Gus Potter

Good post and a good question. To clarify. I think your contractor is talking about a ventilator at the soffit, (the bit under the gutter) the dormer cheeks (the sides) will also have a vent at the bottom to ventilate the vertical cladding of the dormer. Designs like this are generally taken with a big pinch of salt these days. The main reason is that folk started to do big flat roofs using the same principle and these lead to big rot and condensation problems. Basically folk started taking the pish. But on a small dormer the old rules are still applicable. I've counted your tiles and at worst you have 9 x 330mm = ~3m roof that needs ventilated. The dormer "sticks"out the roof so it is going to "catch the wind" and that will promote cross ventilation provided you have good soffit vents. So your builder is not talking out their hat, but check that BC will run with this. Now the above will fly provided you are not installing an ensuite shower room in the dormer.

This is good comment. Quite often I'll design using the British Standards and some of these are quite old. A good example here is when designing a steel portal frame to BS 5950. To comply with BC regs etc you can use older standards but must be aware where the Eurocodes are more strict and take this into account. To simplify, you can use old design codes provided you know where the modern codes have shown the deficiency in places. In this case @Alan Ambrose we are at the leading edge of design, so we must look to the latest guidance, take that into account and form a view. The DIN codes also apply to bolts / fixings and other things, often seen in the statutory CE compliance regs. To my mind the internal vapour barrier (plastic) is essential to stop moisture entering the roof structure in the first place Then, if we get condensation within the roof structure we want to vent that upwards and outwards. The question is, is the layer of ply on the top of the posi joists able to let seasonable condensation out. @Nickfromwales might be able to help here. My own view is to say, lets look at where we may get a high moisture content.. bathrooms / kitchens and do our MHVR to make sure we don't get elevated moisture where we may have vaulted roofs and the damp air stagnates. This is pragmatic design. In other words you remove the potential problem at source. @Alan Ambrose asks a good question. OSB and ply are not permeable when compared with traditional timber sarking with gaps between the boards. Good question. Am I missing something as well as Alan? Help!

Hiya. First thing is that we feel for you, it's a scunner and very stressful. We can see you are commited and enthusiastic, previous posts about your stair case etc. Key thing is not to allow this to grow arms and legs. What we are looking for is the Occam's razor solution. The simple solution. Most importantly, you need to identify all the issues before alerting the planners and your neighbours that you have "a potential issue". Keep this under your hat for now! I'll drop you an email.

That's great news Jack. Your heating system is something that we should aim to achieve. But.. you are a switched on fellow with loads of life experience. My guess is that you controlled your design, built well and are thus reaping the rewards. Unfortunately the build market is full of chancers, designers included! I rest my case. Again I rest. John, I love your technical input, learn lots from you so thanks for that. It's ok to disagree. My main arguement is not about UFH in principle, or about your well presented and knowlegeable approach. My main point is to design in redundancy where pipes are buried in screed / concrete and recognise that your house, to maintain it's value, has to perform and not be a burden to maintain when you sell it on. For all BH folk. This is something you really need to face up to as surveyors can right down the value of your property. The more main stream UFH becomes.. and the more that the big developers cock it up, which they will, the more the light is going to shine on the self build UFH market. Now UFH, controls, home automation are a lively topic on BH. I like to see it as folk are innovating which is great, call it a bit of a hobby. But don't expect me as a designer who is responsible for my Client's money and have a Civic responsibility to the next person that will buy your house to not ask some nasty questions!

They are actually doing you a favour. If you don't have a license to discharge then your house and plot could be worthless unless you have another alternative.

This is not practicable achievable in my 30 years experience. The UK weather is very unpredictable. At times UFH just won't comply, so you open a window or a door! What we should be doing here is saying.. hey, UFH is not perfect, we will never make it perfect but here is how you can get the best out of it for minimal maintanace and running cost. I'll say this again and again, you can design on paper, balance your system and it will work for a few months and the game changes! It's fine if you have all the time in the world to play with your UFH system but lots of folk have families, kids and a day job! Ok interested, where do you live, what are you pipe centres, how much have your maintanence costs been over the last ten years

So I just picked this bit out of you post. If it's hard now imagine how folk are going to maintain this in 5 years time?

