Mr Punter

Surely you have access to an engineer to design this type of work?

It is a shame, but the sole plate may rot out very quickly with the detail that has been built. They need to remove what they have done on this section, build up the masonry, then reinstate.

No consent needed for a WC.

Please don't take the gutter downpipe across the flank wall at an angle. Straight down and connect underground. 40m is a long way to go to the loo when it is cold and raining. Have you costed running a 110mm drain and a 20mm water feed? It can all go in the same trench as the electric.

I don't think building regs testing will apply but if the council have imposed a planning condition, you will need to satisfy it or you may not be able to occupy or sell on. Can you ask your sound test people what they suggest?

Mortar will work OK. I struggle with the gun sometimes as they can block and make me rage. Other times they are fantastic. 5mm is very narrow so a trowel may work better.

Pretty crap plastering. He shoudl have chucked on a few more bags of hardwall and ruled it off with a long straightedge or speedskim. It looks like he has just skimmed it.

Good for you. It will drive you crazy otherwise. A while ago I sent back 8 panes of 25mm thick laminated toughened glass because it was not the specified low iron and I didn't like the green tinge.

I would have thought that any laitance would have worn off through foot traffic and cleaning and your plan seems OK.

It is expensive, heavy, difficult to cut, fix and finish and you don't get the benefits of impact resistance and pull-out strength where you would on a wall.

Why on earth are you using Fermacell on a ceiling?

They do a 3mm-7mm tape but you may find it easier / cheaper to use a low modulus silicone sealant.

That is quite a bewildering selection of materials! Have you checked that the wall textured coating does not contain asbestos? Given the age of the property you need to be a bit cautious.

I have used a broker for some BTL and individual mortgage deals, but not in the last 18 months. I can PM details if you want, but it sounds like you already have someone. Fingers crossed for you!

I think you will really struggle to find anyone who has the appetite for this. The combination of self employed, novel construction, BTL and requiring equity will not work out. Can you take in a lodger or two to boost your income?

I have bought it from ebay before and it was a fair bit cheaper. Make sure you get the Illbruck Compriband. Some of the imitations are rubbish and turn to crumb.

I got a local firm to strip the asbestos and replace with insulated metal sheets. Really good, but maybe not a budget option.

Do you buy in readymix and just get your wife to barrow it in and lay it?

I am doing a full filled cavity with brick outer leaf and I will coat the brickwork with Stormdry Masonry cream. BBA approved, one coat application and 25 year protection life.

Yes someone with you would be best.

I cannot work out where North is on the drawing. Can't see any bifolds. If the 2 windows at the top are the East facing tall windows, then are the French doors facing South? Wall insulation looks a bit thin but you SAP person will say if it is acceptable. Whatever, you may find that decent blinds will help potential overheating.

Photo would be useful. If it cannot be seen, it is not possible to say if it OK or not.

I don't think there is anything to worry about. In powdered form it can be hazardous. For the other ceilings, just skim them, do not sand them.

Perhaps start by looking at what other houses nearby have rear extensions. You could talk to Building Control and find out what foundation systems are typically used and whether there are any foundation issues locally. You will probably want a structural engineer for the project so if you can find one that has dealt with the ground conditions and sewer proximity before they should be able to propose a sensible design.

You could do as @markc suggests but if this is to be a habitable room you will also need insulation in the floor and the roof, otherwise you will have issues with lack of Building Regulations when you come to sell.