Gus Potter

Radian. To get the best response can you do a sketch, take a photo and upload? Give as much info as you can.. if in doubt about how much info to provide just chuck it all in!

Yes it's a dilemma as to a fair charge, Architects / SE's and so on get a bit of a slagging on BH but it's social media! I've been a member of BH for a couple of years (I think) maybe a bit less so very much a newcomer when compared with the mods. Also, there are some past icons such as Jeremy Harris, still plenty folk that really know their stuff contributing and most importantly new members that are coming on board with new ideas as building technology is developing.. The new members, for me, keeps the site refreshed and the "old folk" on their toes! Another attraction for me is the humour that members come up with.. it's a great site for sharing ideas having fun with like minded folk and exploring ideas. I post stuff about the SE side and the odd bit about the gorund but I learn a lot here and enjoy reading about what folk are doing and so on. It's a good friendly site. Ok punloos.. your into electronics and systems.. but you have a brain and common sense. That is the key. Just ask your questions on BH, don't worry about asking a daft one, BH is not a knowledge test! Often I think that folk worry about getting trolled, using their own name. Some folk crop up here on BH that clearly are professional developers asking for free advice, some are trying to play the planning system.. but on the whole I think many are just honest in their intention.. yes if you are in detailed negotiations to buy a plot then remain anonymous but after that.. ? In summary just keep asking the questions, best to ask rather than build it and wish later you had not asked the question! Oh and have you had a Greggs Steak bake yet! I know the guy who was part of the development team on the steak bake..So THERE! my claim to fame

@LSB It's good to ask questions, that is what BH is about.. sharing views and knowledge. I learn loads here and enjoy reading the posts on ASHP etc and stuff that is just interesting. From time to time I may be wrong..but better to ask questions now rather than after something is built. LSB. An experienced SE, Building Contractor, serial BH self builder will often just look at beam/ rafter sizes and form of structure and go..that looks a "bit tight" lets have a closer look at that. I can see that your 150 x 47 rafters are tightly sized.. based on the one page of calcs you have posted. Getting "it tight is ok".. that is economic design. I use my own name here on BH. I'm not criticizing your SE but I am highlighting that the rafter choice should be justified in your calcs, particularly in terms of your deflection limits and whether the rest of the roof covering and internal linings are compatible with those limits. It's important to recognise that if you have say a steel cladding over a timber joisted roof then while the timbers may be strong enough to carry the loads they may bend (deflect) so much that it over stresses the fixings on the cladding. The cladding supplier will specify what the maximum deflection of the underlying roof is to be. Exceed this and you void your cladding warranty. Sometimes on an lean to extension at a 4.0 m span rafter it's easier to specify a 195 x 45 rafter.. this gives you plenty depth to insulate the roof, run the services and ventilate either by an air gap of by way of a membrane, sarking and almost full depth insulation between the rafters.. much food for thought!

Welcome @un355 You'll find a lot of great info here. If you have never built a house for yourself before then I used to say pre covid that with an Architect, some support, a good builder who will hold you hand a bit and a fair wind you could save some 10% - maybe 15% tops if you do a lot of the admin type of stuff yourself, research deeply and not pay too much for the plot. Admin would include things like; sorting out the services, making the phone calls etc. Now, with the current fluctuations I would reduce that to say 5 - 10% to be on the safe side. That is based on building a like for like house you can buy off the shelf. However, it depends on how you measure affordability. With a self build, even on a limited budget you can get a house that is "bespoke" just for you. Also, building your own home is something special.. it's your own castle and relatively few folk do this in the UK. You get that quite satisfaction, sense of achievement from self building and that has value.

@jfb I have a similar issue that I'll need to face up to this year when I come to do the roof. It may be worth looking on the net as there are some reclamaition yards that provide a reclaimed matching service.

