ProDave

I made mine 2.5M wide. More of an issue was getting the height I required, I wanted it tall enough to get the Landrover in. That height requirement ruled out sectional doors. I ended up with a rolller door. they have the big advantage of fitting to the inside face of the opening, so when open, there is no reduction in the actual opening, These don't come in standard sizes, they are made to measure. Cost £500 from ebay.

Can you not build one, live in it for a few years, claim all the exemptions and VAT reclaim, then sell that and build No 2. CIS registration is straightforward at least as a subcontractor, I have to be registered for that as a sole trader for the times when I work on a new build and get tax deducted by the main contractor.

Or cut out a socket box and fit an additional socket All depends where the hole is.

Gyproc Joint filler. Unfortunately you only seem able to buy it in large tubs. It takes ages to dry if you put it on too thick, so think several small layers with time to dry. When dry it sands beautifully to get a nice finish. Must be sanded dry with a very fine paper. Take a sharp stanley knife and go round the hole to cut the paper and taper the hole inwards (think countersinking it) so you don't have flappy paper edges to worry about, I have a large tub at present. If you bring a suitable air tight vessel you are welcome to a few scoops of that when I see you shortly.

The floor is tanked (wet room) and the tanking goes a little way up the wall. The floor was then tiled. Then the wall board applied. Clear sealant (I used stixall) to seal the bottom edge, wiped clean so it does not protrude, then when that has dried a bead of white sealant as a decorative finish. I used the plain boards that have a vertical joint, as it happens there is only one such joint. Theu also do a version where the panels interlock to the next one making an invisible joint. About £100 per sheet from Jewsons They do sell an edge bead to seal the bottom joint but aparently it is very poor and leaves the bottom of the panel sitting in a channel of water. Avoid using that.

Not in Scotland, a sarking board is a (sensible) building regs requirement.

I will comment on the tiles. Don;t. Use a waterproof wall board such as Multipanel instead. No joints, no grout, totally waterproof.

How important is it to have "nothing" at the eaves? Would a minimal overhang do? This is what I have done: The eaves board is just regularised construction timber, fitted before the render. Eventually it is going to be over clad in aluminium painted to match the window colour.

Can you give us any other information about the building? How was it built? masonry or timber frame? did you see it during construction? do you have any photographs? Architects drawings? etc etc.

If you want an idea of the running costs you can achieve with a bit of care, here is ours so far. Walls etc barely to passive house insulation levels (typical U value 0.14) triple glazed, mvhr, ASHP driving UFH downstairs only. Bear in mind also we are in the highlands. These last 2 very cold weeks, we have been using 95KWh for heating, and 35KWh for hot water per week.

My solution is natural. Lots of trees south of the house. In the winter without leaves, they let most of the sun through. In the summer in leaf, they screen the sun nicely.

I think our house is probably a good ballance. Definitely not zero heating, but very low heating required. But it's also a very comfortable house, no sudden changes in temperature, no draughts, and good air quality thanks to the mvhr. I think it has been mentioned before, but when we finally reach state pension age, if they are still paying the winter heating supliment, that will probably poy for most of our annual heating bill. Now if only I could find a way to reduce the council tax by a similar amount to my now low fuel bills.

Most of our walls etc have a U value of 0.14, and the calculated heat loss when it's +20 inside and -10 outside, is just a shade over 2KW, which is comfortably delivered by a 5KW ASHP

I must have a mental block, or a browser compatability issue. I have completed the survey but can't find a "done" or "submit" button??????

The manual for the Upnor system is here https://www.uponor.gr/-/media/country-specific/uponor_com/download-centre/indoor_climate/underfloor-heating/brochures/mi-control-system-controller.pdf?v=00980da3-16c5-40ed-ac3d-a8bebbf3c6af That thermostat has provision for a floor temperature sensor that you don't appear to have so the floor setting will do nothing.

Why bother with masonry? Make it timber framed with some form of cladding then almost all the wall thickness can be insulation.

