Gus Potter

Does make you wonder if stick building is a safe way, good for the local economy at the moment.. You buy the material as you go, support your local joiner etc to build the kit and so on? After all, if you go for a mid range kit supplier then they too may not have the clout to get the insulation etc on time, where as your local guy can pick up a few sheets just to keep you on track.

SER certificates in Scotland. Here is some food for thought. Firstly you don't need an SER certificate to get a building warrant in Scotland even if there is structural work involved. You can submit structural calculations along with your normal building warrant drawings. The argument is made that if you submit calculations (traditional method) it will cause a significant delay or it just can't be done. This is not the case. In fact, if you have a designer who regularly deals with Scotland BC then often it makes little difference. You do get a discount on the warrant fee but this is often offset by the level of information that is provided by the traditional route to get a warrant. To explain. A lot of self builder's don't employ their designer to supervise / manage the contract so a good comprehensive set of warrant drawings with a well written specification can really protect you at the build stage. This is one example of where you recoupe your perceived savings with an SER certificate. An SER registered Engineer follows a checking / audit process. The calculations for say a raft foundation are prepared by one company, the kit is designed by another and so on. All these companies often have in house designers and this need to be paid for. The SER Engineer Ltd checks to ensure that for example the building is stable. Another function of the SER (Ltd) scheme is to check that all the elements of the design are coordinated so that the design is safe. Now you have lots of cooks! Alternatively, you can employ someone who is not a member of the SER Ltd company (for example an Engineer based in Wales, France, England, even USA etc) submit calculations to Buildings control who will then check them. Scotland BC have no commercial interest and their role is primarily to ensure your safety and that of the public. In terms of overall cost it's worth considering getting someone who can design your kit, produce the panel drawings, design your insulated raft, the other bits and coordinate this into a comprehensive work package. That will give you the best chance of a result without a cost overun and trying to herd lots of individual designers, checkers.. like chasing cats. You will end up with one point of contact on tap, on your side, and that is where you will start to make savings. Oh, and Scottish Water.. yes this can take a bit of time, you need to do a bit of work now and again as if you are connecting to, or building over one of their assets. It's fair for them to make sure you are not doing something that will impact on them, but they are fair, reasonable and helpful.

That's some good numbers Nod. The thing is that you have a lots of experience / knowledge and know your way about. When land values are on the rapid increase (or you get a repossession, contaminated site, or overcome any burdens) it's not so hard to make a good return as the mistakes you make on the actual build get kind of lost. But what if you live in an area where you don't have that benefit. Then when you get your build cost wrong there is no cushion. To encourage all is there not merit in starting when you don't have the experience at the 15% .. yes that's tax free too and work from there, if you get it for less then that's a bonus. If you do another and gain experience you can make the kind of savings / profit that Nod mentions.

Just to chip in. Christine. A good few years ago in Lanarkshire (Biggar area etc) a good check to do as a contrator was this, at the last minute before you send out the price. I still use this as a rough check, it's an old rule of thumb to some extent. Lots of folk work on a price per square metre.. but is that internal floor area, external foot print area (includes the wall thickness) or actual floor area (minus the internal wall thickness).. very confusing. As a rule of thumb for an average house a check you do as a contractor on an average self build is to say the labour cost is about a third of the cost of the build. You cross check this against the square metre price. The key thing is that it's easy to make a mistake and this can put you out of business. So if the two values of the sq m price and the labour / material ratio look off then you need to sleep on it and look again in the morning. It does not matter too much at what point you add in the profit margin. Once you have that ( the basics) you add in the high end kitchen, bespoke stuff, ground conditions etc. Then check again. For the first time / average self builder I found that overall over a period of time that the average saving for self building and project managing your self was about 15% compared with buying off the shelf. Buy that I mean that you buy a plot and get a builder to do the lot... Yes, I'm using a broad brush approach. The same rule applies if you are trying to get a handle on what your return will be. If you are a more experienced self builder then you can increase the return.. or as we are normal folk.. you spend a bit more on the stuff you like? I think I can see where you are going with this Christine in that the land value varies so much depending on location and so on and see why you are looking to strip that out to get a like for like comparison.

