Redbeard

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.

If you decide to retain the pipe and do a soakaway then (a) you have to establish whether your ground conditions are conducive, via a test pit, (lots on here IIRC) and (b) you need to be 5m from buildings and xm from boundaries. (I have used 'x' because I have seen 2m, 2.5m and 'If you are close to boundaries you should discuss this with your neighbour.' - Surrey Bldg Control Guidance note). BUT, as mentioned in previous replies, we need to know what the problem was. Did the gutters overflow regularly? Did the neighbour have an unwanted 'pond'. Where does their 'proper' fall-pipe terminate? In a drain, a soakaway, 'nowhere'? It's an odd situation and certainly one to feel uncomfortable with.

I always think of wall-plates as sitting on top of the masonry, but I assume you mean that 'low purlin' as the wall-plate? I cannot see what goes on below the wall-plate/purlin, but there appears to be light coming in -- ?? Assuming the roof continues down in an oversail then why not bring the hempcrete up and over the top of the wall and physically fix it to the back of the VCL? Ahhh.... because you cannot get in there to fix to it. I was thinking of a 50/50 mesh/air-tight tape 'combo', the mesh 'plastered in' to the hempcrete and the tape stuck to the membrane. Goes off to think for the evening....

Have not looked at crate prices recently but it will be worth a comparison, or do you have some vehicular loading issue?

I think if I had been your architect (which I never would be as I am not one!) I might have played with the levels of the majority of the flat roof so that , without diminution of the insulation, I could get a channel in hard against the parapet with the outlets, with a slight fall each way from the middle. The fact that you have chosen GRP makes that easier than with any other covering I can think of. And Robert is your Mother's brother.

I imagine they will say that the TW55 is the VCL, which is true as long as all joints and perimeters are taped to within an inch of their lives and nobody pokes a screwdriver or a fingernail through the foil.

What inherent 'cooling measures' does it have already? Large roof oversails on the 'hot side(s)', smaller windows ditto, external shading, exposed masonry as 'leveller' There, I avoided saying Thermal Mass - Oops! As I understand it quiet, slow-running MVHR systems rarely shift enough air to have a serious cooling effect, and systems which do may be too loud. Stating the blindingly obvious (sorry!) the main effort should be to stop excessive solar gain, rather than to get rid of it once it's inside. I agree with 'passive' measures where possible, but air-to-air HPs do have the advantage of being a winter heating system as well as a cooling system. I think if it were mine I'd do all the passive measures I could (including IWI) *and* fit a/a HP

Have you been in touch with People Powered Retrofit in Manchester? They may be able to put you in touch with householders with ASHPs. My 2-penn'orth: 12 -17 years ago when the Energy Saving Trust did these field trials https://www.gov.uk/government/publications/analysis-from-the-first-phase-of-the-energy-saving-trust-s-heat-pump-field-trial#:~:text=The Energy Saving Trust's ( EST,83 households for Phase I. the CoPs for ASHPs were in some cases pretty grim. Now they are routinely pretty jolly good if the installation has been done well and insulation spec suits lower flow temps, so I would definitely go for ASHP. Indeed I do not have a field or space for boreholes so ASHP it will be. My HP will be a long way from the nearest neighbour, though, so all cases are not equal.

To add to my post above, you almost certainly need a structural engineer (SE) and a written specification for 'making good', particularly if you still propose to remove the full ground floor outer skin. I would expect a SE's spec to include for temporary propping while you remove the ground-floor support for the outer skin and leave the outer skin intact on the first floor (if I have understood you correctly). I accept the inherent tendency of bonded bricks to, well... bond, but the phrase 'hanging in the air like bricks don't' also comes to mind. Re Building Regulations (both stability and thermal performance), you will at very least need to submit a Building Notice (short-form minimal information application for Bldg Control approval) and BC will almost certainly issue a counter-notice requesting further details, including structural ones.

Ooh err! Only just seen your 2nd pic. A little unnerving! Agree with @ProDave and @Mike re ?? stability. I think your plan to completely re-face the wall is at best ambitious. Even if you drop the plan now you still have a 2nd skin to build which will not be tied-in as it once was. You will have to fit screw-in ties to the old wall so that the new bricks can be tied in, or perhaps you could do it with resin anchors. As you refer to plans to insulate internally can I suggest that you 'check-in here at planning stage for that? Interstitial condensation risk, possibility of thermal by-pass, possibly lack of continuity of vapour control layer (VCL) (or indeed the insulation itself)and plenty of other risks worth running past those who have done it before. Remember that, under the Building Regs, you will be 'Renovating a Thermal Element' by 'adding or replacing a layer'. You cannot just put on what you fancy - you have U value targets to meet too. I am more of a fan of rigid wood-fibre than I am of insulated plasterboard - how do you keep the VCL 'tight'?

But you said: Can you show us a bit more? The 'half-bricks' we can see could be headers (the ends of long bricks) but if that's an opening to the right they may be 'true half-bricks'

Firstly, as you appear to describe it, it is not a cavity wall. Is it all stretcher bond (long bricks only visible?). On a 'solid' (never mind about the 10mm gap - it's effectively solid) wall the ties are in the form of bricks laid at 90 degrees, so for example you may see: header (short brick, i.e. brick laid across the 2 skins); stretcher (long brick), stretcher, header. Other patterns are also available. Can we see a picture? Why are you replacing the bricks if you are going to render?

Honestly, I would go with @ProDave's suggestion, or a variation thereof. A bought-in 'caravan' or 'chalet' is highly unlikely to give you the level of insulation you would wish. Yes, you would/may have to go for another PP but that seems a relatively minor issue. 55 years old - does it have retrofit cavity insulation. I have in mind (in complete ignorance of your floor-plan) 2 possibilities something like: Poss'y A: Re-roof, re-wire, extension and external works to suit future mobility needs. When I say 'may have to go for another PP' you might not if the size of the extension is within the 'ordinary PP' or 'Neighbour Consultation Scheme'. Poss'y B: Chop the house at first floor level, form wall-plate and bungalow roof, integrating a new extension at the same time (Full PP). In both cases I would suggest cavity fill and external insulation, including 'proper' detailing across the wall-plate so that external wall insulation can connect tightly with roof insulation. Obviously we do not know about your ground floors. Insulation is desirable, where it is likely that you do not have it at present. If you can give us more detail we may be able to 'build' an idea for you.

OK, I have only used their all-wood offerings but I really rate Green Building Store (21 Degrees) windows. Their in-house fitters were really good too, though come 2021/22 they could only offer fitting in certain areas. I gather they have more sub-contract fitters now. Yes, according to the dictionary definition they are not specialists, but they have a specialist window section. I do not regard them as any less 'specialist' than those who concentrate on windows only.

I'll put on a pretty good bet that it isn't cellulose. AFAIK cellulose is not normally (ever?) used in masonry cavities in UK. If it's white and fluffy it is almost certainly (CWI-grade) Rockwool. Is it only the v small patch we can see? How about chopping out and inspecting (and repairing if necessary) the DPC? Approx age of house? Was it originally done with CWI or was this a retrofit? (I think I have answered my own Q as the 2nd course below the cill course seems to show 2 (CWI) drill-marks at the centres one would expect.)

If a negative can prove a positive this may help... My Water Authority confirmed that my combined (RW and soil) drainage is Private because there is no connection *on my property* with anyone else's drainage. If your 'central pipe' runs from house to house that seems to me to suggest a Public Sewer. Though I could be wrong...