Alan Ambrose

From your description of the changes you want to make, i.e. if you don’t want to change the footprint or roof dimensions, you may be able to just use ‘minor amendment’ applications on the original permission. You can just mark your changes reasonably accurately on the drawings you do have and get any random drawing service to redraw for cheap. You may even be able to submit your hand drawn amendments if they convey reasonably exactly what you want to do. Materials changes may be just a text application with images and specs of the new materials.

We’re still waiting on planning, but intend to do something very much like I suggested above. A bit more complicated once we add in routes for services, a bin store, and drainage connections - but very do-able. SE says, yeah, replace with concrete pipe for load bearing. There’s also as old asbestos (and therefore fragile) water main running between the road and the ditch and parallel to both to add a bit of jeopardy.

For the RH Nuttall stuff: “Thermal conductivity and load bearing data of our high specification Nylatron Thermal Breaks are both readily available on request.” Yeah, right.

Don’t know whether it’s just my in-built cynicism, but it seems a bit hard to find out for these products (a) what materials are used and what kind of arrangement and/or (b) what the thermal numbers are. e.g. what’s going on here? Standard bolt into fibre filled nylon? Metal threaded insert in the nylon? Hows that held into the block? Is that such an amazing insulation breakthrough?

Actually I’ve heard this directly from the East Suffolk CIL people and there are also a few reports here on BH too. The situation is: LPA with CIL; self-build CIL exemption triggered correctly and build started. Before much progress is made, applicant wants to change design - not a minor change or non-material amendment but something which triggers a full PP application e.g. a change of footprint. Applicant gets nailed for full CIL payment. Something to do with wanting to start a new CIL process on another planning application without completing the original CIL process. That is, the CIL status doesn’t seem to be transferable between planning applications even if it’s on the same plot. I have not read the detailed CIL law yet, but it must be in there somewhere.

I would not do the above at all. You can do quite a bit of investigation work before CIL is involved. In fact, I would not trigger CIL unless I was very sure that I was proceeding with the design exactly as approved by planning. The downside is that it fully commits you to the design and you will find it tricky to change without a big penalty - say if you have to move the footprint a little to avoid some roots. Just email the CIL guys at your LPA, tell them what ground investigation you are planning and ask them to confirm that you won’t accidentally foul up your self-build exemption. Wait for the reply and then proceed. I’ve done this 3 or 4 times already.

>>> apply for a planning variation Unless your new design is a minor variation of the old one with the same footprint, you’ll need to go with a full application. You might want an architectural technologist or similar if you have a good idea what you want already. You can, of course, get an architect to do the concept design and drawings for planning and then someone else for the detail design later.

Interesting question. The only somewhat load bearing but thermally insulating materials I can think of are Marmox and Foamglas. Farrat pads are made of glass reinforced polyester apparently. Another option here maybe: https://www.rhnuttall.co.uk/gaskets/nylatron-thermal-breaks/#:~:text=Commonly termed thermal bridge breakers,to unmodified cast nylon grades. - nylon with some stuff. SS is better thermally than standard steel I’m told.

Hi Mike, possible to say a bit more about you slab? Did you, for instance have to pile down through the clay to get some load bearing on the gravel?

Unless you’re unlucky to get someone in a bad mood you should be OK. They have better things to do than argue over small stuff - there are enough people properly taking the mickey already.

Bit of grit in one of the toilet valves maybe, giving the tiniest of all leaks? Should be abe to figure out by selectively shutting stuff off, say overnight. Or open up the cistern and observe any dripping?

So, to summarise, I think there are 2 situations and temperatures to answer these 2 questions: How much energy will I use to heat my house over the year 'i.e. Heating Demand'? Result in energy per annum per m^2. Uses average tempertures per month etc. Multiply by your m^2 and you get forecast annual heat demand. What power do I need to heat my house on the 'coldest' days 'i.e. Heating Load'? Result in power per m^2. Multiply by your m^2 and you get the minimum heating power required to maintain your place at the set temperature on the coldest day. Uses 'coldest' temperatures. However 'coldest' is a bit of a tricky statistical value as it's looking towards the end of a tail on a distribution (see @SteamyTea's graph above) - so it's a percentile number taken from an averaged distribution. In PHPP, both calcs take into account ventilation heat losses, solar gain, internal gains etc. Doesn't take into account how that heat is produced - that's a later step. For East Anglia, PHPP uses -0.4C for coldest temperature.

@G and J FYI I see weatherspark has data for Woodbridge https://weatherspark.com/y/147921/Average-Weather-at-Woodbridge-Royal-Air-Force-Base-United-Kingdom-Year-Round No idea if the data is good or not.