Didn't think of that Onoff. Baw is burst at this end.

Looks like you are on the right track. All the best with the project.

Aye.. good cat! What about strap with 50 x 25 treated on a strip of dpm. Use stainless steel screws. Fix a bit of breathable membrane to the strapping. 100 x 12 -22 thick larch or something light shade that will weather a bit but vertically orientated to give it some appearance of height.. nothing needing paint etc. Leave a gap between the boards of say 10 -15mm, a gap at the bottom and a gap at the top so it all breathes. The membrane is to hide the bricks behind so you can't see them through the gap. Now if you want to earn some extra points you can fix shelves etc to the timbers... and we all love shelves etc don't we !

Well done Osmononame wading through the fire regs. As a word of encouragement I see you're in South Lanarkshire and BC will help you with this if you approach matters in a reasonable way. What you have here is akin to a three storey town house so nothing out the ordinary in terms of fire design. Alternatively, think about the case where you have a two storey house and you want to convert the attic.. thus three storeys, again nothing off the scale. What is worth while doing is to get an SE on board as soon as you can. You will need to pay for this but it will be worth the expense (you'll probably need to pay later anyway) and it will more often than not lead to an over all saving without compromising on the design. To make the enclosure you also need to protect the structure that holds the enclosure in place.. hence the SE early. I would explore the protected enclosure route first before a sprinkler system, not least as you have the ongoing maintenance and testing, mains pressure or loading (weight) from a supply tank and so on.. you can get some pretty acceptable looking fire doors etc these days. All the best.

DavidC.. "Architect has asked for payment in full for work on compilation of Scottish building warrant (equivalent of English building regs) before starting work it. Am I right to consider this dubiously ? " Sounds reasonable. Essentially you are splitting up the "warrant" design phase from the tender / construction detail / construction phase which are separate packages. Once the warrant submission is made then the majority of the regulatory design phase is complete. Once the warrant application is made it's not uncommon for BC to come back with a few queries. Sometimes the queries you get back are already addressed on the submitted drawings, SE calculations etc. Other times it may be a case of clarification of a few points. Some areas to consider are: 1/ BC officers are just like all of us and may not pick up first time on all of the information submitted so will raise a query. Some will be learning / training so it's well worth while bearing this in mind. 2/ The submission may contain input from different designers; the Architect, SE, specialist truss manufacturer, basement designer etc and some of this information may conflict. 3/ An application may be lacking important detail i.e too much cutting and pasting of standard details etc. I would normally expect payment to be made once the warrant application is ready to be submitted on the understanding that the queries will be dealt with in a timely fashion. Jilly - yes good point. A big issue especially given COVID is that if the council take months to process a good solid application then the designer is out of pocket through no fault of their own. If you have a concern then perhaps hold back a 5% retention. However, have a chat with you designer first as this is a matter of professional trust / competence .. so maybe a bit of diplomacy? As an overview a good experienced designer should have sufficient soft skills to be able to lead domestic (inexperienced) clients by the hand without compromising on the creative side so that the points raised above are dealt with before they become an issue. Fee transparency is one vital part of this as it encourages an equitable arrangement and develops trust. At the end of the day this should be an enjoyable and rewarding process for all involved.. it can be done and lead to a saving at the end of the day.

Ta onoff. Not enough hours in the day.. if you get a chance go and post how you got on with that.

Good point Mike. Looks like you are making good progress. A 150 thick PIR can get you on the ball park and if you have "wool etc" it needs to be thick, as you say. It's hard to get a handle on the best way to go about it. For all, I'm being simplistic, but take Scotland / Wales rural parts of England. Here you can often get a bigger plot for not much more. But where plot sizes are limited and the land costs (Mike - Kent where you are) a lot you may want to minimise the wall thickness and thus increase the internal floor area of both the house and the garden. You can still get a good warm house without loosing too much of the valuable floor and garden area. In summary, there are lots of ways to achieve what you want. You may just want a warm house with low biils.. You may want to have a carbon neutral house.. if you really are serious about that then look at for example the carbon cost of the concrete and so on, how your solar panels are made, what it costs to produce the material/ lots of this stuff is shipped from the other side of the world to make the panels, then the removal of all of that at end of life..the fuel / crushing and transport invoved in that and so on. It's an awful lot to think about. My view is to recognise that you want to build a warm house / extension, do the best you can for the environment, be pragmatic and do the best you can given the available budget you have. Mike has made some great posts that are well worth a brouse.

