I have looked at Doc B V1 for guidance and may have missed the required statement, but I am trying to find out if there are any legal requirements for a dwelling in what is basically the garden shed. Don't get me wrong this is not a small 6x4 space or for child punishment it is a large timber out building which is quite spacious and a friend would like to allow there eldest son to use for his own space etc. Would such space be classified by the local authority as a dwelling and would it be suseptable to the requirements of approved Doc B? If so what is the minimum needed, it has a smoke alarm fitted and an extinguisher, one entrance/exit.

You might find that the accommodation, if it is to be used as their main living accommodation, is deemed uninhabitable if there is no internal WC or hot/cold running water. There may also be Council Tax issues to contend with as well.

It doesn't answer your question as such (or maybe it does) but the proposal here is, it seems the change of use of a building from one thing to another e.g. from shed/outbuilding to occupation as a dwelling. If that is the case then this is highly likely to need planning permission for 'change of use' and I would have thought that this would 'throw up' the other issues that you may need to resolve. Planning permission, permitted development and building regs are essentially separate things. The lack of a need for PP (and I think it is likely to be needed in this case) does not necessarily obviate the need for B Regs.

Not necessarily. If there is subsequently a landlord/tenant relationship then I would have thought that some fire related legislation (not FSO) will apply under 'housing' legislation.

For any structure for human habitation you will need building regs approval. Planning permission may be required depending on various factors and you'll need to ask your local authority. They will normally give you an indication up front without you having to submit plans or pay fees. You will never get BR approval. Councils are very hot on this because so many unscrupulous landlords have been converting garages or sheds into makeshift housing for illegal immigrants. Apart from anything else, this proposal has serious potential to be a child protection matter. If the son is under 18 years old he is legally a child. To house a child in a garden shed is likely to be viewed as neglect by the child protection authorities unless it is as warm, safe, hygienic (sanitation??) and secure as the rest of the home. If it's just a day space it should be fine. The test will be if he is living in it.