Gus Potter

Not quite. It cost me roughly 250 k in lost wages to go to uni. When I came out I had to start at the bottom of the SE ladder at the age of 44. I sucked it up until I learnt enough about SE stuff and went back to running my own business. So for me I was very lucky as I don't have kids to support. I'm 62 now. It took me about 10 / 15 years to become a really competant and prove to myself SE that I can hold my own against the best. I deliberately write on BH in a foaksy manner, am chatty as I just want folk to have fun. In my day job I do the same until some idiot starts having a laugh. I also do claims work agaist say the NHBC, I'm not chatty, I can be absolutely brutal in this cases. Sometimes it's nice to take folk down a few pegs and rub their noses right in it and make them pay compensation, you get that feeling.. I warned you and now you are f_cked. My financials work like this. I don't have massive pension provision. But I've got a good brain. I recognised that if I educated myself and used my business exerience I can work and have fun well beyond my 70,s.

That is fab news. It doesn't matter whether you are someone like me that chips in with a bit of free professional advice or someone that has just got together enough funds for a deposit on their first home. It's essential that we encourage and share ideas and most importantly the enthusiasm.. which can make you money. The easiest way is to avoid unforced errors, which is essential if younger and building a pot of funds. BH does this as you can see the other mistakes folk make. There are a number of members on BH that are wealthy, if you look back some have come.. milked BH and then gone. Some have stayed and are giving back. I don't resent that, it's just adult life. That said there are many that I know have saved thousands and can't be bothered ( or are just not socially educated) to donate a tenner. But the Mods really need folk to gather round them, give them some support both financially and morally. The current mods at some point will have to hang up their boots. I would love to see BH out lasting me!

Ask your SE, they should have detailed this out already for you. BC are not Structural Engineers. I might chip in as an SE but I would need to see the drawings first. There are lots of different types of raft. Until you know where the uniform loads are , where any point loads are you can't start on the drainage design.

Thank you for the kind words. To expand a bit.. I do this sort of stuff as a day job.. But once you have designed your first hundred steel beams the excitement kind of wears off. I has to be done and you have to knuckle down as it puts bread on the table and vitally impoprtant you are perfoming a Civil duty. You can't be lazy and drop your guard as folks lives are at stake. There is a common miss conception that SE's and Civil Engineers design for the Client alone. This is far from the case. Our primary duty is to the public, that can be anyone that later buys your house for example. It sets us aside from Layers, QS's etc. Architect's fall between the cracks @ETC. They also have to design so the building is weather tight for example, if it's not it can cause deterioration the the stucture. In the round the Architectural profession and Se is very much bound together. That is why you must foster a good design and professional team. At the end of the day they will stand the best chance of delivering what you expect to pay for. I quote Ruskin on the law of economics. There is hardly anything in the world that someone cannot make a little worse and sell a little cheaper, and the people who consider price alone are that person’s lawful prey. It’s unwise to pay too much, but it’s worse to pay too little. When you pay too much, you lose a little money — that is all. When you pay too little, you sometimes lose everything, because the thing you bought was incapable of doing the thing it was bought to do. The common law of business balance prohibits paying a little and getting a lot — it can’t be done. If you deal with the lowest bidder, it is well to add something for the risk you run, and if you do that you will have enough to pay for something better.” My work is also my hobby. I love desinging stuff. I started out as a builder after getting an HND after leaving school, became an SE and then married up that with the stuff I learnt as a builder to become a designer that also does the Architectural side and everything else that interests me. The best bit of my job is taking on the hard an unusual stuff as you have to design from first principles and then justify your design to other professionals who may be critical. It's a test of my knowledge, my communication skills, a bit of diplomacy, presentation.. all backed up with hard maths and probablility. Yes there still is the SE sums, the admin, sorting out contracts.. but at the end of the day after forty years of learning I kind of feel I've arrived and I derive immense enjoyment from the creative side and working with folk who know I'm not talking shite. If you look up the definitions of what an SE it often says it is someone who practices the art and craft of design. This is what lots of folk are doing on BH.. they often just don't know they are! It's my job to say.. hey folks you are doing great work, lets see how we make it work to get buiding regs / planning approval etc. I hope you are in broad agreement with my above sentiments. Keep posting and don't be a stranger. Take note of this. I learn loads form BH, every day is a school day for me. The folk on BH are often advocating the latest design ideas and innovating. Many come from different backgrounds and are highly knowledgeable both technically and with huge life experience. If I want to keep up it would be daft for me not to take BH folks ideas and ask.. how to I translate that into something that can be practically built. Lastly.. a pure pitch for BH and the mods. They are doing a fund raiser which I support.

