Redbeard

I imagine the lack of replies so far is because people looked at it as I did and got stuck on questions and practicalities. I'll try to start now, and you can tell me if it is of no help! Do you consider that, before you dug out for your extension, your land was giving full, and adequate, support to next-door's conservatory? What it is, or isn't, sat on looks quite sketchy to me (sorry; I have not re-read your whole other thread, though I looked at the time). The question in my mind is whether you have an obligation to provide support or to allow access so that the neighbour can repair/strengthen their footings before you progress your build. You say Why would it be pointless? (I am beginning to remember why I din't get further with my reply last time!!). OK - rephrase that: I take it the main reason for the lump of concrete is to hold up the neighbour's conservatory. Yes? ... and the drainage at the bottom to allow any moisture trapped between the concrete and your membrane to seep down to a perf. pipe? And potentially the perf pipe also receives the neighbour's sh** if it all goes horribly wrong? How would that work? Can you add their soil pipe to your dwg? Surely no 'liquid' could run down 'their' side even if you had a dimpled membrane in (which would face the wrong way, serving 'your side')? And equally surely, a perforated pipe is the wrong 'conduit' for an accidental poop spillage. You would surely have less to do and worry about if your neighbour's 'outfalls' didn't 'fall out'. Lots more info, and details of any further thoughts you have had since posting, please! (Or tell me I have got entirely the wrong end of the stick!)

The sketch shows no insulation to the exposed side wall. Is this the intention?

Got it! OK, so as I understand it you are re-roofing from scratch including the whole timber structure. They show the roof effectively ventilated *over* the rigid sarking, which required the counter-battens which your current roof of course will not have (I assume). I see that Steico suggests the same lambda as Gutes, which makes you closer to complying with the 0.16 target. (I just checked that one. Look at table 4.2 in Part L, re 'new element in existing building', which your new roof would be - target goes up in stringency, down in U value, to 0.15.

Makes one think of the oft-expunged verse of 'All things bright and beautiful'! It's about balance of power.

A Green Building expert gave me a useful rule of thumb re 'hybrid Warm Roofs' (a Warm Roof being one which has all the insulation above the rafters). He suggests a condensation risk analysis for a 'some between and some on top' lay-up, but offered a quick possible alternative, which is that the insulation on the top of the rafters should have at least two-thirds of the R value, with the insulation between the rafters having a third. That reduces significantly the risk of interstitial condensation at the interface. Your '190 between and 40 on top' would not meet that rule of thumb. I realise that there are different approaches with fully-breathable materials (full-fill Warmcel, for example) and I think I may have heard of one of the wood-fibre providers endorsing a lay-up such as you suggest, but it's worth checking with your supplier. A quick calc says 230 of flexi WF with a lambda of 0.039W/mK (Pavaflex, for example) would have a gross U val of nearly 1.7W/m2K *making no allowance for the thermal bridging of the rafters, which will make the adjusted U value worse still. I thinnk Gutex's 'flexi' maybe has a lambda of 0.036W/mK, which would give you a U value of 0.156W/m2K at 230, but again, unadjusted. I can't really answer re the roof height increase. Most importantly, is it detached? The neighbours/planners may not care or notice, or they may. Sorry, I don't knpow, but I am sure others will be along.

About the fast up and the slow down? (I also cannot help noticing that anyone going up the RHS of the Big Stairs is either going to have to be very short or will have a big bump on their head).

A bit late for this info, but: "Is planning permission required for new or replacement driveways? Planning permission is not required for a new or replacement driveway of any size if it uses permeable (or porous) surfacing such as gravel, permeable concrete block paving or porous asphalt, or if the rainwater is directed to a lawn or border to drain naturally. The government's Guidance on the permeable surfacing of front gardens (PDF) explains the different type of permeable surfaces available and contains guidance on the design and construction of permeable driveways. If the surface to be covered is more than five square metres, planning permission will be required for laying traditional, impermeable driveways that do not provide for the water to run to a permeable area. This is in order to reduce the impact of this type of development on flooding and on pollution of watercourses. Please note that these permitted development rights do not apply to flats, maisonettes or houses that have been created through change of use permitted development rights." https://www.bradford.gov.uk/planning-and-building-control/planning-application-and-building-regulations-advice/paving-front-gardens/#:~:text=Is planning permission required for,of use permitted development rights.

Option 3. Do most of the garage fill with EPS, depending on relative cost of conc vs EPS.

Ah, so I read it as: The 'retained side' means the buried bit. So if you are looking at the finished retaining wall from the lower side you will see no strengthening pillars. Any vertical reinforcement required (rather than strengthening via - possibly stepped - thickness alone) will be buried behind the soil retained. That's how I'd understand that, but IANASE!

I realise this post is in the context of EPS-clad blocks, but a reminder that XPS also leaches the plasticisers out of cable sheathing. I was once puzzled as to why I could not move a 2400 x 600 sheet of XPS I found in a loft void. It came up a little but would not 'let go of' something. Found it had 'glued' itself to a series of lighting cables!

Can you? You'd probably need to ask your sol'r since, by doing so, you would be fettering their 'funding stream'. What about water disposal? What are the drainage arrangements? Are they seeking to get you to pay +30% on top of disposal as well as supply? (Or is drainage private?). Arguably it's a sound decision *not* to, for them, insofar as they can charge you if you don't do them. Or have I understood this wrong?