>>> Where did you get the data from? Well the black-box PHPP dataset for East Anglia. I believe this is daily temperature averaged over the month - not sure how many years or what period that's averaged over. I must admit, I've taken it as read, there's a bit more info here: https://www.passivhaustrust.org.uk/guidance_detail.php?gId=27 This is what it gives for Exeter btw: Ah, I think I get the problem - 6.3C is (apparently) the lowest monthly average temperature i.e. the average temperature of the coldest month (presumably averaged over an unknown number of years). That's good for an overall heat calc. It tells you how much heat you'll need on average for January, say. It isn't the average minimum temperature by month i.e. how low it generally gets in January. That gives you a better idea of, say, what your max heating load is and therefore boiler size. Here's some other random weather site's (weatherspark's) data for Hemsby, unknown source, model and averaging dates. It comes up with 5C rather than 6.3.

I don't know if it helps your thinking any - my full basement design has a 100mm screed (with UFH), 300mm slab, 300mm XPS insulation on 50 sand blinding & 100mm MOT. So, that's 850mm. Full dig depth is about 4m. But that's maybe way over the top for you depending on your insulation requirements. You could probably cut most or all of the screed and power float or polish the slab and then depending on SE calcs & soil state have a 200 or 250mm slab and say 150mm insulation on 50mm of sand and 100mm MOT. That might be 500mm depth. 150mm EPS insulation gives you 0.25 U-value which, I believe, is min regs for an existing building. So, that saves about 0.5m from your calcs. Do you have scope to put the extension roof on exactly the same level as the existing one?

Ummm, in the toilet with the others

@G and J btw this is what PHPP figures out for climate for East Anglia - average monthly min/max air/ground temperature is: 4.8/17.3C & 9.4/16.9C

OVD - is that like VPL?

@SteamyTea and his Killerwots I think you mean kiloWhatsOurs surely or is it thermspicoS, or maybe microJoulesYars?

@SBMS >>> the simulation isn't linear (i.e. half the sqm doesn't yield half the required attenuation) and is possibly more like an exponential curve Yeah, I think this might actually be quite hard stats. So, with the 'common sense' adjustments you made, I'm getting about 2x the storage requirement per m^2 that you are? I'm in East Suffolk, so way over to the low rainfall/low storm east, so presumably should get fairly lenient tank volumes. It is true that my LPA doesn't seem to make much of a fuss about SuDS. Where are you on the rain map? >>> Secondly - how did they calculate your discharge rate? Good question, I see 2 l/s/ha mentioned all over the place and my overall plot is 0.13 ha, so that doesn't make total sense. I think it should be derived from the 'greenfield runoff rate' i.e. you are not supposed to make the situation worse than if it was a field. Maybe that explains why they adjusted yours up. Jeez, this is complicated, I see the 2 l/s/ha figure on page 8/9 here: https://assets.publishing.service.gov.uk/media/5a79d1a240f0b66d161ae5d2/suds-consult-annexa-national-standards-111221.pdf

>>> It depends on rainfall rates as well. >>> isopleths ooo, errr Here's the overall rainfall map and a 'storm map' I found in here: https://www.sciencedirect.com/science/article/pii/S2212094721000372. If I've understood correctly, in the 2nd map the East of UK gets v. few 50mm storms compared with the West.

I think that's an interesting problem and situation. You're on a bit of a slope and you're extending behind and you want to make the extension two storey, taking advantage of the fall? That gives you a kind of semi-basement - a bit like a bunch of Nth London houses which have a lower ground floor about 1/2 a storey deep and then an elegant flight of steps up to the front door ? You can excavate from the rear garden fairly easily as the drop there from GL is maybe 1m? Bearing in mind I'm not a groundworks expert (or in anything much 😃) but we are planning a basement, I wonder whether: + get in a couple of groundworks firms on spec for an hour or two for their advice and thinking on the basis you will give them the opportunity to quote. + check what other support methods might work that are cheaper that sheet piling. Is the extent of you plot shown on the drawing or do you have scope to batter back at a lower angle. Low enough angle and you need no or minimal suport. if you have room, sometimes you can step the excavation walls to avoid expensive propping. + the minimal SI you might need is a load test and an angle of repose test - not crazy expensive. The latter will give you safe angles of batter back for the excavation. Local BC might be able to short circuit the need for those if they know the ground and that kind of desgn has been used locally a bit, so you could ask them. + that might all become moot as the design and installation of the waterproofing will need to be done well, so you need either an SE who knows waterproofing or foundations guys that are familiar with the manufacturer-guaranteed systems (Sika etc). Find the latter and they will answer most of your questions and know what to do.

Jeez, they're planning silly buggers with the link tracking.

Well everything bathroom & kitchen is 'famous for leaking' - that's why leaks add up to one of the biggest insurance claims. Careful detailing will help a lot. A 'rubber' strip under the uprights against the wall and also between the fixed pane & the bath maybe? The manufacturers have an opinion?

https://www.planningportal.co.uk/services/weekly-planning-news/planning-news-22-august-2024 Lovely...