Post a photo of where you are are the moment.

It's hard to argue with something like this, best is to just smile politely and wish them the best of luck. Well done you. Big savings to be made here. One practical example is say you have to deal with the water board or other service companies You can be hanging on the phone for ages, then get cut off!. When, I can, encourage Clients to do this initial work but brief them first on the right questions to ask. I get paid for guiding, you save money, doing something yourself and being proactive. It is also beneficial as Client gets a deeper understanding of the project mechanics and who the desing all fits together. They feel they have more control and are better informed. In the example above I allocated 8 days of director time. I had a feeling when I wrote that it would provoke a response, probably incredulous mostly, some may have had a choking fit. But I set it up in the context of a small practice. The director is not trousering £100.00 an hour. That rate has to pay for admin, PI insurance, Software ( expensive), unpaid time spent generating the buisiness in the first place and a whole host of other expenses. Actually the £100.00 an hour is likely too cheep. I allocated 15% profit. You can in life work for someone, often with less financial risk. When you run a business you have to build some capital to cover bad payers, the govenment changing the tax and rating system .. and its fair you should be able to take some reward at the end of the day, maybe have enough to build a pension fund similar to what someone in the NHS may have? Your point on enjoying working with your Architect and have enjoyed working together is hugely valid. This has hidden value as they are invested in the project. I engourage this. Often I keep an eye on my projects even though my formal brief may be concluded. Clients often phone me during the build and say.. Gus what about this? Often with a comment I can save thousands or just reassure them.. and that kind of puts my design fee into perspective. Another way of looking at this. If I save two weeks of tradespersons time that can amount to often over 2.0k.. On BH there are a few folk that do desing / project management as a day job. There used to be a guy called the R_Sole ( something like that) who worked in Scotland, highly knowlegeable but got hounded / many thought they knew better and.. he left. There was a bit of a gap then @ETC turned up with his valuable Architect input. In terms of fee rates for SE's / Architect's I am confident we can justify our rates (which may not be the cheepest but maybe best value) and what you get for your money. Of course there are bad Architect's and SE's, but this is often due to a lack of experience rather than them being chancers. One key thing that can cause you to fall is poor communication with the Client. Fom time to time a Client may ask me something that I can't answer straight away. I just fesse up and say I don't know! , but I'm going to go off and find out, then work it out and give you a reasoned and evidence based answer. If you are generally happy and have a good personal relashionship then grow together, pay their current rate. Last thing today I got asked by a Contractor I work with to come and look at a job where the Scottish SE (SER Engineer) has been sacked by the Client, from my initial findings I get a smell of profession incompetancy. Their Architect has dropped some clangers. They are in mid build. They told me what fee they had paid to the SE (SER Engineer) .. I can't see straight away that it's unlikely they could have produced an competent design for that amount of fee money. I'll not post much more but my initial suggestion was let's see if we can find some tools that might encourage the SE to want to be "unsacked" and the Architect to come back to the table in an "enthusiastic manner" on our terms.