I am not yet engaged with AI except as a method of speeding up meat production, but here's what it says: "Generally, upgrading room-in-roof insulation does require Building Control approval if more than 25% of the roof area is being replaced or re-covered, as this triggers the need to meet current thermal insulation standards. If the work involves replacing or significantly upgrading a thermal element (like a roof), building regulations apply, and you'll need to ensure the insulation meets the required standards. " ..and that's the line I have followed. Bldg Regs defines 'renovation of a thermal element' as 'adding or replacing a layer' (of an 'insulation sandwich')

You have already answered your own question. XPS (I assume) was spec'd so that it would not become a wet sponge if flooding happened again. It has not been used. A dry sponge has, and a dry sponge will get wet in a flood. Obviously tricky as you say most of it is completed, but you did not fail to follow the spec.

If the specification of closed-cell material (XPS, I kind of hope, but OTOH it floats well) was specifically related to knowledge of the flood incident(s?) then it arguably matters a lot. If the builder had the specification it is also arguably their problem. If you expect (at least the possibility of) flooding again then yes, the use of a material which sucks is an issue.

Re my post: should read 'ask for *their* comments'

Have you notified the owners (presumably the local authority, with no budget for such works) that the lack of adequate drainage on their property is causing a periodic nuisance and asked for this comments?

Ow! So sorry to hear that. Hopefully someone on here can suggest a suitable person. Perhaps a minor issue, and perhaps most people will be VAT registered (I never was, and equally never was a 'window person'), but Deceuninck could have ruled out an excellent non-VAT-reg'd specialist there.

I guessed 'Micro-dumper' - and at least one variant is referred to as that. (https://www.cjhire.co.uk/product/industrial/hi-tip-narrow-dumpers/micro-dumper-2/) (No connection with that firm; just my first search result).

That's RD SAP for you! Vague data in; vague data out, plus the way in which EPC assessment was marketed as a money-making opportunity - 'Full-time wages for part-time work' was one of the mantras at the time. I did not believe it because I had seen a similar set of circumstances with (inland waterways) Boat Safety Examiners. A race to the bottom in terms of price and quality. There are still many EPC assessors who want to do a thorough job, but the early (and probably continuing - I don't know) over-supply of assessors meant that prices were forced down to a ridiculously low level. You are right about not liking (and I would add 'not being able to recognise') real construction. I wrote to the certification body of one assessor who did not recognise EWI in spite of all the 'clues'. I told them I was baffled. 'So are we'! They explained that they give all the necessary info in the training, and offer a help-line in case of doubt. To be fair you probably don't have to be a building professional to be a good EPC assessor, but you do have to have, or develop during your training, a proper *understanding* of buildings and of what may have been done to them during their lives, so that you can make an intelligent 'stab' at what is 'beneath the skin'

Are we at cross-purposes? I am talking about insulation in roof voids, on the flat, not walls.

@Pocster, could you post a cross-section of the attic room and the voids surrounding it? If there is, for example, an apex void and reasonably-sized eaves voids it might just be possible to stuff but not too (tight!) them ridiculously full of mineral wool (500-600mm?!) so as to get a weighted average of 0.16W/m2K.

Hang on, it's a long time since I dealt with rentals but does renewal of an HMO licence *really* allow them to move the goalposts every term (how long is the term)? And a Q - Is the '100mm assumed in the roof' PIR or mineral wool? And are there both sloping and flat ceilings? I assume so. No sweat (or not much) to upgrade 'fluff' in a void. More so to insulate sloping soffits, but it can be done. 150 PIR will give you 0.16 or slightly better. BUT I cannot, in a quick search, find anything on the web saying that they can require an upgrade to current standards. Of course I may be missing something. If we ignore the 'base case' R value of a roof (SAP assumption for uninsulated is U value 2.0W/m2K, therefore R uninsulated is 0.5M2K/W), taking the view that thermal bridging of rafters etc may more- or-less cancel that out, then 100mm of mineral wool (with lambda value 0.044W/mK would give a U value of 0.44W/m2K, a long way from 0.16. However if it is PIR it's 0.22W/mK, not so far from 0.16. And yes, they do mean minimum!

What U value have you been quoted for the floor? Is the Perimeter/Area ratio fairly low?

I should have said 'welcome' before I went ahead and answered your other Q. So belatedly, 'Welcome!'. All the answers are here. You just have to know the questions. How old is the house?

Your 1st point possibly suggests to me that the external ground levels are no longer where they used to be, and possibly that the ground surface is *harder* than it used to be, allowing more splash-up. Many many houses have no dpc and no significant damp issues. Your title suggests you *do* have damp probs, but can you give us more detail?. My own experience with inserting a dpc is it is a hell of a lot harder than you think (I thought) it was going to be. A lot can depend on the depth of mortar joints. I am absolutely convinced that a huge number of the injected dpcs one sees were never necessary in the first place. The attitude of many Building Societies and public sector lenders/grant-givers, in the 1980s particularly, led to (I would guess) hundreds of thousands of installations of injected dpcs in buildings which were not damp. More context please Incl. pics of possible, and we can get more specific.