I considered ground source. The pipe that you bury and the antifreeze to go in it exceeds the cost of the heat pump. The other consideration is noise. the GSHP unit will be in the building purring away. I chose a monoblock ASHP instead, it is pretty quiet, but the main point is the noise is in the unit outside, not in your building.

Taping and filling plasterboard is a DIY job. If it needs to be a fireproof ceiling to a habitable space it needs to be 2 layers of the 15mm pink board with staggered joints.

Can you not at least get hold of the design SAP document?

Is there a manufacturers name and model number on that thermostat? Googling DT-37 etc does not help much.

Another here standing up in defence of the WBS. Like @joe90 I have a 4.5KW WBS that takes it's combustion air from outside via a duct, and by using an insulated sleeve around the flue pipe did a pretty reasonable job of sealing where that exits the building, I can't say I have noticed it being a noticable source of heat loss from the house when not in use since I installed it. For me, the No 1 reason for having the WBS is firewood is plentiful and free here. The thought of spending £30 for 6 hours fuel would put me off ever using it. That would be way more expensive than the main heating (which seems to be averaging £2 per day for the whole house so far) in fact that 6 hour burn would cost more than a weeks whole house heating for me, The equation may change if you have to buy your firewood. If you really don't want to burn wood, I would get an LCD screen "stove" instead Overheating has to be thought about. Our house basically has 2 large rooms downstairs either side of the stairwell each with double doors to the stairwell. Doors open it is pretty much one big space and heat can convect up the stairwell. Open up like this the kitchen / diner where the stove is, gets to about 25 degrees and the rest of the house warms up as well. Yes I am sure if you light the stove for too long with that room shut it probably would get far too hot. Finally I will add that we are very pleased with the stove we ended up with, a Mendip stoves Churchill convection model. It has the ability to run at a lower power while still maintaining a good flue temperature, and is the first stove I have owned where I can genuinely say it keeps the glass clean.

If you put it in an outbuilding, it would very soon cool that outbuilding to lower than ambient temperatire. I suspect the climate here in our pat of the Highlands is the most extreme of any on here. In the last 2 weeks we have had temperatures down to -14 one night, more typically -10 at night, and not above 0 in the daytime My ASHP has been keeping the house warm througout this.. I monitor the electricity consumption for heating and hot water independantly, and the HW usage goes up when it is really cold and I observe the heat pump defrosting from time to time when heating the hot water, but when working a lot less hard to heat the lower temperature for heating, it rarely if ever needs to defrost. Another factor is my house is very well insulated, so I only heat it in the daytime, so when we get those very cold night temperatures the ASHP is not actually working which will help a little.

A common theme here is like @JSHarris our house is built either side of a central stairwell. Downstairs rooms heated by UFH, minimal UFH in the actual hallway. With all doors open there is a good convection path for heat from downstairs to get upstairs. Currently the downstairs thermostats are set at 20 degrees and the bedrooms are at 18.5 degrees this morning, The coldest it has got in the bedrooms was 16 degrees, and when that happens we fire up the WBS, which heats the kitchen / diner to about 25 (some would say overheats it) and that excess heat soon finds it's way up to boost the bedroom temperatures a little. There is also an argument if relying on downstairs heat to get upstairs, not to go overboard with insulation between floors.

It is beginning to sound like some "imagination" may have been used in the planning application. I would be wanting to visit the plot armed with a long tape measure and some stakes to measure out what is really there. Particularly with regards to the parking. Then read your councils policy with regard to amenity space and parking space. It is very likely the 2 sheds are going to have to move elsewhere. A hedge may be your best long term plan, but you need to be patient. I had a BIL who lived on an ordinary estate house on a corner plot. The way the estate was laid out by the developers, they only had a small square enclosed back garden behind the house, but they owned a large grass area alongside the house but open to the road. Any fence there would have been in front of the building line of the adjacent road so would not be allowed. But fortunately a previous owner had planted a Beech hedge all the way round, and then allowed the original fence to fall down. The result was they had a private garden wrapping around 3 sides of the house and way much more space than the tiny original back garden.

If it really is an ultra modern super insulated house, then you can manage without upstairs heating.We don't have any. But we need more information about the building, insulation levels etc.