@puntloos"Can you rephrase that last sentence?" Hi puntloos... of course! On reflection I should have chosen a different form of wording, but enthusiasm took over! BH has a great range of members, from folk that are just starting out to serial self builders, professional Contractors, Architects, SE's and other real specialists that really know their subject inside and out. One common trait many have on BH (whether just starting out on you first DIY project or not) is that we spend a lot of time just thinking. I had a recent discussion with a highly experienced Architect (40+ years experience) where we mulled over how much time you "charge for" and how much "brain time" time you really spend on a project. Some folk on BH will for example be sitting having say lunch, a Greggs bakers experience, putting the bins out.. just day to day stuff and presto.. into your head crops up an idea about your build / DIY project, how you solve a problem. This applies to almost everyone including those who make a living from design and construction. This thinking time often does not appear on any invoice / balance / spread sheet. Things can become counter productive when there is a lack of clarity, understanding between the design team and / or the contractor. Most commonly this is precipitated by a lack of effective communication. If you are say a novice self builder then you learn as you go. At some point you may become frustrated that things are not to your absolute satisfaction as you have been learning plenty..and this can start to eat away at you.. thus counter productive or words to that effect?

EW is ΣW (Sigma W) which is the sum of the all the factored load (W is the loads from the ULS column) on the beam. Thus ΣW = sum of total ULS load =0.46 + 0.45 = 0.91 kN/m (kilo Newtons per metre run) * 4.0m (beam length) = 3.64 kN (kilo Newtons) = the factored design load applied to each beam. Zyy Req... Z is called the section modulus and the yy indicates about which axis of the beam the value of Z applies to. The British Standards and Eurocodes use a different axis of notation. Your SE is using the Eurocode here. The letters "req" are short for required. The SE is working out what value of Z (a geometric property) the beam needs to have as a minimum to carry the load. To calculate the Zyy required we use the formula Z req = maximum bending moment / maximum design stress allowed in the timber. The bending moment is shown as m = 1.8 kNm and the design stress is 14.8 N/mm^ (Newtons per mm squared). We need to make the units compatible so to convert kNm (Kilo Newton metres) to Nmm (Newton millimtres) we multiply by 10^6 as below. Thus Zyy req = 1.8 * 10^6 / 14.8 = 121621 mm^3 = 121.6 x 10^3 mm^3 this is the minimum value of Zyy required to carry the load. Next the SE is checking to see if a 150 x 47 timber has a Zyy value greater than the required minimum. Zyy for the proposed timber is calculated by the formula b*d^2 / 6. Beam width = b = 47mm, Beam depth = d =150mm thus Zyy = 47 *150 *150/6 = 176250 mm^3 = ~ 176.3 x 10^3 mm^3 (millimetres cubed) > 121.6 x 10^3 required thus OK. The Iyy is called the second moment of area (units mm^4 ) and you'll probably see this on the next page when the SE checks the deflection.

Lots of great views expressed here. For me the test to apply to your design team is this... Ask them where they see the risk to you in the design. That could be on the Architectural side.. say bespoke materials price fluctuations.., the SE.. where is the risk.. is it in the ground or some where else, the folk that are maybe providing services to the plot. Where they are confident that say the doors, windows, roof will perform in the long term and where they are less sure about long term performance. It might sound a bit odd but a good professional will explain to their Client where the risks lie, inform them and let them make their decision. They will also explain / outline how they are going to save you a fair bit of money that will mitigate their fee maybe make it cost neutral!.. but they won't tell you how until you sign on the line. It 's a case of seeing if they are open on honest about the whole design. You too need to accept that if you want something special you'll probably need to take more risk if you want to keep the cost down. In summary just have an open and honest conversation. If you don't hit it off then find someone else, even if their fee is a little higher, in the grand scheme of things a good designer can save you thousands sometime tens of thousands on a self build. Also remember that designers love working with engaged Clients who communicate with them too! often you'll find that they don't bill you for every hour they work and that when you look at it in the round your shopping about has been fine up till now to enable you to get a feel for the cost but has now become counter productive in the relationship?

Thanks, appreciate your help. Brain fade.. can now see how it shifts the dew point outwards. ta for the heads up.