I think I have blasphemed more than once onoff! It could have been worse, I could have mentioned "screwfix spray" ! and what then. Just a thought, I mentioned conservation work and stainless steel.. is that one of my blasphemes? Your right about the spray. How are you finding the Zinga any good?

For all. In a case like this if you get really stuck then you can sometimes use a thick steel plate, 40 - 50mm. You may be able to pick up an offcut from a fabricator ect as this can be a common heavy industrial column base plate size. To do it all correctly then you want to protect it, if it rusts heavily it can swell and lift stuff so galvanising is one way to go. Alternatively if you're happy then clean the steel, spray it to death with galvanising spray and carry on. Russel makes a good point. Have a look at what is above, point loads and so on. If the load above is spread out evenly and you have a good few courses of brick above then the load (conservatively) spreads out at 60 deg, you'll often see 45 deg mentioned. This trick can come in handy when doing renovations / conservation work, sometimes you'll use stainless steel. I'll try this but here is a link to let you see that plates this thick are standard @ 100mm wide so you may get them at a sensible price. https://www.parkersteel.co.uk/Matrix/10/Steel-Flat-Bar

Yes great spot. Every council is a bit different, you may get the odd delay, frustrated now and again, but you'll get past that, it will be worth it. Have you considered "stick building" it? Here you get a good competant local joiner to cut the timbers and make the frame on site and this opens up opportunities to use local trades persons, get to know people and make new friends. You may also like the savings you might make. There is no barrier to having a passive slab, much of passive slab design is borrowed and adapted from industial building design. The difference is that you would use a ~ 150mm thick stud for the walls and pack that with a high quality insulation. If you need more then you can pack out the wall studs. On top of that you line the lot with an insulated plasterboard to prevent / mitigate cold bridging and what we call ghosting. You can create a gap between the insulated plasterboard and the insulation in the studs and this make an ideal service void. If you cut into a sips you can loose some of the structural integrity. So perhaps not so easy to change / alter things later on. As an over view. If you want a timber frame (TF) a common approach is to go to a TF supplier. They design the frame / roof to carry the loads etc on their software which genreates a lot of drawings for production in the factory. You'll need some input from a Structural Engineer any way. For a bit extra they (SE) will produce the panels drawings, just as a TF manufacture does. You give these to the local joiner and these drawings tell them what lengths of timber are needed in each panel, lintel postions, how to nail them together and so on. All they need to do is follow the drawings. Also, if the brickie ect has got the found and underbuilding a bit off the square say (it happens) , it's much easier to resolve these type of problems as you can often adapt a stick built frame more easily. It's quite common to do it this way. What you do when you are preparing panel drawings is to look at the type of contractor (generates a bit of competition on price?) the location, material procurement (do you need a crane or do you make the panels smaller so a couple of folk can stand them up?) and design for buildability as this can save much more than any panel drawing fee you may incur. All the best, you'll love it!

Hello all. CE Marking and Structural steel holding your house up! But first. Great points all, much appreciated (onoff - both posts were spot on) As an aside, be encouraged. The prices I used were based on Glasgow area, rather than say Linconshire. If you live next to Scunthorpe then you may well get a better price. Also, if you have connections to the trade this helps too. We have some pretty big fabricators up in Scotland so if you are near one of them, again more promising price wise. Currently (don't know how leaving the EU will impact) it is a legal requirement that all structural steel must be CE marked and thus in compliance with the BS EN 1090 series of codes. These codes are partly to do with welding quality, painting etc. It has a lot of benefits, but also some negatives! One of the things that attracts me to this is that you have more control (well you hope so) over the provenance of supply.. seen some bad Chinese steel and forged mill certificates now and again. When you specify structural steel you want to include a reference to these codes and CE marking. If you are designing to the Eurocodes / British Standards for example then you need to be sure that the strength / properties of the steel and welding etc match your design assumptions. All a bit dry, but if you are say getting the house signed off by a warranty provider then they too will want to know that the steelwork that is actually supplied to the site matches the design that they are covering. If it turns out later that it does not then what happens?

