Gus Potter

Hang on here before you chuck in the towel. It's quite usual to find no membrane or bituminous felt under an old slate / clay tiled roof. Can you post some photos so we can have a look at what you have from the inside and the outside. In a new build yes, but when we are considering old buildings and upgrading it can actually be an advantage. The old traditional roofer ( 100 years ago) did not have access to felts and membranes so they gave their slates / tiles more head lap. We can use this to our advantage at times as the roof is really drafty, every cloud has a silver lining!

Agree a bit of air can cause havoc. One way to purge this is to shut off the other loops and open the air vent. You'll need a bucket and a few towels to catch the water. Give it a good go and don't forget to top up the inhibitor once you have finished.

Ok that is settled. First paragraph. The UK oil and gas energy resource is not "fininite" in terms of the next 50 years. There is plenty! It's just that the UK tax system makes it less attractive to extract. If we use our own resource that satisfies and mitigates your point of despot regimes, blatent abuse of human rights. Cut off their money! That is why we need to be relying on the West of Scotland oil and gas fields and fracking. Schiehallion, Loyal, and Foinaven fields. This gives us national energy security in the short to medium term and delivers well paying jobs and income taxes etc from that. . The money we get from this can then be used to drive towards zero carbon emissions. If we just import oil and gas we are paying the Arabs instead, for no benefit to ourselves. You have to remember that us Brits are great innovators, we can't do that if we have no cash! Unfortunatly we have the Greens in Scotland who don't know what a woman is, so we have much doubt about their ability to make evidenced based decisions on the oil and gas industry which impact on all of the UK. You see they can control this through the planning system not least! One of my pals is an SE who is working on this, the actual design of the rigs and how you extract oil and gas in deep water and then get it to shore. It's also to do with the quality of the oil. Much of the oil from the Middle east is a bit crap to say the least and really churns out some nasty stuff during the refining process. Ok, fair enough. But this is a typical response from lefties, mention Reform and you are far right. I mention them as an Engineer. Tice and Farage have said in their speaches that they recognise that they don't have the strength and depth within their party to run the country. But they have said that they will second people from indusrty, Engineers, Doctors to support them where they are weak. Take some time and listen to some of their speaches before you come back for a second time and ask me for evidence. In the round though I think we are of the same mind. Here you make a good pragmatic conclusion. Lastly is ok to disagree!

There you go, how easy was that! Ok to kick this off what is your opinion on nett zero? Here is roughly what I think in broad scoool terms, call it that for now. 1/ The world is an unfavourable place. We are actually lucky in the UK that we have not had a war that has really threatened out soil since 1945. I'm an SE but was trained primarily as Civil Engineer, we have a duty to the public to secure our infra structure for the next at least 50 years and dams above cities for 100- 200 years. 2/ Nett zero in the UK serves to destabalise our economy and reduces our ability to innovate. 3/ You have got yourself into a funk because I mentioned Reform!

I'm not sure if I want to engage with you as I get the feeling you are not technically minded. If you want to use abbreviations then use your abbreviation, put in brackets what that means so the rest of the folk on BH can understand and easily follow the discussion. Do that first, plain English is required at all times. To wet your apetite for discussion I'll make my case as an Engineer who has a Civic responsibility, you might find that interesting?

I think you made the right descision to step away from this. However the seller may sort it out and come back to you. At the end of the day they took your offer seriously. You wanted to by the place / fell in love with it? They have two or maybe more choices, realistic ones are: 1/ Wait for someone daft to by it. 2/ Smell the coffee, sort it out and do a deal with you. They may well come back to you as if they thought you were not serious they would have binned you earlier as a purchaser. Technically yes. But this is what we call an accidental load case. If we designed everything based on this accidental case then the cost of building would become excessive.

Perhaps read more widely.

Ok what I can tell you is that I have designed as an SE a few insulated rafts over the years, once you get down to the engineering there is no ideal world, there is a trade off between engineering cost and satisfying the window suppliers " best performance". Building houses is an art where you have to make informed compromises. You have to recognise that if you go for the best value it will dictate everything else you do and that can come at and often nasty hidden cost. If you pair everything down now when doing you basic costing it will come back to bite you. The best advice I can give is to think about who might build this for you and sound out MBC on their caveats on the ground conditions, if you need steels and so on, point loads from the structure etc. MBC are by all accounts good at what they do but they will charge you for every extra! be that funny loads or funny geometry of you house. Also, sound out local Contractors, they may tell you, keep it simple and stupid, spec stuff we can source easily, and we will deliver an air tight structure. Oh and on a light note. If you are a doggy person then leave an unheated bit in the floor so your dog goes there for respite! UFH is not good for dogs!

