Gus Potter

@Great_scot_selfbuild Ok to add a bit. Let's look at this in terms of how the trees grow. I'll be simplistic but hopefuly this gives you insight. Trees need structural roots... stops then falling over. They also need water and nutrients... the Tertiary roots. Now imagine you are knocking in 70 screw piles and in doing so you will compact the ground! The structural roots of a tree go deep, the roots that capture the water and nutrients are close to the surface as they have to compete with the other vegitation. Your design is complex (as you have made it that way yourself!)and at the moment and I don't think your SE and you have understood all the implications.. you clearly don't understand how trees grow.. if you did then you and ergo your SE would not be posting on Build HUb!. My feeeling is that you are going to spend a pile of money and not actually achieve your design intent. Loom at concrete piers (these will often take care of the sideways wind load) say as a first go, not compact the ground, let the rain water moist the soil, under the building foot print|. On the face of it it's complex but once you get you head around the principles the solution is ofen remarkably simple.. I suspect that you have fallen into the trap of one foundation solution! Time to go back and review! I force myself as a designer to do this as it's part of my day job.. sometimes I find that I have followed the wrong path.. but this gives me time to correct and learn before I isued a design..

Good and interesting info. I'm not trying to poke holes in your design to be an arse.. but from what you have posted so far just it looks a bit bollocks and here is why..but let's start with the upside! I do like how your building sits in the trees, almost Canadian design.. love it! Often when I design I discuss with Clients some of my "whacky" options.. in design it's good to know what the rubbish ones are and the ones that could cost a lot... so you can rule them out. Good design is often about ruling out what you don't really want and then you focus on the things you do want.. and then this lets you focus in on the viable options... prevents you later thinking "we should have done that! after the fact. Your screw piles are a classic case in point.. I think you have not done enough work and plumped for screw piles! I think you might be making an expensive mistake! You don't need to take my advice but to be safe consider it and rule it out.. then you know you are making good decisions. You will kick yourself if you get it wrong and I turn out ot be right! It's not my money after all.. From time top time I act as a lead Engineer on a project.. it my job to make sure everything is safe (in the round but not checking everything roughly). but also that we control cost where I can, call that a soft skill! Now some Cients just want to "do their own thing" Is this you? @Great_scot_selfbuildand are you happy to pay for the privilege. I'll run with that as an SE provided it is a safe design. But this often commands a higher design fee... and the construction cost will go up exponentially! I suspect you have gone down one route and are blinkered! Take a step back and review! My gut feeling is that the design you describe is going to cost you a fortune once you get down to the detail. and getting folk to execute on site. Ok you might be in Scotland? and feel reassured the you have an SER Engineer.. not always my experience when checking their designs! Check the fine print is my advice! Look to see how they shed design and cost liability! OK to be be blunt.. being smart does not always increase the value of you property. In fact it can reduce the value! I think you are trying to be too smart! My gut feeling is that this will trip you up futher down the road and you will get totally pelted when the Contractors submit their prices! You will be lucky to find any good contractor who wants to take on your job! Look ahead and smell the coffee! Ok so you have posted a table of SPT results. When we are at the concept stage we say if in sand take the SPT"N" number and divide by 10! take the top left of the table and divide the number by ten.. look at the rest of the table.. it follows the same pattern! makes you wonder what you have paid for! What is not included is any mention of how the ground may perform when laterally loaded for wind bracing! Ok if that floats your boat and you have the money to indulge then fine. Feel free to spend! But I suspect your SE is playing along and giving you qualified advice. It may be because they percieve you to be an obstinate Client and not taking advice and not willing to pay for it! But further down the road you will need to put your hand and in your pocket for the pile wind bracing.. who signs that off.. who welds it.. @Great_scot_selfbuild you are heading for a hiding here! Give your SE a call and discuss some of my points. Ok but have they shown any connection, welding /bolting details.. Also Screw piles perform less well under lateral wind load as thy have a thin shank.. This is something I would check. It smells like lots of cost and frankly bollocks at my end! @Great_scot_selfbuildIn summary I think you need to go back and review your design and start asking your SE some questions! It all look decidedly expensive to me and loaded with risk (your risk) once you get into the detailed design! If you asked me to review this design I would want to look at the ground, the ground water, see where the tree roots are to provide the structural tree stability and where the finer roots go to get the nutirients. I can see the idea where you want a house in the woods.. that is your starting point. I think you need to understand this in more detail. your 70 piles with the bracing is going to be massively expensive and you'll struggle to find a builder who will do what you want... I would seek to understand the trees, the soil even if we need a heavier steel ring beam on piers the we need to look at piers / vs root damage etc. In summary my suggestion is pay someone 3.0 to 4.0k that can design this foundation for you properly so it performs structurally and protects the trees. If you pay that amount then the design will probably reduce the overall cost and in the round.

