Gus Potter

No because you have not provided any drawings! Fesse up and share your drawings. Folk will then chip in and in return we may also learn a bit from you. Them's the rule of the game!

Good advice. In a standard cavity wall (say 50-75mm cavity) the two leaves act together. When doing calculations we derive an effective thickness of the wall. A bit like this bit from the the BS code. But the strength of the wall as @Iceverge say rapidly decreases exponentially the thinner the effective thickness. There are other kinds of masonry walls. Solid walls are say built with English Garden bond. These you can't really take down the inner skin in any practical way. There is a wall called a collar jointed wall. Here the cavity is no more than 25mm and fully filled with mortar. One key thing here (collar wall) is that the wall ties are much thicker and more robust. Ancon do a wall tie for collar jointed walls. A collar wall tied with the right ties acts like a solid wall so you get more bang for your buck. It's a good idea to value you time. £20.00 per hour seems reasonable. That's £160 a day. A trade rate up near Glasgow can vary from say £100-120 a day for an inexperienced labourer up to say 220 - 250 a day for a good experienced joiner( chippie)... more for a spark and techy folk. Now if that is all through the books and you are doing an extension there may be vat and an extra contractor profit / overheads to go on top of that. When you look at it this way it can be good or bad! If your time spent on site is doing some work then you win a watch. You efforts are tax free and not subject to contractor profit for example. Any time spent keeping an eye on the builder is still worth while as it can head off disputes and extra claims for cost later on. It can help keep the quality of workmanship up too.

True enough but we need a starting point. I suppose it's like asking a farmer for directions. "If you want to get to there don't start from here.."

Aye on the top line full poke for about half an hour to and hour but we have and always have has a contractural obligation to supply to the EU..so they take some of our power and leave us looking daft and our pensioners freezing. I studied this at uni and we have never had 90GW able to cope with a 4 hour peak supply under our own UK steam that was available soley to us without breaching our EU contractural obligations. We have signed up to make the French / Germans cosy! Now even if you take pure peak delivery. Some of that comes from the Scottish Hydro.. (pump stograge) but once the head water is exhuasted it takes time to pump back up... days The 90 GW is bollocks! @SteamyTea We do not have 90 GW reliable supply in the UK. It is far from a non story. We are in / close to shit street! For interest.. I worked on the construction of Torness Nuclear Station and then designed some stuff for the decomissioning of the Bradlwell Station. As a point of note. Biomass takes time to crank up.. oh like a coal station..it takes time to heat up. Wind turbines.. well you don't get peak wind over a whole large wind farm. Twenty years ago we had from recollection some 64 GW of balanced supply. There is no way that has jumped to 90 GW.. even if it had the transmission system has not kept up.

@SteamyTea Had to look that word up! In retort. Genetic algorithsims. I had a dabble in this at uni as we were looking for a way of getting to grips with cold formed steel distorsional buckling behavoir.. but the Yanks / folk in AU got there with a "simple solution" that did not require massive computing power. For the novice (me) mathematician.. we have numbers called imaginary numbers... it's to do with calculus... which us as SE have a interest in? For the remotely interested. An imaginary number is something we introduce to an equation at the beginning to make it work.. and at the end it disappears again! I'm not shitting you! And now you may be wondering why you trust folk like me to design your house! It's ok in my day job I'm grounded.

Hope this helps. There are three generic types of sewers. 1/ A private sewer. This serves your own house and belongs to you.. so you can do a lot. Now if you have a detached house this could run to the sewer in the road. Or you could be at the top end of a terrace.. if so there should be a rodding eye that allows for rodding of the drain along the back of all the other housese down stream.. you need to bear that in mind... keep the rodding eye accesible. 2/ A public sewer. These belong to the water company. These tend to be found along the line of a row of terraced houses at the back. But be aware that these can be deep if you live at the downstream end of the terrace. On occasion I find that these are not economic to get build over permission for if deep. I have seen sone at at least 3.0m which make a rear extension far from viable moneywise. 3/ A main sewer. These are big sewers (call them pylons in electricity terms) and tend to be very problematic to build near. Recomendations. Spend a £100.00 or so and get a utility search from an approved waterboard company.. could be Cornerstone etc. If you have 1 or 2 then it looks promising .. but check the ground levels. If 3 then make sure you get the place for next to nothing to cover your risk.

