Gus Potter

Hi SaveaSteading. Your approach is much appreciated and interesting. Hope this helps. The geology of the Highlands is unique and fascinating. Here are some avenues and my thoughts on how you could continue to explore this. Some may well not apply to you but BH is a journey! Say you look at this in the context of a two supply system. One supply is for the bogs and watering the plants when the good dry weather comes, the other for drinking / washing water. You mention an ample burn and that it may have a journey before it gets to you.. say past a few silage pits, crofts and other folk's septic tanks ,which have yet to be upgraded. If many of the old septic tanks etc upstream have been upgraded (wishful thinking) this only tends to reduce the BOD (biological oxygen demand) but not the pathogens and other undesirable chemical compounds so much. However, the water that falls on your garden will generally make its way to the burn . You could maybe dig a relatively shallow trench that intercepts the surface ground water flow in your garden as it travels towards the burn. In other words your garden acts as a partial filter. In a dry summer it may be that the flow is reversed to some extent. Here your garden would act to partially filter the water as it makes it's way from the burn to the trench. In other words during a dry summer you still get more rain on the higher ground so even if your water table drops locally in your garden you can still draw off a sensible amount of water from the burn. When the next winter comes the flow is reversed back to the burn so your garden filter could be "self cleaning". This is how a sand filter in a sewage treatment plant works to some extent. I digress a bit here but it's worth a mention for other BH members too. SUDs requirements. There are a good few posts on BH about this and folk are aware that it relates to say flood prevention. However, there is another aspect to this. If you have dry spell of weather then contamination can build up on your roof. Many industrial buildings have roofs that are plastic (say) coated and the UV sun rays degrade this. Also, you get birds nesting and so on. If you then get a short burst of rain you wash a high concentration of contamination into a burn / stream that is at a low flow level. You don't get the dilution and this kills the fish and other organisms. Saveasteading.. the same principle could apply in your case. If you are on the West coast of Scotland you'll get more frequent rain.. but the East can be very dry for a few months. If you can find a way of storing enough drinking water/ washing for the dry months then you could in principle be drinking the best water in the world! Once you work your way through this then you can weigh up the economics / practicality of boreholes / spring supply (reliability / security of supply as not on your land) vs say harvesting. Have a look at how you can get rid of your waste water. Mortgage.. maybe some lenders will pick up on the fact that you have an unusual scheme. If you present a good technical case and compare with say a bore hole that may choke up in ten / twenty years time then it's food for thought. One avenue is to show that your scheme complies with the current regs, say in terms of a potable supply of water. From a pratical point of view if your borehole pump breaks down then they are nearly impossible to recover.. I have seen them stuck fast after a few weeks! You often can't get them back out and you have a cable in the way plus a steel recovery wire, try getting a same sized pump back down the same hole! You could get all this to work out with a fair wind. If you wish then post more info about what you know about the ground, the slope, geometry of your plot ect. Your geotechnics and topography could well be a key here to getting this to work.

Hello all. By all means explore using this material, I'm all for using new technology.. it's not that new. There are recognised design codes that cover this material. For the self builder.. a practical point. Using say FRP (Basalt say) rebar for an external "non structural slab" may well be cost effective if just laid in flat sheets. To get the best out of it you need to control the other parameters.. compaction, selection of the concrete type and strength, preparation of the sub base, the extra support to maintain the concrete cover etc..it does not corrode but if the cover varies too much you get uneven stresses in the slab which will promote cracking. This may put your local builder off or they may add a bit to the price. If you are using it say in a structural concrete beam or a basement then you'll often need some bent bars. FRP bends need to be formed in the factory.. you have no wriggle room. Thus if you don't get all your setting out absolutely spot on you have trouble ahead. Steel rebar can be "tweeked" a bit on site.. FRP? You may say.. well.. that is up to the builder to get it right.. you can but this will come at a cost.. For the technically curious. When you design say a reinforced concrete beam subject to downards loading you often aim to design the rebar as the "weakest link". Steel (in the tension zone of a beam) will stretch (yield) quite a lot before it fails. On the top of the beam the concrete is in compression. When concrete fails in compression it is a much more sudden (explosive) failure. In summary one thing you do is to make sure that if a reinforced concrete beam / slab is over loaded then the occupants of a building get some warning.. big cracks appearing etc. You achieve this by taking advantage of the ductility property of the steel once it reaches it's yield point. Ductility and elasticity are two different properties. But FRP (Basalt say) does not have quite the same forgiving nature to some extent as common structural steel / rebar. Once steel starts to yield it can "stretch" quite a bit before it fails. In fact with common structural steel you get a little extra out of it before really bad things start to happen. With FRP it is appreciated that you may get some yielding but often not as much as say with steel. Once you take this safety aspect into account (which you have to do to comply with the building regs in terms of structural design for domestic structures say) and look at things in the round then the difference between the two materials becomes less marked. If you are considering using this for your build then it's worth a bit of research to check that while the big easy areas look good price wise you are not making a rod for your back later.. say with corners / beams or reducing the number of contractors you can go to to get a good price.

