Gus Potter

All good stuff Alan. For me as an SE and the thing that keeps me awake at night is the thought of designing something that falls down and hurts or kills folk. If I did that then there are many examples of SE's that never work again. Persoanlly I would find it a hard thing to live with, I hope it never happens. I've seen fatalities on site. In that context sometime I see folk on BH doing stupid things structurally or things that I can see are going to cause problems with say BC compliance. But this is social media and you all wear big boy pants. Good advice.

This is pragmatism and actually very clever.

Hello Saul Sorry to hear you are having a hard time. Here are a few comments. They are just general but may help you, even if just to rule out. Often ruling things out let's you focus. I do a bit of Claims work now and again, not a lot as I would rather be having fun designing stuff. I'm off the day job so excuse the spelling, grammer and hope you get the jist of my comments! When you get sight of a professional report you must read the caveats and scope of the brief. But as a lay person you will still struggle to understand what these actually mean. This type of report is carefully crafted. You have a lot riding on this and so do the insurers etc. Ok I see you have gone a bit legal.. part of the torture these folk put you through. I was interested when you discussed about the diffferent views on the mortar compressive strength. There was professional who: Now that is almost / true in some context.. An example. Say you have a building that is made out of quality Bath Limestone. The beds are just there to keep the weather out and allow the stone to move so we don't get movement cracks...and shed some of the local stress in the stone. Anyway.. You are in dispute, your text and posts exhibit an often observed pattern from my end. You may be feeling that you are getting stuck as you are focusing on the mortar. Now there are lawyers and so on thta add to the confusion. I often feel this is a standard appoarch by say Contractors / Insurers. From their end it's about numbers, size and frequency of claims. Let me paint you a picture: Let's say you find an SE that is a crusty bugger and who does everything based on evidence, knows how the game is played. Let's also say that this SE knows how to inform your Lawyer, who may be young and wants to learn / win and pocket a bit of cash. For me as an SE part of my claims work is to provide the tools to allow the laywer to fight the case. I always go back to basic design principles and most laywers can make hay with that. You write to your opponent and ask to see the original design calculations for the house and if there are any "as built drawings" Now 99% of the time these will not be provided. No calcs / drawings you now have opened the door! Saul you are focusing on mortar strength, say durability, a professional report is introduced about 1:10.5 mortar mix. Your opposition is tying you in knots, taking up your time, causing you stress, potentially blighting the value of your house. This is standard fair and practice when you go up against developers and say the NHBC.. especially when there may be more than one house at risk. What can you do: Ok you are feeling that you are fighting a big wall. BUT it's an old expression.. just change the conversation!.. it's an old addage from I think 1960's marketing.. but still true to this day! Go around the wall! I do claims work now and again.. I don't take on a Claim unless I think I have a decent chance of winning. The NHBC et all have huge resources.. the trick is to find a way round their firewall. I focus on structural safety / fire safety and how all the other ements of the building rely or not on the wall and mortare for example. You can quickly turn the tables on them and rack up their costs! Importantly you can highlight structural safety issues which puts the shiters up them. They have to address this quick as you might report them to the HSE. You are concerend about say the mortar falling out over time.. I'm concerned as an SE about the current structural safety! To fix this the NHBC often need to fix the structural safety aspect which fixes the thing we started argueing about in the first place which is the mortar strength..there are different ways to skin a cat! Well as a home owner you can write, I'm just touching on a few examples here.. but in my day job I go to town! I'll go into any beam bearings on soft mortar, durability.. the whole lot. Once I get going with my SE design safety hat on it can be free for all. In my experience most insurers just throw in the towel.. but you must educate your Lawyer and a good SE for example will do that. Some question you may ask as a lay person: 1/ I know the roof sits on the walls and puts vertical load on the walls does this report (1:10 etc) take the behavoir i=of the buildingninto account. I would love to see copy of said report for interest. 2/ I know the wind blows on the roof and to stop it moving sideways or upwards it needs to be tied to the walls. I know that the regs require the masonry to be of a certain standard so the vertical and as equally important the sideways wind loads are transferred to the walls all the way down to the foundations. 3/ The floors tie into the walls and for these to work the walls need to comply with the assumptions in the floor design. 4/ The wall ties as recommended rely on a certain strength of mortar bed.. if my mortar is not strong enough then that invalidates the wall tie design. 5/ Fire protection. Now I can see the mortar is falling out on the outside. If it is happening on the inside then the fire pretection in the cavity may be compromised? How do you know it's not? 6/ Bridging of DPC's and wall ties in the cavity.. is the mortar falling out causing bridging? 7/ I have windows and doors.. my supplier needs to verify that the walls they are fixing into to comply with the standards. I've just touched in laymans terms on some questions you may want to ask. Gus (that's me) What I do from time to time is to phone up the technical department of say the wall tie manufacturer and say I'm in a bit of a bind what do you think unoffically ? Is this defensable or do you think I'm right? Remember folks that from time to time I may defend a builder? To close: To win this I think you need to change the conversation.. focus on structural safety and how the weak mortar has invalidated the rest of the design. Try and rack up the cost and time to defend for your opponent. At some point they will come to the table and want to negotiate. That is a story for another day.

