lean-to guidance

Discussion in 'Landscaping and Outdoors' started by Dhrupesh, Apr 12, 2022.

  1. Dhrupesh

    Dhrupesh New Member

    Hi, so I'm looking to build a lean-to in my garden. No walls, just 10mm twin-wall poly carbonate roof. It will be used to provide a bit of shade from the sun and shelter from rain. Seating area inside.
    Looking at putting up C16 47x150mm rafters, same for the ledger on the wall.

    150mx150m tanalised posts on the other side opposite to the wall. 47x200m ledger going across these 2 posts which the rafters will be sitting in.

    Total width will be 4500mm with 9 rafters. The run will be about 3.8m.

    will this be ok since it is only 10mm poly carbonate sitting on top, no other weight other than maybe some lighting.

    or would it be wise to bring the posts forward, therefore reducing the run and leaving some overhang?

    Will be a minimum of 5 degree pitch to let water run off.

    3000mm height on the wall side and the top of rafters. 2600mm on the post side from top of rafter to allow enough of a pitch.

    Thank you in advance
     
  2. Mr Rusty

    Mr Rusty Screwfix Select

    Last edited: Apr 18, 2022
  3. Notnowvicar

    Notnowvicar Screwfix Select

    47x150....you do know that is used as a ceiling joist in a house that supports plasterboard and the weight of a person in the loft...over a clear span 3.08m. I think you will be fine, the twin wall will fail way before that timber.
    The real design consideration will be internal looking out...stand then sit with a mock up of your final height, if you can see the roof line from inside then raise it or shorten its run it its amazing even with poly how much it darkens the reflected skylight, you need to be able to see sky, no sky no light. Poly darkens with age and you can easily be living in a cave., if you want to check it out stand in a room with a conservatory attached and look at the shadows.

    Try and plot the shadow line of your new roof, think if you are in the middle of any room sat down facing the window in any modern house shadow line will be roughly half way up the wall behind you even if its not a window directly facing the sun, due to skylight. I would suggest that unless you raise the front garden side of your new roof so that you cannot see it when sat down you will move the shadow line to the floor by your feet in the middle of the room. Your ceiling will go dark.
     
    Last edited: Apr 18, 2022

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