Gus Potter

Ok the cat is out the bag! For all. @saveasteading is converting a very big argicutural barn into home. I was invited to get involved as I had chipped into a previous project of his. For all. This project has pretty much everything that you need to know if you want to convert a barn to a home and not chuck money down the drain. My SE input has been to confirm what @saveasteading already knows, back that up with SE calculations, chip in with a bit of tough love from time to time, a few ideas and propose some SE design nuances. We all work together, and still are, to get something that is buidable and every pound is a prisoner! Maybe at some point @saveasteading will post on the key points of their journey, from the planning to completion stage. For me all I can say, while maintaining a bit of confidence is, the design journey has been great fun at my end, have had to work hard at times, questioned closely by a very experienced Chartered Enginner with vast experience. (saveasteading) worth the effort. Funny thing is that from time to time I work as a checking Engineer so it's good when you get put through you paces! I've learnt a lot, everyones skills and depth of knowledge has been tested. All the folk involved has decades of experience. Now for all. Yes we have experience but being old is not always the key.. the key is that we communicate, when we don't know something we just fesse up and say.. I don't know and we go and we find out and discuss how we solve desing issues. If you are self building then if you get the right team then you are really up and running. For all young designers out there.. us old crusties don't expect you to know it all.. we just want you to talk while bringing new ideas to the table in return! @ETC does this make sense?

Good. Ah, us Engineers take this as do the rest of the construction industry take this as being the inner surface of the outer leaf.. I suspect you are making a straw man arguement. Seriously how do you get from the "cavity face" to the inside of the walls. I don't know what convention you are using? Maybe you can point to BRE 443 if I'm maybe barking up the wrong tree? You are confused and mixing external penetration of moisture with the internal transfer of water gas outwards and where it condenses. Who deems that inconsequantial? Have a think about the basic thoery and work your argument through. Think about buildabilty, the elements of structure that connect into that. Agree, at times this can happen, depends if you have a porous facing brick or the wall is rendered for example. It does and that is what I've been saying, I agree with you! I have a copy of this. This reverse condensation issue was recognised. It probalby in my view is still valid. I mentioned this in my last post just to highlight how much this is very much an inexact science! BBA certificates! Well they said that about the Grenfell Cladding! Funnily, years ago, I was involved in getting CE certification for a cold formed steel company.. so kind of know how that world works. My advice is.. if you are a self builder then learn a bit and trust your common sense. @ADLIan I half agree with you.. we can debate the language, and different apporaches. One key test is would you personally sign off a design when I'm saying watch out? Remember I'm an SE.. if you do stuff that is going to compromise my structure when I have fore warned you then if it fails you are in big trouble! It's big boy pants time! I'm not sure but the best thing to do would be to crystalize our thoughts and come up with something that would be helpfull to folk on BH?

Hello all. I have a technical background as the day job. As quick rundown. I worked at Torness Nuclear Power Station in my late teens early twenties, then became a local builder for 20 years, that was when Chernobyle accident happened and the Ayrshire farmland got potentially contaminated, that was a worry, went to uni to become an Engineer. That was 20 years ago. My Master's degree group project was on energy, at that time Fuchishima happened. I got into cold formed steel and ended up designing a structure that sat over the cooling ponds on the Bradwell Nuclear power station at the decomissing stage. My litle bit was to do the structure that house the ventiulation units.. but it had to be lightweight.. but blast protected.. so a bit of a challenge, h3ence the cold formed steel. But for fun to design this building we have to look back an understand how it was built in the first place, how far we could drill into the lid to stop radiation getting out. Below is a photo of the cooling ponds during construction. Check out the bowler hats! When I was at uni I got a summer job for McAlpine as a project Engineer. I'm not going to go into my own political views but as an Engineer I think the UK is a bit (expletive deleted)ed as we are living from day to day essentially. We use to be an Empire, strong, we made war and more often than not we won, you don't go to war to lose! . But remember the British ended slavery for example, we paid for that as it was the right thing to do. For me national security has to come first. There are many countries in the world that do not share out values. Appeasment will not work, yes we would like it to, but lots of young folk just don't understand that there are a lot of bad folk in the world. So in the round. Yes we need to reduce our carbon footprint, reduce our usage but there those that say that our oil and gas industry is kaput are talking out of political nonsence. The West of Shetland fields contain lots of oil. There are plenty on BH that advocate this. I disagree with you on a strategic basis. You see lots of folk on BH that are really invested and have made a good go of making their houses "say a bit passive" but they have enough money to do this. They can afford to be that way! Your average punter is just trying to make ends meet! You have some on BH making eco arguments.. but do not look at how things work in the wide world and their actual carbon footprint. Many on BH are just enthusiasts, just like car enthusiasts when it comes to energy usage, there is no harm in that. But that comes at a price. I actually grew up in Africa..been in the middle east.. so I am not some daft "gammon" as many may assume I am. In the round I feel that UK energy policy should be driven by say a 50 year plan ( I wish) that means exploiting our own oil and gas, digging some coal! , using that money to innovate. The Chinese think we are all soft, trying not to offend religions, woke.. well we are let's face it, about half our politicial representatives don't know what a woman is! I despair as an Engineer and am very worried about the future of our kids. Anyway I hope the photo of Bradwell lets everyone see how a plant like this was constructed at the time. Even if you disagree with me then that's ok, just enjoy how these guys constructed a plant that operated safely and is still, to this day, getting decomissioned.. at losts of cost mind. But hey ho just admire what these guys did.

