Roundtuit

I've got similar on my larch. I'm lead to believe the mould is living on the sugars in the sap wood, and will exhaust its food supply in time and then fade as the timber weathers.

I think there has to be a valid planning reason to refuse your application. If there is a valid reason, whether your neighbour objects or not is irrelevant, and whatever private agreement you come to with him doesn't trump planning law. I would continue discussions about acceptability with the planners, not your neighbour.

Yes.

If you ever want to sell, a buyers surveyor will probably be interested in looking up there to establish the state of the timber and the amount of insulation. Hopefully you won't need to remove wasps nests or trap squirrels, but I'd put a hatch in...

Airtightness is important to the performance of your house in terms of heating requirement and comfort levels. In simple terms, you don't get the full benefit of your insulation if the air is bypassing it.

Why have a test before you're ready? For a new build, I'd be aspiring to much better than a scrape through...

Hi. I had one made at Jupiter Blue (also for utility room as it happens). Can't recall the price, but it was reasonable.

Bio Pure 2 here, discharging straight into ditch (England). The ditch usually has water in, but that may be because there is also some discharge going into it upstream.

Still got it! I was pleasantly surprised; seems well made, starts first pull and does the job. To be fair, I've still got a few jobs to do with it before I think about selling it, but I reckon I'll get back most of what I paid if I do.

Sorry, your guess would be as good as mine!

Yes, pretty much, or off any point (internal walls?) deemed solid enough to take the load. Not sure how feasible that is, but I think I'd be trying to come up with a solution in principle with a good builder (they're often pretty creative problem-solvers), before passing it to an engineer to do the maths.

Sorry- misunderstood the point of the question! Thought it was the tank that was the problem, but I see you have bigger challenges... Can't offer any specific advise, but thinking 'out of the box' is there any scope for running steels diagonally from your support points, perhaps to provide intermediate support where there currently is none? Or (and I appreciate this might be a step too far), if you've got weight bearing walls in the right place, perhaps a length of UC running up through a bedroom, boxed in?

Welcome! There's no other single resource with such a diverse range of expertise and experience for self-builders; sit back and soak it up!

Looking at that sort of money, I'd be seriously thinking about re-locating the tank somewhere else and updating your hot water system tbh.

For small pictures I'd use a plug and screw; for bigger pictures, two plugs and screws, spaced appropriately. For heavier stuff, try and position it where you can screw into a batten and just use wood screws.