mr rusty

The cost of a solicitor to try (an IMHO not succeed) in making this a legal condition of planning is most likely more than the cost of new DGU with frosted glass. It won't happen as the OP expects because if planners started to issue PP on the basis of the presence of 3rd party agreements a whole can of worms would be opened. Planning stands or falls on it's own rules

I'm not so sure you will need planning permission because you are not changing the footprint, usage or aspect of the building, but I'm not completely sure. What you will definitely need, and what may be a challenge is building control. It may be a challenge because that "conservatory" doesn't meet latest standards and I expect that re-roofing will bring the project in to the latest regs - You definitely need some good advice - whether that comes from some of the more knowledgeable people here or an external professional, you will still need someone to draw up some plans for a regs application. You might want to consider just upgrading the polycarb to maybe a 5 ply, much better thermally rated material which would then still give you the light and still improve the useability. This might restrict your regs application to just taking down the wall, and ignore the "conservatory" - depends on your budget.....

If it's a summer house with sofa beds which are very occasionally used, who'd know? who'd care?

As a someone this doesn't affect but have an interest, this looks like a huge tier of additional work and cost which can only reflect in the prices charged for new houses, which will drive up the cost of all housing. I came across this:- So if you are a developer, you have the option to buy another piece of land solely to improve the biodiversity to offset against the development. I hope no land sold for this purpose has any connection whatsoever with the panel determining the planning application.... Cynical? moi?

I had a similar condition on a recent planning. The tree survey came back with "during the build (of my garden room) building materials must not be stored in the root area of the tree (which otherwise they agreed was outside the development). The irony was that's where my stack of "may come in handy" building materials, rockery stone etc has been stacked for years.....

I did my most recent extension on a notice too. The key thing is to make sure the builder understands it is his responsibility to build to regs and final payment is subject to a completion certificate being issued. i.e. the builder is on a design and build contract. Do expect to pay a premium for the builder's risk though. In my case it wasn't an issue because the builder and the LA BCO had worked together loads of times and there was mutual trust and respect. IMHO this is a good way to go because it totally avoids any controversy between the designer and the builder passing the buck between each other if there is a problem with BC.

I feared this when we built our garden room which is only 8m from the house next door, but with a 2.1m fence already in place, and 2.3m eaves and 3.3 ridge I was able to show that the shadowing was well under the 25 degree limit described in BRE Site Layout Planning for Daylight and Sunlight: A guide to good practice (2011). 25 degrees measured from centre of neighbours habitable room window. I don't think shadowing of a garden is a thing. You could always point out to the neighbours that if they don't like your building you can always screen it with a row of 8m tall bamboo https://www.paramountplants.co.uk/blog/index.php/bamboo-for-screening/#:~:text=Fargesia Murielae grows to a,forming a dense elegant hedge.

This. And if you're survey doesn't highlight any structural issues, then it's nothing to worry about at all.

I expect, if you have PP for an annex for a relative to live in, that the decision notice says something along the lines of the annex is to be for ancillary use to the main building. My own PP decision notice includes "The proposal is for erection of a single storey outbuilding in the rear garden to be used as a garden room with use ancillary to the main dwellinghouse. " The key is "ancillary" rather than "incidental". As far as I understand it, ancillary means that you can do anything in it that you would do in the main house, but it isn't necessarily a separate accommodation unit (own address, council tax, services bills etc.) or is rented out as a business. If the PP says "incidental use", then it cannot become a separate accommodation unit, but my understanding is that if it is for "ancillary use" it can, and may or may not be subject to council tax depending on how it is used (by family etc or others). To avoid council tax implications I would ensure, if the council are involved, that you clarify it is only being used for incidental use even if the original PP was for ancillary use as an annex.

No big family houses?

I'm with @devildamo here. A purpose incidental to a house would not, however, cover normal residential uses, such as separate self-contained accommodation ( if it isn't self contained accom. this doesn't apply)or the use of an outbuilding for primary living accommodation (if it isn't primary living accommodation this doesn't apply) such as a bedroom, bathroom, or kitchen. The key thing IMHO is whether the use of the garden room is ancillary to the main house as planned/used. If it is, you can do whatever you like in it subject to building regs for electric and drains. Like most things this will depend on the facts. If it's got a bedroom, kitchen, toilet shower then it's very hard to argue it's not self contained accommodation. If it has a kitchenette, toilet but no bedroom, and these are not the primary facilities for the main house, it's easy to argue it's just for ancillary use.

I agree. Hardie or Cembrit cement planks have the advantage that they stay looking like they do on day 1 - no colour change/fading (in my experience at least with paler colours). They also have a very low thermal coefficient of expansion (from what I can tell from specs, about 1/3 compared to composite plastic and 1/10 of uPVC. )

Why don't you build it as two separate units with perhaps a canopy between and save yourself a lot of heartache - <30sqm internal and it is BR exempt.

