Gus Potter

Hi Sally. As Jilly etc allude to it's well worth getting an SE in as early as you can. What you descibe is often called a corbelled brick foundation. You'll often find these. For example up in Glasgow area these can be found in houses / some farm buildings etc predating circa 1930's say. Although the founds may seem shallow (yes they are not deep enough to comply with the modern general guidance for frost cover) they may well be fine. There are a lot of different types of clay, some rock solid that can easily take a bit of extra load, some less so. Also with clays you can sometimes get a "crust". This is where the top layer is stiffer than the underlying clay. Sometimes on new build we can take advantage of this and sit the founds in the crust, the load spreads out as you go deeper thus when you get to say a softer layer of clay the stress on this softer deeper layer is reduced. What this means in practice is that sometimes you are best to leave the soil under the founds undisturbed.. no underpinning etc. As SE will look at the existing structure, see if it has moved about.. or not and may conclude that it is best "left alone". To avoid adding extra load to the outside existing walls you can sometimes transfer some of the extra load arising from the new floor down inside the building to keep it away from the existing walls. This can be easier to control cost wise compared with underpinning etc. Taking a pragmatic approach early can pay dividends. At some point you may well need to pay an SE, so a bit extra spent early on (SE fee) can really be worth while.

Hi Deno. That's great you got the planning permission. I have copied a couple of links below to the HSE website that has info for domestic clients. Much of this is underpinned by the statutory CDM regulations. Well worth a read and they have lots of useful info, templates and guidance to get you off on the right foot. You need to have a rake about to find some of the more detailed stuff, but it is there and straight forward too! Once you get a handle on this it can give you confidence as to what level of method statement you may require and so on. They have another section for small building works that can act as a guide too. All the best with the project. https://www.hse.gov.uk/construction/cdm/2015/domestic-clients.htm https://www.hse.gov.uk/construction/areyou/domestic-client.htm

One thing you can do whether is it a small extension or a big new build with ICF basement etc is to set up some profiles well outwith your excavation. These are a couple of stobs bashed into the ground with a bit of wood nailed horizontally and set level with the bead, ( say accurate to 1.0mm over 1.0m) between the two. You set them at chest height so you don't need to bend down too much. You often used to see them on road building jobs, but less common now. Once you have set these up you take one and work out say how far this is above your floor level. Say your floor level is 1.0 metres above Ordinance Datum. You may find that your profile is 1.5m above finished floor level (FFL) thus the profile is 2.5 AOD, call this your height of Collimation, you can sometimes see this in surveying notes as HOC. Get a piece of wood (call it a storey rod) and mark on it all your critical heights, top of found, top of underbuilding brick etc. If you are on your own make a little stand for it so it will stand (like a xmas tree) upright. Put it where you want then eye through the profiles. This is quite a quick way when say excavating if you don't want to use a laser level. For accuracy string some good gut line ( 50 - 100lbs fishing line or good brickies line) between the profiles and measure down. If you are doing a big build and just want to keep an eye on the contractor then make one of these and you can just have a quick check in the evenings when you get home from work say. They may wonder how you managed to do this in half an hour! The thing is it can really help spot the gross errors before they become too much of an issue.

Yes Temp , I have come across this argument before. However this (welding) is a structural safety issue. The counter argument to this is.. prove that what we see will not fail when subject to the design loads and is equal / equivalent at least to the recommendations in the codes. Initially you are often greeted with silence when you counter this way. The photographs I posted form part of a remedial works scheme. It’s a very long story but the builder went bust, the structure was found to be defective and off the back of that the warranty provider instructed and employed a contractor to carry out remedial work. There can be no doubt that they (warranty provider) are now responsible for the welding you see in the photos as it was they that instructed the contractor who carried out the welding. It is fair and reasonable in my view to expect that the warranty provider will remediate the works to a level that reflects the original “value” and quality of the build that they have underwritten. To achieve this, the remedial works should be capable of resisting the loads etc that were used in the initial design. In some cases there may be an allowance for fair wear and tear but this is in my view not applicable to structural safety as it compromises on what we call the “robustness”. The above is a bit off topic but hopefully if any members are having trouble with their warranty provider then this may point you in the right direction. One way of dragging the warranty providers to the table is to focus on the structural safety aspect. Once you turn this into a safety issue then it tends to focus their mind!