Assume this is a timber frame? Your cavity closing is going to be driven by your external leaf / cladding arrangement. https://envirograf.com/product-category/fire-barriers/cavity-barriers/ They have a good offering which I spec from time to time. BUT to be blunt.. if you are asking about this stuff on BH then please be careful before you swap materials out with your designers spec. To be safe by all means look for similar and cheeper products but ALWAYS check with your designer that it is ok to use an alternative material. Yes fire protection is expensive.. but it has to be implemented. Many think.. well we are young and fit so will exit the building.. but you put the fire service at risk and wallet wise.. your insurer may not pay out if you cut corners and are unlucky enough to have a fire.

I disagree. You say inconsequencial.. but it's not! The way we assess condensation risk is not to say "it never happens" it does under certain conditions. What we do is to recognise this but say to ourselves say.. if it only happens say for a week or two in the winter things will dry out quickly before mould or fungie can establish.. In the long term timbers and other parts of the building fabric can live with that if the occurence is low. Cavity wall insulation increases the risk of occurence of condensation as you move the dew point inwards and water gas condensing. Also if you fill the cavity then there is less free air circulating. You are getting confused between water ingress and condensation. Your arguement is flawed. You either have a cavity or you don't. You say that water penetration is the most risk.. if you have an open cavity then the water drains down the inside of the outer leaf, that is traditional design. A fully filled cavity works in a different way and does shift the dew point inwards and it's how often that happens is what matters. Yes the cavity wall insulation providers claim their insulation will wick the water down to the founds safely.. but any way you want to cut the mustard a shift in the dew point inwards at times when considering water gas moving from the inside to the outside of the wall does occur. Now in some ways lets say you do hit the dew point in a "bad spot". The first thing to ask is does this matter.. are we argueing a moot point? Well it does matter if you are going to make timber /steel wetter more often. The other consideration is that this water needs to evapourate. This requires heat or lots of air draft or a bit of both. The heat can come from the inside of the building or from the outside free air. Remember that much of what we do when we are designing stuff is to seek the best compromise! Just to make things more complicated. Your house is cool inside, the outside air temperature increases and the humidity rises. So now every thing works in reverse! This happens quite a lot in Scotland and Wales. The humid air from the outside penetrates the walls. An easy way to get your head round this is when you have well insulated glazing. The temperature and humidity suddenly rises outside and you get condensation on the outside of the glass.

Great example of what happens if you stand your ground! The info @saveasteading provides is your ammunition!

