Mr Punter

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.

We are on land that has about 2m depth of fairly solid clay and made ground, then 18m alluvial silt, then hard chalk bedrock. The previous buildings on the site had fairly shallow strip footings with no sign of movement. Our replacements are 4 storey and are on 25m piles. Anything founded between 2m and 18m would not be very stable.

The were Sandtoft 20/20 tiles. I think they are all nailed. The dark grey (antique) ones look quite good. Fairly economical too for a clay tile.

Maybe once it is battened you could ask your solar installers if you should leave any tiles not nailed? I recently had some solar put on a tiled roof and it caused no issues. A few tiles were removed and modified with a grinder and replaced.

They all seem to want £300 a day guaranteed for an easy days work.

Request a fixing specification from the tile manufacturer specific to your roof and follow it.

Another vote for a thin layer of external insulation.

How about a door which is fixed shut and to be used only in emergency, plus a high level window for light and ventilation?

You should have a y and a 45, so the flow is in the right direction.

Hello and welcome. You have a fair amount of work there. You may find there is not a huge benefit in installing UFH on the first floor and loft. The heat will tend to find its way up anyway. Have you calculated your heat losses?

That probably saved a fair bit on Party Wall Surveyor fees.