onto the eaves support tray
    Thanks that's a detail I didn't know - saves having that horrible bit of membrane sticking out.
    • CommentAuthorgravelld
    • CommentTimeFeb 3rd 2018
     
    Oh right... is it fastened in any way? I guess it would need to be a heck of a wind to flap it about. I suppose there's not a lot loose after the batten fixings?
    • CommentAuthorgravelld
    • CommentTimeFeb 5th 2018
     
    Here we go then... hopefully I got this right!
      eaves-lean_to.JPG
    • CommentAuthorgravelld
    • CommentTimeFeb 5th 2018
     
    Now to be annoying...

    If I replaced the wood fibre with EPS, what would be the effect, how would I have to change the design? My understanding is now I have a membrane anyway it won't have any effect.
    • CommentAuthoradam_w
    • CommentTimeFeb 6th 2018
     
    With regards to the small animal prevention issue, Marley Eternit do a steel insect screen angle for their Cedral Weatherboard, that may be useful in this scenario?

    The EPS is breathable/permeable and non-degrading so I can't see why it wouldn't be interchangeable now you've added the membrane over the top, its how im planning on building mine!

    When is your start date? My old garage is coming down in about 4 weeks time!
    • CommentAuthorgravelld
    • CommentTimeFeb 6th 2018
     
    Start date? Hah, not quite there yet, want to agree these details then file with BC, then draw up a tender pack of some sort... Basically, it'll be done when it's done, but the current windows aren't going to last forever!
  1.  
    The drawing looks good, but do you need something to support the top of the fascia and stop it rotating? How about putting the false rafter feet in the second layer of insulation? The fascia would then be fixed at the top by the false rafter feet and at the bottom by a batten fixed to the top of the horizontal soffit. Alternatively, you could alternate the false rafter feet between first and second layer of insulation. If doing this I would use a sloping soffit rather than horizontal.

    The eaves support tray's lower end should drain into the gutter. It's upper end is under the tiles and counter battens, so it shouldn't flap around. If you have a rigid ventilator there's no need for insect mesh; they are designed to keep out insects. With this set of details you can replace the woodfibre with EPS.

    David
    • CommentAuthorgravelld
    • CommentTimeFeb 7th 2018
     
    Thanks for answering all my questions in one dense post!

    Fascia rotation - doesn't two fastenings into the rafter feet accomplish this?
  2.  
    Two fastenings would stop the fascia flapping in the breeze, but would probably not resist someone stepping on top of the fascia.

    I had another idea last night: how about fixing a stop batten in the top layer of insulation at right angles to the false rafter feet and tight up against the back of the fascia? This is normal in warm roof applications to stop the insulation sliding off the roof and would have the benefit here of giving you a second fixing for the fascia.

    David
    • CommentAuthorgravelld
    • CommentTimeFeb 8th 2018
     
    Is this what you mean? I've removed the fascia and membrane etc here.

    How should the stop batten be cut to meet the fascia? While I'm at it, how should the soffit wedge be cut to fix to the rafter feet... is this just common sense - cut an angle for a flat surface for fastening?

    BTW would love your feedback on http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15558&page=1#Item_2
      stop_batten.JPG
  3.  
    No, I meant the stop batten to be horizontal on top of the false rafter feet and going across the full width of the roof. You could use a bevelled batten with triangular cross-section cut to pitch of roof, so that it offers a vertical face to the fascia.

    I imaging the role of the soffit wedge being performed by false rafter feet cut plumb, i.e. so that it offers a vertical face to the fascia.

    David
    • CommentAuthorgravelld
    • CommentTimeFeb 9th 2018
     
    Sorry about that. Is this it? Except the upper edge of the batten is also bevelled?

    Will the banner be a lot thinner than this, meaning the insulation needs to extend further?
      stop_batten2.JPG
    •  
      CommentAuthordjh
    • CommentTimeFeb 9th 2018
     
    Posted By: gravelldIs this it?

    Why not mount the square/rectangular batten directly on the rafters and cut just the one edge against the fascia?
    • CommentAuthorgravelld
    • CommentTimeFeb 10th 2018
     
    Oh I see - directly on the end of the rafter, elongating the overhang by the width of the batten? Sounds sensible, maybe I misinterpreted "on top".
  4.  
    What djh said: just bevel the top outside corner of the stop batten where it meets the rear face of the fascia.

    David
    • CommentAuthorgravelld
    • CommentTimeFeb 12th 2018
     
    Really sorry - I don't understand what you mean by top outside corner? I thought what was meant was...
      lean-to_eaves.JPG
    • CommentAuthorgoodevans
    • CommentTimeFeb 12th 2018
     
    I think they mean like this
      rafter tails 2.jpg
    • CommentAuthorgravelld
    • CommentTimeFeb 13th 2018
     
    Fantastic! Thanks.
    • CommentAuthorgravelld
    • CommentTimeFeb 15th 2018
     
    Here we go then, I hope!

    This does feel a little intricate to have to repeat for every rafter, but if this is the best way...
      lean-to_eaves2.JPG
    • CommentAuthorgoodevans
    • CommentTimeFeb 15th 2018 edited
     
    Posted By: gravelldThis does feel a little intricate to have to repeat for every rafter
    well one false rafter every rafter - all the rest is continuous along the length.
    •  
      CommentAuthordjh
    • CommentTimeFeb 15th 2018
     
    Posted By: gravelldThis does feel a little intricate to have to repeat for every rafter

    What exactly do you mean by 'this'?
    • CommentAuthorgravelld
    • CommentTimeFeb 16th 2018
     
    Posted By: goodevans
    Posted By: gravelldThis does feel a little intricate to have to repeat for every rafter
    well one false rafter every rafter - all the rest is continuous along the length.
    Sorry, you're right... wasn't thinking it through.

    @djh I think that covers it.

    So is the order:

    - Insulate between existing rafters
    - OSB on existing rafters, other AT work, test AT until happy
    - Construct entire false rafter assembly separately (including soffit and fascia?)
    - Fasten assembly to existing rafters
    - Insulate over and inside false rafters

    The run is about eight to ten metres (sorry don't have measurement to hand). Too heavy to do at once?
  5.  
    I would construct each false rafter to the main rafters separately and then attach the other components separately. Purely due to the size and weight of the false rafter assembly.
    Not shown is a method of attaching the soffit. A batten on the bottom on the fascia would do the outboard end but the inboard end is unsupported as shown. Perhaps a batten screwed/nailed to the side of the rafter (at the wall) projecting down to the level of the fascia and then a horizontal batten attached to this to which the inboard end of the fascia can then be attached.
  6.  
    Looks good. I would fit a sloping soffit to the underside of the false rafter feet.

    David
    • CommentAuthorgravelld
    • CommentTimeFeb 16th 2018 edited
     
    The main reasons for that are aesthetics and ease of installation (no extra battens), right?
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