Requirements for a lean to shed?

Abbey10

Hi All,

We are planning on building a lean to shed against the side of our house Nothing fancy, just a wood fence with a felt roof. Part of the boundary between our house and our neighbours has their detached garage running along it. I have attached a small diagram of the area and the boundary is marked in red. Its essentially in an alcove of our garden, won't impact sunlight and could only be seen if other neighbours look into our garden from their upstairs.  I am looking for some advice re planning permission and building regulations because of the proximity to the neighbours garage. Unfortunately the local authority planning team will not answer my questions, they can only direct me to their planning portal.

I have checked the planning portal on my local authority site and understand that it meets the requirements of a permitted development (max height 2.5m and less than 50% of the total area around the property) therefore it doesn't require planning permission. Provided we build it so that the max floor area is 15square metres I understand that building regulations don't apply. However, I can't find anything mentioned about proximity to their garage. Can anyone clarify if there are additional requirements or regulations we must comply with due to the proximity to the neighbours? Is there anything specific for drainage? We plan on contacting guttering to our downpipes.

Thanks in advance!