Hope this helps. For NewToAllOfThis. Lots of fabricators initial estimated prices are based on a price per tonne. If you are buying say 70 tonnes the price tends to be less. If you want a small amount for a one off job the price per tonne goes up. This is partly to do with the sequencing, taking off the quantities from standard drawings, programming, the cutting and drilling line and so on. The 203 x 203 x 46 are what we call a universal column section, UC's, you also often see mention of UB's these are more of an I shape where as UC's are more squat. For NewTo.. You have 70m of UC's @ 46kg weight per metre = 70 x 46 / 1000 = ~ 3.2 tonnes. Take roughly a mid range domestic one off figure of £2200 per tonne. If you get it for less then you can spend the saving on something else! For a smallish domestic job budget on .. 3.2 tonnes x £ 2200 per tonne = £ 7040. For this you get the steelwork with the connections, painting and so on comes next. Often some connections will be a bit more complicated and need heavier, different types of welds and so on, the fabricators know this when they are estimating. Some connections will be very simple, some not, but on balance it often all evens out for standard stuff. Next you need to prepare the surface of the steel. This needs to be done whether you are galvanising or painting it..neither will adhere properly if this is not done. Preparation of the surface is also controlled, often you see a term, shot blast to grade SA2.5.. this is to do with the amount of cleaning, preparation. The steel can lie about in a yard for a while and get a bit of surface rust, it also has what is called "mill scale" which roughly is loose material on the surface due to the rolling process. The shot blasting cleans this off. Here things start to diverge a bit. Some fabricators use the surface area of the section to work out how much paint they need. A 203 x 203 x 46 UC has a surface area of 1.19 m sq /per metre length. So 70m is 70m x1.19 ~ 84m sq. The paint varies a lot in price and the thickness is also important. But take the shot blasting and paint cost as say £ 10 / sq m thus you add £ 840.00 to the 7040 = 7880.00. Work that back now to a painted price per tonne.. 7880 / 3.2 = £ 2462.00 per tonne. All the figures I give are ex vat. The galvanizing is worked out in a slightly different way. Here the galvanizers often work on just a price per tonne but again it's partly due to the section shape / area. The cost of the zinc moves about a fair bit. Take a figure of £ 330.00 per tonne for galvanising. 330 x 3.2 = £1056 + 7040 = £ 8096 / 3.2 = £2530.00 per tonne Not much difference.. but much depends on the length of the section. One of the keys here is that if you have a long section then it needs a long galvanizing bath and there are fewer galvanizers with "long baths" so the price varies accordingly especially if it is a smallish order. If your section is too long then the galvanizer needs to double dip the section, this takes time and uses more zinc. However, there is often an extra transportation cost as the fabricator needs to fabricate the sections send them for galvanising and return back to their yard. So this needs to be added to the price too and these handling etc features can add quite a bit to the cost. What you can do is to introduce splices into the sections and thus make them shorter, yes there is an extra connection cost but this is offset by the range of galvanizers you can approach so more competition on price. Another benefit for the self / extension builder is that often you can collect the steel on say a trailer from the works , thus saving on the costs of a large wagon. Generally galvanising is more expensive than standard red oxide type painting but it tends to last longer. However if the steel is not exposed to the weather then painting is often sufficient. Lastly you may find that your Enginner has specified a grade of steel that is suitable for external use. The steel specification can vary when the steel is external and exposed to lower temperature (steel becomes more brittle in lower temperatures) than internal steel. This again can impact on the cost of the steel.