Help ma boab, Onoff, that reminds me of a post while ago where some poor sole had their house flooded with heating oil when the old tank was not sealed and the oil delivery driver filled up the old tank by mistake! Can't find the thread.

No wonder, I nearly killed myself a few years back in a farm yard when I started to cut through a bit of blue alky pipe and found a live cable inside, something made me stop and check but it could have been someone younger?

Hello all. It's worth having a chat with the builders, hopefully some pro's on BH can chip in. While there are lots of different insulation options you can explore some are much more labour intensive to install and this comes at a price. Also, for the small domestic market.. to keep your tendering options open then perhaps you don't want to put off your "local builder" by introducing a system / something that requires for example; more complex fixings / more care to install, that needs a specialist tool to screw something in. Remember that some of the insulation systems are primarily designed for large projects for installation by folk that are doing it day in and day out. It's often more economic for small DIY / projects to go for the simple stupid option.. yes you may pay more for the insulation (need more thickness maybe) but this is often easily offset by the labour savings and the fact that you will get more local / small builders saying to themselves.. yes this looks pretty straight forward.. I know / am confident how much profit I'll make off this as I'm familiar with the product so the risk is reduced to myself, thus I won't add on an extra "hassle factor" to my price. By all means if you are total DIY then have a go, but if you are going to get a contractor in then it's worth a thought.

Hello all. Just to pick up a bit on ZacP's point. A good comprehensive design should include a desk top study, site visits, Site investigation etc.. a lot of this is laid out in the good practice guides. Of course, it is up to the client as to whether they wish this type of comprehensive design. To avoid doubt the designer should spell out in their brief what they are and are not going to do. This is particularly important when dealing with less experienced domestic clients for example. Once work gets underway it's worth considering what will happen if you encounter the unexpected, or the contractor starts to "go off piste". If you start getting a feel that all is not quite going as it should then having the designer locally based can often nip this in the bud. On the upside you can also find that you maybe don't need to excavate so deep for example. Having the designer "round the corner" means that they can make on the spot decisions that will usually save you money. At the least they may stop everyone from falling out! Lastly the use of ICF is becoming more main stream. The basic mechanics of sitting a structure on "squashy" insulation is faily well understood, the Canadians and those designing cold stores have long experience of this for example. On the whole the basics of designing structures to rest on an insulated base is not too difficult, the devil can often be in the detailing of the reinforcement, drainage and other "quirky" bits. Here you can often add days to the detailed design time and this comes at a cost.. hence the variation that folk often see in the structural design quotations.

The good the bad / ugly? Here are some photos from a project that is covered by one of the major home warranty providers.. who have been arguing for some time that there is nothing wrong with the welding. The steels and aluminium sections you see are holding up a substantial glazed structure subject to snow drift loading in addition to the run of the mill design loads. I think I may have shot myself in the foot earlier by extolling the virtues of CE marking...but there are benefits. The fabricator who did the work claimed they were CE marked but on investigation it turned out that they used to be under their old company before they went bust. Anyway, some key points are: try and avoid site welding unless you have access to a real pro who can over head weld etc. Believe it or not the “goodish” and the “ugly” work was carried out by the same firm.. I cannot explain.. If this sparks some interest then I’ll try if I can post a blog on what to look out for if you are self builder looking to buy and get some steel fabricated and some practical tips I know of to get best bang for your buck and so on. As always if anyone feels free please comment. The "goodish" Not a bad end plate weld on the box section, it is covered with a galv finish though.. seen worse. Oh dear going downhill! And now we are somewhere else.. how do you classify the quality of the weld when it is kind of not there?