I agree with you. there are a lot of conspiricy theories.. but I'm inclined towards looking at what I know. The fire protection got blasted off the steel.. it got hot, failed, which cuased the building to collapse. The planes impacted on more than one floor. Where the plane hit was at the height where there was a lot of dead load from above. Once that dead load started moving the dynamic effects were multiplied. You only need to lose say 1.0 or 2.0 metres of column fire protection over a number of columns to promote what we call disproportionate collapse. I still find it personally uncomfortable to distill and write about it in this way when so many people lost their lives. No is a hotpoint and looks good! I'm in awe of the Space X Engineering team. Stainless steel is a wonderfull material.. it's ductile, forgiving but comes at a cost. I love what Space X is doing.. they have the best Engineers.. we British used to be like that! For me it's about how the marry up the best young talent with old school testing engineers.

xxx for you! Yes you are right.. I can't think of a time when you have been wrong! wish I could., just kidding. For low rise domestic design we try and limit the SE fee. At foundation formation level (the depth of the hole we dig) we dig a bit of soil out and put some concrete back in. But then we often make the founds wider for buildability and call it a day. Good point. We as SE's have a term called load sharing and load spread..,. similar to electrical diversity when sizing a supply or consumer unit. The piano and Eltons "charisma" gets spread about by the time it reaches the founds. While we do calculations some of these are based on a best guess and experience. The soil under the founds is variaible , best guess. If we are blessed with say 4 Eltons on a floor then that is where the safety factors come in. Anyway Elton does not stay more than a few hours which will not impact on the long term settlement.

I'm dabbling with a bit of AI off the back of some of the help and suggestions I've got from folk on BH. Thanks all. I've found it usefull in that it acts as a prompt. My own problem (I have more than one) is that I've been in the construction industry for some 40 years.. I forget stuff while at the same time I'm still on a learning curve. As new stuff (like what BH members are doing) crops up I'm working out.. how do I design this, where can I use first principle design and so on while sticking to the ethos of say the building and structural design regs. What I have learnt so far.. is to treat AI like tabloid news.. with a large pinch of salt. About 20 years ago I first got involved in producing cold formed steel SE calculations for the biggest supplier of cold formed portal framed buildings in the UK, it was great fun and they supported me in my SE training.. In some ways they were not actually a steel company but a software company that manufactured and sold steel buildings. Their big market was actually in Australia (huge mining companies and so on).. the UK was a bolt on with R&D, engineering tech from the uni I went to. l got to work with computer programmers all over the world, still dabble a bit when I get the chance. What I've learnt about software development is that you have to fly by the seat of your pants. If you want to get software perfect with no bugs then by the time you do that the market has moved on.. and you will lose all your investment money! Matt. I think the construction industry is going to have to embrace AI in terms of some design, the paperwork, call it that for simplicity. I supsect you may be wanting to go at 100 miles an hour (160 kph).. but if you have time go back and read the Sir John Egan, published in 1998. Matt can you explain what you do do in laymans terms and what you seek to achieve?

