Tony K

I happened to have access to them through my work. Not sure how I'd have got them otherwise to be honest.

That's my concern! I can see the logic in leaving extra gaps to the sides of PIR and filling with an appropriate foam when fitting between timber joists. I suppose those joists may swell or shrink, or just move a little over time and what was a snug fit the day you fitted the PIR might be less so (or too much so) later on. In my case, I'm putting PIR onto a concrete slab, inside blockwork walls so I don't expect movement. I reckon I'll fit the PIR as snug as possible, then add a small bit of spray foam where there are gaps. Then wait a bit, then add some more, then repeat, then panic when the PIR starts rising up, then rip it out and swear a lot.

Afternoon all. Once I finish the DPM detail, I will be laying 100mm PIR boards down over my ground slab before UFH and screed go over the top. I will of course be taping the joins between the PIR boards, and am minded to fill any gaps around the edges or between boards with spray foam. I have seen a few useful debates about filling gaps in ceiling or roof PIR insulation, but not for ground floors. Regarding ceilings/roofs, there are those that argue in favour of cutting your PIR undersized relative to the gap between joists, leaving about 5-10mm gaps all around deliberately so that you can foam-fill the edges, thereby achieving a better tightness than you might if relying on cutting boards to size. Is this practise advisable where the floor is concerned? Does anyone have any recommendations on techniques, tools and materials for this purpose please? Thanks

Yep, that's how it works, though most local authorities are increasingly aware of the implications of operating in the way you describe. As a local authority you only get to lose a certain percentage of appeals against your refusals before the government class you as 'underperforming' and (potentially) remove your decision making powers. That has generally filtered down to local authority chief execs and planning heads, who now take local councillors far more firmly in hand than was once the case. Over the last couple of decades central government has used the threat of the big stick (removal of LPA powers and/or funding) to address both speed and quality of decisions. The implications of this for applicants varies. When I first started, old planners were still in the habit of taking absolutely ages to decide applications. Sometimes this was down to inefficiency, but mostly they were engaged in significant back and forth with applicants and relevant advisors, the mindset being to work together over time to get the best scheme, rather than to make a decision within 8 weeks, as is the aim now. It's good to have a nominal end date when applying for permission, but it does come at the expense of ongoing, fruitful communication with planners. You probably can't have both, at least not often. Regarding the quality of decisions (a good decision being one that complies with planning policies and so should survive at appeal) the major reason for measuring performance is to ensure that local politicians and residents don't get in the way of national strategies. If the nation is short of houses then the regions are set targets for how many new ones they should approve. If the region doesn't meet the target then they have to be less fussy in their assessment of proposals for new houses. If they aren't then they lose at appeal. If that keeps happening then they get cut out of the decision making process altogether. The opening part of my design and access statement addresses that context. I doubt I'd have got permission for my SB ten or fifteen years ago, when national policy didn't lean so heavily on my side. All of this creates an interesting tension between the centre and the regions. I have found that tension most evident between Conservative governments and Conservative local authorities. The former remain focused on national economic performance and deregulation, the latter on reasonable nimbyisim and preservation. They are on the same team, but pulling in polar opposite directions. Finally, don't be afraid of appealing against a refusal, even if only to narrow down the issues ahead of a revised resubmission. Some seem to consider a refusal to be some kind of black mark, but it is often part of the process of knocking an idea into shape, so long as you have the time.