Hi Bramco. Have a look at your soil report. It may mention what is called the soil shrinkage potential also known as the volume change potential. This a rough estimate on how much it will shrink and swell between say winter and summer.. it can be very little or a lot. Here is a link to the NHBC guidance, plenty diagrams etc to give you a feel for things. https://nhbc-standards.co.uk/4-foundations/4-2-building-near-trees/4-2-10-heave-precautions/ There is a bit on how trees can influence the design. Once you have got the basics, then you should be better placed to look at identifying a good solution particular to your site, recognising that you have a stiffer "crust" over a softer layer. For plenty of domestic stuff ground bearing type slabs can be made to work above an allowable bearing capacity of 50 kPa without spending a fortune. It's the swelling / shrinkage and things like trees that can put a bit of a spanner in the works.

Hello all. As George says it's an interesting material, the price is coming down due to volume etc so can be an attractive option for the self builder. I can see why SE's are cautious.. for a reason. As an overview we can see that say the Orlitech bars have a significantly higher tensile strength than steel rebars. ~ 2-4 times say so you can see how they are "stronger". But they are much more stretchy! This is reflected in what is called the modulus of elasticity.. Youngs modulus. Ordinary steel rebar has a modulus of elasticity of say 205 GPa while these types of glass/ basalt/silica based bars have a Young's modulus of say 60 - 90 GPa. So they are say 2 -4 times more stretchy.. elastic. This elasticity is important for concrete design as the concrete has to move more before the bars take up the same load as a similar sized steel bar. Thus you have to be aware that you could either get bigger cracks.. or more of them. If you are doing a basement that needs to keep water out then crack control can be essential. If you are say designing a beam then the beam will deflect more before the bars take up the load. Again this needs some thought. In the main you can increase the diameter of the bar (or use more of them) to mitigate the deflection.. and this impacts on the economics. @kxi Here Kxi is doing an external slab say. Often you may use say a A142 mesh with sawn joints say every 4 -6 m depending on the geometry for a hard standing area. The larger the area of the slab between the joints often the heavier mesh. These sawn joints encourage the shinkage to take place at the joint where you don't see it and this leaves the slab looking good.. if you have taken care laying it, the sub base and curing it properly. If you use a more stretchy mesh, Basalt say, then you may get more cracking where you don't want it. In simplistic theory you could argue that if you have a ground bearing slab resting on a very very slippy DPM then it should behave a bit like a steel reinforced ground bearing slab when curing and shrinking.. but it will be more flexible when you come to run a few waggons over it. Thus it may not last as long? Kxi.. by all means use it for your external slabs or the drive, it will be a bit of an experiment to some extent. The key to getting this to work is careful and exact preparation of the sub base, get it evenly compated.. as level as you can, use a plastic DPM so as the concrete shrinks it can easily slip about so that the movement takes place at the edges or at the joints.

