ProDave

Yes I thought we had established you don't need to go more than 1200 deep. Draw it at that and it won't look bad.

I revise my "next job" estimate to 2021

The error must be a start up thing, a valve not opening quick enough and the HP thinking too soon that the flow is too low. Re jug the controls so the timer / thermostat opens the 2 (or 3?) port valve and the feedback contact instructs the HP to start only when the valve is fully open.

Next year you mean?

But for example (as happened on my first build) when they started digging they found they needed to go deeper than expected. There was a clause for an additional cost for each additional course of under building. Want a window or door moved. Additional cost. Usually comes in the form of a "notice of variaton"

They will be the ones that turn the stat up to 30 expecting it to heat up quicker, and when it gets too hot, open the window.

There is a big difference between an estimate and a quote. If you have quotes they should be a fixed price but will likely be full of clauses that allow extra charges if there is anything ANYTHING different to what the quote says.

I don't see why that should not be capable of being used with any size PV array. Sure it won't use up as much excess due to a lower power heating element, but it would surely still work.

Could it be like mine, that the HP manufacturer provides a temperature probe that goes into a spare thermostat pocket on the hot water tank so does not actually use the standard tank thermostat? What else is connected to that tank?

That looks like the safety overheat thermostat. If it trips, you unscrew that little black thing and it reveals a reset button. But normally there are 2 thermostats, one that the user can adjust, and this last resort cut out. Often (usually) they are in the same case together. It does seem odd you don't appear to have that one.

I will just add my tuppence about thermostats. Plain old mechanical ones are fine as long as you connect a neutral to them, they have a built in "accelerator heater" to overcome the otherwise inherent hysteresis with a mechanical thermostat. Mine are working just fine and giving good control of room temperature. Not to everyones taste if you want fancy digital things but don't feel you have to. Don't bother heating internal corridors (other than incidental heating by pipes passing through to get to their destination) Our first build I let a "professional" designer design the UFH system. The hall and landing loops never came on and were a waste of pipe and effort. I bought all my kit from ebay. The only caution I would say with that approach was there are a lot of manifolds on the bay that come with IBO pumps. They are as noisy as hell. I have already changed one to a Wilo pump and will be changing the other one shortly.

Most machines, at least any that I have had anything to do with, go through a "homing" sequence at power up, driving each axis until a home switch is found and setting that as the zero datum. Such a homing sequence would synchronise the 2 stepper motors.

You build the entire structure of timber frame, regardless of how many and what shape "extensions" there are. Then you enclose the whole structure in brick or block. Don't over think it.

We regularly got mice in the loft of our old house (cold roof) I never actually saw how they got in but I believe they just climb the rough cast wall and in through the eaves or soffit vents.

Complete knock down and rebuild entitles you to reclaim the VAT so 20% cheaper. If building control will allow re use of the foundations how about a beam and block floor over what is there to raise the floor level?

The foundations thing. It is generally accepted that the load on the foundations extends outwards and downwards at 45 degrees. So if the foundations are 600mm deep, and you dig on the centreline between the 2 houses, so 1 metre away from each house, then that load bearing area would be virtually 1.6M down anyway so you are not going to disturb that in any way. A little less in practice as you project the 45 degree line from the outer edge of the foundation, so it depends how wide the footings are. But in any event digging at 1.2M is not going to bother anything.

So work it back. If your invert starts at 450mm, and follows a 1 in 80 fall down your in laws garden, how deep would it be by the time it got to the gap between the 2 houses? Unless I have done something wrong, I make that 0.825M deep, so you could probably make that 1M deep and have a bit more fall on the run down their back garden. 1M deep should not bother their foundations. The run from there to the drain will have to be a lot steeper, there are methods to do this but I don't know about them, drop chamber being one I hear about.

I can't see the pump working that close to your house. As I understand it, the pump raises it a bit, and from there it falls by gravity to the sewer. So more typically it would flow by gravity from your plot to somewhere on your in-laws house, possibly just behind their house, from where it would be pumped up into an inspection chamber at a higher level from where it flows by gravity into the sewer.

Cantilever beans above the windows to support some of the weight and require less of a corner post. Might cost £££ more to enable a thinner corner post.

I think you need to re address the rest bend thing. I worked my drain levels back from the treatment plant. I knew how deep that would be and I knew what the finished ground level would be. This resulted in the last drain entry to the house being a bit high. Okay different foundation system, strip foundations with suspended timber floor, but the rest bend is not fully encased in the concrete of the solum. But so what. As long as the bend of the rest bend is below FFL I honestly cannot see a problem. So mark it out accurately, and see what level it would be with a 1:80 fall to the main sewer. If you can avoid a pump station I would.

You seem to be in a market where I believe houses are under priced. By that I mean if you build a house you would do very well indeed to sell it for what it is worth. We are the same. I am self building and expect to come in at an all inclusive £220K. That works out at a build cost of about £1000 per square metre plus land plus fees. By doing a LOT of the work myself I have probably saved £30K so if I had just got someone in to do it all, it would have cost about £250K, which I would be lucky to sell it for if indeed I wanted to sell. Your only options seem to be project manage yourself and possibly do a lot of work yourself and hop to get the build cost between £1000 and £2000 per square metre. Or just sell the plot. I must admit I don't have a lot of confidence in this sort of "tender" bid. The very first house we built, architects were telling us it would cost £300K to build (and based their fees on that price) We built it for half that.

Changing the pump looks easy, when it is at normal level. Usually by the time you know the pump has failed, the level is way above normal, and you need to get it pumped out somewhere before you can even see the fittings to disconnect the pump. Been there, done that, don't wish to do it again. If asked again it is a "plumbers job" and I decline.

I understood you need a chamber whenever there is a branch or change of direction to a pipe run.

I am not sure they can insist they do all the work. Ask then to break down the quote into contestable and non contestable items. If your builder holds a minor street works permit (might not be the exact name) then he can do most of the excavation, though he will have to apply for a road opening permit (the DNO hold a permanent road opening permit). But talk to him first to make sure it really would be cheaper for him to do the work. As I say in my case it was all done by others, The DNO came, pulled a cable through the duct that was in place, made the connection in the connection pit that was open, connected the supply head, and left. Cost just over £1000

It will be the street works that are costing the money. Though I have to say getting a footpath closure order seems a little OTT. You could try approaching an independent street works contractor to get a price to do all the highway excavation up to the location of the joint pit, and install a duct with a draw string to pull the cable through and see if that is any cheaper.