I can see how you might not follow. I said something like this: Now typical rates for a structural engineer working under the IR35 scheme in the UK are about £350 to £500 a day, equates to £45 - £70 an hour as they get paid for a full 8 hour day. Much depends on experience! I'm taking this as a new build, much of the below is just general and intended for all BH folk to let folk see a bit of what is behind the curtain. Lastly please excuse my spelling and grammer as I'm off duty. For a bit of fun I've copied your brief items 1 - 8 below (made it gold colour text and italic) and tried to guess the time (with a bit of interpretation) that I may set against each item to work out the time. Once you know the time you set the rate.. then add profit and VAT if applicable. It's going to be a guess but hopefully it lets BH folk see how someone like me puts together a fee quote and the thought process behind it. I've put my own slant on the time. Oh now.. you know Lawyers do it but the 1/4 hour or less and have different rates. If any want to quibble then convert to legal rates.. and we can work back from there... just joking. No worries... The fees to date cover items 1-8 below. 9-21 are another couple of thousand. We have planning approval, have discharged the pre-commencement conditions and we're probably 50% of the way through the remaining points. PREPARATION 1. Development of initial statement of requirements into the Design Brief on behalf of the client confirming key requirements and constraints. Half a day to meet you, ask questions, listen to what you want,understand how you live. Interrogate you a bit, gently. Work out if we can get along. If the personal chemistry stinks then walk away. Often I find folk are actually nervious and that comes over at times as a bit aggressive on the Client side. You have to have the skills to recognise that and cut folk a fair bit of slack. Half a day to do a bit of background reasearch, quick due dilligence on you, the Client. Half a day to think about the design, what the Client has told you and what they have not. When I go to meet knew Clients I observe how the live curently, I encougrage them just to talk about themselves. Say husband and wife how they try and communicate their ideas. Once I'm in the room the answers they give are often different from the way they talk to each other. One day to put together a design brief of requirements / constraints with some ideas on how you go about meeting thier requirements. This can be things as simple as.. we want a traditional pantry. We want that to be cool and ventilated for example.. plays a bit of havoc with the U Values but if that is what is required then srecognise that. 2.5 days work. For context: You are running a small Architectural or Engineering practice with 2 / 3 Directors and a few staff and generating plenty leads then the hit rate should be between 1 in 3 to 1 in 5 jobs. Less than 1 in 3 and you are not maximising profit. More than 1 in 5 you are wasting money. This is an old accounting rule of thumb. Many practices have repeat customers so you can maybe drop the price a bit due to regular custom in these cases. On a personal note.. you have to want to do the job. You are going to invest in the project and if your not then the Client will sniff that out, it's not a good look! 2. Surveyor and measure the house. DESIGN Ok on a new build you get a setting out engineer that has all the right equipment. Their stuff can cost 15 - 20k for a high end total station. Say a day for them. Get their info, take the data into you CAD package and think about what you are seeing. 1 day 2 days work 3. Prepare a number of sketch designs as your brief and for discussion purposes. This can include hand sketches, 3D computer modelling and physical models. 2D cad sketeches, use colour to helop visualse: 3 days 3D This is something that Architects love but usually is complete mince and gets put in the bin later. Hand sketches fine. Physical Models.. few these days can do it. 2 weeks. At this stage the contract is signed and the objective is to get the key information you need to communicate with the Client. It's early stage stuff. You can much more quickly adapt 2D drawings than a 3D model. The secret is to produce lots of 2D concept drawings to narrow down the options before you go into 3D mode, if you ever have to. Ok say 4 days for this item. 4. Prepare final design/make alterations in accordance with your instructions this will be weighted at 20% of the design fee. 3 Days Planning 5. Prepare planning drawings and other information if needed. 3 days for the planning drawings, making the submissionand all the paper work etc. other information is open ended, can't put a time on that as no idea how much work is involved. 6. Submit the Full Plans and Design Statement. 2.0 days, design statement 1 day as you have already spent a bit of thinking time. Say 3.0 days. 7. Act as clients agent during the planning process and advise on planning requirements. 2.0 days 8. Notify the neighbouring owners of the construction under the Party Wall Act etc. 1996, prepare notification letters only under the act. Applcable to England only, not my bag but say 2.0 days. The above adds up to about 21.5 days work. This will be roughly split between a senior person and a technician. Split it 3/4 technician and 1/4 director. 3*21.5 days / 4 = 16.0 day technician @ £30.00 per hour = £ 3870 1*21.5 / 4 = = 8 days director @ 100.00 per hour = £4300 Sum of above is £8170. Add profit @ 15% = £ 9395 ex vat. Now the above is probably going to raise an eyebrow or not. Someone like me who just works for themselves will be cheaper. But I can tell you that for 4.0k you are not going to get much quality information that you can later use. I would say that they are too cheep and you are likely to get stung. For items 9 onwards there is no way you are going to get any useful information for 3.0k. You are likely going to get absolutely pelted by your builder and are putting yourself at massive risk. |Your advisors should be assessing your competancy, ability, h ow you are going to manage this, what work you are going to do yourself and so on, advising you on your chances of satisfactory copmpletion and telling you where you are likely going to need support and then detailng and drawing accordingly. That is the skill you pay a good designer for.. they recognise you weak spots and where you are strong. Now actually all I have to do is save you a couple or three week site labour time and I've washed my face even if the fees appear higher at the outset. Sorry to dish out the tough love. But you are tying you own hands at this stage. To do this amount of design work for such a low fee.. you designer would be much better off working a Tesco/ Are they insured?

