Temp

Water gets into regular sealed units through the smallest of holes because the gas inside expands and contracts with changes in temperature. That pumps air in and out taking water vapour with it. So unless the whole thing is one triple glazed sealed unit it will be near impossible to keep it out. If the humidity is high small reduction in temperature is all it takes to start condensation. Perhaps the other window gets slightly more sun.

PS: You might consider telling the Builder you would like to be there when the BCO makes his inspections. Not to check up on him but you are just interested in how it's done.

Based only on the photo it looks ok to me. I mean the general quality looks ok. Possibly one of the joist hangers could be neater? This sort of thing (where the beam goes) often involves compromises such as trading off increased headroom for thermal bridging. It generally looks better if the beam in in the ceiling rather than boxed in under it but that can increase heat losses. This sort of beam should really be designed by a professional, typically a structural engineer or similar. They will specify how big the beam is, how its jointed and supported. Frequently the Building Control Officer will ask to see those calculations/design. The job of the padstone is to prevent a "cheese wire" effect by spreading the load of the beam along the length of the wall which it is doing. Laying it flat would make it overhang the sides of the wall and that would have no benefit. The area of the padstone in contact with the wall is what matters and is calculated based on the load and the crush strength of the wall. Is it going to be a warm roof (insulation above rafters) or cold roof (insulation between rafters with ventilated void above the insulation) ? Edit: Ideally the padstone should be centred below the beam but even that may not be an issue especially if the pad stone is longer than necessary.

Doesn't make much difference either way. Might as well do your bit/both at same time. Joint ownership of property can be full of hidden issues. Be sure to get a solicitor involved to do the paperwork. Consider what would happen if one of you dies or gets made redundant or you had a falling out and had to move out. How would you get your share out? It should define your share of any bills like council tax? Maintenance, insurance etc. If you want to be able to sell it as two separate properties I believe that would need planning permission. Two lots of council tax etc.

I believe the problem is the single glazing on the outside. You can't avoid water vapour getting into the 18cm void and the single glazed outer will be cold. I think it would be better to have a sealed DG unit on the outside, an 18cm gap and SG on the inside. That way the outer unit would be warmer. Probably too expensive to change now. Try putting dehumidifier crystals in the 18cm void?

We left the EU in 2021. After that...

Quintec switches are wireless. You can put a quintec switch anywhere. So you could have one of their switches next to an outside door where there is no power. That switch can talk to a reciever in say the garage where your outside lights pick up power. No need for wires from the switch to the lights. The switches are powered by your hand moving the switch. So no battery required either. They also have a PIR sensor that is also wireless. This can also be paired to control your lights. It has a dusk to dawn light level sensor so the PIR only turns the lights on at night. https://www.tlc-direct.co.uk/Products/QUPIR.html?source=adwords&ad_position=&ad_id=&placement=&kw=&network=x&matchtype=&ad_type=pla&product_id=QUPIR&product_partition_id=&campaign=shopping_switches_sockets&version=finalurl_v3&gad_source=1&gclid=Cj0KCQjw3ZayBhDRARIsAPWzx8pc0t4tphYjRwJLKUNjTeC_R0IZdyqzTj0-Sc0bjQ9U4ei5EBDX9yMaAt0SEALw_wcB I've not used any if their kit but it's all fairly straightforward to understand.

Think I would jury rig some Quintec switches to try them out before installing. Sometimes it's nice to have our outside lights just come on when you arrive home or step outside. They do a PIR sensor you can use.

Think I would check for eggs. If none block access. They can nest elsewhere.

Write the plumber a letter certifying that their work is on a new build. Quote your planning reference number and all your contact details. Use the words "I certify..." Show them VAT 708.

If the plumber buys materials they must zero rated them to you same as their labour. So you have no VAT to reclaim. Waiting on receipts from them so you can reclaim the VAT isn't an option HMRC allow on a new build. Only on a conversion where it's 5%. The plumber isn't out of pocket as he reclaims any VAT he pays.

Not sure I follow all that but my understanding is the boiler modulates down to keep the flow temperature below some set limit. They can't modulate down to zero. If they reach the minimum flame power they start cycling on/off.

How can you have a soak away design without having done a percolation test? To correctly size the soak away you need figures from the percolation test. Unless you guess.

Would be hard to get a wheel chair past the cars parked on the pavement?

