Redbeard

From bitter experience... if you use a hot air gun (on low!) wear gloves. If you get it too hot your fingers will break through the oter layer into the molten hot butyl. It sticks and it burns. Can't tell you how I know.

dpc? I guess...

I could be wrong but I believe that a lot of cavity wall insulation companies are members of a self-certification body, so they can sign off against Bldg Regs. However I feel pretty jolly certain that they could not sign off a job which was not a cavity wall.

Yes, I think you need BC. You already have the calcs so do a Building Notice, which is just a pro forma telling them briefly what the works are and when you will start (no less than 2 days from the date of the notice) ... and a fee. I have not read all the thread but it is structural work. Any that I have ever done has needed BC approval.

Hi, when you say that do you mean you feel you have no recourse to the builder? Or does 'we...' include the builder re-doing the work? It is not ideal but while you would almost certainly not get a satisfactory result by patching you may be able to re-coat entirely. Not that I am recommending this at all, but 16 years ago an apparently well-thought-of insulation company managed to quote for 50mm phenolic EWI (which would then allegedly have given a U value of 0.35W/m2K). They then had their sub-contractor (part of a nationally-known company which subsequently dissolved) do the installation. The sub-contractor used 40mm board. When questioned I was told 'we always use 40mm board...! What they should have done then is taken it all off and done it with 50mm. What they actually did was to adhere 20mm phenolic on top of the top-coat and re-render. While I cannot commend this slap-dash approach what it does prove is that base-coat render has a good hold on underlying top-coat render after 16 years. So if you hold any money owing to the builder you could, after consultation with the System Provider, consider asking the builder to have a trusted renderer do it again (base-coat and top coat) over the existing... (Or tell them to hack the lot off and do it right. Is it on EWI or block?)

Yes, but cob has worked for hundreds of years in the UK. It has also failed spectacularly where modern materials (sand/cement renders) have been used to repair it. Yes, it is 'newer', but there is at least one straw house in USA over 100 years old and many an awful lot older than 20 years. Straw bale in the UK is pretty young, so yes, 20 years may be 'the norm' in UK, but arguably (and I haven't checked the true figures) because the 'start' was only 20 years ago. It doesn't mean they won't last another xxx years+. You are right that lime and a big roof oversail will help a lot.

First hit on 'Neighbour consultation permitted development' gave me: https://designfor-me.com/project-types/extensions/what-is-the-neighbour-consultation-scheme/ So a 3m extension will not be consulted upon with your neighbours, and a 6m one will, AFAICS. I do not know any more about the specifics of the consultation procedure - can a neighbour somehow block a development, for example - but there is an appeals process, it appears, so I am guessing that a 6m ext'n is not a 'done deal' till it's 'done'.

Very well done! I'll stand down my tape then!!

Is Ubakus German, or did I make that up?! If it is, I wonder if they do not use the IP/90-type Perimeter/Area convention, which gives a lower 'base case' U value than the old 'Uninsulated floors are 2' - IIRC then you'd expect a higher U value. But then I may be talking rubbish since, even if it's German, this appears to be the English version, so maybe it does use IP/90

(Sent PMs)

Packers for slightly-out-of-line studwork, I had assumed.

Bu**er! That was my favourite! Hope you find it.

This?

I think last time I did a B. Regs app with more than one element the cheapest one was halved in price, so in your case it could be £809 + £275.50. I think I would be tempted to do it on a Building Notice (Simple Bldg Regs app with a brief descr of works and no other detail) rather than Full Plans, but then I'd be building it myself. Depends on the degree of complexity and how much you trust your builder. Planning looks like it ought to be really simple, I *think*. You could draw that, and thus do the Plg app, yourself, perhaps. Re struct eng'r I suppose you'll at least be changing lintels, if not roof timbers, so yes, you need them, I think.

I would have said mortar, had I not assumed that you were looking for a very quick fix.