I ask my self. The idea of a balcony is that you can see out. At times you may want privacy.. but you use say pot plants for that. You also want to do a bit of sun bathing. There will be a few eco enthusiasts that do this but most in real life will give it a swerve. Why don't they just fix solar to the walls instead?

Ok in my day job I spec windows doors etc. Now on my own home I've got some high end aluminium windows, doors and roof lanterns. The deal on the headline is that the overall installtation has a warranty for ten years.. but the fine print says the glass units are valid for only seven years. I was pleased with the product on my own house. I ask my Clients to have a look at their product. Now I'm in year six and one glass unit is starting to mist up. I think the supplier is going to be keen to fix it, as I pass business their way. Here is a key point. There are loads of folk building ordinary self build houses that are trying to get the U values down.. but they don't realise that the glass may fail after 7 years and they have no come back. It is financially complete bonkers to spend money on high end glazing units that may be out of warranty in seven years.. but still there are folk on BH doing this. Ok if you have loads of cash to burn / may be dead in ten years time then fine. But for young folk just starting out it's complete nonsence. I my case the window supplier is not far and locally based. Buying stuff from abroad comes with greater risk! It's like that wee baldy chap on on Dragons Den that says he can get everything cheeper from China. If you want to buy windows then the two things that matter most are; the warranty on the glass units and the back up advice on installation. It's very rare that the actual frame fails.

Great thanks from me for responding to my question.. which was what did you get for your 1%. Say your build cost was 400k then 1% is 4.0k. For items 1 -8 that is ok ish but most of the info will be general. The rest is much more expensive.

On balance the chances are that provided you did not add too much water then your founds will be ok. For all. I reported on foundations in a dispute that was about to go to court. It was an extension that had been badly built, BC got involved and asked me to verify as an SE that the founds / concrete stength was ok with the added water.. I got the concrete delivery ticket and eventually found out just how much water had been added to the mix. I then had to back calculate the reduction in concrete stength with the added water and show the founds would still be ok. In this case I could. In laymans terms if you add water it means there is less cement / aggregate per cubic metre. It's like say dense hardwood with lots of cellulose, small cells compared with softwood with larger cells and less cellulose matrix. A hard wood has more "stuff" thus stronger. The same principle roughly applies to concrete. The mechanics work a bit like this. Below is me taking a chart, working out the change in what we call the water to cement ratio and arriving at a reduced concrete strength. And the spot mix ticket looked like this in 2022.

For less than 1.0% you must have got the most basic service which is not for all. Can you let us know just what you got for your 1%?