Ok, so put it another way, it looks good. 30 years ago I started experimenting with UFH. It looked good and my first system worked, it was fantastic, to have the luxury of warm floors, no radiators., freed up wall space. But it wasn't perfect when compared to what I know now! But hey ho, I built it with a basic mixer valve, an oil fired boiler and it was installed in a house that had U values much higher than what we are seeking to achieve in this day and age. So my philistine hat back on. What you bury in the floor must have redundancy, be over designed. At the back of my mind is that ASHP etc may be able to run on lower temperatures in the future, so the pipes in the floor you can't change, we need lots of redundancy in terms of flow capacity, and if the pipes get a bit clogged, but the plant above the floor can be changed. Think of UFH in terms of the cost of a car which need servicing and eventual replacement and that the pipes in the floor are your forever home. Design the pipes too tight and a home valuer will right the value of your property down! Surveyors are clocking this potential liability so don't say I'm not warning you! Think about maintenance costs! It's great to talk about the thoery if you don't have top pick up the bill in 3 - 5 years time when the parts start to get sticky and weep water! I'll say again.. is there anyone here on BH that is thinking about this.. or is it just me. OK I'm going to take my philistine hat off and put my toe in the wacky techy water! In the old days we had wall thermostats that worked on a bimetalic strip. The hysteresis was, a bit blunt, incedentally I used to rear Pheasants and built my own incubators, these needs tighter control. So now we have lots of more precise data. I work from home and if I use the oven the temperature graphs spike, if I leave the door open between the highly insulated part of the house and the old house the graph changes again. If the sun comes out as it did the other day for a short time the room temperature rise. I shit you not Sherlock, I don't have weather compensation as I can look at the weather forecast! So can anyone tell me how weather compensation copes with this and rugs on the floor? Also if you put 4 - 6 people in a room it heats up.. explain please! Also, say yoiu have a bath and the room gets hot, you open the doors and all that heat comes out. To my mind an ASHP or good UFH system should just look after it's self, not cost a lot to maintain. If you want to cool stuff then you have two basic choices. Open the windows and doors if the temperature outside is less. If more then you need to be able to cool floors, the furniture and beds quickly and that justiufy my appraoch to over designing the pipes under the floors. Come on teckies.. lets see your costs curve for long term maintanace performance, how you cool a floor fast..given the above.. sorry it's just me being practical. In an ideal world in the UK we don't want to spend money cooling a house. I'm also a big fan of passive stack ventilation, story for another day. The UK is an island, I grew up in Africa where the climate is different. The UK climate is something that we should enjoy and learn to live with. Here is my roughed out UF that I built just to keep the house warm while I was doing the work. It's gate valves from Screwfix, Youkshire fitting for the manifold, but the blender valve is expensive. I'm a bit behind with the work but this has been working ok for the last few years. I have a new gas condensing boiler installed roughly at the same time as my DIY manifold, Valliant. Just mid range. Anyway I know lots of folk are tacky. So if you are on a budget. Spend lots and build in redundancy into your pipes buried in the concrete. leave a bit of space so you can change the boiler, manifolds as technology advances. Have fun and remember when we meet in heaven I'm not a crusty in real life!