Hello all. Bri44, I feel for you, it's torture when stuff like this happens. Unfortunately, I see this type of problem more often than I wish. I hope the following will help crystalise your thought process. For all, when faced with a problem it can help to rule things out if you don't know what to do next. This leaves you with a short list of your options and this can make the decision making process easier. A lot of folk buy a property in good faith, if there is no trust then life is pretty poor for all of us. I'll leave out quality of workmanship / competency of design, detailing and so on here as others with more specific knowledge and experience have touched on this already. Suffice to say some of the briefs realting to build problems (which relate to warranties) I have seen are frankly unbelievable, a bit like Harry Potter... That is fun this is not. It does not reflect well on the building industry. I'll run through the previous posts and chip in my thoughts. Bri44.. will a developer buy back a house? .. yes they will. I have seen this offer tabled.. Mr Punter.. good point.. in fairness it's not always true that small builders won't step up to the plate when they get it wrong. In terms of quality of work and so on the big builders can be just as bad as small ones. Don't forget that often a big builder will perhaps get a better offer from say a timber frame manufacturer half way through a development. Someone will make a commercial decision but often no one will make sure the cheaper frame is still compatible with say the founds and the original design.. It’s often a case of "well I'm only paid from the neck down"... not my problem. Russell... I would council not to appoint a Solicitor at this stage. That is actually what I often think they want you to do. I may be that they just want to shift something onto next year’s financial balance sheet! If you get a solicitor it will cost you. For the warranty provider/ big builder it essentially becomes some sort of accountancy problem until they actually need to cough up? At the top end, remember that the warranty providers are an insurance company. The NHBC started out in the public interest when the government set out to improve the housing stock after the war.. Whether they are still doing so and by how much is for them to answer. My experience with the NHBC differs from their original statutory brief and I'm happy to stand by the statement I have just made. In summary I often form the view that this enables them to wage a war of attrition, use their financial clout etc and this can head off having to settle for large amounts... they ( NHBC and Developers etc) know that a lot of people will give up or can't afford to seek professional advice. This is a way of mitigating the number of claims that need to be paid in full if at all. Mike makes some good points. As I roughed out earlier, small cracks are hard to diagnose. If you can be sure that the movement does not pose a structural / safety risk then you maybe want to just look at ways of managing the small cracks that will appear from time to time as the building moves about, over the seasons say. The are a good few expert folk on this site that know about rendering systems and so on so hopefully they will chip in with some advice on how you can apply render systems that can cope with a bit of movement. Declan also make good practical points.. all very well on paper and sitting in an office but practical experience counts for a lot and is intrinsic to any build. Experience counts! Mike Graham.. Mike makes good salient points, material behavoir and the importance of looking after the materials before installation. Onoff.. good forensic question as expected! No mucking about here! Bassanclan touches on the NHBC...I've said enough for now and await developments. Turning back to BRI44. Bri. Advice I often give is once you get to this stage where you have battled away, got a bit of a result but no conclusion is to seek out someone who can take the time to undestand your particular circumstances. As a word of encouragement the email chain in this type of case can extend to more than a thousand so you're not alone. If you can find and SE for eaxmple who has some experience with warranty providers, knows how they operate and can get under the bonnet then your are off to a good start. I have found that once you drill down, cut through all the periferal sales and quality guff and really poke them on the technical and structural safety side of things they start to engage. They may be great on damp proof membranes but generally they are not so strong and also less resourced else where.. this can help bring them to the table. It's not a technical thing per say. You use the technical side to appeal to their bottom line and it is this that get results. It make them nervous as some.. don't have a well resourced solid structural / technical side. The argument I make is that this is going to cost you a lot more than you think! So get serious and start negotiating as adults. I'll caveat that by saying that there are some that don't take this commercial and cynical view. I don't want to prod too many bears at the one time. If you want to do a bit of research look at where most of the warranty providers funds come from and draw your conclusions from that. Lastly Bri, although I laid in a bit much of this is to do with people skills. There are say SE's, Surveyors, Contractors and so on that have seen it all... or most of it They are old salts at dealing with this. Often what you may need is just half a day to sit down with them. They will charge you for their advice and for listening to you but for a relatively small fee they could unlock the door. I find that sometimes when dealing with builders, developers and warranty providers that rather than confronting a problem head on and playing against their strengths it's easier to just back door them.. cynical yes.. but hey it was them that let you down so what do they expect.. no friends in the desert I think is the expression.