It's interesting how this is panning out with the pricing and erection of kits. I've been mucking about with this as a contractor and a designer for a good thirty years in Scotland where we embraced TF a bit earlier than down South. Some of the Scottish TF companies have sold out to the big outfits, some truss manufactures also. What I can say is that it is worth a look at getting your local builder / joiner to price to stick build the kit and buy in the trusses. And / or spend a bit more earlier and get your SE to do you a traditional kit with the roof you want, if you need a bit of steel then it's relatively cheep for your local SE / Builder to sort this out for you. Even 30 years ago it was hard to compare like with like from TF suppliers, now the waters are further muddied. Really unless you are a developer / or have a lot of technical knowledge you have no chance at getting like for like costs from the TF folk on a one off build. What you do need to know is what could you build based on stick built with you supplying the insulation and so on, how long will it take and then make the call on what suits you. Then you have a real base line. I often do the panel drawings for the local builders and spec easliy sourced stuff (truss clips / hangers) and rough out the truss design with the key dimensions to make the roof bracing work. You'll need to pay up front for this but I have found that it is often an economical way of doing it in the long run. It can also work for some folk on the cost plan where you don't need to stump up a big deposit for the kit up front.. you buy the timber.. belongs to you then you pay as you go as it gets erected. Also on the "soft side" many self builders change their mind as they go.. stick building can offer more flexibilty to "just change your mind" without the financial penalty.

Good thread this and learning all the time. I have an ex council house two story terrace with cavity brick wall.. which has a howling draft in the cavity. Was contemplating EWI. Problem is that the inner leaf of brickwork holds up the roof and first floor... and at ground floor level there is a 4" x 3.4" inch timber wall plate build into the load bearing brickwork, all be it it is pitch pine. In other words someone thought it would be a great idea to put in a bit of wood instead of a bed of mortar in the inner leaf which is carrying all the load from the house above! So not keen to fill the cavity as the timber could rot and the house settle. @House man check you don't have the same dillema as I before progressing.

@MattB67 Glad you got it sorted! I'm old sckoooool but the old plumbing / hydraulic rules still apply even with modern unvented sytems./ ASHP etc. It looks great having all the pipes level and well clipped, nice to see on an electrical system but on plumbing no. We know we need to get the air out so lets run the pipes on a slope so we can get the air to a place we can easily vent it. Don't do your smaller bore (any pipes if you can) pipes so air, debris can get trapped.. no funny U bends just under the rads say.. run them so that the metal gunk gets picked up by the magnetic filter. Make it easy to flush out the stuff that the magnetic filter won't catch.. it basic stuff and good workmanship. If you are using under floor software to design your loops make sure you check you bend radius is compatible with the pipe you are using! And when you are installing pay particular attentions to the bend radius or you are inviting trouble. Worry less about the pipe spacing as if you choke a loop you will have much more to worry about! If you take care of the basics you'll save yourself a lot of grief later and get the best out of your tecky controls. Take care of the basics and this will allow you to get value out of your high tech controls. For me I would go for the simplest design that you can that is easily maintained by your local heating Enginner. Save your money.. and spend it on insulation or making your house just a great home.. buy some furniture, pots pans etc.

Temp..Yes good /great summary. @LSB Is there another page or two of calcs relating to the roof? I have deduced that the calcs are based on Eurocode 3 rather than BS 5268. I did this by comparing the SLS (serviceability limit state) to the ULS (ultimate limit state) ratio. Your calcs give a ratio of 1.35 and 1.5 for SLS and ULS respectively and that correlates with the Euro Code safety factors. The BS code is different.. I'll leave the explanation out for brevity. Before making any further comment it would be good to see all the calcs relating to the rafters and the cladding on top. A 6" x 2" rafter spanning 4.0m invites interest even at 400mm centres then you have the insulation.. closer centre rafters the more bridging effect.. sometimes the lightest structural members can be counter productive? I can see an alpha factor... 16.0mm Assuming this is some kind of deflection limit then BS 5268 recommends a limit of span *0.003 = 12.0mm but the Eurocodes allow for the limits to be agreed to some extent between the Client and Engineer... they cut you a bit more slack.. allow you to innovate. I'm interested to see the if the rest of the calcs take into account the deflection limits set by the metal cladding provider and the internal lining provider.. say Gyproc? While the roof may not collapse it may bend so much that it tears the cladding fixings and causes cracking in the ceiling. If you are going to stretch the deflection limits as an SE you should be pointing this out to your Client and let them decide what level of risk they want to take on. Have you got a good builder who has said.. mmm, these rafters look a bit small?