Bit of general comment from me re slab thickness and UFH, pipe abrasion / expansion, concrete slab shrinkage and stuff. Excuse the spelling and grammer please as I'm off duty. I'll start with my plumbing / concrete hat on, also bringing to the table that I've been "experimenting / sefl building" with different UFH designs for the last 30 years. Ok if you have structural slab you probably want to put the crown of ( the top of the pipe) UF pipe say 40-50 mm below the surface. This allows for a sensible construction tolerance and the unexpected pipe overlap when you make design changes at the last minute. There are some that advocate for less but this is self building.. cut yourself and the builder some slack. **This is self building.. you generally don't have the same control over workmanship as say on a major contractor project.. keep things simple stupid. If you are anal and want to tie down your builder to tight tolerances then you either need to be able to check this or you will end up paying for something that never gets delivered. I see this all the time! Now if we have a simple ground bearing slab on say EPS then I would put the anticrack rebar mesh near the top of the slab. I have on several occasions tied the UFH pipe to the mesh.. with zip ties. Now this can be great thing to do yourself. It gives you that feeling.. here we are putting in the pipes that are going to make our home warm.. it's romantice and gives you a spurt of joy / keeps the spiits up. I say this as I've done this and felt it more than once. Get the builder to lay in the mesh and tie down your own UF pipes! A good way of getting it right. Now lets look at the behavoir of the concrete and the UF pipe preparation. Most UF pipe is rated to 10 bar (it decreaes depending on temperature). I tend to pressurise the UF pipe to 4 bar and hold that for a couple of days. Now I lay the concrete. The concrete has plastic shrinkage ( first 7/ 8 -24 hours / then drying shrinkage. My own experience tells me that the concrete shrinks a little (a mircon of two) away from the pipe and the rebar. Pretty much all heating sytems have a pressure relief valve set at 3 bar. In the round my view is that pipe abrasion can be shown by calculation to be negligeable / none at all. BUT .. SE hat on now. If you have a concrete slab is a structural raft with big point loads then you can still put your UFH pipes in but I'll tell you where you can't put them. Generally it's not to onerous but you'll need to pay me a bit more to do you a couple of drawings.

Hello Will. I've not been about much as busy with the day job and trying to get a bit own own house done before Xmas. Excuse spelling and grammer please.. just knocking out my thoughts. I can see you have put a good bit of work in trying to get to the bottom of this. Well done you! For me that is the benchmark. We want the mortar to be no stronger per say. Ok they seem to be taking things seriously. Insurance companies per say.. delay, deny, defend.. a pattern of behaviour which I see on a regular basis. So nice of them.. as they know it will cost you lots! They are chucking enough at you, getting some testing done to see if this will head you off at the pass. Did the report give an interpretation of the results and the knock on consequences SE design wise? Well done you! Smart thinking. And here is your simple way in I think. When we design masonry cavity walls we allow for the inner and outer leaf to interact. This allows us to take an overall effective wall thinkness.. both the inner and outer leaf work together.. which gives us an overall effective wall thickness. This means that both leaves have to reach the design standard. Also the wall ties are critical as is cavity width.. something to check later to make sure the ties have the correct embedment each end. Now if the inner leaf is sub standard and is contributing to the effective thickness of the wall then someone is going to have to prove that the cracked inner block and mortar with extra air is still able to meet the design codes.. and that will cost them a fortune! Now the questions I would be asking are: OK we have a BRE report. But has an SE had a look at this to check to see how the wall was initially designed to resist the vertical and importantly the horizontal loads and if the inner leaf still is able to contribute to the effective thickness of the wall.. especially for lateral wind load. THIS IS I THINK YOUR WAY IN at least expense / risk to you. In som way they have started the forensic process. The NHBC et al do this, get a report that is confined in scope with no interpretive element.. the knock on consequences. I would go back to them and thank then for the testing. Then say can you give me a structural Engineers report supported by calculations that check both the inner and outer leaves for wind loading and slenderness under vertical and horizontal wind loading.. give the information we have on the cracking in the inner leaf and the mortar findings. They need to provide you with an interpretive report. what does the testing / findings mean?.. and I guess at that point they may shit a brick! My gut feeling is that they are intending to appear they are doing something and racking up your percieved risk aspect. It's a game they play... gambling odds. This is going to open a can of worms as the SE that has to sign off on this will want to know lots more! The main thing here is to force their hand and not spend any of you own money at this stage. For me this is a structural safety issue.. and that concentrates minds. Now as a word of caution. If you instructed me to go full pelters to win as much as possible on your behalf then we could find lots of other issues. As and SE I can't sign off on the stuff that suits you and ignore other stuff I find. Depending on how things pan out you may have to make a declaration to your home insurer and you must make sure you don "blight" the property by a simple administrative error. Now say it turn out that these defects are prevelant over the whole structure? What then? That's it for now. Don't act in haste here.