This is a good point. On normal low rise houses we may go to site and dig a few trial pits and find CLAY soil. We can do some tests on the soil (or just look at and mould it in our hand) and based on that information we can calculate how much load we can put on the soil before it fails, like just totally gives up the ghost big time. We don't want that to happen so we may say let's put a factor of safety of 2.0 on that. An example would be.. say we calculate that we can put thirty tonnes (about 300 kilo Newtons kN) per square metre on the ground before it totally fails. Puttinga factor of safety on that of 2.0 and that gives us a number of say 15 tonnes a square metre. But CLAY soils settle over time. The next calculation is for settlement. In the UK for normal low rise housing we often limit this to 25mm over 50 years. This gives us another load that the ground can carry without settling excessively. We pick the lower of the two numbers.. and often you'll see on you SE drawings what is referred to as say.. "this design is based on an allowable soil bearing capacity of 100 - 150 kN/m squared which is about 10-15 tonnes. When we have a SAND soil ( I capitalise as the use of upper case denotes the dominant component of the soil) we carry out a similar calculation but are very keen to know about the level of the ground water and where it might be in the future as this can half the strength of a SAND soil. Ben. The biggest number on your drawings is 12.5 /5.0 unfactored load. Now take that as is and add the dead (the weight of things) and live load (people, snow, roof access and so on) together which give 12.5 + 5.0 = 17.5 kN per metre run of wall. Now say that sits on a simple strip concrete foundation with a bit of A142 mesh to stop it cracking too much. Also say that your soil can carry an allowable bearing pressure of 100 kN per metre squared. Let's see how wide the foundation needs to be to carry that load. 17.5 kN per metre run / 100 kN/ m squared capacity= 175mm! But that is the theory.. Incedentally if any of you have renovated old Victorian houses you may find internal walls that are just sitting on bricks laid sideways on a bed of lime mortar on the soil. So while the number above look crazy it's not actually in old money. Anyway back to your build Ben. You can't reasonably dig or fit a wall onto a found that narrow. When we go to set things out for a DIY self build found.. we may be not get the marking that straight. If your builder / you get a local hire JCB they often pitch up on site with a 600mm and 450mm wide bucket and a blade bucket for scraping the ground and tidying things up.. Thus on a house like yours I would say can we just do the narrower internal wall founds with the 450 bucket, the external walls with a 600 bucket. Make all the foundations 200 mm thick. Alan is spot on, this happens! In the UK we still use a combination of the British Standards and the Eurocodes. These codes have different factors of safety and we combine the loads in different ways depending on which code we are designing to. By providing the unfactored loads we allow the different suppliers / package designer more scope. That drives down cost.

Good point, as aways. Steel is an elastic material, like all materials. In the UK we don't suffer from particularly low temperatures, but in some cases where we have structural steelwork that is exposed to low temperatures we select a steel grade that is more ductile (less brittle). Going in the other direction when we heat it up it starts loosing "strength" that give designers concern at just over 300 deg C. @saveasteading is correct about the oven There is some softening of the steel at 250 deg but it is for all intents negligeable. . Below is a typical fire curve for steel from the SCI. Simplistically when we design steel for fire we may pick the 550 degree curve. Work out the loads on the building during a fire. When we do this we don't assume the building is fully loaded in the same way as when we are designing for day to day use. Fire is what we call an accidental load case and we reduce the factors of safety and the loads to reflect that this is an accident. If we did not do this then building cost would often be prohibitive. Fire protection is about providing a protective layer of material that insulates the steel in one way or another. Or for example you can use say sprinkler systems that reduce the heat and duration of a fire. Fire is a terrible thing. What we aim to do is to provide warning of a fire first. Smoke and heat alarms say and this lets people exit the building. We aim to provide them a safe route to do so. Here we may see reference in the regs to escape windows and the like on a single story house, we avoid having a room off a room with no escape window for example. On a three storey house we often want to have a protected stairwell or a sprinkler system with an enhance fire detection system. Once buildings get taller (often 3 habitable floors or more for domestic use) we need to think even more about people that may be trapped. Here we want to further protect the floors, walls, the structure and so on to provide a safe shelter space until the fire brigade can effect a rescue. During and after the rescue we need to protect the structure so it does not collapse on the fire brigade or set light to any surrounding buildings.. and that is where the other structural aspect of fire design comes into play. Often if your house is well away from other buildings the fire brigade (if sure no one is left inside) will fight the fire from a safe distance.. or if in doubt just let it burn. I take Nick's point.. but at the end of the day it's often the insurer that has to pick up the tab. The more you can limit the extent of the fire damage the less they often need to underwrite and that is reflected in the premium.