Hiya. Your curiosity is a challenge! Will try my best to answer. The following is lengthy but I try and put forward the basics of my views. They don't apply to all so do your own research. Good to see you are doing a self build. The following is also a bit general. I don't want to identify my Clients for obvious reasons so need to be a bit vague at times. Hope the following helps build your confidence, gives you some pointers about the questions to ask. I'll start with a broad summary to pick up on my last post. Please excuse my spelling and grammer as I'm off duty so to speak. 1/ We had the 2015 CDM regulations. One element was that designers had to put in place a pre construction phase and construction phase plan. The intention was to help prevent designers designing stuff that could not be safely built and to stop Contractors putting safety to the back of the queue. Grenfell happened. Now some of the dirty laundry is coming out in the public wash, but there is a lot more to come! Basically this is leading to a recognition that many folk lost their moral compass (some never had one and some will never have, thus the need for more stringent regulation that also captures the self build market) and that designers were just designing in isolation, like the work packages many folk go for on BH. The game is changing and I can see that fabricators / manufactures's are recognising the new business world. This is driven mostly by commercial / competetive market raw boots on the ground stuff. The key here is that the additional regs are partly intended to stop folk designing in isolation and to stop Clients changing the design as they go after they have got their BC approvals. There are quite a few on BH and in general who get their Architect to do their bit, the SE to do their bit, get the approvals and then go off and do their own thing. So what you end up with is a potantially and unsafe structure. So what is an unsafe structure? Well we know it should not fall down, most say, well that is the SE's job! But a structure also has to last say at least 60 years. If the detailing is bad then water ingress / condensation can happen / drains can fail for example and that can lead to an unsafe structure. What is now happening is that BC are starting to say.. we are interpreting the new PD rules in terms of the BC regulations that cover water ingress / condensation etc, so we have skin in the game long term. They then point to the new PD regs and some BC may say, hey you need to appoint a PD! I'm now going to give two examples of a couple of jobs on my books. The first is a job in Scotland. The second is a job in England. We can compare and contrast. Scotland job Client 1 - Low rise self build in Scotland : Key BC points. 1/ In Scotland there is no private BC. The BC function rests with the local authority and the bible is the Scottish Building Standards. 2/ Contrary to popular belief you don't need an SER registered Engineer to get a building warrant in Scotland. I'm not a member of the SER scheme, some of my work is in England. It sometimes takes a little longer to get a warrant in Scotland if not a SER member, but often the warrant process is driven by water / sewage / other agencies chipping in and the BC officer going off sick or on holiday. Client 1 got someone to do their plans (not a Chartered Architect and not insured, a mate, at mates rates who did a good job). Got their SE design accepted and the warrant was issued. In other words in Scotland you can do your own plans, detailing and the Structural calculations yourself! But BC will look at all of this in detail. Their in house Engineer will check your SE calcs in the larger councils, the BC officer who is often a Chartered member of the CIOB will check the rest of the design. Funnily, when I submit SE calculations the smaller councils send my calculations to be checked by and external SER Engineer as they can't afford an Engineer of their own. 3/ Scottish BC did not stipulate a PD as a condition of the warrant. However. The Client had started the work and was seeking a back dated warranty from ProteK. ProteK initially insisted that the Client had a PD. What they roughly wanted,to start with, was someone who would sign their life away to say the everything was perfect and would be in the future. This has nothing to do with PD rules and everthing to do with limiting their liability. After clarification and some comment from my self asking what they were actually insuring, they gave in and removed the PD condition for an admin fee (from memory) of £150.00. Summary. Scottish BC in this case did not stiputlate that the Client appoint a PD. Thus we need to ask, why are English BC asking for this? England job Client 2: Low rise but with basement etc . More complex project. This Client has private BC. The Client is MSC qualified (a Masters in a science subject) with extensive life experience, widley read, atriculate, challenges designs and thoughtful. Their private BC has as I understand said that they can be PD. There you go! I'll summarise this nextish. The new PD requirements a rough summary: The way I see it is this. You have high risk buildings (HRB's), fire risk mostly is a hot topic. These could be blocks of flats / high rise, so you do need to have extra training to be a PD on these projects. But to be sensible to apply this to a large basement under a London house that could destabalise a multi story building next door. .. we need to think up as well as down. We could have a house close to landfill ( real potential for ground gas / chemical contamination ), hanging over the edge of a quarry. So the new PD regs also capture this kind of stuff. In this case a PD would be advisable. However they also are trying to stop folk going off and doing their own thing on site. There are many examples of folk on BH that have stepped off piste on advice from the Builder and later regret! The shit hits the fan, BC get involved and so on. The new PD regs are intended to capture this and are trying to stop folk avoiding responsibility, but also to encourage people to think holistically about the design, execution, long term seviceabilty and safety. This is the key! CDM, PD is about having enough knowledge and common sense to know when to seek professional advice. You are clearly saying you are in regular contact with your Architect, that's what PD's do! It seems to me that if you have got the where withall to write the way you do on BH then your not 14 years old! And it comes back to this. You are clearly not stupid! It might be worthwhile putting your Architect on a formal retaining fee, call it a watching brief. Confirm to BC that you are following the approved design religiously and that you are keeping photographic evidence. Define the procedure if you encounter the unexpected on site, how you will manage any changes on site. i.e.. you call the Architect / SE. At the end of the day your Architect and SE has an approved design. Your Contractor is responsible for the CDM 2015 safety and drawing compliance. Ask BC why they think you are not competant to recognise if you have changed the design! and, ask them to define the competancy requirements for a low risk building. Well maybe not in the first letter, just say how you are going to manage the PD and list the professionals you have retained. That may be enough to get you over this hurdle. But that said! you need to deliver what you say you are going to do! This is what I do from time to time on a self build. The Client is the PD but I hold their hand / provide advice, a friendly ear, sometimes tough love, for a fee of course. But at the end of the day the fee is not massive as I love seeing stuff I've designed, had a hand in getting built.