Hiya. There is not much for us enthusiasts to go on here.. I'm guessing as you have not told us much about the ground and so on. I've had a read through the thread and here are some of the things I am interested in. Screw piles.. ok but if you have an element of sand coupled with a high water table that could significantly reduce the performance. Now if you have investigated the ground, say carried out some cone penetration tests then with a refusal at say 2.5m you might have some competent ground. Why have you ruled out sitting your ring beam on concrete piers for example? These could often stop at ground level and then continue in steel if need be. Ok but you'll have wind (horizontal load) on the screw piles. How do you deal with that force? Screw piles are not that great when subject to horizontal loading. I wonder how your SE is dealing with this. Lastly always think about buildability, the labour / material cost and how many Contractors may want to put in a price. Unless you are going to do it all yourself then this can often be critical to the budget. It's a hard fact that while you may be an Engineer and want to go down one path you may have to pay more for the privilage.

Hope this helps. If you are using ordinary bolts then here is a bit of info below: But if using resin anchors you'll often find the torque setting in the manufacturer's data, don't exceed these! The main thing is to apply common sense. Don't let the bolts get dirty or lose the manufacturer's oiled coating or store them badly for example, don't add oil either! Now in the table above we can see a typical torque for an ordinary bolt with a spanner 460mm long. For an M16 bolt we are looking at approximately 90 Nm. What does that mean on site? Ok roughly 100 Newtons is about 10 kg. If the spanner was 1.0metre long then we would need to apply 9 kg to the end of the spanner to generate 90 Nm on the head of the 16mm diameter bolt. But say your spanner is 460mm long (0.46 m) or 18 inches roughly. The sum is 10kg / 0.46 = 22 kg applied right to the very end of the spanner. So very roughly imagine you lift a 25 kg bag of cement with one hand... get a feel for that and then try and apply the same force when bolting up. For bolt groups you'll know that we tighten them in sequence, gently going round an tightening them in stages. All the best with the project and post some photos if you feel able.

Take this on board. Ensure your research is sound.

Good but it willl be a bit different as you have learnt a lot of stuff. It will come back to you as you go. I'm a big fan of stick building. The financialrisk is reduced, getting mucked about by TF folk, it is a flexible way to do it as often you can change your mind as you go. And this the great thing about this way of building, the flexibility and the ease of costing, it's just timber and almost a day rate for joiners to knock it up. The game has changed a lot. While you may be able to do the drawings someone will have to keep you right and that will cost more than a professional doing the drawings right first time. The biggy is finding someone who you can; work with, is flexible, do your panel drawings, your foundation design etc and do the SE stuff and works in Scotland. This is how I make my living. I'm nippping off on holiday but PM me if you fancy a blether.

Architecturally..but can you explain how that is going to work structurally when the SE has to then fix the stuff that you should know about! You can go chucking in DPC's, rocker bearings, thermal breaks at will! If you want to profess about changing stuff them maybe go onto explian how it impacts on the structure. Yes, I know life has got harder for Architects and the thermal regs but the same applies to SE's.. strart collaborating and learning.

@ETC I don't always agree but on this point good advice.

All the members of your design team have a responsibility. The big problem that a lot of them will have is that you are not paying one of them enough to coordinate it all. If this was happening you would not be asking these questions on BH. It's that simple!

Have you had an SE input yet? SE's can help smooth things out.. if you are willing to pay for a fair days work.