You make a good point. An oak frame building is constructed from green oak. I have a farmer pal who bought a log cabin kit house to rent out out as part of the farm business. The oak frames shrink a bit.. the log cabins.. we are talking 50 - 100mm! I'm fine designing this way provided you design for the movement. This is very much different from what we have been discussing where we want to have strict control over shrinkage. As an SE / designer we need to understand how the different materials move / shrink / expand as it can have a big impact on how we connect things together. For the self build market we need to recognise that self builders often don't get economy of scale like the big builders when buying stuff. The economy of scale also applies to hard / complex details and the labour cost to execute these. On a big job with many houses you work with the Contractor on a template, resolve the buildability problems. In other words the folk on site practice on one house and then get faster at it. But you don't have this luxury on a self build. @saveasteading is into lean and cost effective design. The original barn steel frame is having to pay it's way, no free lunch for it! I've seen some posts where folk in England are converting agricultural buildings to homes. The planners suddenly think they are SE's / designers and insist that the steel frame of the barn is a structural element before they can approve. Now this can be done and often a design case can be made that satisfies the planners and the Clients design intent. The basic appoach is to analyse the existing agricultural frame, which 99% of the time fails under the more onerous domestic loadings, then transfer the excess vertical and sideways wind loads to the new timber frame shell inside and connect it all together. Good to have you on board and good comment. There are things you can do on site when drying timber, on the FLAT, not vertically. It takes time but you stack the timber, batten it to let the air through. Then every week you lift the timber off the top. Turn it up the other way and turn it end for end and put it on the bottom of the pile. Do this with every second row vetically , then alternate. The way this works is that as the timber wants to bow and twist it is resisted by the weight of the pile. You can add extra weight to the top of the pile by stacking some concrete blocks or anything heavy that distributes an even load.

John, your experience is showing, admire, one sentence only! Take John's advice and see how it pans out. The builder may just chuck in the towel. At the end of the day they knew there was a cable somewhere, the depth is a bit of a moot point.

Hiya @Julestools interesting thread and good questions. The following is a bit of back to basics, for the less initiated, maybe new folk to Build Hub. This is a very rough run down but intended to introduce folk to something that may be less familiar. When we insulate walls we want to make sure that any water that condenses in the wall can be expelled outwards or inwards before it causes any damage. When you cook or breath out you expel "water gas". This does no harm. The harm arises when the water gas turns to a liquid.. water droplets. Mould, dry rot, wet rot, most bugs / fungie need liquid water. At the bottom of a wall we often see damage due to freezing water (spalling of bricks / render) when it becomes excessive. For the water gas to turn to a liquid it needs to hit what we call the dew point. This varies depending on how much water gas is in the air and the air temperature. For example if you live in the tropics the warmer air can hold much more water gas, lower the air temperature a little and you get heavy rain. In the UK it works the same way, but a bit less dramatic... but the UK weather is it's own animal, I'm not covering this just now. If you have a 1970's brick cavity wall to start with with say 15mm of plaster on the inside and roughcast on the outside then the dew point is likely on the inside of the outer leaf of masonry, the obvious cold surface. The cavities are often drafty so lots of water gas will get vented. You can analyse this but in most UK weather conditions the water gas condenses on the inside of the outer leaf of masonry. Any condensation was designed to run down the inside of the outer leaf. In actual fact in the 1970's there was no condensation "analysis" as we now know it.. it just worked! These houses were designed based on the knowledge at the time and proven to work in most cases. If left alone they will continue to perform as originally designed, although not meet our modern insulation expectations. Cavities at the time had residual air circulation. But now we want to make them warmer! To get a handle on this it's often a good idea to research what the designer at the time was thinking and what knowledge they had at their disposal. I love this stuff! Miss Marple! @Julestools "The cavities were filled with a mineral wool type fluff in the 90's." That has two immediate knock on effects. The natural / residual air circulation in the cavity is blocked off. The cavity insulation moved the dew point inwards, so you no longer have the really cold surface of the inside of the outer leaf of wall acting as the dew point surface. The cavity wall insulation installers often sold this as they say the insulation will "wick" the water away safely downwards and not come inwards! Make of that statement what you will as adults. @Julestools " I'd love to hear your thoughts and knowledge on this approach to internallly insulating cavity walls." You are fortunate not to have any timber ( floor joists say) near the bottom of the wall. If so it becomes very tricky as the ends of the joists are more prone to getting wet. For all, BE VERY CAREFUL IF YOU HAVE TIMBER IN THE WALL! You want to improve the U value of the wall. You insulate on the inside. You shift the dew point further inwards. Qualitively, if you improve it a lot you will shift the dew point further inwards, maybe even to the inside of the inner leaf or in it. Don't forget.. the calculations in the design codes are theoretical.. we need to apply common sense, this is most important! Given the above lets take a pragmatic view. The first objective is to control the humidity in the house. Bathrooms and shower rooms need extra ventilation.. we know that. Next question is... we can select breathable insulation.. but the critical areas are bathrooms, kitchens. Folk paint them and tile walls. Say you sell the house or some really "keen" BC officer pulls you up as they say someone may use the wrong paint on the walls.. it's a fair question. Putting my SE hat on.. it is important! In some ways I think your are over thinking this! The first objective is if you are going to create excessive water gas then you need to expel that as soon as you can, but you need to have a certain humidity in the house to stop your sinuces playing up. A house that is too dry is a nightmare! In the round, if you are air tight, particularly in the wet areas, have good room ventilation then it may work. If you have ANY timber in the dew point zone then that is trouble. Yes to be CLEAR if you insulate on the inside you WILL shift the dew point inwards. Look to see what you could damage if you do this. To summarise. There is no point in trying to model the whole house, you'll drive yourself nuts! Just have a think about how a basic wall might work the way you are proposing, be conservative at this stage. Make sure you have no timber in places where water may condense. Make sure you can stop moist air by way of ventilation getting into the walls in the first place. I'm a desinger and SE in my day job.. there is a place for calculations and a time for pragmatism when dealing with older structures. @Julestools hope this helps, check you are spending your cash in the best way! It may be that you are not seeing the woods for the trees? To make a point.. if someone paints the walls with the wrong paint then all you efforts are moot.