It's good to get an update and some feedback, thanks for that. Structural depth difference 650 - 457 = 193mm. Pity it's not working here, can see you have a height restriction. A few questions, observations: 1/ Your beam will need an end rest at each end. I'm just checking, is your 8.4m the clear opening width? You'll want to insulate the reveals thus the structural opening will "grow" a bit. Can you get a beam delivered to your site at the length you need without splicing the beam, in other words is there an access / delivery to site issue. Check with your SE that the UB can be continuous. Any splices (depending on how the are designed) can potentially intrude downwards and that can thwart your glazing detail. Flush splices are expensive to fabricate. 2/ I don't know how much load there is on the beam but if single storey is there a way to reduce the roof load by say transferring part of it to an internal wall? 3/ For steel the devil is in the detail. How close to the sea are you? If less than 2.0 km LABC and NHBC can raise questions, your beam might need to be galvanised and the fixings more durable. Keep an eye out for that. The beauty of ICF is that you can change the grade of concrete and mostly the cover to the rebar if near the sea. If you are near the sea can you check your ICF designer SE has taken this into account? Sometimes folk miss this in the heat of battle, so just check your wall thickness and rebar cover. Post a couple of sketches if you wish and lots of folk on BH will help you with the detailing. What you are doing is not run of the mill, every day is a scoool day even if you have been doing it for decades, cut yourself some slack!

My error. Anything that is buried in the screed, concrete is permanent. Supposed to last the lifetime of the house. Anything that is above the floor can be changed as technology evolves. As in many things UFH is becoming more mass market, prices for controls, boilers, heat pumps are dropping relative to historic cost. If you think back to the 1970's a TV was a very expensive item relative to income. My point is. Over design the pipework that is in the floor as you can't change that, call that redundancy. There is debate about whether you should put UFH pipes under kitchen units. What if you later change the kitchen units / move the furniture about or change the flooring for a thicker timber or different materail? More loops means less resistance and that gives you the opportinuty to cool things more quickly if the sun suddenly comes out. It does of course work the other way if the temperature suddenly drops. I'm all for UFH, it's a great way of heating a house, so while at times I may seem overly critical it's often to make a practical point and encourage folk to think about what they want out of a design and, think 10 - 15 years ahead.

So you posted this 3 hours ago, hopefully I caught you in time. I might not have. but hey ho. Points: 1/ If you are designing your heating cooling system based on what is available above the floor, ASHP then I think you are making a big mistake. STOP NOW and make sure you build in redundancy into your fixed UFH pipes that are not maintainable. If you dought me go back and ask you designer if they will warranty what is going on under the floor and for how long. Ask, what if I come to sell the house, is that going to impact on the asset value. 2/ If your UFH pipes don't have the flexibilty to accomodate in the future a different ASHP then you are totally locked in. You will regret it. @SBMS In the meantime - has anyone managed to design and install this system to produce an FCU cooling loop at 10 degrees. To do this you need more loops. This also does my head in. You have a sofa, say big patio doors, the sofa insulates the floor but just inside the glass doors the floor gets hot! UFH design is a craft, but most is commonscence. What is not good sense is to take software output and think the computer knows best which far too many on BH are doing ! The software is a guide and that is it! Let common sense prevail. But at the big glass doors in the winter you have a thermal bridge so the floor gets cold here, drafts come down off the glass, I close up the loops here! Loop cad does not pick this up for example and many designers just bury their heads in the sand. In the summer the floor next to the glazing gets hot, so here you need to cool it most so the closer centres helps. What I'm trying to say is that you do your pipes under the floor with pragmatism and benefiting from the "no shite" advice I give you. That then opens up what is going on above the floor and gives you options for a system that will work for 50 years and not pelt the asset value of your house.