It can be if you know how to go about it. You use basic trigonometry to do it. Onoff.. you can cheat and model it in 3D to check the maths. As an aside having visited a few precast outfits they use an almost dry sand / cement toner mix and mechanically whack that into the mould in layers. It's not like concrete we pour for founds say. If you want to copy what the precasters do then I think getting a really sturdy mould (shutter) is one key. I have seen the precasters using the expensive pigmented mix next to the shutter and no pigmented stuff in the middle. That said I have cast chimney copes say in ordinary concrete hand batched in a half bag Belle mixer and carried up in pails with a drip and a good DPC under.. I passed one the other day and it's still looking good after 25 years..but my glasses are a lot thicker these days. If your DIY precast cill is a bit permeable then make sure you spend time getting the DPC all neat and water tight.

On paper it looks like a nice neat concept in part..but.. I wonder how much horizontal load they can take. When the wind blows you can generate some 100 -150 kg/square metre ball park wind force say on the sides of the building. I had a quick look at the brochure and they show a timber structure with a shallow pitch roof. These types of roof can generate quite a bit of uplift and really need to be well tied down. When you couple the uplift with the horizontal load one might conclude that you have a building on roller skates. I wonder if there is some detailed load tables available for example that cover the above? Extensions are a substancial investment. Don't skimp on the founds. Once you dig deeper into this you may well find that if you are using SIPS panels say you need something heavy in the ground to fix to, stop them overturning / lifting up anyway. Going for a light weight found could make a rod for your back later.

Thanks volcane, dp and Peter for reading. When I was doing the formula bit I thought readers would loose the will to live!

Jeremy. That's a nice looking gable, bit of brick detail and loads of garden trees by the looks of things. The garden / trees look full of potential to have fun. Peter et al have posted some info on the "Heritage House" link below previously and there are threads on BH that discuss various details. https://www.heritage-house.org/damp-and-condensation/managing-damp-in-old-buildings.html Have a read at this. My own view is that while informative they are punting their own business / academic credentials.. so I take some of the stuff with a bit of salt. One thing is that if you over insulate the bathroom you could shift the dew point inwards..the point that water vapour starts to condense. It may be worth while using a bit less insultation in the bathroom external wall.. not super insulate it. Compensate for this loss of insulation elsewhere.. the rooms that have less moisture. But before you do all of this have a good look at the pointing on the external walls, the mortar, ground levels and external drains. gutters and down pipes etc. No point in doing all this internal insulating and upgrading if you don't let the building breathe on the outside. All the best and look forward to seeing how you get on.