Yes, if for example you are on reasonable rock. In this case the found will not be a traditional strip, almost like a "skin" of concrete. For all, if you have a taller structure on a small foot print, introduce large areas of glazing etc on the ground floor you often find that when the wind blows it wants to "topple" the structure. To deal with this you need to design your piles to not just carry the downwards load but also to resist uplift and that can add to the piling cost as the piles need to work in both directions.. up and down. If you do have a site with rock close to the surface you may also find that BC still ask for the founds to have frost cover (min 450mm) and thus for the unwary you then spend a fortune on a pecker carving a hole in the rock just to fill it in with concrete. There is often a more economic way to do this than just blindly following the regs regarding foundation depth.

Two different points of view here. I can see both sides of the equation. On the one hand you have folk that have welding certificates (grandfathers rights) and loads of experience, play by the rules. On the other you have those that don't. For example you may get a price for box a section fabricated steel frame. There are two types of box section.. cold formed and hot finished.. they are two different animals but there are very few folk that know how to distinguish between the two. This is can be a big safety issue.. you find that the cowboys often substitute a cold formed section for a hot finished one as they (cold formed) are cheeper.. and that is where the trouble can start. It's also to do with the provenance of the material. I have surveyed buildings for extension and found some really odd steel sections. Turns out that these were basically fakes from elsewhere, they look like BS sections but when you put the mircometer on them the flanges are thinner! Then you have the quality of the steel to contend with. So yes, on one hand it seems like we are "controlled" but on the other this scheme has gone a long way towards improving safety. Make no mistake.. there can be a big difference between the person (and the conditions they do it under..factory or out in the rain) that welds up your garden gate from the one that welds up the end plate (with the associated quality control) on your steel beams which could be carrying literally tonnes of load! I would happily go back to the "old days" but you can't turn back the clock. Remember that modern design aims to be more economic.. thinner and lighter steel sections... less margin for error / material quality To achieve more economic design you need to have tighter control on the quality of the material and welding process, the bolts, the actual steel erection, grouting of base plates etc.

Just a thought. One of the best ways to approach this is to start with the basics. Always check, then double check the obvious to make absolutely sure, then you can proceed with confidence. Have you looked under the floor if suspended? .. have you checked your roof, gutters, rain water pipes and drains to make sure all is in order. If you have neighbours in close proximity..have they been up to anything? If you have only done this once then do it a second time! For older structures in particular drafts are good, that is partly why they last so long. What you are looking to do is to maintain ventilation while at the same time introduce insulation.. and as each house is different, like a vintage car you need to get a feel for your own home and work from there. Remember that often you won't be the first to have tinkered with the structure! Look outside. Do you have a locally variable water table, have big trees been cut down? Big trees can also take a lot of water out the ground in the summer when it's warm so removal can result in a lifting of the water table locally thus in warm weather this may manifest as high humidity. And to state the obvious look at the ground levels and what the ground surface comprises, the falls away from the house and so on. For all. Although Benjseb has a period house this applies to all investigation. It's best to really get a handle on these basics before you start spending a fortune of ripping out walls / changing insulation and so on. If you don't, you run the risk of just transferring the problem somewhere else. Benjseb.. Another key to this is to be patient with the old house.. the best way if you have time to is to make a change and see what happens..

