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I guess you didn't tape the windows & doors yourself then. The only place i can think of that might have let down my score was the fact that the floor screed did not flow as hard to the edges as i imagined it would and the sole plate being a little suspect. I can imagine that once pressurised, air was getting down past the edges of the screed and out through the sole plate gaps. Either way its costing me no more to heat than i was paying for my old 3 bed semi at less that half the size.

From this weeks comic. Tree bark microbiome has important overlooked role in climate Tree bark has a total surface area similar to all of the land area on Earth. It is home to a wide range of microbial species unknown to science, and they can either take up or emit gases that have a warming effect on the climate By James Woodford 8 January 2026 Melaleuca wetland forests in New South Wales, Australia, are hotspots for tree microbial life Luke Jeffrey / Southern Cross University The bark of a single tree can be home to trillions of bacteria, and these microbes may have an important but neglected role in controlling greenhouse gases in Earth’s atmosphere. The total surface area of tree bark on the planet is thought to be around 143 million square kilometres, nearly as much as the world’s total land surface area. This surface makes up an immense microbial habitat known as the caulosphere, but the microbes that live there have received little attention from scientists. “In a way it’s so obvious, but we have always overlooked tree bark,” says Bob Leung at Monash University in Melbourne, Australia. “We never thought of microbes on tree bark, but it makes sense, because bacteria are everywhere, and if we can find microbes in soils, on tree leaves, then most likely there will be microbes on bark.” Leung and his colleagues began by studying a wetland species commonly known as paperbark (Melaleuca quinquenervia). They found that there were more than 6 trillion bacteria living in or on each square metre of bark, comparable to the volumes found in soil. Genetic analysis of 114 of these bacteria showed that they mostly came from three bacterial families – Acidobacteriaceae, Mycobacteriaceae and Acetobacteraceae – but all of the species were completely unknown to science. Remarkably, these microbes have one thing in common: they can use hydrogen, carbon monoxide and methane as fuel to survive. Hydrogen (H2) isn’t itself a greenhouse gas, but through reactions with other molecules it can increase the warming effect of methane in the atmosphere. The researchers then looked at the bark of another seven Australian tree species from a range of habitats, including casuarinas, gum trees and banksias, measuring, both in the field and in lab conditions, whether the bark of the different species absorbed or emitted greenhouse gases. They found that all barks consumed hydrogen, carbon monoxide and methane in aerobic conditions when oxygen is available. But when trees are submerged in water and oxygen is limited, such as in swamps, bark microbes switched to producing the same gases. The canopy of Melaleuca quinquenervia trees in an Australian forest Luke Jeffrey / Southern Cross University The team estimates that the total amount of hydrogen absorbed by bark microbes globally is between 0.6 and 1.6 billion kilograms each year, representing as much as 2 per cent of the total atmospheric hydrogen removed. This is the first time scientists have attempted to assess the contribution of tree bark to atmospheric hydrogen, says team member Luke Jeffrey at Southern Cross University in Lismore, Australia. “Discovering the hidden role of trees doing more than just capturing carbon dioxide in their wood is very important,” says Jeffrey. “They are active cyclers in other greenhouse gases. This is exciting, because H2 affects the lifetime of methane in our atmosphere, therefore H2 consumption in bark may help in reducing our growing methane problem.” However, the global picture is highly uncertain, as the team has only sampled eight tree species from eastern Australia. “A lot of work now needs to be done across various forest types, tree species, microbial communities and site conditions,” says Jeffrey. Brett Summerell at the Botanic Gardens of Sydney says the study highlights how little we know about the composition, diversity, abundance and role of microorganisms in bark. “How this might vary across a broader range of tree species, particularly in drier climates such as savannahs and woodlands, is interesting,” says Summerell. It will also be important to understand the interactions between fungi and bacteria in bark, he adds. Journal reference: Science DOI: 10.1126/science.adu2182