Interesting thread. When I was a young lad I worked at Torness, nuclear. When I went to uni at 40 my degree project submission was on nuclear and compared that with other energy sources. I got an understanding on how the western system is skewed, basically by politics and realised that is a price you pay for democracy. Cf how they work in China, no democracy, their energy policy is driven by engineers with a remit to make as much money as they can for the system, the populase come last. Later I did some design for the decomissioning at Bradwell and I revisited what I had learnt. In summary, UK policy has been driven by totally the wrong people for decades. As someone said earlier, if your vote actually mattered they would take it away from you. Reform UK at the moment. They seem to be the only party that are going to get professionals into sort out out energy market and policy, we have tried everthing else and it has failed. We need to take radical steps to safeguard our energy security not least.

Hi Don. Admire the effort you are putting in, you will be rewarded. Jeremy Harris is an icon on BH, I've learnt a lot from his posts. His spread sheet is a good aid, a great tool to use as a sense check. I've opened up the spread sheet to see what inputs you are using. I do a quick sense check, mainly to see if the numbers look ok and where you are pushing the U values to think.. how much is this going to cost, get a supplier and so on. Your inputs are screen shotted below: So to compare with the Scottish target U values, which are quite stringent but will serve you well if living further down south. The objective of my comment is to get you to think.. how much is this going to cost us to build, get local contractors interested in competing for you job and, can we spend our money in a better way. I wonder, where did you get the values you are using for your inputs? and can you post some details on how you are going to construct the basic elements of the fabric. The U values for the glazing look a bit optomistic. Best to be pragmatic and conservative at this stage to avoid disappointment later.

Hiya. A few observations. Your temporary propping looks potentially dangerous. There is no bracing to the props and the needles appear to be not able to carry the roof load, never mind any internal floor load. It may be the way the photo is taken, but please, contact your SE tomorrow or NOW, DO NOT believe your BUILDER or BC! Your gable wall is not braced so any shift in the temporary load could shove the gable wall out (all it needs is 25 - 50 mm) and that leads to an excessive / uncontrolled collapse. From the photos I see this look dangerous. The prop and the needle on the right side of your photo will be carrying a lot of load as the lintel over the first floor window will be shedding load towards it. Seriously, please get your SE out to the job as this could be massivley unsafe! BC are NOT Structral Engineers and often won't understand (justifiably) the nuances. You are potentially taking your life and family in your hands here! I don't make such comment lightly. Get your SE to not just check the temporary works but also the building sideways stability in terms of what you are building. Are you sure this is what the SE is telling you and do they know, what you are actually doing on site, and if you have deviated from their design in any way? Please take my advise. Any SE is going to help out here if there is a safety issue.

Yes, treat all this with a big pinch of salt, check their fine print. You must look at their technical spec, the range of moisture content, expansion edge gaps and so on and make sure that the way you want to live fits. In other words, say you bail out to Spain in the winter and turn the heating low.. or rent it out and folk dry their washing!

I'll try here to give a bit more info. I can see why you may think I'm being a bit rough, but with 40 years experience in the construction industry I've seen stuff, not all good. But some designs are very elegant, clever and you'll often see these cropping up on Build Hub first. What makes a bad designer is someone who thinks they know it all. I don't and one great learning resource for me is Buildhub. As a member of BH you really have access to a lot of clever folk who are innovative. I'll try add some detail. Remember though you can ask ten different designers and you'll get ten different answers. Your job is to work out what best suits you. My own view in design is to provide Clients with information so they can make an informed judgement. If they don't take my advise then that does not mean the job is going to be a disaster! Call this differential settlement. To avoid one big crack we design the building with movement joints in the external walls and try to position these so we get more cracks but smaller ones. Then we need to make sure our internal walls are not introducing stiff points that stop the external walls from moving about. In doing so we have to consider the Architectural constraints as SE's. Then just as we feel we are getting somewhere in the design we have underfloor heating that often needs to be zoned. There is a heirarchy in the design process. We are mixing up all sorts of different materials that repsond in different ways and then asking a builder to execute all of that at a reasonable price while taking cognisance of air tighness and ensuring the cold bridges are built as the design. Now all that is a big ask! This can be achieve but along the way you always find you have to make compromises. There is no "perfect design" in practice. That is one reason I ecourage more loops as it lets us introduce more movement joints in the floor if we need to. This is a really good question and observation. Here is a basic explanation about concrete with some numbers. When designing say a concrete slab, could be a first floor slab or a ground bearing slab. The first thing we want to ensure is that it does not fall down or in the case of a ground floor slab suddenly fail. Call this designing for safety. The next thing is that we want to know how concrete shrinks. There are two main types of shrinkage. When you first pour it we get what's called plastic shrinkage. This is the phase where all the chemical components in the concrete are reacting to "make" the concrete. Now your UFH pipes are in the slab so the plastic shrinkage can start to introduce tensile stress in the UFH pipes at this stage. Next we have drying shrinkage. The concrete dries out and this causes it to shrink more. Again more tensile stress. But in all cases the shrinkage causes "micro cracks" and all these induce tensile stress in the UFH pipes. They can cope with this. Now we know about the above so as concrete designers, even for screeds we ask ourselves.. can we put a number on that.. and yes we can. The starting point is to say lets design our concrete so no cracks exceed 0.3 mm. For say an ICF basement wall where the ground water is at ground level our starting point is 0.2mm. Now for UFH design we can do a big slab / screed with lots of rebar / fibres, to control this shrinkage, or smaller, movement jointed slabs with no reinforcement. This is more practical and achievable given my earlier point. It also means we can use self levelling scredd and so on. To sumarise. Yes you are correct to say that UFH pipes can tolerate shrinkage but they are absolutely not able to tolerate potentially 5 - 15mm of stretching over a localised area. Ok. The surveyor turns up, values the house on the basis that the heating works, they make this clear. You move in and say on day two you find the house is not warm enough. You call someone like @Nickfromwales who really knows his stuff. He crawls over it, provides an evidenced report that says... it does not work, and never will work well enough to comply with the building regs. So as a consumer you have been sold a pup. Nick then says in his report. Ah, to fix this you have a number of options.. none are going to be cheep. You can open up stuff and put in some supplementary radators, but that will mean opening up walls and possibly floors. Then you need to reinstate, make good, alter the boiler plumbing, add more components and find space for the radiators. Or you can start digging up floors to try and find the problem. Now that is going to be expensive! But UFH is becoming more main stream. At some point the RICS and insurers are going to say to their members.. look we really need to be taking this risk into account as we are supposed to be giving professional advice that keeps up with the times. We can't just keep saying to folks and thier lenders.. you have 7 days to report a problem with the heating. I'll stand by my point.. if your heating does not work as sold then expect at least a 5% write down. You counter my points well. Yes, there is more conjestion at the manifolds. As I said earleir there is not perfect solution. But I always come back to this. What buried in the floor is "forever". Once you get the pipes out the floor you can change the controls and boiler mechanics to suit the technology as it develops, or you can just stick with simple stupid. Ok so say you want to run your pipes in cooling mode. In the UK the weather can change rapidly. The thing about the UK is that the sun can be full on, but go 50 miles up the road its a dull day. Your weather compensation is not going to help you here. The solar gain can be rapid, thus you need ability to cool rapidly. This supports my approach towards redundancy. Ok I've had a go at responding to some of your points. Main thing is to have fun at this stage and enjoy the design process. One main reason is that when you have finished you can look back and say quietly to yourself. I made a bloody good job of that!

