Could you do a very slow, DIY loft extension

[KatyMac]

Doing each bit, as you can afford it and taking maybe years?

Did the rules change for planning permission a while back - would that make it easier?

TBH if we had a staircase to get into the loft space it would make our lives easier even if we did nothing else

Same goes for electrics and insulation only needs upgrade if going to be habitable room. Electrics may need some work to extend but as long as you use a person on competent scheme they can self certify.
If you want to make it a habitable room however it is going to cost as you will have to do it properly to make sure it's safe but should also increase the value of your home so I guess that's the trade off.

Sorry to clarify you may not even need fire doors if it's non habitable ie for storage except to the actual loft space.

Yes, building regs actually has nothing to do with the quality of the work.
They, for some reason are more concerned with the size of our gas bill which means we have to put in a lot more loft insulation because we put a conservatory on the house and shock horror took a pair of doors off.
We have done it, but now they don't actually seem to care and have not answered my emails and phone calls for 4 months.
Useless department.

But, BR in my council, 'don't really believe people that it's not going to be habitable - so you have to do the lot'

There are different bits of BR you can apply for (different fee bands) if you go for the category of fees that says Loft conversion then they will assume you are doing a full loft conversion but if you just want to limited works you should be able to apply just for alteration sections. As long as your drawings match what you do this Is within the rules. I rarely deal with Local Authority BControl as our clients prefer to use private inspectors but when I have used them I find if you tell them what you need rather than ask them - you usually get it (or maybe I'm just very stubborn).
We made additional usable storage in the loft space of our offshoot by getting a larger access hatch cut, a new timber access ladder like one of these www.abru.co.uk/ladders/timber-complete-loft-access-kit and boarded the loft space out, over the top of the insulation between the joists. We had lights fitted and it's a really useful space for all our crap spare stuff. It's not a conversion and the electrics were done by an electrician so self certified, so saved us lots of hassle but eked out a bit more space for all our stuff.

if you don't have Building Control and Planning Permission, then you will have one of the very common non-compliant partial loft conversions.

These add negative value to your home, because a potential buyer has to assume that it has not been done to the correct standard, therefore the ceilings and walls might fall down, and he has to factor in the cost of ripping it all out and doing it again properly.

The surveyor will not be able to inspect the quality of build because it will all be hidden behind plasterboarding and under floors.

It is very common for non-compliant loft conversions to have weak floors, which sag and make the ceilings crack; to have had timbers cut out of the roof structure to give more space but thereby weakening the roof, and to have insufficient insulation and ventilation, leading to cold and damp.

I wouldn't buy one except with a very big price reduction.

Exactly what piglet john said except i wouldnt buy it at all!

Shame you can't get it signed off by anyone except the council

With my dad being a structural engineer, we would definitely do the 'structural' bit right (he is already muttering about pounds per square inch & point loads)

But the whole habitable room vs storage vs occasional use is a nightmare

Actually you can get it signed off by private building inspectors instead of the council but I'm not sure if they would get involved in such a small but if work. approvedinspectors.org.uk/about-approved-inspectors/what-is-building-control/

Of not if

As already mentioned ring up the planning people

I had two different builders giving opposing advice about a job, I rang up my local planning off (Old Trafford), spoke with the lady who comes out to asses things and found her very nice to deal with. Lots of great advice tips and reassurance about the work.
Great customer service and more than happy to answer questions (even after my 5th "oh and just another thing...")