Yes I agree. In simplistic terms there is chemically "locked in water" in the plaster board. The heat transfer is slowed as the plasterboard "soaks up the heat" as it is forced to change chemically. But.. often the fixings are the vulnerable point. An easy way of getting your head round this is to go to the BC standards. They talk about fire "resistance" and fire "integrity" The resistance bit is to do with a material transferring heat. The integrity is about making sure that the fixings and the things the fixings go into remain ok.. as if they fail then boards say fail also. The regs combine intergrity with resistance to give you the overall number. In summary though. Say you are completely new to this. I would explain that steel starts to lose its strength when it gets hot.. that can start at temperatures similar to when your oven is at full whack.. say 250C.. this lets the home owner get a feel for what we are talking about in terms of how quickly steel can loose strength when it gets hot. What we need to do is insulate it so it does not get hot. Then we look at the different ways of doing this. @saveasteading and others have pointed out the different ways we can go about keeping the steel cool.

This is a tricky question. Time? The internet allows you to work in some places in the world as I've done for a long time. USA is a no, AU is ok... for now. We have large cavities due to say blown cellulose insulation. Thank you for the compliment, I like to have a chat as you know! Seriously though.. It's a very good question. I'll mull it over and try and come up with a coherent, reasoned and justifyable answer for folk to discuss.. I'm learning too folks about wide cavities, how they behave and how you insulate and so on! It not just the cavity width.. its the way the roof loads are transferred to the walls that is often changing, the way the floor joists / floors are connected in to avoid cold bridging is changing and on top of that we need to get it buildable, the works sequenced and cost effective. One of the things is that a lot of the masonry design codes are based on; calculation, partly emprical (call that Grandads rights) and partly based on test results. As soon as you go off "piste" in terms of the design codes you often need to go back to first principle design and that can be conservative and too conservative can add a lot of cost.

Hi @ETC there use to be a bloke called @the_r_sole who was a right down to earth Architect and massively experienced that gave up his time to contribute to BH. He really knew his stuff.. a bit like you. You can find his posts in two ways.. on google and with a BH search.. hard to find. Try and look them out. His writing style probably is similar to yours, no nonsence. I have my own informal style of writing / shite spelling ( story for another day).. it's ok to be different and give Clients a different offer. @ETC I'm chatty on BH, (just sharing my knowledge) when I pitch for a design brief.. I seem to win briefs.. but when I deal with industrial or hard nosed folk I can play that game too. I do now and again Claims work.. my head does not zip up the back. My style then is a different animal... but I'm confident in my ability... my style sets me apart from the competition. Even when I do claims and just day to day jobs. Over the years I've learnt my design craft.. but also try and improve the way I can communicate what are often complex design issues into simple concepts that a lay person can get their head around while enabling them to make informed financial descisions. @ETC that in my view thatv is the mark of a good professioal. I think the mods on BH are ok and if you get a bit of business, it's ok provided you don't take the pish. Now and again someone from BH engages me, often these are folk that are really stuck, bad builder. and so on. About two years ago I commented on a post about bad blocks from Ireland.. got a email couple of days ago.. can you help. That is the thing I love about the BH community folk will come back to you for help. My basic qualification is in Civil Enginnering and that key word is Civil.. we work for the public. For all I'm proud of that and will never forget my civic duty. @saveasteading has expanded on this civic duty. It's like being a doctor.. we have a duty not to harm, you as Client are lower down the list even thought you are paying the bill! The sole put his heart into BH but basically got hounded off BH as there were too many twats that thought they knew better, they thought all Architects were arseholes. So going back a bit and not picking anyone out in particular..I'm just saying remember when the sole was doing his best. @nod @MikeSharp01 and the rest of the mods. On the other hand @ETC what about using your own name like I do? I would like to see you tighten up many of you comments, you can't have your cake an eat it? For me I read what you write and think.. mmm here is a smart arse.. It would be good if you went on to reason out your comments so the lay person on BH can undestand.. that is what I try and do.. give it a go!

