Unparellel Lean to shelter

[holy85]

Hi all, this is going to be slightly complicated for the average diyer?, but hopefully someone with some roofing knowledge can help.

The lean to/car port I'm building has a ledger board attached to the house and a support beam connected to posts, which does not run parallel with the house.

I'm having an issue setting up the roof/rafters. What angle should they be, A or B?

quick mock up with tooth picks so you get the idea what i mean.

clear plastic sheets ontop
leaning towards the left with gutter
rafters passing the support beam will be cut

 

[holy85]

i tried option B, but i found the rafters needed lifting up at the narrow end on the support beam side, to match the wider part rafter, hope that makes sense.

 

[datarebal]

B and cut the bottom of the sheets

 

[holy85]

B and cut the bottom of the sheets

I tried B and it didn't work. If both sides were parallel it works perfect. As one side is further away the angle of the rafter is less where as the angle of the rafter on the narrow end is more. Both support beams are perfect level.

What did you mean by "cut the bottom of the sheets"?

 

[holy85]

do i need to put my side support beam at an angle, to make the roof level? is that the correct way to do it? Thanks

 

[holy85]

The shelter with a clear roof will be this type of shape attached to the side of the house.

The slope is towards the red side. When i use option b and install the rafters on a slope they don't align up at the top even tho the beams are level.

 

[Notch7]

do i need to put my side support beam at an angle, to make the roof level? is that the correct way to do it? Thanks

Yes.

If you want the rafters to all have the same pitch, then you have to either the wall plate or the open end support besm not level.

It is because with the same pitch angle, a longer beam will end up lower.

The complication you have is that the rafters will have compound angles at 1 end -not impossible just a bit tricky to deal with

 

[holy85]

Yes.

If you want the rafters to all have the same pitch, then you have to either the wall plate or the open end support besm not level.

It is because with the same pitch angle, a longer beam will end up lower.

The complication you have is that the rafters will have compound angles at 1 end -not impossible just a bit tricky to deal with

Brilliant thanks alot for clearing this up for me. It's been bugging me for afew weeks. Just wasn't sure what the correct way to do this was

did you mean a compound angle at the birds mouth cut?

 

[Notch7]

Brilliant thanks alot for clearing this up for me. It's been bugging me for afew weeks. Just wasn't sure what the correct way to do this was

did you mean a compound angle at the birds mouth cut?

Yes.

Thats assuming your rafters will be at 90 deg to house wall (as viewed on plan).

If you want to work out the slope of the timber plate that fixes to the wall, draw a plan view of your rafters.

From that you should be able to see the dist of the longest and shortest rafter as viewed on your plan.

Find an online right angled triangle calculator.

Enter the distanc and roof pitch: the calculator will tell you the height (which will be the triangle side opp the pitch angle).

If you do that calc twice, you can deduct one number from the other. The answer will be the amount the wall plate drops over its distance.

 

[noseall]

Stick a flat roof on it.