This is going to take you time to sort out.. allow for 1 - 2 years, if sooner then you have won a watch. For all if you have this kind of thing get a hold of the NHBC and the Blockwork folk. Make sure you identify the blocks! Each well known manufacturer has a different scratch pattern on their blocks. The scratch pattern identifies the manufacturer and the block strength. I've screenshotted the scratch pattern for Themalite so you can see what I'm on about. But.. what's going on here @Will A.. are you declaring all the info you have. If you want a bit of advice then can you expain how the petrographic test came about? Who paid for that? Where are you in terms of the NHBC / Builder?

In my own house I have a mix of products. The windows and pass doors are Origin.. Its high end stuff and expensive... they have performed well to date. SE wise and in terms of large areas of glass.. its a mine field. Very few of the glazing suppliers will give you the data I need as an SE to design an adequate system. My arse.. the glazing system needs to be integrated with the structural design. If not the guarentee is void. The glazing system is a big ticket item and thus you need to get an SE involved early (pay your SE a little more.. it will be money well spent) so they can guide you on the selection of the glazing system and how you fix that to the structure so the horizontal and downwards vertical deflection of the stucture is compatible with the glazing system. Armed with this information from the SE will help you select the right glazing supplier. Express Bifolds are a mass market outfit.. there is one up the road from me and they don't give away too much and that often leads to trouble later on in the build.

I can see how you may think this is jobs for the boys as the process if far from transparent. There is another thread that talks about the planners being corrupt. When I first started out 40 years ago as a builder there were brown envelopes flying about... before that we had the Polson scandel... which was corruption on a big scale. The planning and BC process is much more professional these days in the spirit of things but the basic delvery of service is very poor. A lot of these young folk are graduates but have no sense of business etiqette. They have not been taught professional manners.. even just to say.. I got your email.. I'm busy. In my view the "corruption" occurs at the political level ( by directing funds and resources.. with a pension pot).. we have lots of this in Scotland, its not cash.. or a free holiday or getting photographed with a call girl. For me I work with builders.. who are on my tender list. They all know I play off a straight bat... but in return they will get a crack at some good profitable jobs. BC and the Planners.. some are just totally incompentant.. but I don't think they are corrupt like the old days. @ThomasB The SE needs to pull up their socks. To put this into context. We as SE's carry a lot of liability. £80.00 to £120.00 per hour is not an unreasonable fee. Your Lawer will charge you more and do less.. funny thing is that it take less training to become a Lawer than an SE or an Architect... and folk moan about our fees!

To add context. Prof Hasseltine wrote a lot of the brickwork design codes and has acted for the NHBC. I had the privalge of working for the "other side" and found him and his reporting to be wonderful. He agreed with me.. the NHBC lost he case. What stuck me about him was his pragmatism and the way he as an educator was able to distil complex issues down to something that the layperson could understand.

Sorry to hear you are not satisfied with the service. As an SE myself I write my reports for a particular audience. I could write a report that deals with say complex structural behaviour that is intended to be read by other professionals who would be expected to have a basic knowledge.. even then I would summarise my explanation so it could be understood on a basic level by a lay person... who could be a Judge. When I write a report for a Domestic Client I ensure that I explain not least: 1/ Why I was there... the context of my appointment and the concerns that have lead to my appointment. 2/ What I saw when I arrived (photographs). Who the movers and shakers are.. You the Client / Builder and so on. 3/ What background research I had carried out before I attended site. 4/ What I was able to observe visually. If I take any measurements what were they, sometimes this is not easy as folk have furniture / the garden is full of stuff! Now that sets the scene. The detail: What can I see and also what are folk telling me. Frankly I tend to take everything folk tell me with a pinch of salt! I listen everyone and look at the evidence. Construction disputes are a bit "excited" at times. My report: There is a recognised SE reporting structure which I follow but then adapt for my audience. I'm a guts and all SE with 40 years construction experience under my belt so most of my reports use simple language and I take pride in using simple stupid basic English. I got my inspiration for simple English from Professor Barry Hassletine, who is in my view an exponent of this art of communicating.. and I'm still learning. For example a builder or the NHBC may need to read this. The NHBC are an insurance company so we need to make it simple for them, many builders have a higher level of understanding.. but not all. @ThomasB.. your builder seems a bit streetwise hence bringing in an SE. And here I smell..shite as you probably do! If there is testing required then this should agreed..what needs tested.. the scope and who is going to intepret the results of the testing. Who pays for this? In the round I can see why you may be naffed at the £700.00 but that is not bad for a basic report well written.. but it seems you are not pleased with your SE's command of simple English? If you want to take this further then post the report and more detail.. who is going to front the cost?