No, you need to go back to the SE AND the Architect or the person who made the drawings and ask why there is a high bond DPC. If you decide to swap DPC's then you are exposing yourself to a big risk. You could also be acting in a dangerous way. If BC come out and find you have swapped out materials then you could be in big trouble. Re read my post. Be safe and ask the question.. it costs nothing. It's OK to ask "silly questions".. what is stupid is not to ask the question at all. I think you are mixing up the different types of NHBC guidance. We used to make cavity trays etc out of DPC (folding it and so on to make a tray) and before that heavy duty bituminous felt. .. but modern brickies are crap at it.. at it so the NHBC are leaning towards factory made trays. The High bond Zedex is more associated with the structural performance of the walls and that is why I'm doing my best to encourage you to just ask question.

For me, in my last life, as a local building contractor I learnt to have a look at who was making the most profit. Business is a learning curve. You get subbies in.. say ICF.. tie them into a contract, learn and if it looks profitable then cut them out. There are no friends in the desert. Profit is sanity, turnover vanity.. especially if you are carrying risk for someone else's turnover that is leveriging that... you can end up being a useful idiot. Not just in the way that the finances work but as soon as they get enough well completed jobs they will ditch the local guy. The pressure to do this will come from above.. the folk that are making the ICF insulation. Now a case in point. Advanced Foudation Technology have got accreditation for their own product. This requires a serious amount of investment. I know about this kind of stuff as I've been involved in developing cold formed steel buildings and the raft foundations they sit on, be these insulated or not. I'll leave it at that for now other than to say I may have been into this for a long time... and spent a lot of time learning about what is cost effective or not.. I've made a few mistakes but that comes with the innovative process. The building trade is brutal. I work for contractors as an SE at times, we trade blows. Sometimes they say to me.. hey Gus I can get an SE for a few hundered less. I say go on then, give them a go on a few jobs.. I'll not get offended.. too old for that. Sometimes they come back..once they realise that others designs are not buildable.. but the ones that don't are probably cutting corners and being unsafe. Yes they will get away with it for a time but God or the tax man will catch up with them. For all I've touched on this before.. insulated rafts are not new. ICF is just permenant insulated shutering. I have serious doubts about the economics of this as there are just not enough contractors about to make it a competetive market. By all means if you want to go ICF, have the funds and it floats you boat then go for it. As a designer / SE advising a young couple with a few beans to rub together then I would look at other options rather than ICF, even if to rule them out. There are folk doing ICF in the North of Scotland.. great until you have an on site issue not least! These type of folk tend to have a large contingency fund.. but if you are a nurse on an average wage it's bollocks. But see in terms of getting paid as a contractor and on time .. the nurse is probably your best bet provided you do what you say you are going to do as as a contractor. If you are a building contractor reading this then don't feel unconfortable about making a profit. Many people work for the NHS like my wife. . some of the contractor profit allows them to go on holiday.. in the public service this comes with the job. But for all.. see when your builder is off on holiday they still need to keep the wheels running..

I'll take that as a feather in my cap if you don't mind?

Hi all. This fire protection thing crops up often on BH. I'm going to pick out some of the folk that often chip in on fire design. Now you could be a designer, a contractor or just someone that has done a lot of self builds. What you see is a lot of is folk saying we did this and that. But if you are a newcomer to the self build or internal alteration / extension market then unless you all then go onto say why you did what you did / or do then it gets even more confusing? I've just copied a bit of an extract from posts. There is nothing wrong in the above or right. It's a best guess on limited info on a building forum. @nod you do this stuff as a day job.. time to step up to the plate design / theory wise? Now there are a lot of folk here commenting as above. What would possibly be more helpful is to say.. we had to do this because of this type of design. I use my own name. I write stuff., over time I've been a member I've said some daft stuff, BH members and the MODS have cut me a lot of slack. yes this is a place where as an SE you can shoot the breeze if off duty. BH is also a place where you can make mistakes and folk will forgive. So in that context folk surely you can go the extra mile and say.. here is why we think we did what we did. in terms of fire protection. In summary, folks who comment on fire protection often. We should be stepping up to the plate and saying.. this might work and here is why. We kind of owe that to new members?