Hello all. To get the best out of things we often need to start talking to each other at the early stages of the design, lining up the contractors you think that you might want to pretty much invest your life savings in. You also need to concentrate the minds of Architect's, SE's and so on. I've attached a concept model that I made for making a hole in a house wall, and it has some chatty guidance notes, not contractural but friendly guiidance. But the text is the bit worth a real read. It's tailored for my Client as they have an eye for cost and buildability. This Client is very sucessful in the building trade but will not tolerate any bollocks. It's a tricky job in terms of buildability, programme and avoiding disruption to the house. There are big loads coming from above and sideways wind load. The text on the right is to let the Contractor see how they can build it, and also see that they have my support and that should let them sharpen their pencil. What you see is only part of a larger project but this bit is the bit that could cause a Contractor to add on 20 plus k.. I'm letting them know they are not alone, but in return I expect them to give the Client a competetive price.. I've done all the hard work! Yes, the Client has paid me a bit more but they will make more savings than what they paid me to figure this out! This drives down cost! What I'm deliberately doing here is to force collaboration from everyone involved in the design and execution, all for the benefit of the Client. Now many of you are doing builds. The fad is to split up the work packages.. to my mind unless you can coordinate all that your are going to pay for the inevitable gaps.. and pay dearly.. and that will come with grief. What you see also ties down the Contractor.. as if they later come back and moan about it.. I say well I suggested how you might do it! You don't have to do it my way but have a read of the text and pick out the bits that may help you phrase some questions when you are dealing with the "design team and builders" BH 3d METHOD STATEMENT Steel frame to main house A1.pdf

From experience you can go into an attic and think ok.. here is how I might get it to work. You are creating another floor that requires more onerous loading. Now I also know that we are all prone to looking at things with rose tinted glasses. I have learnt that when assessing the potential for attic convertion you need to make sure that when you change the loading and paths that all that can get transferred down to the foundations.. and at that point you find that you don't have wall continuity on the ground floor for example. The cost and potential disruption can rocket. Unless this property has a high value my gut feeling is that when the final design and costs come in it won't be worth it.. @Mubbashshir I think you will, at the end of the day get more bang for your buck by extending out the back if you can?

To quote myself... bad form I know! Ok. The first few times I tried it was with welding rods and found it worked. An agricultural contractor showed me how to do it. I was gob smacked! Yes it does not work all the time but in the absence of any other info it's worth a punt in my view as it costs nothing.

This is a fab observation... and demonstrates to me a knowledge of timber. To explain SE wise. You'll often see joists or a flitch beam (commonly two bits of timber with a steel plate between) fixed together with the nails / bolts towards the outside edges. If your new timber starts to cup it pulls the nails / bolts, sets up secondary stress and causes havoc as often one of the timbers will split along it's length rendering your hard work useless. When sistering joists we need to look at the end grain. You want to put the younger wood next to the old joist so when it cups the gap is in the centre and the top and bottom of the timbers remain in contact. @Nickfromwales is demonstrating good old school knowledge. Years ago a joinery apprenticeship used to be a lot longer and the kids got taught this stuff.