Interesting thread this. Good technical points made by Peter,Craig et al. To add my thoughts, partly technical, but mainly to open up design options you can consider that are cost effective, that won't lead to problems with your mastic etc on the finishes, sticky door issues, glass that fails due to adverse unforseen loads etc and the subsequent arguments. Don't forget that these large glazed openings cost a lot, the glass, slim frames etc. A bit of technical stuff. The formula for deflection of a steel beam is 5* w* L^4 /384 EI. For the keen, often domestic steel beam design ignores what is called shear deflection but for timber beams this needs to be accounted for as it is significant. To explain the formula for typical domestic steel beams. E is Young's modulus.. a property of the steel which does not change with beam size. w is the load per metre run of the beam. I is what is called the second moment of area and L is the length. Now you can see that if E, I and w all stay the same then if you have a beam 3.0m long then L is to the power of four i.e. 3*3*3*3 = 81 units, if you have a four metre beam we have 4*4*4*4 = 256 Now 256 divided by 81 = 3.16. So you get over 300% more deflection on a four metre beam than one that is 3.0m long all other things being equal. The thing to draw from this is that beam deflections are very sensetive to length. Extrapolate this to an 6-8m opening and you get this exponential deflection which plays havoc with your doors. The next parameter you can vary is the second moment of area "I". To get your head around this the formula for a rectangular beam is I = b*d^3 / 12 where b is the width and d is the depth. You can see here that if you have a rectangular beam 200mm deep beam d^3 (cubed) is 200*200*200 = 8*10^6 mm^3 (mm cubed) but if you have a same width but 300mm deep it is 300*300*300 = 27*10^6mm^3. So buy increasing the depth of the beam by 100mm you reduce the deflection by 27/8 ~ 300%. The way a steel I beam works is that you cut out the sides and place more steel in the flanges. This give a much more efficient shape so by moving the material to the top and bottom flanges you get more "I" for your buck! Now for a big glazed opening design the starting point is how much deflection will be ok over the head of the doors. There are general structural recommendations in the codes that go along the lines of beam span / 360 but these are mainly to do with the other elements of the building. If you have an effective clear span of 8.0m that is 8000mm / 360 = 22mm. That is going to jamb your doors, break the mastic seal (at times you will notice the bend over the opening) on the outside and probably damage any wall paper inside. It's easy to fall into the trap where you see the deflection as being say 22 mm, so you put in 25mm of say compriband.. but if you compress compriband or similar down to 3.0mm it will start to extert load on your doors.. it's good (squashy) but not that good! You also need to make sure that when the load is not there that the compriband will recover and not leave a gap. The next thing (Craig, Peter etc have touched on this I think in the past) is that there is a difference in how you install bifold doors and true sliding doors. A sliding door head can be installed with a bit of a gap over the head as they now tend to be all bottom supported, but bifold door heads need tighter packing at the head. In other words bifolds are less forgiving in terms of beam deflection. If you think about it. When the bifolds are open there is a lot of glass weight hanging out from the building so the mechanism at the head of the doors needs to be held firmly in place so that over time they still perform, the tolerances are tighter and less compatible with the structure. As promised. If you have read this far then if you have a single storey extension with a large opening you may have a flat roof above. Here you may be able to use the upstand on the flat roof to accomodate a deeper beam thus reducing any downstand in the extension. If you have a two storey house with large bifolds etc below you can start to look at turning the upper floor external wall into a big truss. This in the right circumstances can allow you almost take the doors right up to the ceiling! The secret is that there comes a point where a big steel beam is no use / economic if you have some height above to do something. If you have a modern house, say with an "L" shaped roof" and go in the attic you may see lots of thin prefabricated trusses. But at the "L" bit you may see some sturdy looking trusses.. girder trusses. You can apply the same principle to creating a large glazed opening on the ground floor. If I was looking at designing a 3.5m plus opening for glazing I would use start by saying.. I want no more than 6 - 8mm deflection at concept design stage under say snow loading or roof access. I would then look at the type of construction.. masonry, timber frame. Timber creeps over time so that has to be accounted for. I would also look to see how much the founds may settle.. if there is uneven loading.. differential settlement. Once you get a handle on the "feel" of things you are on your way to getting a problem free solution. This all may sound expensive as you need an SE, experienced designer that can look holistically at this but it may only cost a little more for the extra design input. Ideally it may end up that you save money!

What is on the outside of the solid external walls? Is this a breathable / permeable layer?

I would hang fire with the beam and block. Leave the piles and ring beam as they are. If you install the beam and block and leave it for a few years then if something starts happening in the void under (water ingress, mould etc) then you'll have to fix it.. that won't be easy and not good for moral. Also, it does limit your options. Practically you may want to run services in the solum space.. planning that far ahead? Maybe get some free draining goetextile membrane (B&Q?) and lay it over what you have. Then infill back up to ground level. Pick an inert infill material that is easy to dig out and recycle... hence the geotextile membrane. This could be a layer of recycled aggregate. Or you could just dump some broken brick, another layer of textile then some decorative aggregate, some plant pots etc so you can use the space while you wait. It may be that you have a gravel drive.. use the same aggregate so you can "top up the drive" once the work is complete. The key really is to provide a layer of material to protect the underbuilding and solum from frost. Gardeners turn over the soil before the winter to let the frost get in and break it up. Same will happen to the soil under the solum if you don't protect it from frost. The concequence will often be that you end up having to dig the material that has softend.