Hi Adam. @AdamJ Thanks Gus, I take your point that a whole life assessment including transport and disposal would be better. I agree, though I don't know yet how to factor those two additions in easily. As SteamyTea said, the ICE database does include some transport emissions. The authors say the database has a "cradle to (factory) gate" scope, covering modules A1 to A3 in the EN 15978 standard. A1 Is the extraction of the raw materials, A2 is the transport to the manufacturing site, and A3 is manufacturing. To be more comprehensive, I should then add in transport from the manufacturing location to my site, and energy I use on site in building with those products. I'd want to have a rough idea on how large a proportion transport-to-site emissions are before putting a lot of time in comparing so many different systems. I don't have any idea how to estimate the end of life emissions! I do know that the a lot of the neighbouring buildings to my site were built around 1880-1890, and then another lot around 1960, so are between 60 and 130 years old. I hope my house lasts at least as long (longer because it will be such a good house! ) I would love to believe that SteamyTea's 500 year statistic will apply to my house. Even if it only lasts 60 years, the decision on how to dispose of the house at at the end of its life will likely fall to someone else, but I could design it so the parts could be easily re-used. If I was designing it for re-use, though, I might be looking at using steel beams and columns and pre-cast concrete planks, because these are most easily re-used in new construction projects, from what I understand. Again, before embarking on a comparison between end-of-life emissions on multiple systems I would want to find out what sort of proportion of the whole they make up. Can you give me a rough idea? Adam I think you are doing a sterling job here exploring this complex issue. You asked "..Again, before embarking on a comparison between end-of-life emissions on multiple systems I would want to find out what sort of proportion of the whole they make up. Can you give me a rough idea? " I wish I could! A bit off topic..life span of your house. For all, when the loadings are calculated for your house they are based on the probability of occurrence. Take the wind loading, (an environmental load) here we often base this on a return period of 50 years and design for that and when you apply for a mortgage the lender works on a similar probability to ensure their asset is protected. However, we know that timber framed buildings last a lot longer than that, hundreds of years, often it's fire that ends their life. I can't see for example how a modern timber framed house cannot also last well beyond the " design life" if it is well maintained. Turning back to fact that I can't answer your question! Modelling is often an intrinsic part of modern development and the build process. Structural Engineering has benefitted from this, the computer models are significantly more advance even compared with 5 or 10 years ago and this continues as the processing power of computers grows at an exponential rate. But as we know predicting the future and how the materials we use now can be recycled later is difficult to say the least. This uncertainty can throw any model right off. Also, these modern models generate a huge amount of data that needs to be stored.. and that uses electricity, I try and avoid thinking about how much electricity data storage requires. The energy requirement for this may well increase as we start to gather real time data on home automation for example. But at the moment this is one cost of innovation and this will pay dividends in the future. As an aside. A colleague who works in the oil and gas industry recounts hearsay where they were analysing the all up loads / stresses on a rig using FE analysis. The output was a bit on the red side and they felt that as the client was not an Engineer they may have a concern as there was a lot of red on the model. Someone joking said, just change the colour palate on the graphics... the same can apply to the carbon model. At the back of my mind when I was posting on this was.. What if you are on a limited budget, first time self builder say but want to do the best for the environment. We know that for example the latest technology.. some batteries, circuit boards, complex systems often have rare earth metals in their construction. It's reported that there is growing activity relating to mining of the seas for these elements and we intrinsically know that this is probably not good for the planet. To be clear, I'm certainly not suggesting that we should abandon innovation. But if you are on a budget maybe select the materials that we already know are not too bad for the environment.. sheep's wool insulation, straw as a good example, although timber , steel etc are already proven to be easily recovered and recycled. Lastly another way you can also protect the environment is to spend the time getting the quality of your build up to scratch, good detailing and workmanship to keep the weather out and so on. A well slated roof can last for over a hundered years if properly done, a bad one much less. I do wonder when you see the complaints that are raised against new build how much of a carbon cost is attaching to shoddy building practices and workmanship. Keep posting AdamJ and thanks again for sharing.

