ProDave

I marked mine myself, by measuring with a long tape measure, and then when I had it marked out I painted a single white line on the ground marking the centre of each trench. I then dug it lining up the centre tooth on the bucket with the line. My builder said it would never be accurate, then ate his words when he found no alterations needed to the trenches before pouring concrete.

Board one side, fit insulation, board the second side.

The halfway house I adopted, was I excavated and laid and compacted the sub base. I interpreted the 1M from the highway unless fenced literally. and banged a few sticks in and strung out a "fence" then I was working on my land adjacent to the highway but fenced off. I then got a highways approved contractor to lay the tarmac on my sub base.

Buy something like this. https://www.ebay.co.uk/itm/134888823698? I have 2 such systems in use, one Panasonic, One Sony. Both old and almost worthless as you can see from the pricing, but in their day expensive good kit. Still working well and sounding good. Though no doubt not as good as @Pocster £4K new system.

Pester him to do that drain pressure test. Only that will tell you if there is a leak in any part of the drainage system. Without that he is poking around at random, getting nowhere and not solving the problem.

That reads as someone that got the hump because you want to change something. Yes it will need some SE design. As for the rest pipes will be on display? How many pipes do you expect to have going into a vaulted ceiling and just where will they be going? Exactly NONE. They all go through the service void in the walls. MVHR vents are the only ones that can be tricky. But each case is individual and you will find a route. And just because the structure is built as a vaulted roof which makes building a good air tight well insulated building a lot easier to detail, you do not have to have all rooms open to the roof space. We had one bedroom fully vaulted with a mezanine floor as a feature. The master bedroom was partly vaulted with a higher ceiling but still giving a loft space above it, and the landing and bathrooms had normal 2400mm ceiling giving a larger loft space above them. So much flexibility and options you can choose as you go. And any loft space you do choose to create, will be just as warm and dry as any other part of the house.

Vaulted ceiling requires you have a ridge beam running end to end of the roof, and then probably larger rafters hung from that down to the eaves. It completely removes the need for the raised tie and all the truss members, leaving you a simple roof easy to detail. In our case we built as a hybrid roof, 195mm deep rafters, full filled with insulation and 100mm solid insulation above the rafters.

Why can't the slope go either way? surely whatever wall plate you support them on would be on a slope so the next joist along is a little lower etc. Is this not allowed? Are you forced to put them all level and add firrings? And if that is the case, whichever way you want the slope it would have to be dead flat in both directions then firrings added?

You don't need a site licence to self occupy a single caravan on your own site. The advantage of building as a caravan is that in some cases might be easier to get planning (or you might have it already) and it largely avoids building regs. There was a Grand Design building a "caravan" at 100 square metres and looking every bit like a house but it fitted the technical description of a caravan for which they already had planning permission. Why don't you build it as a house on proper foundations? What was your motivation for trying to make it as a caravan?

Post a picture of this narrow plot showing the adjacent buildings.

If you are building this as a "caravan" on a park home chassis, then a different set of rules apply to the dimensions of a "caravan" and those don't specify a maximum eaves height. They specify maximum overall dimensions and a maximum internal ceiling height of 3 metres and only single storey but no eaves or ridge height specifications. A "caravan" is also mostly exempt from building regulation. A "caravan" does not actually need to be on wheels, it must be transportable and lifting it with a crane onto a low loader qualifies for that so it need not be that high off the ground. For a self build you almost certainly will not be able to reclaim the VAT if building a caravan.

Span all the joists the shorter 5.2M dimension?

I built it entirely myself not from a kit. The only bit I bought was the rail and sliding gear I think intended for wardrobe doors. and the irnmongery. All the woodwork I just made.

The devil is in the detail. We used a sliding door in a previous house to comply with the (at the time) 2 doors between a kitchen and a WC. It was a sliding door between the kitchen and a short corridor. The door slid 100% into the pocket with a recessed finger pull on the end if you wanted to pull it out, and recessed handles each side to slide it. And it never ever got closed.

That's what I did. I fitted my door frames to match the doors, not the other way around, so no trimming of doors whatsoever and the ventilation gap left at the bottom. I also ommitted the door stop along the top of the door frame. It adds nothing to actually stopping the door, and adds another small space for ventilation.

Post some pictures of the work done and the gap. Who was the "Landscaper"?

I would "just do it" But I would not put it remote from the house as you have shown, I would put it adjacent to the house wall just around the corner on the side. Hidden by a tall fence and hedge I bet nobody will notice and you will get away with it. If you are served enforcement notice, then just move it around the corner so it is now on the back wall of the house and thus no closer to the highway than any part of the building.

the leak appears to be starting here What's going on there? Is that a hole in the tank? What for?

I have one of those. It is set up as a stupidly large tv in the smallest spare bedroom. But the real reason I keep it is as a spare. We have 2 large tv's in the two main rooms and if one breaks, I don't want to be rushed into getting a replacement, so I like to have a spare one that can be put into use while I either fix or replace the one that has died.

I am of the opposite school there. A pixel fault is likely a screen issue and unlikely repairable so I would have used the period when the fault went away to sell that so someone else before the fault comes back and possibly gets worse.

Personally I never see the need for an "AV Amp" That will route all input sources through that and output sound to the speaker and video to the tv. But more complicated to set up and my bugbear another remote control to juggle with. Instead I let the tv do all AV input selecting. Take Digital audio out from the tv to my very much simpler surround sound amp which is in fact just a DVD player with surround sound. I use 2 of these one in each living room and as they are old tech, you can get them cheap as chips I paid £20 for one recently a Sony, when it's predecessor failed and beat my attempts at fixing it. What is your budget and do you have to have new?

Some pictures of what you have might help. Trying to understand how you widen and lengthen a garage without knocking any of it down?

How about the largest touring caravan that will fit? or even 2 of them?

Very dependant on local LPA In my case they tried to force an "under your control" clause in, until I pointed out a few months before another planning app on the same road had been approved without an under your control clause so they removed it. During the discussions with highways about it they said of someone obstructs the visibility to inform them and they would come and deal with it.

A dead mouse under a floor board or kitchen unit etc can smell really bad for a long time