@Pappa and all.. hope this give you possible further insight into what your SE is up to. Attic conversion are an art with often some crafty engineeering. The following I hope gives a bit of an insight. The SE will have considered at least the following: 1/ It needs to be strong enough, the joists and connection not to break. Call this strength design. 2/ The deflections (the amount the floor bends by) need to be controlled. 3/ Head room.. increasing the thickness of the floor is often not possible. 4/ Disrupting the walls where the existing joist ends rest, you often want to avoid that as they tie the walls together. 5/ If I'm going to sister up joists in this way.. where is the best place to put the joints? usually where the bending force in the timber is least onerous or at least we can achieve the best balance between the bending and shearing forces in the timbers. 6/ How to I connect the joists to each other so the forces get transferred around the lap joints. @Pappa To start with lets assume the floor is uniformly loaded, no point loads from wall say. How much load might we be talking about? I'm going to simplify the factors of safety (ignore them and assume your SE loads are working loads) as they vary between the design codes. This is just a rough qualitative look at things and lets carry out a common sense check based on the info you have provide.. don't lay into your SE if you think something is wrong ask them to explain a bit.. which they will be able to do. But for the curious let's see if @Pappa numbers roughly look credible. Say the self weight (dead / permanant weight of the floor is 0.75 kN/m^2 ( about ~75kg) and we have what is called the live (imposed) load which is people, funiture etc. The design codes require us to use a value of 1.5 kN/m^2 (~150 kg/m^2) for a dwelling. Add the two values together gives us 0.75 + 1.5 = 2.25 kN/m^2. I've picked a ball park figure for the dead weight of you floor, could be less or more. Take the longest left span and pretend that here is just one beam spanning between the left wall and onto the middle wall in isolation.. this is what we call a simply supported beam. Taking a 1.0m wide strip of floor with a beam span of say 6.0m gives us a total load of 2.25 * 6.0 = 13.5 kN per metre width of floor and for a simply supported beam the load per metre run of ledger would be 13.5 / 2 = 6.75 kN/m.. but see below what @Pappa's SE says. The load I've just calculated is some 45% more (call that an over stress) than the SE's load, even if you have a lighter floor then on first glance there looks to be something wrong. The first obvious thing is.. can the floor be loaded with people over it's full span, is there a coomb? If so then the ledger load is going to reduce at the left wall end. Say the coomb extends in 2.0m from the left wall. You need to maybe to allow say 0.25 kN/m^2 for using that space as storage? I'll ignore that for now to keep the maths short. That will maybe knock off about 1.5 kN/m run ledger load. 6.75 - 1.5 = 5.25 kN/m run of ledger. still more than your SE's 4.58 kN/m For all I worked out this qualitative reduction of 1.5 kN/ metre run of ledger by saying we have 4.0m of floor that could be loaded by people towards the middle wall. Thus 4.0m x 1.5 kN/m^2 = 6.0 kN and that 6.0 kN acts as a point load 2.0 m in from the mid wall. Thus for a simply supported beam 2/3 of the load will be carried by the mid wall and 1/3 by the left wall. So 6.0*1 / 3 = 2.0 kN/m reduction and I've added a bit back in of 0.5 kN/m to account for you storing stuff in the coomb and that is how I arrived at the 1.5 kN/m reduction I used above. But the 5.25 kN/m per run of ledger is still an over stress! Here I think your SE is doing what you are paying for.. this is "crafty bit" and demonstrates engineering skill. To explain we need to look at some basics first. When designing beams etc we are primarliy interested in the bending force in the beam and the shearing forces. There is a lot of other stuff going on but let's just stick to these for now. Engineers use diagrams to repesent these forces. Below is what we call the bending moment diagram for a simply supported beam holding up a uniform load. And diagram below represents the shearing forces in the beam. @Pappa we want to know a bit about this, where your SE is showing the sistered joists stopping short of the left wall. But in this case the SE is lapping and joining the joists together so it's intuitive that we must be getting some transfer of forces between the left side and right side and here we can take advantage of this and while Nick below is correct about the weight not changing the way the weight influences the joist behavoir can change a lot, or enough to make things work. Let's now look at the doubled joists and how the bending and shear forces change even though the weight is not changing. You may have heard SE's talk about stiffness and how stiff things attract load. Here is an analogy, let your mind wander and wonder! Say we go to the gym (cough at my end) hold out a kettle ball at arms length. The ball causes a bending force at the shoulder and a downwards shearing force. Now you have a pal, also with a perfect body, that comes up behind you with super glue on their fore arm and sticks their arm to your humerus region thus some of the load will get transferred to their arm. This will stiffen you arm and some of the load will get transferred to your pal. We can take this analogy and put some diagrams to that as below as this is what looks to be happening in @Pappa's case. Now when you get a helping hand from the right wall side timbers you can see that on the main 6.0 m span the bending force is reduced. But also the shearing force at the left wall reduces. I've just sketched the diagrams so not perfect!. I've just done this roughly and for ease and have shown the floor fully loaded. But SE's will consider the left side full loaded with minimum load on the 4.0m span as this will give the maximum shear load on the left wall where the new sistered joists stop short and we need to check the remaining short part of the original joist. Now lets look at how much the floor will deflect. @Pappa's SE has sistered the joists over the longest span and will have calulated the deflection and checked it is ok. Where the joists stop short of the left wall will have little influence. In this post I've not looked at how you design the bolts and so on.. it is complicated! @Pappa. Hope this helps. My recommmendation is that you stick to your SE drawings and connection recommendation, don't go swapping things out without checking with your SE first.

Thank's for the lesson, every day is a school day for me @Nickfromwales I looked at that and wanted to ask! I had my doubts.. but we live and learn. Thanks for sharing your knowledge Nick in terms that I can get my head around. Ta from me for a great explanation!

OK @Nickfromwales let's not split hairs here. You recognise that we need to at least have some residual heating under the units.. that is so common sense! Folks. @Nickfromwales does this as a day job.. listen to what he says. I've also been dabbling in this UF malarky for 30+ years. I agree with Nick. Nick says ( i think in the spirit of the discussion).. essencially reduce by half the spacing under where you are confident your units are going to go. That is what In would do.. it is so simple! It stops damp problems and just acts as a bit of a stop gap, provides a bit of redundancy when in 10-15 years time the system stops working so well.