Just a thought. Embodied carbon is one measure. AdamJ. Yes.. to make the best job of reducing your carbon foot print starts on the drawing board as you are doing. At some point you need to often dig a hole in the ground, cart muck away. Then you often need to pour some concrete, the sand/ aggregate requires transportation to the concrete plant, the cement takes a lot of energy to make it. You need to cart muck away and so on. You purchase PIR insulation.. oil based product, maybe concrete tiles, hard to avoid. Then at the end of the day the building has to some extent a limited life so someone has to dispose of all this and that carbon cost may well exceed the saving you may make during the lifespan of the building. Ideally you want to leave the site "just as you found it" It's fine crushing up an old block of concrete flats for recycled aggregate, but if you then cart the stuff fifty miles or more and sit with the wagon engine running in a traffic jamb / unload it on site / the operatives come to work in van to do this and so on then it kind of defeats the purpose? As an aside and ask.. look at how many houses are getting knocked down at the moment partly to do with the VAT system. Ideally and one expression, is to "walk softly and leave no footprint" that is what your house should do. So my view is that if you are carbon aware you may want to think about what you are leaving behind you and not just reducing your footprint when you are living in the house. Once you start to think about this then you can start to look at your basic structure. Take an ICF basement. That is often a big hole, lots of concrete and lots of oil based insulation product.. I'm not convinced that your air source heat pump etc will offset the overall carbon cost and the subsequent disposal cost.. or do we want to leave that disposal issue for the next generation to solve? yes you may save a bit on electricity during your occupancy and so on. I think that if you really want to make an impact then it's worth looking at the project in the whole, the carbon cost of construction.. fuel for wagons, concrete, insulation and so on. Then the carbon savings when you are living in the house, then the reduction in your carbon footprint at the end of life stage. When you weigh all this up you may find that you can save some money while also leaving significantly less of a carbon foot print overall. If you look at it this way then you may be able to afford carbon wise the extra odd luxury while making a positive contribution to the environment. Although this may sound cynical I have written this in the hope that BH members that want to self build with a limited budget, while doing the best for the environment may be encouraged to look at the whole of life carbon cost. It is not always necessary to buy the "latest" and usually expensive technology when you can skin the cat in another way. Self building can be a great journey, often folk move on, you can see it on BH.. lots of serial renovators and repeat self builders etc!

Davejura.. I suspect that you secretly you want it too!...but.. just and so on. I built a house with UF on both ground and upper floors, suspended solid timber joisted floor on both the ground floor and first floor. The first floor had the plaster board ceiling, 195 mm deep joists and 22mm chipboard, carpet on top. Glass wool between the joists 100 deep, netting over the top of the joists to which the UF pipes were attached to with bits of garden tie wire we cut up. The netting tended to hold the pipes up against the floor and surprisingly it all worked pretty well. Didn't destroy the carpet. It was all done on a shoe string budget a good 25 years ago. I still keep in touch with the folk that bought the house and it is all still working. With hindsight I would have gone for the plaster board ceiling, some 9.0mm thick OSB board on ledgers attached to the sides of the joists, with a lean mix screed encapsulating the pipes. This adds mass, thus sound protection and spreads the heat more. The down side at the time was that this extra load of the screed added to the cost of the joists so I took a chance. We know heat rises so keeping the bedrooms on the ground floor is a good idea as you know if you want a cooler bedroom to sleep in. All I would say is that at the concept design stage make an allowance for the extra weight of the screed when sizing your floor joists, keep your options open, at the very least if you don't at the end of the day go for a heavy screed then you'll still have a good stiff, non bouncy floor. Oh, and the West of Scotland is a great place to live. All the best

Thanks to all for contributing to this post, every day is a school day, much appreciated by me! Nod and many others are making great practical points so thanks. A bit off topic. The flat plate I think comes in handy when your boards go over the standard 2.4 m as the flat plate acts a bit like a noggin (dwang) and supports the horizontal plaster board joint so you don't get a crack in the finish. Again turning back to Nod. Similar cold formed sections can be used to create load bearing walls too and here the noggings etc often start to play a structural role. I don't know if anyone has posted on BH about a fully cold steel formed structure ( external frame + internal racking / load bearing walls) but I'll hazzard a guess that Nod and others have worked on them. Once walls become load bearing then the flat plate can start to form part of the fire protection. The white book as you can see above and the "site book", see internet, provide some great info and the real practical tips you will get from the likes of Nod etc.

