• I built one with some help about 20 years ago, it's still standing...
    Go with what around here is called a "shed" roof: that is, a single plane with a shallow angle to it. I built it on an 8' by 8' plan but should have gone 8' by 12' since we're allowed up to those dimensions without a permit - would have been perfect then though it's good enough as it is. Mine is fully insulated and even though our climate is much colder than in the UK or Europe, I would still encourage you to do the same.

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