I've taken the advice from @Nickfromwales and I've put the batten idea out of my mind! The XPS solution sounds excellent and I've been researching over Christmas in preparation. I like @garrymartin's idea of a second layer at right angles, as this will give me depth for dropping in an XPS shower former. So from concrete slab upwards: 1) 50mm Ravatherm XPS (https://www.insulationuk.co.uk/products/ravatherm-xps-x-300sb-extruded-thermal-insulation-2500mm-x-600mm-50mm?variant=52655697101134) stuck down with S1 tile adhesive. 2) 20mm XPS tile backer board stuck down at right angles, again with S1 tile adhesive. A 20mm XPS shower former will then be level with the rest of the floor 3) For the walls, 12mm tile backer board 4) Tape all joins then membrane over the floor 5) UFH mat, then - if feeling brave - S1 tile adhesive straight over for tiles My subfloor looks in fairly good condition for attaching the XPS (the slab doesn't reach the wall, however, and there is an area of sand where the drain is embedded): Does this sound about right? I'll take the same approach for the kitchen floor. Will I need to tape all joins here as well? In the absence of a polythene VCL it would act as a VCL to stop moist air reaching the slab, although in a 17sqm room all that tape will be expensive! Thank you again

Hi all, I want to add internal wall insulation to my 1970's block cavity walls. The cavities were filled with a mineral wool type fluff in the 90's, which appears to be dry where I've been able to see it and there is no evidence of damp or mould in or on the walls. The external render is also in good shape. We are leaning toward a stud frame fixed to the inside of the external cavity walls with mineral wool bats like knauf RWA45 or RS45, with plasterboard over. Our reasons being, it's cheaper than using celotex or insulated plasterboard, it's a breathable option which, from what I gather, would carry less risk of issues with condensation and mould and we don't mind losing a bit of internal space. I'd love to hear your thoughts and knowledge on this approach to internallly insulating cavity walls. Is it a good idea to do it at all? Is a vapour-open breathable approach better, or should I use a vapour barrier, as some manufacturers suggest? Any and all thoughts welcomed! Cheers, Jules

Doesn't sound like it.

. In my instance, it's an existing building that had a combined system before we began works and due to the terrain, being on a steep slope and where the down pipes are located, there is no choice other than to do it because the existing underground drains are in the way so we can't dig any new ones. And yes, will absolutely be into a trapped gulley

Isn’t it all brand new??

https://www.screwfix.com/p/flomasta-potable-expansion-vessel-24ltr/131kk £40 each from Screweys, so that makes it £310.40 for labour (including the VAT) How long did they say they would take and how many people?

Thanks for all this, @Gus Potter. I've designed all my metal web floor joists so they're inside the inner block leaf; those that meet the outer wall will be hung on ledger boards. I've done this to make air tightness easier to achieve, & there's a thermal break benefit too. With the ideas @Iceverge has provided, the tops of the rafters will all be insulated, but at the bottom they'll run from inside to outside over the wall plate, of course. The SE has specified UB19 for the beam in the section picture you posted. This is a fair bit chunkier than I was expecting - only because I can lift the mild steel box section back bone chassis of an old Lotus with ease, & they're very strong. These UB19s (there are 6 of them) are in lengths of max. 4.55m, so that's 86KG to lift into place. I think the top of a UB19 will be 7.9mm thick & the web will be 4.8mm, so it will be good to have insulation along the edges of these UBs, & it's worth considering what's going on at the beam ends too. My plan was to wrap the beam ends that penetrate the inner cavity block leaf with VCL membrane, bring the membrane inside & fix it to the wall (I've got notes on how to affix). The cavity between the block inner & rendered block outer leaf is only 150mm & will be filled with EPS beads. I was thinking it may be worth sticking a rectangle of super insulating something or other inside the cavity on the beam ends. If anyone has any suggestions please let me know. & is it worth sticking a block of high R-value something on the top flanges? There's not much gable end wall going on top of these UB ends. I looked for high R-value padstones, but I gave up this search & decided to rest the beam ends on regular padstones.

And quote.

Regardless of all the above, a good SSR does not make that horrible click/thump/buss that a contactor can. More specifically on safety, and as @ProDave mentioned, two contractors in series. Our sunbeds used contactors and they welded up on a regular basis (about 7 kW inductive loads). We initially rewired to have duel contacting, then changed over to SSRs. Newer solid state controllers came along and took the problem away in the early 1990s.