That is some house.. no wonder you are excited. I wonder what the views are you'll have. Setting aside the Architectural scheme. At first glance there are a good few opportunities here to explore in terms of structural design particularly on the rear elevation in terms of sideways horizontal) stability of the building. The corner windows on the rear elevation? Frameless glass (cantilevers?), corner posts or hanging from the roof structure..? You have that large area of glazing on the rear elevation coupled with a partial basement.. in Engineering terms it sparks interest. what is the ground like.. will there be significant differential settlement.. if so how much and if realised how do you deal with that while not compromising on the Architectural design intent.. The form of construction; steel frame, timber frame, traditional masonry or some hybrid with ICF basement.. so many opportunities / options! All the best. Look forward to seeing how this develops.

As with all drawings; planning applications, BC drawings (warrant drawings in Scotland) you are seeking to convey information. Adding photgraphs to your drawings can be help the planners etc to visualise what they are being asked to assess, it may even help speed up your application! If you are going to add photographs then I would put them on perhaps the elevation drawings rather than the site location or block plan. In Scotland for the last few months (COVID) some of the planners are / were not making site visits so providing photos can help in my view mitigate some requests for extra information.

@Mr PunterYes usually with standard scaffold poles which have an outside diameter of ~48.3mm. The top part of the prop (inner tube) is the same diameter as the scaffold tube so you can make 90 degree connections with a standard double coupler, angled (diagonal bracing) connections with a standard swivel coupler. The outer tube of the prop has a diameter of ~60.3mm so here you use reduction couplers.

Hi Jilly. @JillyYes, you can do your own structural calculations and submit them for your own extension but you should be competent. There are other factors worth some discussion. Here are a couple. The first is to recognise that Building control will make reasonable checks to satisfy themselves that the design meets the Building regulation requirements. For example, they may check 10% of the maths in the calculations and look at perhaps the stability system. However, it is the responsibility of those carrying out the work to ensure that the provisions of the regulations are met in full. You could look it another way. If BC were responsible for the design then there would be less of a requirement for an SE say to hold the level of PI cover that they do. Secondly, if you do your own calculations and something goes wrong where do you stand from an insurance point of view? I would recommend that if you are going to do your own calculations then it’s worth having a discussion with your insurer. Before you start.