Cracking crops up on a petty regular basis and it can cause concern to say the least when it's your home. It is a pretty complex subject but here is an attempt at a lightheated over view of some of the in's and outs. I have caveated some stuff here and there. Looking at the photo (in insolation) that Bri44 posted the crack is relatively small in nature. If you can stick your finger in a crack then you should take action and seek advice. If you notice the crack is getting slowly wider or translating (moving sideways say) over perhaps a few months then think about getting some advice but don't leave it, if days or less then act quickly and take professional advice. You need to be a bit like Columbo here. Strangely, small cracks are often harder to diagnose than big ones. There may be only one or two cracks or there may be lots of small hairline cracks. Often when you have say one big crack the causes are more easily indentified. The stating point is to recognise that houses move all the time. The materials they are constructed from tend to be different - timber - steel - concrete - brick etc and all these materials age and behave in different ways. They expand and contract differently when the temperature goes up or down for example. The house sits on the ground and this too moves about. Bri44 has a clay soil. Clay behaves in a different way from say sandy / gravel type soils. One key difference is that they can shrink and swell depending on how much water they have in them (moisture content). With that in mind some of the things you look at are: Is the site level? Are the founds at the same or different depths - If you have a dry summer then the upper layers of clay tend to be drier than the ones below so they shink by different amounts. Thus the foundations go up and down by different amounts and this leads to differential movement.. which can cause cracking. Do you have any trees or hedges near the house. When in leaf the vegitation sucks the water out the clay soil and causes it to shrink. If you have cut down a tree then it can take a number of years for the soil to read adjust and it will move a bit (usually swell) when it does so. If you have a leaking drain then it can cause the clay to swell locally and this can lift the foundation up while the rest is staying still or shrinking or moving down under perhaps dry summer conditions. Again, if you have installed a new drain that is deep with say pea gravel round it you can sometimes drain the clay and this can cause it to shrink. There are a multitude of factors to consider so it's not always easy. If you have a house with very deep foundations at one end and shallow ones at the other and with a lot of infilled ground round the house at the deep end then as the fill settles over time it can drag down the walls a bit, add load to the founds via the dragging on the walls and they settle a bit more. Often if you are designing piles with made ground you'll examine this effect closely. Moving up to the superstructure. The type and shape of the cracks can tell you a bit. You have a look at where any movement joints are placed in the walls and if they are in the right location. Has the building been altered? If you have knocked out a load bearing wall and put in a beam you often change the way the founds are loaded and this too can result in a bit of cracking. Importantly you want to look at the rest of the house. Are the roof tiles out of alignment. Go inside the attic and look here. Small movements at ground level can be amplified up at roof level so are sometimes easier to spot. Are the doors and windows working ok.. have you notice they are starting to jamb in places? Has the house been left unheated or over heated... are the floors level. Is there other development going on, under or near your house.. The above is just a flavour of what you want to look at. Once you gather all this information you hope that you'll have some idea as to the causes. Then you work out if you need to do anything or just monitor the situation and see if things settle down. More often than not for small cracks it a case of keep an eye on it. You can use "tell tales" or precise levelling techniques to montor movement before you resort to drastic measures. For the curious there is a good document published by the BRE (BRE251) which gives some good guidance and goes some way towards categorising the size and type of cracks. Lastly, Columbo always solves even the most complex of cases. But with small cracks you may just end up with a short list of suspects but no arrest and subsequent conviction.

Absolutely agree Nick. Flitch beams seemed to be falling out of fashion for a bit... like flares (the trousers) but they are back in fashion now! This is a great friendly site for passing on / picking up tacit knowledge and so on.