You can potentially save yourself a pile of cash if you post some sketches. You seem to be at an early stage. Here we look at the overall design, areas of glazing and so on (this is for structural stability.. side ways wind loading for example) and try and look at the insulation strategy and how we do the SE work for this to make it buildable and economic. The rafter spans you are talking about are modest.. no need for expensive I joists unless these can save you money on insulation... you may have a preference for what kind of insulation and roof covering you want? Sometimes we over engineer things so we make the buildability and insulation less costly for example. The best advice I can give you on limited info is to try and figure out what stops your house moving sideways when the wind blows! If you have massive area of glass then these are sensitive to sideways movement and reduce the available walls that can resist the wind. If I was teaching student Architects..(I do teach some and they in turn reciprocate) I would say.. bear building stability in mind and you'll have a good chance of actually getting your design built!

Help ma boab ( Scottish expression for surprise / aghast)! This needs investigating properly. Agree. Send them your marked up photo as I think this will grab their attention. Also send a photo unmarked. See what the NHBC and the manufacturer say first.. let them do some leg work before you get an independant SE involved.. which may not be required... but you may want a second opinion anyway.. will be cheeper for you if the donkey work is done by those who build it and underwrote it. Question is.. that's the bit you can see.. what about the rest that you can't see! Sorry to say it but..

Have had a look at their website and signed up for the download. "That’s why we're simplifying the path to Passivhaus ownership, by taking the complexity out of the build process." Now that would be refreshing if they can actually deliver what it says on the tin. From their website.. A People Centred Approach Founders Clare and Ross Booth share how their people-centred approach and compact Aberdeenshire team... Aberdonians tend to be of practical mind with their head screwed on the right way.. sounds hopeful.

Agree. Disagree as there is a lack of understanding.. still in the building trade and by designers who have practical site experience. Its your money.. spend as you wish. Can be achieved.. so there! Ok to sum up. Look after your Thermalite et all blocks when they get delivered to site. Use the right strength of mortar with plasticiser. Use a brickie that is properly trained. Now we are getting technical. We call this aggregate interlock.. same thing happens in concrete floor slabs and how you can design joints in slabs taking advantage of the aggregate interlock. This is a clue.. but there are loads of other factors. Here lies a big clue! Depends on what kind of cement you buy. Most brickies unless properly trained have no clue, I caught one the other day with a bottle of Fairy liquid lying beside the mixer.. used to entrain air.. this is a no no!

Plus One!

What a great piece of advice from @Alan Ambrose Now the next question is how do you find the right SE / Architect / Designer. I'm an SE / Architectural designer, to be honest I started out as a local builder, went to uni.. learnt about SE stuff. When I look back my education gave me the tools to teach myself.. and that changed my life.

Much appreciated. Your post is a mine of infomation. So that is a big thanks from me!

Hope this helps a bit.. but when we want to create a void above the wall head level the forces in the roof members change a lot . The following is very simplistic but intended to give folks an insight into some of the things we design for and hopefully give you all some ideas. Below is a standard fink truss. This fink truss is triagulated, very economic an importantly the loads at the supports are downwards.. and upwards when you get wind uplift. A lot of roofs can be "uplifted".. Below is what we call a raised tie truss. Here we have an extended leg. The ceiling tie and wall support create a lever arm... like having a long spanner to take off a wheel nut on your car. This type of truss depending on the length between the ceiling tie and the wall support causes other forces / sideways movement which can grow exponentially with a small increase in length. An important one is that this kind of truss can push the wall outwards (sideways movement).. so you often need to have "special" sliding truss clips at the wall head or a very strong wall.. and if you have a very strong wall then there are other options! Now the above truss generates some nasty forces at the connection between the ceiling tie and the sloping rafter. Timber connections can be quite weak and they are hard to design economically / buildability wise once you reach a tipping point.. which can be quite early on.. this can be a hard lesson for a Graduate Engineer / self builder. Below is a scissor truss Here you can see that the sloping ceiling tie stops the forces that want to spread the walls outwards as the bottom of the scissor is conneceted to the wall head. Often when we design timber roofs one of the problems is not the size of the timber but having enough timber to make the connections work ok. If you have an old house with a traditionally cut roof you'll see that the ceiling ties and soldiers (the short upright bits) are 1/3 to 1/4 checked. Below is a screenshot of one of my drawings that shows this. The dark green bit is the rafter, light green the soldier/ ceiling tie framing in. But there are only three nails! The one shown here is later detailed as having only 3 no 90x 3.1 mm dia Passlode ring shank galv nails. The three nails are there just to hold the soldier in place when there is say snow / access and roof self weight on the roof. The check in the timber allows for direct bearing.. timber to timber contact... much "stronger" than a few nails! Also we need to watch out for nail spacing and edge distance.. to many nails / to close to the timber edge and we weaken the timber so folks bear that in mind. The three nails are enough to hold the connection together when the wind is trying to suck the roof outwards. To sum up. Timber roof design is a bit of an art.. but hope the above gives some insight into what it is all about. The key thing is that often its the connections that govern the design rather than raw timber size. A good starting point is to go into some old buildings/ terraced houses and see how the roof is put together. @ProDave If you want to chew the fat then would be delighted to hear from you, mind you I'll want to pick your brains too so no free lunch!