Acrow props – is there an alternative that won’t fall down? Yes there is in some cases. Much depends on your programme, whether you wish to give it a go yourself and how much time you have on your hands. Please feel free to comment / question. I’ll answer if I can (if not, I hope some other BH members will be able to) and provide more detail. Photo 07 showing holes for the needles and the first few temporary works studs going in. The base of the studs are sitting on a sole plate fixed down to a temporary strip foundation. Part of the sub floor has been built up and concreted to provide a working platform. Photo 04 (copied from previous post) In my case I have been dipping in and out of our project. I reckoned that I would need some 25 – 30 Acrow props for the temporary works which would take me about 4- 6 months as I was also mucking about with other bits of the build. To hire 25 props at £ 5.00 per week = £ 125 per week! I could have bought the props but I would have needed to get rid of them after in my case, just gave up on that. I have two or three old props that were used to help tighten up (pre load / stress) the timber propping. The timbers 145 x 45 (grade C24) to form the needles studs, top and bottom sole cost ~ £350.00 ex vat plus a few screws (about 250 number 5 x 80 gold screws I think) to fix things together. I knew that I could recycle the temporary studs to form a new floor we needed and that if I cut back the needles I could also use these to prevent the top steels from moving sideways. This is called simplistically “ lateral restraint”. Also, I used same needles to provide additional what is called “torsional” restraint to the top beam , a slightly different effect, but is it to do with the fact that I used one beam with a top plate to support both the inner and out leaf of masonry which can be loaded in different ways at different times. These different loading patterns cause an uneven loading on the top of a single beam.. resulting in a twisting (torsional) effect. You can see more photos in post 01. Fig A 01 showing proposed rear elevation. How does it work / stay up? The starting point here is to calculate the amount of load. With this house the roof spans front to rear, the attic is full of stuff, the walls are rendered brick cavity walls and you have part of the weight of the new extension roof that is now attached / built into the outer leaf of the house. Once you calculate this you end up with a working load you need to hold up of round about 25 kN/m run of wall. Approximately 1.0 kN (kilo Newton) is ~ 100kg so 25kN/m is about 2.5 tonnes per metre run of wall. Thus if you put your needles at 600mm centres then each cluster of needles has to carry 0.6 x 25 = 15 kN (1.5 tonnes) and the studs supporting the needles at each end need to carry a vertical load of roughly 0.5 x 15 = 7.5 kN (0.75 tonnes). These types of loadings are as about as much as you can “do” for this type of system. There are other ways but you need more height for timber needles. To make life a bit more difficult the window lintels on the first floor cause the load from the roof to be unevenly distributed so some needles need to carry more load than others. You can see from the photos that some needles are in pairs, some are a cluster of three. In terms of the studs these needed doubling up in places and the whole lot horizontally braced at mid height with some diagonal bracing just to stiffen the whole lot up. While this sounds like a lot of work once you get going it’s actually quite quick. This approach is a little different from using Acrow props. With Acrows you wind up the prop to preload the system so that the upwards force is approximately equal to load the wall you are taking away is carrying. Aside, If you are Acrow propping things then be careful not to over tighten the props as you can easily start to lift parts of the house accidentally! Here, what I did was to use a combination of the spare props I had combined with timber wedges to pre stress the system, one set of needles at a time. The other thing is that over time the timber can shrink / creep a bit so I was careful to get the timber dry first and then monitor the system as I went along. All sounds complicated but once you grasp the principles a lot of it is common sense and this is not a reinvention of the wheel. I know a few old joiners and brickies that still remember doing this when they were serving their time. Some extra information that may help. As always, comments welcome. Options for beams- In terms of material vs labour cost it can sometimes be beneficial to design the steel beam as a single beam with top plate. The one you see here forms part of a double flat portal frame. You will also see designs that use a separate frame for the inner and outer leaf, a question of balance, each project is different. You can introduce a problematic thermal bridge at times if you deploy these single portal principles to an external wall, but in my case the steels are now internal.. the thermal bridging is resolved in the main. Propping considerations. Below is a screen shot of part of a temporary propping design for a set of 4.0m bifold doors etc. There was another big chunk of the rear wall to come away at the same time which is not shown. The contractor here was stopped from working until remedial action was implemented. Screenshot propping.docx Fig 02: The purple lines are the props and what is called the lacing / bracing system to stop sideways movement. Work was stopped when this was discovered. Part of the contractor’s defence was that “he was insured” Photo 08 Photo 09 A few points. The Contractor had not investigated the ground under the slab and the base of props can slide about. The site investigation had revealed this ground was very soft. Use of Strong Boy type supports at the head of the props.. these have a reduced load capacity and not suitable for the loads to be carried in this case. Props well out of plumb, no bracing.. further comments welcome. On a finishing note the timber propping scheme may look a bit rough but it was designed and executed with no unexpected movement. If this approach may suit you then as always check with or be a competent person. Thanks for reading.