Bang on Nick about the trim out for the roof lights. As you say, it makes the detailing / buildability of the roof lights easier. Gus

For all. Here is an old rule of thumb which I have applied to Ian's case. This can be used just to get you a feel for how deep a flat roof joist needs to be. Appolgies for mixing units. Ian.. what about this? if you have enough support and it's a warm roof (insulation on top roughly and thus no ventilation required to the joist void) then run a beam within the roof depth to bridge the bit of the kitchen that juts out. Now you have 26 joists @ 4.4m and 7 @ 1.6m. The beam needs to span roughly 7 x 400 mm = 2.8m so you should manage to get something within the roof joist depth that does not result in the beam downstanding from the ceiling. Based on an actual joist metric thickness of 47mm and a spacing of 600mm (2 feet ) then.. Ian has a 4.4m span domestic roof ~ 14.4 feet. Take the span in feet and divide by two.. 14.4 / 2 = 7.2 inches. Add one inch = 7.2 + 1 = 8.2 inches. Now convert to metric 8.2 x 25.4 = 208mm. Take the next metric size up for a C graded timber = 220mm This is the ball park depth you need for the joists. A common length for a bit of structural timber is 4.8m so it's off the shelf = cheeper than say a longer offered length of 6.1m as they generally need to be cut from bigger trees and so on. You may be able to form the transfer beam from say three 220 x 47 timbers, if that is not enough then you can introduce what is called a flitch beam (two bits of timber with a steel plate between & all bolted together) or if that is still not enough! then a small steel beam. The attraction of this is that all the 4.4m joists will bend and sag over time by roughly the same amount. You are working with solid timbers which a lot of local builders / diy folk are more comfortable with. If you cut a joist too short, nip to the mechants and buy another off the shelf. The connections between the timbers and transfer beam can be done with off the shelf timber hangers too. If a steel beam.. you bolt timbers to the steel I beam web and fix your hangers to these, this avoids trying to fix the joists to the steel directly. Now you have a rough joist size and the concept you can start fine tuning. Watch out for other "non standard" types of load such as snow drifting off a higher roof and so on. You can fine tune stuff by changing the timber grade, closing up the spacing of the joists and so on. Lastly the same old rule of thumb applies to solid joist floors with normal domestic loading at concept design stage but generally you add 2 inches to the depth instead of one. This is an old rule so now we also check explicitly for floor vibration and so on. Once you weigh all this up, the skills of the bulder, practicality, material procurement and so on you may find that solid timbers are the most economic / least risk option? All the best Gus

Hobbiniho makes some good points. I’ll weave some other TF stuff in as I go which I hope helps all. In reverse order. Yes, when you look at the configuration of the roof it appears to be fairly standard. Generally, truss designers start out with 600mm spacing as this fits with the spanning capability of standard tile battens and so on. You can then close the spacing / double up if need be when you start to get stuck, say where you have extra localised loads – dormers etc. What you try and avoid is to start changing the depth of the members as this starts for example to cause problems with the alignment of the roof bracing. If you have a good height and want to convert the attic later and the ceiling joists / rafters are different depths then how do you floor / line it out easily? A lot of TF houses throughout the UK don’t have sarking or boarding on the roof. This sarking/ boarding stiffens the roof and often stops people from falling though during construction and maintenance. An SE will often take advantage of this stiffening (called diaphragm action) to shift horizontal loads (loads cause by the wind for example) to where they are more easily dealt with. When you go in the loft you may just see a vapour / moisture control layer and you can feel the tile battens and so on through this. If so, you should see more diagonal type timbers bracing the roof. In old money you’ll often see roofs in Scotland say with rafter spacing of 18” (~458mm).. this keeps the roof member sizes down a bit and lets you use a thinner sarking board. If you are slating onto sarking you don’t want “bouncy” sarking as it’s really difficult to drive the slate nail to just the right depth to keep the slates tight. The closer truss spacing can help here. In other words you need to look at things holistically and not just the trusses in isolation. As a general point. If you are building a single storey extension on a house that has big roof you need to think about snow drift loading. The snow can blow off the main roof and overload the extension roof below. It can drive against any wall above the extension roof and fall back. Snow drifts can be heavy. Another great example is where you have an large span, high eaves height agricultural shed..lots of snow available to pile up on a lower lean to roof. Glenboy posted a couple of drawings. There may well be others that show more detail. While some features of Glenboys drawings may look a bit odd under scrutiny they look to me like concept / early stage provisional drawings. Often a designer will just add rough stuff or notes when a Client is just trying to get a budget price for the works. What I think these drawings are doing is to say to the builder... We need some kind of beam in here, we need some trusses and so on and this is the size of the thing... so give us a rough price for that. The detailed design comes later in the process. In terms of the timbers stacked vertically. I would like to see the rest of the end detail and the TF panel drawings before exploring further. For all. Every house is different and has it’s nuances. Sometimes, where you are tight for height for example you need to go back to first principles of design and this can throw up some less commonly seen details.