There is a story there @ProDave, and one that leads to another topic of possible interest: post-submission alterations. Firstly, the parking issue. Our current house (next to our SB plot) has no off-street parking, or even on-street parking nearby. You have to walk down a footpath to get to the house. That's not for everyone, but we like it. I agreed with a neighbouring landowner (an absentee landlord) that I would seek planning permission based, in part, on the use of part of his land for my parking, and that we would agree the terms of a lease thereafter. Many will be aghast at the lack of formal contract, and on most occasions I would agree, but I felt my application had only a 50/50 chance. To be frank, in that context, I really couldn't afford a formal arrangement. During our pre-application conversations the neighbouring landlord told me that he wanted to keep his current tenants sweet, as they were paying him well over the market rate in rent, but he was certainly keen to get a few more quid from his land, this time out of me. When the application was submitted, those same tenants objected not only to the Council but also to the landlord, who, faced with losing his over-paying tenants promptly wrote to the Council to deny any knowledge of the application. This made no difference in one sense, but did in another; you can apply for planning permission on land you don't own, even without the owners agreement so long as you give them notice (which I had). Of course, even if you get planning permission you cannot, in reality, proceed to use it if you don't own the land or have an agreement to use it. Which leads me to the subject of post-submission alterations. As per an earlier post of mine, most planners just do not have the time to discuss your application with you once its in, and certainly not to advise you on amendments you might make in order to achieve permission. In this instance however, I met the planner when he did his site visit and the subject of the parking land came up. The end result was that I removed the neighbouring land from my plans altogether, agreed to an extension of time for the Council to decide the application (it was well overdue anyway), and supplied an additional document (copy attached, might be useful to someone) demonstrating that the over-supply of local on-street parking space justified the absence of off-street parking in my scheme. Problem solved. I don't have a parking space (or the cost or headache of the legal arrangements) but I do have a house, and in hindsight I should have gone down this route to begin with. Finally, to finish the story of my application, I came to the conclusion that flat roofs throughout (addressing a point of yours @Big Jimbo) and a less excavated bedroom block would be preferable. I thereafter made a second, separate planning application seeking approval for the same house but with those alterations. This was approved quickly and without comment, as can often be the way when the principle of the thing has already been found acceptable. I attach the D&A statement for that second application, which again might be useful to someone. You can see is a much shorter document, aimed largely at justifying the differences between the permission I had and the one I was seeking. Cheers 1389349718_ParkingSurveyRedacted(1).pdf Design and Access Statement v2 redacted (1).pdf

Glad to see some people have found the statement useful. Something I didn't explain in my original post but which may be apparent anyway, is that once I had a good idea of my preferred design I asked myself: 'If I was the planner assessing this, and if I was being as harsh as I could reasonably be, what would be the specific grounds on which I could refuse it?' The statement is partly an exercise in anticipating those possible grounds of refusal and addressing them in advance. That is easier for me as a planner than for many others, but it's not rocket science. Look at the adopted policies and supplementary guidance on the council website, and read the planning officers report for a few applications in your area to get a feel for how those policies are applied. You'll find that you get the gist pretty quickly, even if you've never looked at a planning policy before. Its not impossible to discuss and debate your plans once they are submitted (though it is increasingly rare to get the chance), but really the idea is to make the most substantive and comprehensive case upfront. It is for the applicant to support their proposal, not for the council to tease out everything that is good about your idea. Ultimately of course, if you've designed something that obviously doesn't meet the policies then it doesn't matter how thoroughly you state your case. Equally, if you've got a design which plainly meets every criteria then you shouldn't need to sell it to the planning office. Most plans sit somewhere in the middle of those two extremes, where there is inevitably a degree of subjectivity, so put the work in to show the extent of compliance with planning policies as part and parcel of your application. You do of course get the odd stroppy or difficult planner, but not half as often as you get a stroppy or difficult applicant! However frustrated you might get, remember that there is a significant difference between making an argument and having one.

Hi, As a small step towards repaying the valuable advice I have received on this forum I thought I'd share the attached document, which I hope will be useful and/or interesting to forum users. I am a planner by trade, working in local authority. My SB is on a relatively small, highly inaccessible plot neighboured by mature trees, and tightly bordered by existing houses. The plot was a 'detached' back garden of sorts that came as part of the deal (and something of an afterthought) when we bought our current house. Nobody had ever even considered the prospect that it could be a building plot, and for many years I discounted the idea myself due to the restrictions listed above. Five years ago, having outgrown our house and exhausted other options, I decided to at least try to self build on the plot. I obtained permission at the first time of asking (albeit not quickly and not without having to make a tweak or two). Everyone, without exception, from family to neighbours to building tradesmen to delivery drivers to other planners, have commented on how 'well' I've done to get permission. Some of them probably thought I'd made a mistake, or that the Council did, or that there was some old pals act involved because I am a planner myself (even though I don't work in the borough where I am building, and it really, really doesn't work that way anyway). They are all wrong. I obtained permission because I did the thing that planners spend their working lives telling others to do - I read the relevant planning policies, designed a development that was in line with them, then demonstrated as much in the application. That is what the attached statement does, it goes from global to national to regional to local policy, then explains the thought process behind my design, in that context. I cannot tell you how many architects, developers and would-be planning consultants fail to design development proposals specifically to meet planning policies, and then spend ages moaning, appealing, resubmitting, and generally wasting time. I can't promise that if you follow the thought process in my document you'll certainly get planning permission, but I hope you find it a useful insight into how a planner approached self-build, and specifically the matter of seeking planning permission on a plot that the rest of the world had discounted. Cheers 647910914_DesignandAccessStatementRedacted.pdf