Food for thought: Another way of approaching this is to ask. What would it cost you to get a washing machine repair Engineer? Say £50- 60 quid an hour? Ok they have a "down time" that they don't get paid for as they may be at your house for an hour then have to drive to the next job, but someone has to pay for that. Now typical rates for a structural engineer working under the IR35 scheme in the UK are about £350 to £500 a day, equates to £45 - £70 an hour as they get paid for a full 8 hour day. Much depends on experience! Go to a self employed SE/ Architectural Designer like me who has no employees then the rates are about the same except that I have overheads. These are primarily my software, my PI insurance and admin costs. Admin / business generating costs. Admin is admin, I pay an accountant, have to keep records, a secure data base etc.. but quite a lot of time is spent generating business that a contractor under IR 35 does not have to do. Turning now to say a small Architect practice with four or five employees that are innovative, expanding and so on. The overheads shoot up, often dramatically. How long is the string? Well it has no end. This is a summary for sake of conversation. It used to be in the old days that say Architect's, Engineers, Surveyors got a percentage of the build cost. But as the market got more competetive and folk like say MBC timber frame (the list is endless) came along and offered a design service then the main designers.. like Architect's, SE's just shifted part of the design work onto them. Now all that worked ok for a bit.. but now it's got to the stage where the lack of coordination is really causing problems. This is not helped by TV programmes ect that often suggest you can pick builder and design sevices like something off a barber shop menu and it will all be ok at the end of the day. My take: It's vitally important to understand what you designer is offering. Not just in terms of say doing a few drawings but also their understanding of how the design process works practically and how you go about communication to and finding the right builder. . I find that often once I explain this "added value" then many are happy to pay for a service that includes much more than drawings and some structural calculations. In the round once you become a competant designer then the rest is down to communication.. which is a skill in itself. 2% of a build cost for an Architect Take a house extension at 100k.. you won't get much for your two thousand pounds. take a new build at 300k with all the work that goes along with that, dealing with the roads, environments, water board.. all that stuff all for 6.0k. Just maybe but I would not do it as I know I would have to cut corners.. which will come back to bite eveyone. Quite often these days I break down my quotes / estimates into how long I'll spend on each element of the design. I'll maybe say.. two days to survey the site, at £xx amount per hour and so on. I find Clients embrace my transparency. It is very rare that they come back and say my hourly or daily rate is too high. In the round I don't think applying a percentage fee cost works anymore.. you have to be much more streetwise.

Well done you! Keep us posted.

As purely an observation. Many posts on BH relate to BC / Planning and in the round tend to take, let's say.. a disparaging view. In my day job as an SE I often get phone calls about this kind of stuff. Many calls go along the lines of.. Gus can you give us a report that says it's all ok. In particular we would like you to say by all Ok we mean.. everything is ok.. structure, insulation , condensation control etc! We would love you to say this as we want to maybe get lending and later on when we come to sell we need your paper work. But to report (and for my PI to cover you and I) I need to know if there is anything that is going to compromise say timbers.. hence I need to look at say condensation risk, weathering details and so on. I could of course say.. the structure is fine.. but caveat, as I must do, to protect myself.. and then the lender will ask for more detail. We end up back at square one. Nick. In technical, insurance and SE reporting terms this needs clarification. Most of this stuff is designed for a 50 year life span. SE's design on the probability of the maximum load occuring over a 50 year period. It is fool hardy to say if after 20 years it's going to be fine going onwards as the structure may have not been fully loaded up yet. In the next 30 years it may be subject to the full design load. This is the difference between someone like me that is going to have to carry the can if someone gets hurt later, or a claim is made and someone who has lots of experience.. but only 30 years of it! This is not an abstact concept. An easy example is say a loft conversion. You have a kid.. they grow up to be a rugby prop, they ask their mates round to the attic room, they party, there is a bit of "dynamic" loading. Very quickly you can exceed the design load and eat into the factor of safety. Another is snow loading on a roof. Now over the last decades we have not had lot's of snow. But the climate is changing. The air can be warmer, the cold fronts more defined. The risk is that we get a heavy dumping of wet and heavy snow that traditionally would blow off a roof to some extent. Wet snow just sits there. I base my SE judgements partly on the experience of SE's and Civil Engineers over that last 200 years (often more that) which have been woven into the modern design codes we use today. This then allows insurer's to write premiums and banks to lend. Now insurers understand how SE's approach risk and vis versa, the probability of failure and where they can seek recourse to say an SE's policy. Probably the thing you should be concerned with most is to ensure it is not going to fall down or later the structure start protesting. Really!

Ok I'm going to give you the benefit of the doubt here. No photo as it's dark o clock! I might be able to reassure here, but not promising anything. If you want hand sketch what you have on A4 paper, photograph and post. Show a plan view and annotate the depth to the bottom of the trenches you have dug relative to the highest finished ground level 0.000 m . If the ground is sloping mark the highest ground level as 0.000m and then assign values to any ground that is lower. Also show you main house founds. Show all foundation widths, mark the plan dimensions to the outside of the masonry walls and the outside edge of the foundation. Confirm anything you are placing on the founds is single storey. Provided that the highest part of the found is on competent ground then an extra 200mm is unlikely to result in excessive differential settlement. All parts of the house will settle differentially due to variation in loads, depths and soil variations, SE's design for this. The most common problem is folk leaving a soft layer where everyone has tramped about, essentaily laying the concrete on a slurry. If you are stepping the foundations then make sure the mesh extends over the step.