That is a bold statement to make! The design of the links can be complex, depends on the level of shear stress, usually in and around the pile heads. I won't comment further as I don't know what loads are on the beams / piles. Plus one to that, good advice. This is what often happens, sometimes a quick phone call between the engineers can sort it all out. Oh, it's ok to design to BS 8110, so long as you are aware of any parts of the more modern Eurocode that superceed the older BS 8110 code.

I assume you have a suspended timber ground floor with timber joists. Take a step back and check that what you are doing will not compromise these joist ends or any joist running parallel to the external wall. If so by how much and what are the risks. The basics of timber preservation are; keep it in the dark, cold and with plenty air circulation (drafty!). Once you get a handle on this then the rest of the insulation strategy / air tightness is based around that.

I read your blog a while back, onwards and upwards, well done!

Enjoy your holiday., but see you are still monitoring comments. So in that context hope this helps. Agree. I've put my day job hat on and thought, how would I go about sorting this out, bring discipline to the process? You mention that you are keen to avoid stressing your personal set up, that is a material consideration and probably the most important one. The rest is just building mechanics, how much it's going to cost to build and recognising that at times you need to make reasoned design compromises in places and then compensate where it is easy to do so. As I've said before I like your design, not everyone will but beauty is in the eye.. Now as a word of encouragement, you are not the first to experience this, and you won't be the last! If I was going to tackle something like this I would probably just spend half a day, may take two goes at this, say a day, listening to your journey, trying to understand what you actually want from the build, how you got to where you are. Often when I go to an initial site concept design meeting I try, insist, that all parties are there. So that would be you and your partner. This works well as I have the "day job" advantage, if there are two of you then less chance something gets missed, questions not asked by you. I would ask questions as prompts, let you talk and from that it lets me build a picture of your basic requirements, the things that really matter to you. The conversation needs to be general, technical stuff comes later. One of the things I do it to assess what time you have, your skills, where you lack them, where you need help, where you can learn and help yourself and how that help gets delivered. Now all that sounds wishy washy and a bit woke, but once I get a handle on your capability and situation it lets me put together a costed design brief after figuring out what needs to be done to bring order to the project. Yes you don't "want to go back to the beginning". The next step is to look at what you have, what is useful, viable, what relationships can be salvaged and what can't. What do you need to do to get BC approval, an approximate build cost. A bill of quantities (BOQ) is a different animal. @Tony L I think you'll get there in the end so keep your head up! For all, this is worth a look at as there is often confusion about what all this means. The following is a bit of a summary, not perfect mind! Often self builders on BH will employ an Architect / designer to get planning permission. The same will produce a set of drawings with sufficient detail, thermal calculations and the like to get BC approval and many use these drawings as the "construction drawings". Sometimes it's fine bit other times it leads to dispute about money, lack of fit up on site, changes made by the builder (as they go off piste) that compromise the structural design big time. Some divide the design into work packages, say the foundations, a timber frame, but the interfaces never get thought through, again money and time is lost as these interfaces never get properly designed. The Client is left disappointed as they can see they are not getting what they think they are paying for. Client may then go back to the designer and might say, your drawings are crap, the designer then says, I was only contracted to produce sufficient info for BC approval, and I have excercised reasonable skill and care in the sense that a competent builder should be able to fill in the gaps, my drawings are not detailed construction drawings, see my terms and conditions!. Cost is not a primary consideration, safety is, no one can run about designing stuff that has no chance of getting built safely! The next step up is to produce a full set of detailed construction drawings. This is kind of the level that @Tony L is going into at the moment. From that you can generate a respectable bill of quantities (BOQ), on Tony's job it will be lenghty, cost a fair bit and this falls much within the remit of a Quantity Surveyor. There is no point in spending loads on a comprehensive BOQ unless that is coupled with a recognised form of building contract that eveyone signs up to., or at least something similar, a bespoke contract, risky though! Few domestic self build Clients do this, unless it's a mansion and you have loads of money! So say you have a set of construction drawings, a BOQ and a recognised building contract. You now need someone to Admimister the contract. They may or may not be the principle designer. Story for another day. But the new PD rules now require in essence a much more hands on approach to what is going on on site and ensuring that the builders / Client does not go off and do there own thing.. which they often do! The risk for the administrator is that if you authorise a payment to the builder and it turns out you have authorised too much then you are on the hook and liable. Most adminsitrators will authorise payment but caveat, from what we can see visually the works are at this stage. They do not certify the quality or accuracy of the work for example. This is a key thing. What is NOT offered it seems, is what we would call a traditional Clerk of works service. A traditional Clerk of works is on site pretty much all the time and they are responsible for standing over the builder at every stage, absolutely nothing gets covered up.. every thing is checked for workmanship, level, setting out and consitency for example. My own PI insurance covers me for SE design, Architectural design and contract admin, it explicitly says that Clerk of works function is excluded, and for good reason.

