the_r_sole

Get the mineral wool out of the cavity and put some rigid insulation on the inside of the kit panel. Check the joist manufacturer details for the fixings, most of the ones I've seen are on hangers rather than built into the wall like you've shown... engineers will give you panel drawings, although it's not rocket science!

I once had a client who decided not to appoint me for site inspection work, I happened to be passing the site one day and went for a nosey... the builder had decided, instead of my nicely detailed warm roof, that he would put 50mm insulation on top of the deck and 100mm under it because he didn't want to get the profiled facia pressed and this would "look just the same" I told the client that you can't really do that as you can end up with serious problems, and I'm 100% sure the client didn't believe me and thought I was just being a picky architect in a huff because they were going to ruin the look of the building. Luckily he did some googling into the problems with hybrid construction and called me the next day to apologise! then made the builders take off the roof finish and built it properly! (they still made the roof verge detail absolutely awful right enough!) If they can't read the drawings well enough to build a warm roof, I'm not sure I'd really trust they could be careful enough with a membrane installation!

ancient woodland can be a right pain in the rear! Killed a house site near me recently! You're going to get into a bit of cost with those consultees! Archaeology can get a bit open ended, I've not had too many nightmares with that to date (touch wood)

Is it just the standard stuff or any potential show stoppers?

the kingspan/celotex/any other manufacturers calculations all account for the amount of timber in the wall construction, the uvalues are area weighted, you don't do different calcs for each bit of the wall

what calculator are using for those values? Kingspan calc gives a lot better on those thicknesses https://www.uvalue-calculator.co.uk/calculator/walls/timber frame/insulation between timber studs with (insulated) plasterboard/140mm/timber cladding/37.5/80/

Usually we'd go for 120mm between (140mm studs) and 35-50 internally

From what I've seen of them, I'd say fakro is a better window (i've seen the sales rep jumping up and down on one in a roof to show how secure they are ?) I think that it's a nicer window which feels a bit more substantial to the velux, I think they've tried to develop the design rather than just copy it - but as I say, usually they are more expensive....

I'm sure they'll do whatever you want in any size, but the costs might come into play - I think the even do a quadruple glazed unit...

Fakro are usually more expensive than velux but it's a better product imo - if it's special sizes I can't see how it's cheaper than velux at all! If the spec is what you want and you're getting the right flashing kit etc then it's a no brainer for me but I check the specs thoroughly as fakro have endless options

the uvalue calcs take account of the amount of timber in the wall construction - with 100mm kit you'll definitely need some insulation on the inside too rather than just between studs

Glasgow City Council?

It's just about the context, the building regs are pretty straightforward in what constitutes a material change of use https://www.designingbuildings.co.uk/wiki/Material_change_of_use Planning is a whole different ball game and if you're relying on planning appeals which are based around interpretation of case law then you can get down an expensive rabbit hole pretty quickly to make your case...

If they make the system better then it would stop people ignoring it! I don't think people should as a rule ignore planning but I've just had a young family be refused planning for a site which has had planning approved twice (in error apparently, even though the site selection was done by the planning officer on site!) If they'd just bashed on and built it they'd have a house but now they've got a legal battle to try and recover the money they've sunk on the incorrect guidance of a planner

tbf - given my recent experiences of the sh!t show that is local authority planning - I applaud anyone that can afford to take the risk of building something without planning permission!! A favourite quote of mine (which is never the advice I'd give formally to a client...) "it's easier to ask for forgiveness than permission" maybe doesn't apply to everything right enough ?

If you've only got 1950 clear and you're adding 1000mm internally you're not going to have much over 600mm left for access around by the time you've built a wall! I still don't get any real sense of what you want out of it, I get that you want a bigger kitchen but you've haven't said anything about the quality of space you want, I know you're starting from the practical point of saying we can add 1m all the way round but is all that expensive floor area working hard for you? As a thought, do you need the doors between the kitchen and the lounge? I would be tempted to remove them and then push the kitchen to that side (using the extra wall room you now have) and then extend the width of the kitchen out to where you need and have a dining table in the area of the current kitchen... Or do you really want a wc and utility? were they just added in because you can?

I've got lots to say on this but don't have time right now! Just posting so I can find it again.... The first question you've got to answer is what do you want out of the alterations and extension? what spaces are you adding, and what character of space are you trying to create? Is it just making the spaces you have slightly bigger or is there a different problem you are trying to solve with the alteraions?

Planning and building regs are different things altogether so the interpretation of a planning appeal isn't going to give you anything at all for building regs

No one can guarantee planning approval, no matter where they might have worked. Planning constantly throws up surprises... (Although in your case, I guess you'll be ok)

Interesting points @Gus Potter I remember doing a couple of warrants with the small buildings guidance back in the day too... I guess for me, I have a small group of engineers that I use based on experience of dealing with them, and I've not asked any of them to do a package without SER, the last engineer I used who wasn't SER had hand drawn details (literally biro mark ups of my drawings) ?

Have a dig around to get the precise policy wording and see what the exceptions are. "Nearby" is too loose...

this is a strange one - it's definitely not framed right but I just can't figure out exactly why/how! Get yourself a copy of the lead manual and you'll be able to flash anything ever! I can only think of one job where we've specified valley tiles before - it's not uncommon for the pitch on a dormer to differ from the main roof at all

It comes across as confirmation bias tbh Building houses is full of compromise - there are very few people who have the budget, site and knowledge to the deliver the "perfect" house. It seems you are absolutely determined to discount timber frame even when presented with the arguments, which is fine, but it's throwing the baby out with the bathwater...

This is a weird thread, guy comes on asking for advice and opinions but then discounts everything that anyone says because he's only looking for confirmation that his way is the best way. Timber frame has been around for years and years, in wet/humid climates you will notice that the number of Timber frame houses built in those climates over the last 50-100 years compared to concrete structures is very different. Just because something can be done badly doesn't mean it has to be done badly...

They'll be able to price it up, I think you are overthinking it, get the drawings and design done for the stage of the project you are at, and if you need more information down the line you need more information. If you're going with a kit manufacturer they'll produce their own engineering calcs etc anyway