I learnt about ovens from my Father in law, what to look out for in terms of cleaning, the control display sizes and so on. Off topic.. Don't panic Jilly. NHBC regs touch on this, have copied below their text in italic from section 5.2 D10 of their regs. A minimum void of not less than 150mm should be provided below the underside of floor slabs and beams. On shrinkable soil where heave could take place, allowance should be made for the void to accommodate the following movements according to the shrinkage potential of the soil: high potential - 150mm medium potential - 100mm low potential - 50mm. If you get stuck then I would look to see if the ground has recovered from any trees / hedges cut down in the last two years or more.. this causes ground to swell. Also, have a look at what time of year the solum is installed, at the end of the winter where moisture contents are high and the ground has lifted/ swelled. If conditions are right you can make the point to the BCO that the ground has swelled (heaved) upwards close to it's potential maximum so once you put a dry building on top it will go down and increase the void. A reasoned argument coupled with a pragmatic BCO could resolve. This is a bit of last resort stuff to get you out a hole if you get stuck.. say main underbuilding levels set.

If you are keeping the same geometry then the oak will perform better than the soft wood. Roughly, if you think about a bit of soft wood it is made up of mainly cellulose with air gaps in the cells, it has a certain density. Oak is more dense than softer woods so you get more material and less air... thus it is "stronger". In principle the members should be fine. However, it is the connections between the timbers you need to have a look at just to make sure they are ok. If you are swapping a prefabricated softwood truss with nail plates say for an oak truss then it's worth a check on the connections. Alternatively it may be that you have a traditional cut timber roof, nailed, maybe a pole plate on the wall head. All this may need is a quantative check on the connections. In other words you can say.. the timber has a higher grade than the existing, calculate the capacity of the existing fixings and provide new fixings equal or better than the existing.

Ah.. dangti6.. can of worms here in terms of floor slab tolerances, quality and variations in level. I have attached a copy of a report that was published on the web that is very informative. It deals with floor level tolerances and flatness. A floor can be flat but not level! Many domestic contractors say a slab will be smooth.. but..! For all.. it's well worth a read if you are into ICF, basements, floor slabs etc. Page 5 onwards could save you a lot of grief. Credit is due in full to Combined Flooring Services Ltd and the author Martin Rogers. I have found this report to be a very handy reference document. Thank you Martin if you are reading this. If your slab is a structural slab then it is important to control the thickness and variation in thickness. This is where control over the level top / bottom and finish is important. Floor_level_flatness-survey.pdf

Hi cwr. Run this by your SE. The thing is that the SE may be relying on the frictional / bond resistance between the floor slab and the wall to provide lateral stability to the building. If you introduce a slippy bit of plastic between the slab and the wall as tonyshouse says you could be making a rod for your back. Foaming up the ends of the slab looks a bit simpler as suggested.

For all: A thing that is worth while putting on your drawings for conversions / refurb if you are an SE is an approximate steel size. State this is to be confirmed by the contractor on site along with a note that explains the allowable tolerance. For example it's good to see a note such as.. "this steel beam has been designed to accommodate an increase in length of up to +/- 50mm. Should the site measured length increase beyond this then the SE should be consulted prior to fabrication" or words to that effect. I'm a bit surprised that on a refurb / conversion the founds were not fully explored at the very early stage of the design. This is fundamental to any conversion / refirb etc. You must understand what it is sitting on and what you propose will impact on the sub structure. Strolling now through the design process. On a barn conversion, extensive refurb say your Achitect should have discussed with you the benefits of getting and SE in early, the design/cost risk if you don't. If you are resistant to this (unless with very good reason) then they should walk away from you as a Client.. An SE should also walk you through the structures side and explain how and what they need to do to realise the Architectural design and how they are going to collaborate with the Architectural designer while keeping an eye on the structure cost which you often don't see. Again if you are resistant to this then you should be left to your own devices. As a Client why buy a dog and bark yourself? Sort this out and it gives the contactor a clear view of what they need to do, how they will make a fair and justified profit, what help and support they will get from the design team when problems occur and what the concequences will be if they don't hold up their end of the bargin. Have a fair contract and you are well on your way. On a refurb / conversion this can fundamentally impact on the design process / cost. Not just in terms of the structural design but on how you deal with the design / interface of the insultation envelope and the associated labour / material cost. Often understanding the existing founds, level changes, the existing wall construction, moisture control leads you to the simple stupid option which is effective and most cost effective. From time to time you can, if you get your SE in early and are prepared to open stuff up (intrusive investigation) then you can get your steel work and fabrication drawings pretty much spot on. You need to spend the money up front with the SE, opening up / exposing founds, but it reduces your risk later on. Also, the more information you gather early can allow for a more collaborative approach which tends to be more enjoyable for all involved in the project. Lastly, if folk are enjoying the job they may be a little less heavy handed wth the invoice pencil and spend more time getting the job done.