Ok it looks like we are still in love but just disagree on some points. That is the great thing about BH. Ah, but as an SE's we design for around 25mm settlement, often differential settlement over a 50 year period. This is a common value for most UK house builders. I design raft ( semi passive) slabs for intitial plastic and drying shrinkage, on a standard smallish house this can be 10 - 15mm. Unless you really know how your SE has designed the slab / foundation then your UFH pipes are vulnerable. You can't have you cake and eat it! To expand. The concrete found / slab moves so it is a "bigger issue". What it means is that you need to know and understand what you are putting your UFH on and account for that. Unless you want to pay a lot more for your underbuilding.. which is nuts. I love the challenge.. design and who is availble to build it. I can design lots of stuff but if the Client can't find someone to build it at a reasonable cost then it's a waste of time. Funnily enough it's not that hard if you look and understand how the structure acts as a whole.. but the big problem in the market is that every designer is acting in isolation. Often they are conservative which drives up the cost of the build. But if they work together then the cost should go down! It's mostly to idiot proof it! The UFH design look great on paper but life on site and a bit of rain makes for potential problems. If you are willing to stand over the Contracotr on site, then yes you may realise the design. No it's actually really high as unless you have put in the pipes yourself, contractors don't give a shit. If they kink the pipe they will just straighten it out so it looks good. You won't see it. That is why you see lots of regular and experienced members saying their UFH works well, as they are aware of the pitfalls and have supervised it the right way. I can tell you I also work with UFH that has been put in by developers and the pipes, radius bend are a complete disaster. But you can't design for low and slow when you then put rugs on the floor! This means you need to up the flow temperature which technically can breach the design values for the rest of the floor finishes, say engineered timber. Do you know how much a large sofa insulates UFH? It's a lot but no one on BH has acounted for this. Ok to complete, see if you get a joint leaking in the middle of the floor.. that is going to cause complete havoc! You can't easliy fix this! As a designer I design from the ground up, I have my SE hat on, my cost hat on and my Architectural hat on. I look at all the variables, how folk want to use the house. You have to have a deep understanding of how all the components fit together, the materials and so on. But as self builders you ain't going to be doing this as your day job. But it is well within you remit to think.. see this stuff I'm installing.. will if still be ok in 15 -50 years time ot more and if not is some surveyor going to come round and knock value off my house. No, as you have to run pipes to it. One of the great things about UFH is that it frees up wall space. So retro fitting a rad can be much harder than you think. Also rads tend to run at a higher temperature.. how are you going to make that work? From my end on the face of it your quick retort sounds good but practically.. just how are you going to execute that? and how much do you think that will cost? Why not just follow my advice and put in an extra loop, redundancey. My gut feeling is I'll never convince you... but hey ho, it's your money, not mine!

This is brilliant, great explanation of the fundamentals.