Creating a wooden lean-to off shed

[EmD]

I want to construct a wooden lean-to off the side of a shed with featheredge roof. The area is 3.5mx3.5m.

Can anyone tell me the following?

a)can distance be spanned in one go or do I need more supports?

b) How many braces would you need across the width of this to support the featheredge boards.

c) Do I need someting else underneath to make it waterproof e.g. felt.

d)Any ideas on slope angle away from the shed in event of snow?

Also what depth for upright foundations - have read varying recommendations between 300-600m?? confused..

Any ideas much appreciated for this diy novice...

 

[Deluks]

What does your existing shed sit on for foundations? What are you using the lean to for, as a base you can get away with putting down paving slabs for a simple garden structure like this. Certainly not 2 foot foundations.