Hi Grant. I'm not too far away from you, based in East Kilbride. Pity it did not work out with the builder. Don't worry too much about the steel that is encased in the concrete. For all, one way to look at this is as follows. For simple domestic stuff it's a bit of a rule of thumb. You'll often see that simple strip foundations have mesh in them. For foundations bearing on the soil the cover to the steel is often specified as being a minimum of 75mm. Roughly the first 25mm is to account for the fact that the machine you dig the found out with can't reasonably get closer than 25mm tolerance (much worse in real life) and pratically ~ 50mm is to account for a bit of the "nesting" of the reinforcement when you lap mesh etc and for soils that are a bit aggresive to concrete) it's all a bit vague. However, roughly the main thing is that is you have a good couple of inches of concrete round your steel and this protects the steel from corrosion for a good while. Grant.. you can see here that once the columns are embedded in the concrete pads that part of them will be ok. It's the little bit just above the top of the concrete that is a little more vulnerable. Practically, your Architect is in my view is on the right side of the argument.. but a key question may be.. will they take that on under their PI cover. The steels in the photos seem to have been reasonably primed , it's just that some of this seems to have been abraded at the bottom when the founds were poured. If push comes to shove then it's a question of examining how much if any of the steel is in direct contact with the soil, the soil type, how much is in the cavity and protected to some extent and how much on the inside is in contact with the inert fill under the floor. This information would be used to underpin an evidence based argument should someone (BC) query the view that the steels as they are good for the design life of the house. In terms of insulating the column. I can't quite see how the kit interfaces with the column but having a guess I would aim to get some good PIR insulation into the web on the outside, then for good measure foam any gaps in case it comes loose later. Here you are already starting to reduce the cold bridging. To make a proper job I think you still have to insulate on the inside but by filling the web on the outside you are going some way to avoiding making a rod for your back later. It would do no harm to keep the continuity of the kit breathable membrane running past the outside of the column as at the very least if you don't do this you'll be creating a weak spot in the vertical lap on the membrane. Much easier to just run it by and staple it to the timber kit each side of the flanges. One thing to look closely at is how the kit is fixed to the steels and plan that bit and the insulation / window details near the steels etc carefully. If you can post some section details so folk can see where the kit sits in relation to the steels you'll get some good positive responses.

Seems not.. pride comes before the fall and all that.

Hats off to all. Great "Columbo" work. Here is my go. Could it be the sampling chamber before all discharges in to the "Canal"

Hello Grant. That looks great, enjoyable to see folk embracing the portal frame principle. Good size house! You have two slightly types of portal as one seems to be creating a large volume, the other supporting a floor.. for the keen the two types of frame perform in different ways depending on the floor level. It kind of looks like a Scottish landscape the trees and grass, maybe Wales I don't know. And that leads me to the steel corrosion. I'll take stab in the dark here but it looks like you may have had some tree stub muncher in so it's hard to see the soil, but looking at the type of trees it may be that you have a shallow clay soil, a bit sandy maybe. If so the soil is likely to be a little acidic such that it promotes a little corrosion compared with a more alkali soil like limestone. I would have a look at the SE spec not just for the steel but also for the grade of concrete used under the ground. If the grade of concrete is high then that may indicate aggresive ground re corrosion potential.. ask your SE. If you are in Scotland then this steel protection should have been speced to get your Building Warrant and the Builder should have followed this specification. It may be that the the detailing is such that the steel is ok re corrosion. Interestingly @Jilly was posting about something similar recently. I would have a word with your SE, if the builder has deviated from the spec then discuss. There are often easy solutions to this.. sometimes you just need to re appraise and all is proved to be ok. The SE may say.. don't worry there is plenty sacraficial steel available to deal with the corrosion so cart on. They may say..mmm I don't know. In this case ask why then raise the possibilty of introducing some cathodic protection. You can find info on this on the web but it't just like protecting a boat from corrosion and it should not be horrifically expensive especially if you good wet clay soil.. There are members of this site that know about all about the physics of this. But simplistically (I think) you could just bury some lumps of zinc in the ground and electrically bond this to the frame, (check with the Electrician if need be so that what you are doing is compatible with their work) make a note to monitor every five years and get on with enjoying what looks like is going to be a great new home. Hopefully this is some reasurance.