...unless you use hooks

I think you have to ask yourself where the design risk sits. If you have a comprehensive design from an architect and pass it to a builder in the round and say "build this", then without too much doubt the design risk sits with the architect. If you have an outline design/specification and issue a design and build contract to a builder where he builds what you want according to a general specification, and the builder ensures all BR compliance, the design risk sits with the builder. If you have an outline design from the architect, and you act as project manager and employ trades people to complete work as and when you want it done, then the design risk mostly sits with you. Inevitably on the project there is a "risk pot" somewhere, so it's a good idea to be very clear who is holding it.

If it's any help, conc lintels are shown on NHBC https://nhbc-standards.co.uk/6-superstructure-excluding-roofs/6-1-external-masonry-walls/6-1-12-lintels/ My local supplier provides all the BS numbers and span tables for the lintels they supply - I'm guessing yours are not much different. https://www.cwberry.com/prestressed-concrete-lintel-100-x-65mm

Yes, so would I, but under a PIP this could likely be the only reason for refusal (unless there are other issues) in which case an appeal would be a one-issue appeal and the government national guidelines would be the focus of the appeal. As I say, I'm no planner, just interested - I bow to the vastly superior knowledge of most on this forum...

I am not a planner, but is there any mileage in going down the PIP route? make a planning application for permission in principle, get it rejected because of the sequential test issue and then take it straight to appeal on the basis that national planning guidelines say you are exempt? https://www.gov.uk/guidance/national-planning-policy-framework/14-meeting-the-challenge-of-climate-change-flooding-and-coastal-change clause 168 footnote 56?

Single storey flat roof extension? you don't necessarily need regs drawings at all. Employ a builder on the basis what he builds has to comply with building regs, (i.e. he won't get final payment without completion certificate) and just do the job on a building notice. Best if the builder is local and knows the BC team. It's all pretty standard stuff, and if a builder doesn't know how to build a simple extension to regs, he isn't a builder. If you take this route you must use a builder you can trust to get it right.

I'm intrigued. What sort of machines are very tight in a 24sqm utility?...

FWIW I've just read the Ombudsman's webpage and I think the OP has a good chance of getting some compensation towards rectification https://www.lgo.org.uk/make-a-complaint/fact-sheets/planning-and-building-control/building-control I think I might be pragmatic and pay for the misting system and try and get reimbursement for reworking all the plastering and decoration due to their incorrect approval. The fact that they issued a Notice of Approval (i.e. a formal contractual document - which is my interpretation of a "notice") must carry some weight.

mine:- https://community.screwfix.com/threads/garden-room.256842/

Have a look at the projects forum at DIYnot.com for some inspiration. A small extension like that is eminently do-able for a competent DIYer. You could do it on a building notice so no building regs plans required. You could employ a builder just to do the footings/slab and the opening/beam on a "design and build" with the condition that payment is conditional on BC sign off of those elements. The brick/blockwork, simple roof, etc is DIYable - just make sure you conform to building regs with regard particularly to insulation. Is a cavity tray needed? At that size you should easily get the materials down to ball-park £10K for the shell which would leave you a fair bit for advice/subbed labour and fit-out, electrics etc etc. All depends on how handy you are. I'd do it.

In fact, when you read the decision from @Devildamo, it is a nonsense. "The physical scale....is excessive and is therefore not incidental". How on earth can scale which is about size, shape and form be related to "incidental" which for the purposes of planning is related to purpose and use. For this decision to conflate the two in the context of planning law surely would not stand closer scrutiny?

Sometimes you have to just do it. Even in @DevilDamo quote above the building is "deemed to be" rather than it actually was proven to be outside any regulation, which puts it firmly in subjective territory. The description of "store, study/games room and shower" is somewhat incompatible with the size and the smallish footprint of the house , which does suggest the applicant was possibly trying it on, and the rejection was possibly justified - nor is there any indication how controversial this development was generally. It is very easy for a planning authority to impose an "opinion" when asked, ahead of works starting - there is no downside for them. It is something of a bigger challenge for a LA to be so confident they are on such solid ground that they can initiate enforcement after the event which might entail going to appeal. The law makers went to the trouble of writing in all the restrictions for Schedule E. If they had wanted to impose a restriction in size as a proportion of the main dwelling, it would have been a one liner in the Act. They didn't, so IMHO it is challenging for a LA to try and interpret a restriction as existing when it isn't actually part of the law governing developments. The garden office @36sqm is very small in comparison to the plot size and I can't see there would be any reason for it not to be incidental, even if it has a use as a study. A garage is a garage, and if not used for anything commercial is literally that by definition - incidental. I am no expert, but from my own personal research for my own garden room, my opinion FWIW is just do it.