Sorry for the OT post but maybe you have a rebate you can work with. When you have old solid walls it's a challenge. Your starting point here is look at how the wall is constructed. In the late 1600's the weighted sash and case window caught on for houses but this was high end stuff at the time. Have seen some steadings that have sash and case but the steadings were subsiduary to the main house so some Lairds were not that keen to share the luxury with their "workforce". There are steadings ( folk lived in part of them) and buildings for housing animals (barns / byres ). Sometimes you just have no rebate especially if the wall is 14" instead of 20" thick. The key here is that to fit a sash and case window they created a good rebate behind the rybats and lintel. The rybat is the stone up the sides of the window often looks like a key effect from the outside. Now with modern windows (even a sash and case window) you have space here to be innovative. Modern sash and case look alike windows are often fitted with spiral balances instead of pulleys and weights leaving you room to play with to get some insulation behind the window frame and up to / against the rebate. You do need some discrete fixings which act as a thermal bridge but.. you can't have all the cake..

Welcome Ruth. Great place to build. You'll get plenty help and friendly advice on BH. All the best with the project.

Speced this tank on a new build job about 2 years ago. No adverse reports so far. https://www.wte-ltd.co.uk/pureflo_sewage_plant.html It's a bio digester, no underground moving parts. Key drivers were; 1/ 4 bed house with substancial principle living space but Client is abroad for a number of months only a cleaner in from time to time. 2/ When Client is back only two of them living in the house but from time to time have full occupancy with guests, two dishwashers running etc. 3/ That it has a CE approval which ties in with the regs and design codes in Scotland. In summary was looking for a tank that would work based on variable flows and loads. Much like a holiday home. In reality how they perform is based on how you look after them. Some folk that take a holiday let take their own bleach and chuck it down the bog! some put other items that don't bode well for anything "sewage". In an ideal world for the self builder who is using the house on an irregular basis / or with variable flows and nutrient loads then some extra control over the air blower would be helpful. Maybe like the app you have on your phone for controlling the heating. A few days before you go away you turn down the blower so that you keep plenty live culture ticking over with the odd boost to clear the pipes. Then a couple of days before you come home you crank it up a bit so its all ready to receive your homecoming gifts. Hopefully someone will make this technology readily available.

Have you been "at rest" after your days away or doing something else? Apparently the human body "at rest" produces around 0.1 kWh but this can increase significantly when active. I'll stand corrected of course.

Why did you knock the old house down before embarking on this journey?

Onoff. The steel fabrication is done outside. All you are doing is making up some bespoke truss shoes out of 10 / 12mm flat bar.. well within your skill set.

Got to the age where you dabble in all sorts, realised there are folk that have forgotton more than you know, hence enjoy being on build hub, every day is a school day here for me. Keep up with the research Zak.

Yes the raft with a void is an option not least as it provides a service space under the floor. Have done some jobs this way. On the technical side if you find a ground bearing raft is loading up the ground just a little too much then the weight of muck you dig out to create a void reduces the loading on the soil and bingo! it all works out.

Hi Zak S. Yes that looks pretty soft right enough at certain depths. Looking at the cores the ones to the right seem to be from the surface, the left ones in the photo from greater depth? The shallower cores look like there is maybe a stiffer crust with soft clay below and that the bungalow founds are using this crust to spread the load out before it reaches the softer clays... The folk that designed the founds for the bungalow may have taken advantage of this crust. I would still expore the raft first. If the water table is high and not likely to drop then the soft clay can't shrink as it will always be submerged. It also can't go anywhere.. it is confined at depth. Once you go down a bit the pressures in the ground from a raft are often found to be very modest so even a soft clay can carry a surprising amount of load with acceptable settlement.

Hi Onoff. Will this work as a concept in terms of space and fit up. You have a purlin, binder below with a couple of soldier studs. Introduce a couple of diagonal braces from the purlin ends down to the middle soldier at binder level. Plate up the joints each side with marine ply screwed and glued with say Cascamite structural glue. Now you have created a girder truss. Put in a ridge beam to prevent the ridge from dropping and causing potential roof spread. Now you can remove the internal diagonals. You can beef up the floor with steel box section underslung from the binder if need be. Where the girder meets the stack you can support the ends of the girders by fabricating an upside down triangle. At the top weld on ledger pieces that recess into the brick at the sides of the chimney. For good measure fix the ends of the girder and steel triangle so it can't move away from the brick or sideways. Deploy similar tactics at the other end by creating a shoe with a ledger turned into the blockwork.