To provide a bit of context to become an Architect takes about 7 - 8 years, a degree coupled with professional development and on the job training. As an SE / Designer I agree with your Architect. Your Architect is giving you good advice. If BC pick this up they may ask. But at the end of the day do you want a safe house or not? BC are not there to make sure your house is structrally safe or be SE's. There may be some way to strengthen the roof in a cost effective way to make it compliant.. don't despair.

Ok have you sounded this out with the SE and buildings Engineer? They may be as equally frustrated as you are. If they are willing to support you then one of the two can often have a quite word with the Architect on your behalf (you keep it at arms length) along the lines of.. we don't want to make a big thing of this but what about if we certify our bit.. and you do your bit... by way of the Architect's certificate.. otherwise the Client may instruct us to look more closely at your work and delivery.. and we don't really want that to happen as we are all busy! If an agreement is made in principle then any oustanding fee element can often be "made to go away" Your Architect's certificate is often separate from the JCT.. and that will depend on what kind of JCT contract you have entered into.

I did the structural and foundation design for @Russdl, just call him Russ. It was a great journey for me as a designer. At the outset Russ kind of knew that he wanted to use Geocell and he had good valid reasons for this, had researched widely and already has one self build at least under his belt. Key factors; the ground conditions, the shape of the structure (odd shape) drainage, boundary proximity, site access, muck away cost, the odd planning constraint and cost awareness. In summary this lead to a flat raft type foundation with masonry walls, EWI and cold formed steel roof joists supporting a warm flat roof. Russ build most of this himself and put in a lot of hard work sourcing and fine tuning the installation, his door insulated solution is remarkably good, I'm going to pinch some of this final (on site understanding) threshold detail off him! Ok the Goecell. Russ and I chewed the fat for a while. Me with my SE hat on, him with his practical hat and attention to detail. At the end of the day we ended up with a flat slab on the Geocell.. it is really simple. No edge thickening. His slab is pretty big so I added extra anticrack reinforcement near the doors and funny corners. The objective was to do the slab in one pour and avoid day / control joints as they would then translate up into the super structure.. and cause problems with the masonry design. Folks there is no free lunch and that is why all parts of the design need to be coordinated. What you do at foundation level can have a cost implication later on. At my end one trick was to use standard reinforcing mesh site bent at the ends to give the reinforcement anchorage. I selected the slab thickness to make it a structural slab (a raft) and no more. For the tecky.. my starting point was to have 0.13% of rebar which turns it into a structural slab (cf a ground bearing slab).. if you make the slab thicker is needs more rebar to comply with the minimum % for it to qualify as a structural (raft) slab.. I aimed for the thinnest slab.. and from memory this was driven by how flat you can get the Goecell and having enough of a bend on the reinforcing mesh to anchor it. Now the Goecell. It has a good bearing capacity cf a crappy CLAY soil. We know how the slab will impart the loads. We also know we just needed to provide enough compaction to consolidate the material.. no compacting it to death as this is counter productive. In summary, can be a bit hard to get your head around but you kind of need to lay Geocell in layers and give it a "shoogle" and not actually whack it to death. Russ is posting some of my drawings which I'm pleased about. I hope this helps give folk on BH some ideas / inspiration. Just remember that Russ' job is bespoke so just use them as a bit of food for thought. For old / historic buildings it is a pretty breathable matrix.. Historic England I think have a bit on this, lime floors floors and so on. In summary this sort of stuff floats my boat in terms of how as an SE /designer you make the best out of this type of product in a cost effective manner .. if the opportunity presents!

Thank you, much appreciated. Gus