Tony, what's done is done, anyway, there are occasions where you may for one reason or another needed to get some sub structure in place, it's called speculative desgn. That's actually ok! You have an outside envelope into which you need to fit structure, the external appearance and materials have been established, happens all the time so take that as a positive. The first thing and I'll say again, what you are doing design wise is really hard especially the detailing! This cavity tray detail for example does not work, not least as the piece of masonry on the inner leaf will just come loose when you bed the cill, probably before that, there is no insulation under the cill. The shaped insulation is not achievable. What will happen is that you will end up paying for something that does not get delivered on site. I've looked over your thread and conclude. You have set you heart on the outside, it looks great. You have an established plan for the general internal layout and finish, again good! But you are struggling with the structure, how you insulate that, do the interfaces work thermally but also provide the lateral structural restaint and connections to the main structure. Now I've distilled your probem down. So all of a sudden that looks a bit more hopeful! What has happened is that as you have learnt more about the bit inbetween the outside and the inside you are discovering that it is hard and often I think the case here with you is.. you can't see the wood for the trees. This is not uncommon so don't take this as bad. It happens to many people, even those who do it as a day job! You are not alone! Consider trying to find someone who has the skills to review your design in the whole, identify a way forward that is buildable, knock heads together when required. That includes knocking you into shape. Many self builders are stubborn! That is ok at times but from time to time it can be to their own detriment. They pay professionals, but only from the neck down! Someone like this will work with you very closely and explain where your ideas are good and where you are going wrong. At the end of the day it's you paying the wage, it does work! Now that will cost you but for that you get not least, an advocate, a friend and someone on your side. In my experience the fee you pay is often offset by the savings made and enjoyment you get when someone says.. you are on the right track, always have been, but we need to add this critical bit. I'll leave these thoughts with you.

Post overlapping here Tony. I'm trying to warn you of the challenges you face. I have not considered your internal ventilation, only that the structure is going to work insulation and ventilation wise. The fire protection is always a challenge. Your house is only two stories and detached so pretty benign. In your case so long as any roof steels are not contributing to the stability of a floor or structural load bearing wall they may only need minimal protection. Talk to your SE and you may find it all works boxed in by ordinary plasterboard and buried in the roof dpeth.