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+1 Should be tax free. It can be hard for a novice builder to make money actually building a house. Dont always believe the figures they quote on Grand Designs. You might make most of the money just getting PP and selling it to a developer. You could add covenants precluding them constructing a basement if you want or giving you a share of the profit if they reapply for a different/larger building.

Your best bet would be to build the new place for yourself and move in tor at least 3 years. Rent out your current property. CIL - None as self builders are exempt. VAT - reclaimed on materials, not paid at all on labour. Standard rated on architect. CGT - Probably none if you sell your current property as for most of the time its been your Principle Private Residence. Remember to make a will as IHT could be significant.

Be careful.. If you build to rent them out i don't think you can reclaim the VAT. https://www.macfarlanes.com/what-we-think/in-depth/2017/build-to-rent-vat-issues/#:~:text=Typically a residential developer will,purchase price for the site.

Is anyone likely to complain? If not you could just build it and see what happens. If someone complains the planners will send you a letter saying you need planning permission and you can make a retrospective application. If its refused you can appeal. If that fails you would have to reduce the height or knock it down. If the planners take no action for 4 years then you can apply for a certificate of lawfulness on the grounds they can no longer take enforcement action.

I would suggest getting a heat loss calculation from someone not trying to sell you ASHP. What boiler do you currently have?

We put in a rainwater collection tank but its only used to water the garden and the car so no need for filters etc. Doubt it pays for itself but is handy in a drought.

As I recall the manufacturer also has to approve their socket for use in a bathroom/humid area.

Welcome to the forum. Can I recommend you beef up the insulation and pay attention to how its installed. If there is one issue with ASHP that comes up regularly it appears to be undersizing - specifically the heat loss being greater than expected.

Perhaps you could put a flourescent dye in the system that woukdn't evaporate away?

You can't tell. At best you can say its less than the volume of the expansion vessel because there is still some pressure in the system.

37 x ?? Some buildings only have small ceiling rafters rather than loft floor joists. In other words they are only intended to hold up plasterboard not for people to walk about on or store things up there. If you want to store things up there or convert the loft to storage space the loft floor may need reinforcing.

I think that might be the only place in planning law where a completion time limit is specified? Are there any others?

In Belgium they say... Build your first house for your enemy, your second for a friend and the third one for you.

They almost all smell of burning paint when new because the heat is needed to fully "set" the paint. As for smoke.. go outside and check where the smoke is going. Could it be lingering around the house and coming back in via trickle vents?

If the builder was negligent then his insurance co might still be on the hook. It would be his insurance co back then rather than now.

Got me wondering whats on my roof. We have valley tiles..

It doesnt look unused. Can see where its been walked? Animals? First thing to do.. 1) Do a search at the land registry to find out who owns it. You may have to request a "map search" as its unlikely to have an address. This involves sending them a OS map with the land highlighted. Make sure to use the real site which looks less professional than the fakes! 2) Find out from the footpath officer or map on county council web if there is a public footpath. If nobody owns it and its not a public footpath you could try claiming it. However the full process takes 12+ years and there are no guarantees. You have to fence it off "to the exclusion of all others" for that time. Ideally with a 6ft fence but planning rules mean it may have to be a 1m fence. Then see what happens. Chances are Mrs Miggins of number 22 will claim she's walked her Pickneese Tricky Woo there for the past 200 years. In which case she may have a right of access and your plan is probably history. If nobody raises any issues you would then need to look at the planning situation. The staircase may be considered a "side extension" and i think there is a 4m height limit above which you need planning permission. If its going to be capable of "seperate occupation" you may need Planning Permission. What you need to do for Building Control Approval may also be an issue as the specification for floors between separate dwellings is different to floors within one dwelling. May also need its own electricity meter, gas, water meters?. If its retained as part of the house, the house becomes 3 storey. That can have implications for your ground floor. For example you may need to replace doors on the ground and first floor. More if its open plan. Lots to think about sorry.

Insulation perhaps?

You might also consider talking to a solicitor if the NHBC can't help. If there is sound insulation over the pipes then someone has been negligent. Keep the reports you have had done and possibly get an expert to comment specifically on the sound insulation issue.

I wonder what the return temperatures are like given..

+1 In awful lot depends on how well insulated the house is, double or tripple glazing etc. Mine built around 2006/7 needs much higher flow temperatures than either suggestion to achieve 20C room temperatures in some rooms where we have 21mm wood floors over UFH. Based on your numbers.. A TOG of 2.1 is equivalent to an R-Value of 0.21 or U-Value of 1/0.21 = 4.76 W/m²·K. The power dissipated per square meter would be U-Value * Temperature difference At 21C.. = 4.76 * (23-21) = 9.5 W per square meter. At 26C'' = 4.76 * (26-21) = 23.8 W per square meter. I'm not very familiar with the SAP/EPC figures but if you have that info perhaps someone can comment if this is all consistent.

I'd say yes. Normally they fail by filling with water instead of air then when the heating is turned on the pressure rises pushing water out of the PRV. The pressure rise appears within limits and no water coming out of PRV.

Regarding Building Control.. Its best to document all communications. Eg after a call follow it up with an email or letter confirming what actions were agreed and who would do them. Same for any site visits.. what actions were agreed and when you should call him next. I would invite him to inspect the foundation trench for the new wall.

Do ASHP come with the sensors needed to monitor the actual COP achieved?

I think those pressures are in the right range. The increase might be slightly larger than normal but not by much. Can't say its definitely a problem. Normal is around 1-1.5 An increase of more than say 1 suggests there might be an issue with the expansion vessel. Anything over 2.5 is getting close to opening the PRV.