Now the funny thing is that most old houses are off the plumb and 99% are not square. An example is that you could knock a hole in a old wall, put in double (French type) doors and fit the frame out of plumb. If you do that then the doors can "take on a life of their own" and shut themselves or open. But with sliding doors that won't happen. So think.. if they are out of plumb will that stop them from operating? If you fit them plumb then you'll have to marry in the plaster etc as you say. Have a look on the internet about how you heal and toe doors, a door fitting carpretery skill. It's ok if things are not plumb.. you just need to identify if it matters and try and avoid unessesary work. "Dry fit" the doors out of plumb, see if they work and look ok first. If not pack out and fix the plaster.

Hi John. Good post, I may need to eat a bit of humble pie here but happy to do so as I'm not always right, I have an opinion, but if you ask ten designers you'll get ten different answers! Anyway as you say "it just gets on with it" and that is the key. OK you have weather compensation. Fine by me ( I do my own UF heating system), as it's a litle bit of "tech" which I'll be the first to admit is good fun to play with ( first slice of pie) but there are too many folk on BH that are using and desinging UFH using loop cad and stuff but none of that takes into account that you may put a rug on the floor or have a big sofa that sits close to the floor level! So while folk think I'm living in that dark ages, have an axe to grind, I don't, I'm just saying.. hey the UFH maths is often a lots of bollocks when it comes to building it and making it work for 50 years or more. The maths may work on day one but then it is all down hill as you need to get someone to install it! And, as this is the building trade that is a challenge! I can back this statement up with examples of how I have found UFH systems that are design by sales folk rather than Enginners. I can point to a hospital, domestic stuff.. I can argue my case so I'm open to anyone on BH that can turn round and say to me.. hey I have UFH and it's been in 30 years and it's working well and here is what it costs us to replace parts. You see.. I know as I have this data on a couple of jobs that I look after! What I do as a design engineer is to look at the maths, how things actually work in practice and make an enginneering judgment based partly on maths and partly on practical and long term experience. Now I do a few insulated "passive raft type designs as an SE " and a well designed and durable UFH system starts from the ground up. It's something that I plan for as an integrated design. Next is that folk are using a computer to produce nice pipe layout diagrams but not realising how often that won't get translated on site with the trades folk actually doing the work. Yes, if you want to stand over them all day, hold them to the contract.. but the reality is that this will lead to a falling out on site, it does on big strictly supervised contract but self builders don't have the money or expertise to pay for this level of supervision. @JohnMo "There are no fancy valves, only a 3 port diverter for DHW heating. In fact the system only consists of ASHP (with it's controller in the side of the ASHP), diverter valve, cylinder and UFH manifold. No additional pumps (other than one in ASHP) no mixers, no UFH manifold actuators, no fancy stuff at all." Ok second slice of pie for me. I missed you spelling that part out. It looks to me that your system comprises stuff you can buy from screwfix. That to my mind look like something simple, easy to maintain and long lasting. There will be some on BH that say.. hey it not totally efficient but over even an 8 peroid I bet you maintenance costs will be lower than lots of folk on BH that are trying to get UFH to do something that it is not suited to do. @JohnMo "Yes I live in Scotland, not many places get the -20 anymore, still get variable seasons in 24hrs." Don't bet on it John. My sister lives on Tiree and has two tandem ASHP to run a big house. The winter temperature is like you could grow palm trees.. the ASHP just run at their best speed, but that said, if there is a little shift on the Altantic sea currents.. it could be see a change, or if we get a wierd wind from Norway.. don't count your chickens just yet!

Bit of pragmatic advice for all. On a TF house or thatched house fit a smoke detector in the attic void. It costs little ( I have it in my own house) and can save the day. There is a tendency for folk to dry logs in or around a wood stove, if they catch light then then what? I deal with lots of building regs.. some are a bit general and not practcable applicable in cases.. or make common sense.. but some are really good and it is wise to follow the good ones.