As @epsilonGreedy says have you consulted with someone who knows a little about the ground? Hope the following gives you some food for thought. By all accounts the existing bungalow is sitting on competant ground. The good news is that for many domestic houses clay can be a good medium to build off. One early thing to do is to identify the type of clay you have. Starting with the basics. Have a look at where you live and look at how far the last ice age extended. Ice is heavy and has often pre compressed the clay we encounter today. We call this an over consolidated clay and this can carry a good bit of load without excessive settlement. You may have this under your bungalow. Dig a hole down to foundation level and have a look at the clay. Is it like pottery clay that you can easily mould and press your thumb into with little effort? or is it a mixture of different sized particles and harder to indent and mould? Grab a copy of the "Structural Engineers Hand Book" F. Cobb and you find info on how to relate this to the soil bearing capacity. You'll find same info else where also. Spend some time on learning about clays and you are on your way to saving money! The next step is to ask.. ok we want to put a heavier structure on roughly the same foot print. Can we just add more strip foundations similar to what we have and put something under the ground floor that will spread the higher loads over more strips? You can back calculate (on the back of a fag packet) the loads the bungalow is imposing on the ground and compare this with the weight of the extra storeys. There comes a point where you need to many strips of founds. Practically they become so difficult to set out on site, dig with a machine, clear away the excavated soil and pour that you abondon the idea. Technically the bulbs of pressure under the strips start to interact and you are faced with the law of diminishing return anyway. The next stage is to say.. what if we just join the strips together.. and make a raft? Rafts are a different animal but they work a bit like concrete beams with steel to carry the tension loads, the concrete takes the compression. If you have plenty depth to play with, often occurs with rafts compared with say a concrete beam holding up a floor where depth is a factor, then you explore different thickness' of slab. This is partly driven by the soil and if you have insulated under the slab. The secret here is to find a slab thickness that uses the least steel and just as importantly to make the steel common sizes, easy to source, easily read drawings and quick to fix. This widens the field when finding a contractor.. go for the simple stupid! It's easier to pour an extra 50 - 75mm of concrete into a found than make / use more steel with complex bends and laps say. Putting insulation under a slab is not difficult provided you keep it simple. I would try if you can to get to grips with this. Then if you can't make it work start to look at other options. What you do learn will serve you well even if you find the strips and rafts are not suitable.

Hello Sole. Appreciate your perspective and experience. I have enjoyed reading your posts. One but not least was how you explained how you aim to submit a comprehensive warrant / planning submission. I commend you. I hope praise does not offend. Your right though. I think you may deal with Argyll and Bute Council more often than not? Have dabbled in this area on an off over the years. I can't recollect many happy times when submitting calcs. It's to do with the funding I think mostly. Some of my family live on Tiree and thus have experience with the warrant / planning process so I have a bit of local knowledge. I did a SE type job for a developement at Glensanda Quarry a few years back and some other commercial stuff round about Lochgilphead, all through the calc route. For me in the Glasgow / Lanarkshires of Scotland belt my old school submitting calcs approach has worked fine.. so far. Like you I aim to make a quality submission. I actually get very few written queries back from BC, maybe less than five a year relating to the actual calcs. I get a few phone calls from other SE's as they are often just curious about some of my innovations. On the whole though a well presented and correct calc pack sails through. Where you get stuck is that some councils have cut their funding of BC and paid off their Engineers. This then leaves a small group of SER Engineers controlling the domestic extension / self build / renovation market. Yes you get a discount on your warrant fee. I easily mitigate this by including extra information on my drawings which at the end of the day saves many a Client far more than the discount. To finish. Yesterday I had a BC officer call me to say that as I had submitted calcs the warrant would take 8 weeks longer. I have worked with him in the past so know him. He said.. Gus I can follow your calcs and they look fine to me but I am no longer able to sign off so need to send them for external checking. I said.. that is fine as I have told my Client that as I don't offer the SER certificate it will take longer to get the warrant. Funnily I have had some warrants with calcs through faster than the SER route so make what you want of that! Hope this gives folk applying for a warrant in Scotland some food for thought.