If you have corrugated steel profile roof sheeting something like this may be more suitable for the weathering detail. Your air tight layer is further into the depth of the roof. The issue is sequencing of the build process. Weather proof steel sheeting is probably going to go on first before you start to introduce plasterboard and air tight layers. You probably need a second flashing to pipe gizmo that you can bond to your air tight layer. Your air tight layer is usually a plastic membrane so we need something that you can use to bond the plastic to the soil pipe. Remember that soil pipes expand and contract a bit when you empty the bath warm water for example, thus we need something flexible. Can we just rely on air tape or do you want something more " professional" looking. Like this:

That looks a good theory.

Ok that works if you have an eaves and ventilated ridge with a 50mm air gap. Slate hooks are a nightmare, and dangerous for folk going onto the roof to maintain it. As part of HSE stuff you design to make sure, say in roofs, you don't have exposed sharp nail heads, slate hooks are nasty and are a puncture / trip hazzard. Why not just do the job properly? Slate hook are more associated with remedial works.

Hello all. I've started a post but ties back to @Digmixfill Sometimes (often) things are not level etc or we have a complex roof shape with lots of different angles framing into hips that need some support. This, even for the experienced, can be a challenge to visualise itnever mind build it! Then you need to find someone with the skills to actually do it. If it looks hard then they will hike the price. When we have to check / chamfer timbers / do 3D cuts, particularly large ones then if the joiner makes a mistake then they often have to pay for the wasted material. Cutting joints in the rain or techincal ones just adds risk and stress. Below is a design where I'm trying to reduce the risk and help everyone visualise what needs to be done and the sequence of the work. Below is a 3D model to help eveyone see what we are trying to do. The roofs are at different angles and so are the hip rafters. The red bit is the main padstone support. Below is what the rafters and hips look like in 2D on plan. I try and name things to help everyone easily identify what parts of the roof we are talking about. In true technical drawing terms I you don't need to be "so chatty" but it avoids confusion. Some of the dimensions are used in my structural calculations so are not actually "Architectural" in purpose. I put gridlines on things. I still amazes me why "Architect's" don't do this, even if they hide the layer for visual Client presentation. It's just stupid in this day and age not to. It makes it really hard for SE's to line up floors for example, that wastes time which Clients end up paying for. Below is the way hip 02 connects in detail to hip 01: The edge and end distances for the fixings are critical, hence dimensioned out. In 3D it looks like this: Now here is the secret. You could try and rebate hip 01 over the padstone.. very hard to do and the joiner only get's one chance. Or you can leave the hip H01 as is and make up a seating plate for it from offcuts of timber. This way the joiner gets as many chances for free, they can make it up on the ground and you don't have to cover the risk element! To finish. Lots of this stuff is about making things buildable and if you have funny angles, things not level then coming at the problem from a different direction, always of course with a view to cost can help. No point in designing something if the money is not there!

Posts overlapped!