I did write in another thread some time ago about how the coupling on the internorm windows was rather neat. .. oh dear, I should have looked a bit closer. From the top it could be seen that the coupling unit had been propery installed and the window was tight together. All good then, I thought. Except no, just because the top 75% of the window was ok, I should not have assumed that the window fitters coupled the windows tightly together all the way to the bottom. I have recently discovered a gap between the windows that starts at about 50cm from the bottom. Such a gap seems strange, as I imagine the frame must be bent for this gap to be only at the bottom. Like this: I am fairly cross with myself that I did not see this earlier, before recent construction around the window. This is a full height window with plasterboard installed at the top and it will be a major headache to remove and refit the window. The window has an opening pane on the right which hinges on the right, so that it closes against the secion that may be bent. It opens and closes ok, I think, but I need to get my laser on it to see if and where there is a bend in the frame. There is a lesson here for anyone reading this at the planning stage.... do not have big windows that need to be glazed or coupled on site, it introduces risk of the fitters totally cocking it up. One of the fitters will be visiting in the next week to run through the long list of issues. The question is, what do I do about this? Do I insist the window is fixed, which would mean deconstructing the surroundings and, potentially delay the build, or, as our builder would prefer, throw some CT1 in the gap, or glue a panel over the gap, and press on.

That's total *******. The entire point of land registration was to simplify the transfer process so that you didn't need to use a solicitor, which you don't - most of the people who do conveyancing are minimally qualified staff and not solicitors. Of course, they will still try to maintain their monopoly by implying that you're not allowed to do it yourself, but that's just an attempt at intimidation. Some of them will try to make life difficult for DIY conveyancers. Yes, the various aggravations make it not worth it now.

The foul drain might be an issue, it’s only for circumstances which mean you absolutely can’t use a soakaway and you absolutely need permission to do this. I’d avoid it as being flooded with foul water isn’t a joke! Might need a trapped gulley if so?

Yes, I think the fixed section only hence the isssue. Currently being plasterd so humidity is in the 90s hence the condensation, but there is more on the fixed pane that was glazed on site. For reference, all five of the other windows that were glazed on site have broken or porrly fitted trims with air coming through the holes in the trims on at least three of the windows. So glazing on site was rubbish. The fitters also left behind as box of internorm fix-o-round sealant that internorm supply to be applied round the glazing units. The missing sealant is probably why the air is coming trough the broken trims, around the glaxzing units. I did ask the fitters about the sealant at the time and they poo-poowd me, saying it isnt necessary. That isnt what internorm would say though, so they will be refitting all the glazing with the sealant applied. Although the box I have on site is out of date now. Thank you for this. So, your seals are the same on both fixed and slider section? That is very useful information. I'm compiling my list today.

Paperwork just come on email, seems we may need to get expansion tanks replaced!

I don't think it's possible now on the buying side. Im going through the motions on a plot atm and the vendors solicitor couldn't even communicate with me because of law society rules. I said to the agent what if I was diy conveyancing he didn't really have an answer apart from its rare. Also the money laundering regulations are insane now I don't know how you'd convince vendors solicitor your money is legit.

I am currently using the THE system and experiencing under capacity of heating as no UFH . It is not maintaining a cosy feel as has used 234 kw this week, its only Friday.

I've zero rated jobs in the past there is no form you have to fill in with site details. It would only ever crop up if investigated and I think as long as vat man can see a newbuild has been built at x address which your invoice is for you're good to go. The works could of potentially been done months before its invoiced out.

i've already bought the materials so it's only on the labour. i like my plasterer so i'm reluctant to go hunting for a new one now. i'll just take the hit on the VAT then.

I have this question as an issue I've been kicking down the road. Building Regulations says either into a drain (by whatever means) or soakaway. My first BCO was happy with a french drain out onto the sloping ground in front of the house (but this wasn't followed up in writing). Now I'm being asked to either have it into drain or soakaway. A customer recently had an extension done to their house and they used a drainage channel to get to the foul drain. I might do the same if I can.

Good point, me too. If its only the skimming labour could you not find someone who isn't vat registered? They're gonna put a markup on any materials they supply I'd have thought.

You are only allowed zero vat when working under planning permission. At sign off of a completion certificate (you are stating you are complete) thereafter you are no longer working under planning permission, as that has been closed. Fudging and using a no longer valid planning number is down to you, but not for me say it's right/wrong on an open forum.

Is there a minimum vat reclaim amount? I have seen somewhere councils can verify bng self build exemption by way of proof of vat reclaim rather than Unilateral Undertaking. If using a contractor to build and they are zero rating could you literally buy just like all your driveway blocks at the end and claim for only these? I suspect you'd get a phone call but surely couldn't be refused? There must be similar occurrences where people have employed a contractor upto a certain stage then finished off themselves?

diy plastering? no chance! i'm completely s**t at it. 🤣