@Nickfromwales Would your idea be equivalent to the traditional "Surrey Flange" The dip pipe concept.. it invites problems?

And here you are demonstrating common sense! I know @nodyou have a vast amount of experience and I think we are of like mind. Ok.. I hear you maybe saying .. on the odd occasion I might concur with Gus. So long as you at least make it it bit future proof then spot on. OK folks: In my mind future proofing UFH is; no fancy controls, no apps and shite, basic plumbing components that your local plumber can buy off the shelf. I'm an SE (reinvented builder) and primarily we design with no bollocks! Things need to last! If you think about it.. UFH is just a large radiator on the floor. But by applying common sense you can heat different parts of it by having loops.. and then fine tune it where the cold comes in..and where the floor gets wet.. this is improtant to dry out the mats at the door so you don't stain your oak flooring say or soften the varnished / oil finish. In my own house.. it's a bit eclectic we have rugs and stuff on the floor, my wife is a bit of an interior designer.. it totally stuffs any loop cad things and the U.. value calcs. We have some furniture.. big sofas.. they trap the heat. Now when you take all that account any heat loss model is just an estimate. When I first started out on the UF malarky some 30+ years ago ( folks.. I've not always got it perfect by the way.. have learnt from my mistakes) we struggled to get it to emit enough heat as the U values of the walls, roof and glazing where much higher. But now the regs make UFH much more viable. But the same basic rules still apply. For all on BH that are thinking about UFH.. go for it..trust your common sense.. it does not cost that much more but.. the luxury is.. from my experience.. well worth it. Even my old Mum at 94 does not have to bring her slippers!

That is why I say on my drawings " or similar and appoved by me" It is because what you should be doing is going back to your designer and asking.. is it ok for me to use this.. but you probably wanted the cheepest price from your designer in the first place so they would not have included the time to keep yourself right and hold your hand. There is no free lunch here! Do you honestly expect the person on the sales counter of a builders merchant to ask what the load ratio is when they are selling you a Catnic Lintel for example at a bargin basement price? The load ratio is the difference between the load on the inside and the outside of a steel lintel. If the guy on the counter can tell you that he / she stands a good chance of getting a job in a design office.

To add a bit.. of a rant! My day job requires me to use some complex software. But if you put rubbish in you get rubbish out. With modern software you need to construst a model, could be an SE model or UFH model. I've learnt that in UFH design you can get a feel for how much heat you need to put in but most importantly you need to know where to apply the heat. A badly thought out UF design can be disappointing to say the least. I'm going to go back to some old sckool stuff to demonstrate a point. Say in the 1980's when folk were able to afford gas central heating. There were two basic schools of thought.. do you put the radiators under the windows.. where the cold comes in or do you put them at the entrances to the rooms where you are less likely to put furniture? Now the cheapest option was to keep the rads at the doors. But you set up big convection air currents in the room. The same applies to UFH. Think about where you need the heat. We often have big areas of glass and open plan spaces.. that is where you need the heat.. where the glass is, I reduce my UF pipe spacings in these locations. This is where part of the art comes in.. in fact it's just common sense. Say you have a door then you want the floor there to be hotter so it gets rid of any moisture that may be coming in from your shoes. It's design touches like this that make UF work well. Loop cad etc will get you so far but to get the best out of UF requires you to trust your common sense..

Philistine here.. Nod makes a good point. I've run my UF pipes under my island units. The cupboards are warm... keeps the pasta dry for example. I have a gap at the top of the plinth to let excessive heat out. Where I have my fridge and freezer I opened up the pipe spacing.. just to provide a bit of residual heat. I've been doing this for decades. UF is a pragmatic art.. the focus is on the art! What I do is have plenty loops, and short flow adjustable loops. Commercial companies will try and be smart and seek some cost advantage.. which is bonkers when you think that UF should at least last the lifetime of the house.

I does work. I've seen Farmers do this.. it's a developed skill that can give you a hint of where things might be.

When designing raft slabs and screeds I set a level and flatness tolerance so this should not happen. It can add to the initial price but at the end of the day someone has to do it. Remedial works always cost more than getting it right first time.

Welcome to BH by the way Deborah. That is glowing report. Agree. But there is always an inherant risk about buying from abroad. If things start to go wrong then there may not be a local resource you can call up to fix things on site in the heat of battle... like phone a friend. If you are on a tight programme then it's a balancing excercise.. do we go local or not.