Hi cs21. Thanks for responding. This is a bit of a quandary. There are lot's of folk that have building experience that have a feel for what will stand up..it's just that often folk don't consider that we mainly design for a 50 year life span (domestic loadings for dwellings.. flats are a little different) and the loads that have a significant probability of occuring over that time. That is why we have safety factors. We very rarely see a house failing drastically due to over loading alone (I can't think of a case off the top of my head.. there have been some localised floor collapses due to folk hoarding stuff I think).. it's usually due to bad workmanship, changing the specification of materials without consulting the designer/ making what appears to be a small change in say levels of ceiling joists, inadvertantly altering the way the roof trusses work.. suddenly what seems to be a minor change can impact on the loads paths and result in an unstable building. I may have interpreted this wrongly but is the roof already vaulted? If so do you understand how the horizontal thrust from the vaulting roof is resisted. If you are proposing to remove the existing ceiling ties to form the new floor (bottom truss chords say or an existing floor that is set 2 feet down from the wall head that is providing some tying / lateral stability to the existing masonry walls for example) do you fully understand their function and the consequence of removal. Also, have you considered the practical issues relating to how you install the anchors, how they will fit with the coursing both vertical and horizontal so that you maintain the edge distances between the fixings and the mortar joints. Will your runner sit flush with the wall or will it stand off a bit in places if the wall is not straight. If standing off in places then you introduce a bending force into the fixing and this has to be considered. The capacity of some of these fixings can drop off four fold and more depending on the type and condition of masonry you are fixing into. Have a look at the manfacturer's load data and you'll see there is a bit of thinking to do to get this to work. Look carefully at the data as many fixings are only certified for cracked concrete.. not masonry.. even then much is based on EU brick / block sizes not UK sizes. It may be that you just want to cart on based on what you think is fine. But if you pass this house on to relatives or sell to say a young family then you would surely want to know that if they use the house in a different way it will still be safe? Also, say you come to sell and you are asked to demonstrate that what you have done is compliant with the regs in terms of the structure. Will you be able to do this?

Hi Peter. To get the best out of BH then consider posting your drawings. This way you'll get better / focused feed back, maybe a few tips that could save you money.

Hi cs21. Can I suggest that you reflect on the fact that there is a difference between being confident and competant to design and execute the works in a safe structural manner while also keeping an eye on the cost, both short term (the works) and long term.. if you come to sell. George is giving you a heads up that could save you a lot of grief. Yes, you may have managed to size your joists (ten minutes work to get a concept joist size for an SE / competant experienced builder) but there is much more to this than just sizing joists. You are asking about the fixing types, hangers.. no mention as to how your proposals may affect the global building stability. If you are competant then no need to ask the questions you are. I would spend a bit more time mulling this over, a bit more research perhaps? BH is a great place to find the info you need.