Hello David. Welcome to buildhub. You'll get lots of different ideas here.. the best thing is to mull them over and adopt the ones that suit you best. Lastly, excuse my spelling and grammer! You asked for thought! The following is to give you some power to your elbow, not intended to be any form of critisism, after all you are still at the preliminary design stage. Shetland eh!. My sister lives in Tiree both can be increadibly windy with driving rain. As such you really have to almost go above and beyond the normal call of duty when considering the design details, which are crutial. I'll start from the top down.. the slates. You have two choices in terms of nailing. Traditional or modern. Traditional method: In the islands for smallish slates we often go for one nail in the head of each slate then every third course head nailed and also cheek nailed. The cheek nails restrain the slates below as they have effectively 3 nails in a triangle. Now at the verges and eaves, around Velux or chimneys.. anywhere we are going to get horrible wind vortices we do one nail in the head and fully cheek nail. Now the great advantage of this is that it works! but also lets you maintain the roof for the next 60 years. Modern method.. as per most manufacture's recommendations. Two nails in the head..but the roof will cost more to maintain in the long run, likely to leak more before you spot it. There is a tendency these days to use larger slates. each slate gets more wind load and the nailing points get more stressed.. more failures. Consider the benefits of a smaller sized slate.. even though they cost a bit more to buy and fix. The NHBC, slate suppliers only guarentee for say 10 years. If a slate cracks you don't see it as it does not often fall out as it has two nails in the head! In other words.. I often suspect that the suppliers and warranty providers are aiming to reduce their liability over the warranty period and don't care what happens after that. Suggestion: Have a chat with your Architect and if possible traditional local slaters. This part of your drawing has potential conflicting information and design approaches. The slates are shown on battens and counter battens on a breathable membrane on sarking. If you go traditional then the slates get nailed directly to the sarking, no battens or counter battens. At the eaves there is no undercloak slate shown, the overhang into the gutter is short. In Scotland we often use timber sarking. Us SE's make good use of the roof stiffening effect it provides. Normally we specify that the timber sarking has a 5.0 mm gap between the boards and is no wider than 100mm. This provides suficient repeating gaps to allow the breathable membrane to function. Now you don't have any eaves ventilation shown..that is ok as you have the sarking gap. Sometimes you see the permeable insulation between the rafters going right up to the underside of the sarking. Your drawings show a 50 mm gap. This indicates that there is possible a lack of understanding. A 50 mm gap is usually mandatory if you don't have sarking gaps etc and rely on eaves and ridge ventilation. Normally what we do, and I do a lot of this as do many Architects I work with, is to leave a 20 mm gap under the sarking.. just to disperse the water gas so it reaches the sarking gaps and gets out. Now that means you can make the insulation between the rafters 30mm thicker which takes it up to 200mm. Now often we are looking for buildability and at material procurement. It just so happens that TP10 etc is commonly available in 100mm thick sheets. And what you try and do is use same sheets where ever you can in the rest of the build. Your drawing shows a timber frame. The detail at the wall head looks off. The cavity barrier (fire stop) is not going to work as fire will bypass that. The fire stop batten needs to have a panel top rail or head binder behind it. You are building in Shetland.. it's also very wet at times (likely any wet timber delivered) will stay wet so you have to be much more aware of timber shrinkage. The external walls stay pretty much still but the kit shrinks thus you need to leave a gap between the top of the blockwork and anything connected to the timber frame. This is the time to get your head around some of this stuff in case it later causes havoc with the detailing of your windows and door height for example. On first glance this means you fascia boards need to be deeper as in Shetland wind driven rain goes upwards more often than you think! Suggestion: Have a chat with your Architect about whether you are mixing and matching design approaches. It's ok to do that.. but you have to be clear about the design philosophy. Turning now to this top left part of your drawing: In Scotland in the central belt BC 99% of the time accept render on block with no cavity tray. But where you are you get not just ferocious wind and rain but persistent rain and a bit of steady wind. This is also very onerous.. watch out! I would put cavity tray over the door and window openings and dress the breathable membrane over that. They don't need to always be expensive ones. A good brickie can form up a tray with a weep vents out of a standard roll of DPC. The thermal break in the timber lintels should be further out. I would with my SE hat on omit this and if need be use deeper timbers for the lintel and lose possibly the timber frame (TF) top rail over the lintel. It's also got to do with timber shrinkage and the postition of the loading from the floor joists. In terms of insulation. You show the opening reveals as having 25mm of insulation. If you are loking for a high performance house then aim for 50mm.. but then the windows don't fit! I often use 50mm reveal (called ingoes in Scotland) insulation but to make this work we need to ask the window / door supplier to include a thermally broken frame extension kit. Suggestion: Have a chat with your Architect, ideally make contact with BC and see if they will give you some advice, hands on experience of what works in Shetland. Turning now to this bottom left part of your drawing: I'll not make any comment on the floor slab etc for now. But you'll need more of a drip on the window cill. NHBC require 40mm, the arrangemnt shown is not adequate. As it's TF you need a fire stop under the window cill and you'll need cassette vent to ventilate the timber frame cavity. Ok that is probably enough for now for you to digest. I would go back and review, learn a bit more before you spend too much time calculating in detail exact u values etc as once your SE get's their hands on this and Scottish BC you don't want to end up back at the beginning again. Hope this helps and all the best.