With care you can hide the cistern and frame for the wall hung WC in a stud wall. The main issue is the waste pipe run. We clad our bathroom stud walls with 12mm Hardibacker board before tiling. It's hard to cut but it's bomb proof and allows you to fix most things like towel rails or lights anywhere. Obviously something like a wall hung basin needs more. I think the weight of Hardibacker helps a bit with sound proofing.

Shower trays are normally bedded on mortar (or flexible tile adhesive for thin beds). I believe this is to reduce the risk of the tray cracking by providing distributed support. If your installer hasn't bedded the tray you have to wonder what sort of job he is doing elsewhere.

What's the roof covering going to be?

I thought the pipe is in place when you pour. You just wrap the pipe with something compliant and support it at the right height and angle and pour concrete.

It has been done. Very dependant on the planners. How similar are other house in the road? The more variety the better your chances. If they all have a very similar style then planners frequently want you to propose something similar/complementary and may even want you to use the same bricks. The service you get from the planners is also very variable. In some areas you would be very lucky to get a meeting. They may just advise you to send in a proposal and pay for pre-app advice. The pre-app advice you actually get ight not be very useful or constructive. In my area the planner (singular) appears to be shared with another county. Conservation officers are also part time. No wonder we can't built enough houses. If they want to see a proposal first I recommend including a street view drawing. This would typically be a drawing of your proposed house and those either side as seen from the road. Our Architect did this using pen, ink and water colour. The use of that media allows some artistic license and harmonises the three buildings more than CAD drawings or a mix of photos and drawings would. Many CAD programs (Inc Sketchup) can convert a CAD drawing into something that looks like an artists sketch using styles. I wanted to build an oak clad building and the CAD model gave every plank straight edges. Using one of these styles made it look far more rustic.

I would be tempted to make the door reveal several inches wider than the door sill and run the breather and cladding down the reveal to below the sill ( same level as the rest of the building). Leave a 1" gap at each end of the sill so it doesn't have to be sealed against the reveal.

It appears everyone is parked wheels on the pavement both sides. Would the road be too narrow for an ambulance or fire engine if cars parked fully on the road both sides? That might be an argument for making one whole side of the road no parking? But that would make you really popular. Pavement parking is illegal in London but elsewhere the rules are mixed. I suppose it might give police/Council the power to move the car when they otherwise cant?

Many of us have got an elderly disabled relative. Perhaps ask council if they can yellow line a short section so you can access your driveway when your elderly relative is staying... https://www.honestjohn.co.uk/askhj/answer/128671/is-it-possible-to-ask-to-get-double-yellow-lines-painted-outside-our-house-to-stop-inconsiderate

Yes you can run the boiler flow temperature hotter than 60C. Perhaps test carefully to ensure the system cannot send a pulse of very hot water into the tub when it starts up?

A. i) Not sure. ii) I would expect it to deliver close to 28kW. Even when the return is 40 and the flow 60C. That's also a 20C uplift. But I think you should check the data. I might be wrong. iii) yes. Corrosion inhibitor in the tub water? B. i) Google suggests heat exchangers are about 90% efficient so you won't quite get 28kW out if you put 28kW into a heat exchanger. ii) I looked at the 30kW heat exchanger here... https://heatpumps4pools.com/myfiles/file/Elecro-G2-heat-exchanger-Leaflet.pdf It has a table for the power transfer vs delta T.. If your boiler is 60C and the tub at 40C the delta is 20C. The data for that exchanger says the power transfer is in the range 11kW to 15kW. If your boiler is 60C and the tub at 20C the delta is 40C. The data for that exchanger says the power transfer is in the range 20kW to 26kW. Perhaps use a bigger heat exchanger? iii) I think once the tub is upto 40C the boiler return will be too hot for condensing. C. If we assumed the heat exchanger power transfer was a constant 15kW thats 15kJ per second. To raise the temperature from 5C to 40C requires 35*1000*4200 = 147MJ. That would take 147*10^6/15*10^3 = 9800 seconds or about 2h 45 min. 147MJ is about 40.8 KWh (units) not including losses due to efficiency of boiler and heat exchanger, pipes etc. I'm not a boiler engineer! This is just physics to me.

Should be fine. The compaction of the soil is because invariably there are some spots that are soft because you had to dig or rake to get it level.