Garage Extension

[brittan]

My garage is fairly small (built in 1933) and one side wall is 35" from the property side boundary.
Some years ago (over 4 years) and in order to make use of that 'wasted' space between the garage wall and the concrete panel wall belonging to the neighbour, I built a long thin 'cupboard' in that space.
I made a concrete base, the side wall is wood framed with uPVC cladding on the outside which is approx 3" from the concrete panel wall. I made the door from aluminium chequer plate. I extended the garage roof rafters by bolting on extension pieces and so the roof of the cupboard follows the slope of the original garage roof (standard A shape). As per the original construction there is no guttering on that side.

I would like to incorporate that long thin space into the garage and make it wider. This would involve demolishing the long thin cupboard, digging out the concrete base, laying an appropriate foundation, building a block wall 3" from the neighbours concrete panel wall to connect with the existing extended roof, demolishing the existing garage side wall and sorting out the interior concrete base.
The garage door would end up as an odd size so I'd have to build a bespoke door but I am capable of that.

I'm sorry for the long story, but my question is, are there any planning or building regs traps waiting for me?

[tony.g]

If the enlarged garage will have a floor area of less than 30 sq.m.,it wil lbe exempt from Building Control
if it is a detached structure.( If it is attached to the side of your house, Building Regulations will apply regardless of its size).

As regards planning; again, if its a detached structure, it will not need planning permission subject to certain conditions, including; it must not be more than 2.5m high (at the highest point, eg the ridge);
it is not forward of the front of the house; it won't occupy more than 50% of your garden areaa.

[brittan]

Thanks tony.g, the garage is detached and behind the house and the floor area when enlarged (as opposed to footprint) will be approx 31 sq metres.
The existing long thin cupboard has been there for over 4 years without objection or comment so I'm presuming that I can replace it with the more permanent structure. The new structure would be substantially fireproof which isn't the case with the existing.