Ok I can see you are wanting to explore this. It's a good thread you have started as it delves into what can be possibly achieved on paper and what can actually be built at a sensible cost. Don't apologise, you are not sitting an exam here! Neither am I as I've clocked off the day job. Mortar is less forgiving in terms of movement so consider lead, even if to rule out. Yes they are. But so is PIR insulation. Below is the data sheet from Steico for thier high compressive strength insulation. And below for thier internal insulation. I won't go into detail about how SE's do the sums for compressive strength.. other than to say we do not use for example this value when designing as it squashes to much. For you the main thing is to look at the thermal conductivity of the two offerings. The higher compressive strength has a value of 0.048 W/(m.K) the lower (weaker insulation) 0.038 W/(m.K) which is about a 20% difference. If you remove the repeating bridges but even use the higher strength stuff you may get a better result. It's likely marginal.. but as I said before.. you need to look at the perimeter details, noggings etc and buildability. I understand what you are trying to achieve technically. I'm familiar with how this sort of stuff can work, the references you cite. But I can tell you it is almost unkown to be able to build this. It might be a good idea to start to produce some detailed drawings of the junctions / interfaces between the different elements. Even if you do this as a day job it's going to be demanding. All the time you have to think.. how do I explain this to a builder and what are they going to charge you for this.

Stick with lead for the skews. If you put forward an evidence based design then most accept. Like in all walks of life there is a bit of "personality" involved at times, younger BCO's and designers are, by default, less experienced in communicating which can lead to crossed swords. Client's sometimes are the same, maybe they don't allocate enough funds to the design fee element. In summary if your design is sound then BC will accept.. you often need patience. Ok I can see what you are trying to do, a few comments in line with your text which I've turned into italic. Plasterboard 50x50mm horizontal battens with 50mm wood fibre insulation batts between You horizontal timber battens on the inside introduce a repeating bridge. You can test this repeating bridge effect by using say Kingspan online calculator. I often use a continuous layer. But you need to check that the plasterboard can be fixed through the wood fibre on the inside.. it works for PIR. Intello VCL membrane Not sure about this. I would be inclined to use something impermeable like plastic. existing 150x50mm rafters, fully filled with more wood fibre batts This sounds ok in the main body of the roof and on paper. But around the roof edges, these are weak spots. leave the full fill insulation 10 -20mm shy of the underside of your ply just to let the water gas / moisture disperse. . I'm not going to to explain in great detail here but the principle of the sarking is to have gaps between the boards. You full fill is not compatible with your marine ply.. which is pretty impermeable. wood runners fixed to the inside of each rafter along its whole length Ok see that you are doing. But you have structural problems in terms of the edge distances of you fixings. 25mm marine ply fixed to runners and joists sitting flush with outer surface of existing rafters Now marine ply sounds great.. but trying to drive a long copper nail into this is not that easy.. ask an experience slater. Again it may be ok in the main body of the roof.. but you are going to have massive problems at the edges and any roof lights / service penetration. 35mm Steico tongue & groove woodfibre sarking Ok.. if you follow the manufacture's fixing detail. vapour and air open waterproof membrane Ok.. for now. ~8mm "heavy" slates with 75mm+ stainless or copper annular ring nails, two per slate centre & off-centre to prevent rotation I would not slate this way on you job, rather I would adopt the traditional route. In Scotland as we do a lot of traditional sarking we do one nail in the head, every third course cheek nailed in the main body of the roof. This lets us maintain the roof easily. Commonly in England the slates are fixed to battens. I think I can see your design intent.. but I very much doubt you can get anyone to build it dilligently. TYou design has technical flaws. In summary.. my advice is to say "I had a good go" but let pragmatism and budget cost prevail.

I kind of think back to when I first joined BH. I took me a while to get my head around how it works. BH is not like some woke Blue Sky place, but I can't really think of anyone who is deliberately horrible. @WisteriaMews post more info with lots of details as I said before and loads of folk will rally round.