No.. it was not. Please re read OP, anyway it's something I aware of as I do lots of TF design so am cautious. I'm also cautious that folk may change the stove so unless you have that written into your O & M manual for the house (which I bet you don't have!) explicitly then you are being irresponsible, some young couples may buy the house, change the stove and not be aware. The ONLY time that you can maybe reduce the clearance between a TF and the back of the stove is when it also heats the water so the back of it does not get above 100 Celcius. Good response from the fitter.

Dave, can you go back and check the value of 200mm. Woodburning stoves and timber frame are not good bedfellows so we need to be really careful here! Don't forget folk that if your house goes on fire, while you may get out safely your insurance comapny will look for any avenue not to pay out! It is an I'll ask you to specify why you think you don't need an air gap to act as a thermal break between the heat shield and the timber frame.

Ok so you do a bit of EWI. The concept is that this will be good for 50 years.. but what if the outside starts to get a bit dull looking and the new owner goes to B & Q and gets some air tight / impermeable paint and uses that? Under the new PD rules we should have an operation manual for the building. Wrong paint can cause unwanted moisture that impacts on structural performance not least. Valuers should be picking up on this.

I feel for you. Unfortunately planning and BC is a legal process. In day to day life we often cut folk a bit of leaway for genuine mistakes. It sounds harsh but if they cut one person a bit of slack then the same slack applies to developers who seek every avenue to take advantage of the system. This is encouraging, it's an appeal process. I can't see any reason for an appeal to not be retroactive.. which is what an appeal is. The motto is, check and check again. Everyone on a design team will make a mistake at some point. Some are moot point's so are not material, some in this case have caused lots of grief. I suppose the worst case is to resubmit the planning application if it's not lapsed and tick the right box this time? Beware folks in Scotland. If you submit a planning amendment (BC often change the number) it often gets a different application number and sometimes is then treated as a new application. But the period for activating the planning is not extended as is the period of validity of a Building Warrant.

Conversation for another day. I missed the floor layout as was looking at other aspects. That said, you are quick on your feet, have knowledge that I don't, admire that. But the self build market is changing a lot... there is lots of opportunity for folk like us!

My Sunday name is Angus, by my Mum. Great county to live in. But the soil is a bit like that heavy clay that churns up. On the bright side you don't have to worry too much about the soil swelling or shinking. If I was to relocate then this would be an area of choice. The diversity of topography is stunning, the folk, pragmatic.. in the round there are few better places to live. Forgive me for being blunt and maybe @ETC can chip in but the elevation drawings you have posted look like someone has had a bad Architectural day! It looks like a Heb homes design gone badly wrong, my view. And Heb homes don't always get it right, although they claim to be specialists in design and execution of the build. Anyway.. too late to turn back now. That is my own view but once you get some planting round about then it will all become a moot point. Key point.. make sure you or your builder follow the drawings and fixing specification as it is VERY windy in Angus County and is SNOWS a lot!

In Scotland the U value for a floor in 2010 was 0.2 W/m^2K. See below for the value above the red box. This is an extract from a energy calc I was doing on a retrofit, looking at the roof, so had to dig out past regs. Current Scottish Standards are for individual elements on say an extension, but a good starting guide for new build. As it's a bit baltic up in the north of the UK the English regs, I guess, at that time were using a value of maybe 0.25 W/m^2K as traditionally the English regs are slacker than the Scottish regs. Current basic Scottish regs are below. One thing to take away from this is that the Scottish Standards are more onerous than in England, have not look at NI yet in detail.

Great post John.

Feal for you, what a scunner as we can see you have put lot's of effort into your design. Hopefully you can resolve it ok. Often boundaries are a bit vague, particularly in the country / rural. Main thing is to check and check again your deads and information, avoid if possible alerting your neighbours at this stage that there may be an issue. Looking ahead, if less than 1.0m from a boundary often the fire regs (fire boundary condition) become more onerous. I'm surprised your Architect failed to consult with you. It's something I do often as due dilligence, make sure that the Client understands and agrees the boundaries.

Can I sum up.. "wankers" is I think the word that is on the tip of your tongue. At some point you want to ask is "stick" building easier in the round, does it give me more control over the programmes of works, price, money up front, ( in Scotland we say "your baws are up to the post once you part with a big deposit) ease of late design changes, general hassle dealing with say Posi Joist / Easy Joist folk.