Justin. What a project! Roughly where is it? How far north, west or east? What are you doing with it? For all. If you are introducing insulation and start to seal things up then you start to loose the drafts.. roof / floor ventilation and so on. Again for all.. generally dry / wet rot etc does not thrive in cold, dark drafty environments. The more drafts the drier things tend to be.. but that does not fit with the way we want to live now.

Hi Sean. Great link to Tulse Hill, just shows you what can be done! Hopefully you'll find a builder, if not then..go your self. May take you a bit longer but you'll save some money and have that quite satisfaction of having done it yourself. The difficulty many face is finding the time. Apparently a day on Pluto is 6.4 Earth days..

Love this stuff! Don't bother with a slate cutter. To get you started, buy a slating axe. I have a left handed one..as I'm cack handed. I use an off cut of a steel I beam over which I dress the slates. Some basic points which I hope may be of use to someone. You need to grade the slates. The thicker and wider ones go at the bottom near the eaves. I grade second hand slates ( you need to do this with new slate too to make a proper job) into three piles. You can do four but you may lose the will to live. Grading the slates basically helps you keep the roof tight and flat. Have a look at an old slated roof and you will see thicker wider slates at the bottom, thinner narrower ones at the top. When you get to the verge or a valley you need to turn the slate and trim it the other way. What you are doing here is to encourage the water to move back into the roof in the case of a verge.. so it does not drip down the gable walls. In the case of a valley you are trying to stop constant dripping on to the lead valley and making a hole over the years. You try and channel the water down to the gutter so it drips here and this is where you often have a thicker lead piece. You call this "tailing" of the slate. This can't really be done with a machine..it's a craft. In Scotland it rains a lot, much is light rain.. so it drips a lot. In England say you tend to have much more intense rain.. thus the flash flooding but more dry spells and less of that constant dripping. I want to have a rant now! The new home warranty providers and a lot of the slate providers require that all slates are double nailed at the head. Great if your poviding a 10 year warranty, eg if a slate cracks you often don't see it as it does not fall out like a single nailed slate. But a good well maintained roof should last for at least 80 years? For the roof pro's.. repairing a double nailed / every slate roof is hard going? You can fix the slate but the slate ripper causes more damage that is hidden? Yes there are repair type clips and so on but.. A common traditional method of slating in Scotland is to single nail each slate in the main part of the roof. Every third course you cheek nail a row of the slates, these slates now have three nails and stop the ones below from lifting off in the wind. This way when you want to maintain the roof you can get into turn the slates and easily extract the broken one without damaging the felt / membrane underneath. It's worth I think trying to master this skill, it can be very rewarding. I have left this out but make sure you choose the slate nails carefully depending on whether you are near the sea or not. You'll have a bit of wastage until you get the hang of it. Use the trimmings / wastage as decorative material for paths etc? What is worth while doing is investing in a slate holing machine. You turn the slate upside down. The punch makes a concave hole in the top side of the slate and the nail head sits nicely inside so it does not tip up the slate on top..helps get the " tight roof". You can hole the slates by hand but I would suggest getting a feel for cutting / shaping / tailing them first. All the best. Gus