Really helpful advice (as always). Thanks everyone.

Re-reading the advice I was originally given regarding the footings dimensions, I was actually told to go with 450mm deep and 450mm wide footings. I have rounded up the linear metres to 18 to give me a margin for error, but the small amendment to the footing depth and width reduces the number of jumbo bags to seven. If I use a 1:2:4 ratio I'll need 1 bag of cement (or 34no 25kg bags), 2 jumbo bags of sand and 4 aggregate. Unless I've missed something, but I'll find that out on the day! Thanks all.

Sorry, I should have said, access is seriously limited so I'll have to mix the footings on site.

Sorry, I should have said, access is seriously limited so I'll have to mix the footings on site.

Thanks @Canski seems an awful lot for my little project but I can't argue with your sums!

It's only six blocks high, laid on their sides. It retains about 700mm of ground at a boundary where I have dug down. The footings were suggested by a knowledgeable friend, who might have been mindful of the fact that I've dug down into the thick clay. You think that's over the top?

It's the footing. Thanks, but I know it's 4.5m3, what I need to establish is what quantities of cement, sand and aggregate I need for that volume of footing.

Hi all. I'm doing a small garden wall footing but struggling to get accurate quantities from the various online calculators, which I think are being thrown by my dimensions. The wall is 18 linear metres, 50cm deep and 50cm wide. I'm planning on a ratio of 1 cement 2 sand and 4 aggregate. Anyone any good at QS?! Cheers

Very nice @Gus Potter. I note your comments on the trade off between a smaller aperture and better insulation (although you've hardly scrimped, even in the upstand). I have a cold deck roof, and I feel that I will need to narrow the internal opening by lining the upstand with a little extra PIR to address the tendency for cold bridging. I am using a flat roof flat skylight, so I have to build a slight fall into the upstand, whereas you (I presume) would build yours flat and level to accept that lantern?

Thanks. What sort of size was the 152kg light?

@pocster, what is the relative benefit of aerogel over PIR?

Thanks @Dreadnaught that's very useful. Is the upstand shown in the detail a pre-produced one? It doesn't look like something a person would make themselves. I am veering towards making this kind of thing, then adding insulation into the gaps between the beams, and perhaps across the face of the beams too.

Evening Does anyone have a decent cross section or detail for timber skylight upstands that show insulation details, please? My SB is single storey, flat roof, EPDM rubber roof, cold deck. I anticipate making the upstands out of ply sheets for the four faces, and framework inside, like a stud wall. It's really the insulation detail that I'm unclear on. I understand that skylights can be significant cold bridges, so I want to get the insulation right. Cheers

Absolutely, the case for warm deck is clear and convincing. However, a cold deck van work perfectly well with adequate ventilation.

Interesting. I know some of the pro-warm deck arguments, and they all seem sensible (I'd have gone warm deck myself under different circumstances) but am not familiar with such anti-cold deck arguments that would make the good folk of Scotland ban them. Is it a different reading of the same technical pros and cons, or is it that parts of Scotland literally have a different climate to England that results in such a divergence in the regs? I'm currently getting my head around the apparent conflict between my cold deck and a vapour barrier, by the way!

I'm very close to other houses so went for the lowest height I could. How do you mean you're not allowed to use a cold deck? Who forbids it, and on what basis?

Yes it is.

I'm sure I've seen board lifters that double up as trolleys to help get boards where needed. I shouldn't think they can climb stairs of course...