Hi Moonshine. What you have looks like a reinforced masonry retaining wall. I assume you are using dense concrete blocks not aerated. Nice to see them being used, a bit like timber flitch beams which seemed to go out of fashion for a bit, like bell bottom / flared trousers. Yes 325mm ties to allow for construction tolerance so you get your min 50mm embedment. Peter has suggested (I think) using A142 on the flat to create the wall ties. I would maybe give this a swerve as the blockwork is more porous to moisture and air than well compacted concrete. I think this risks corrosion of the A142 in the blockwork courses. The issue here would be that when steel corrodes it expands and can exert a huge expansive force on the masonry which could damage it. This effect can be seen on historic buildings where iron straps, cramps etc have been built into the stonework resulting in disappointment. I'm curious as the cavity fill is quite thick.. I wonder if the wall is fairly high for a reinforced masonry wall or if you have a clay soil that has a low shear strength. By that I mean a clay soil say that is pretty soft thus exerts a fair bit of lateral pressure on the wall. I can see that the ground slopes up from the wall so this tends to add lateral load to the wall too. I would be interested to see the detail of the rebar at the base of the wall and how the base is working. For the curious these types of reinforced walls are quite clever in how they work, it's the simplicity that attracts. To explain a bit of the theory. Imagine you have a reinforced concrete beam spanning between two walls subject to a downwards load. The bottom of the beam is in tension. Concrete is not so good in resisting tension so you add in rebar in the bottom which is good for the tension. The top of the beam is in compression and concrete / masonry is good at resisting compression. Now, if you make the beam deeper the tension and compression forces at the top and bottom edges reduce as you have a longer lever arm between the bottom and top of the beam. A bit like using a longer spanner or car wheel nut brace. Imagine you take said beam and cut an imaginary slice through it just off the middle of the span. In the very top you have a compressive force acting in one direction, a tension force acting in the opposite direction at the bottom of the beam. In the middle of the depth of the beam these opposing forces are at their maximum in the direction of the span. For the very keen these longitudinal forces are often called complimentary shear forces. In summary, they are most onerous in the middle of the beam and reduce to zero as you move towards the top and bottom of the beam. Now a reinforced masonry retaining wall wall works by recognising that these complimentary shear forces reduce as you move towards the inner face of the wall. There comes a point where the concrete has enough bond strength to the block to resist the complimentary shear. You hit a sweet spot where you can get the concrete and the block to work compositely, like a metal deck floor. The wriggly tin resists the tension, it is bonded to the concrete which resists the compression. Again, great to see this kind of reinforced masonry detail. They can be a great addition to your design armoury. For the self builder they can deliver savings, particularly if you have lot's of masonry on the job anyway. Like many retaining walls they are often height /soil sensetive but they can be great given the right conditions and save you money. Moonshine..One key thing is that you need to make sure that you keep the inside of the blocks clean, no chucking the washout from the mixer down the cavity, letting soil fall into it. Also make sure the brickie does not butter up the inside of the cavity as you want the inner face of the blocks as rough and clean as you can to make all work. Keep the blocks moist when pouring the concrete as you don't want them to suck the water out the concrete on a hot summers day which will encourage the concrete to debond from the blocks.

Hi Puntloos. Copied some extract from your last post in italic and added my thoughts. "My own design, but in particular note that the external wall is much thicker: 435mm: skim 5mm sandcement plaster 15mm medium block 100mm EPS blown beads (with stainless steel wall ties perhaps) 200mm medium block 100mm sand cement render 15mm But perhaps more importantly, split the large glass pane into two much more modest windows. Would your suggestion of the 'portal frames' still hold? My pier design and location is somewhat more central to the main area. The piers don't contribute as much as you would like to the horizontal stability, unless you have plenty load coming down from above to assist in resisting the overturning moment from the wind. With a 435 thick external wall it kind of rules out some kind of portal frame with a bottom shelf angle to support the external leaf as you probably generate too onerous a torsional moment (twisting effect.. does not interface well with glazing) which will cause problems, not least with the portal connections given the space you may have to form said connections. It may work well with a portal for the inner leaf (deals with the horizontal stability) which will carry the first floor and roof loads and some off the shelf lintels to support the outer leaf. If you can decouple the inner and outer steel it makes it a bit easier to deal with the thermal bridging.

@canalsiderenovation Hey on the upside you're in now. Suggest two diagnostic approaches. 1/ Ask everyone .. again, if they have "done something they should not have done" in the shower.." Explain that you have been on BH and unless they come clean you will find out and make it public... if that fails..(and it probably will as I bet you have already explored this) then option 2. 2/ Buy a plunger, one of the ones that act like a bike pump may be the thing. Get a big drum of warm water (not boiling as you may crack the tray) pour it into the tray to get a head of water say 50m m in the tray. Plunge like your life depends on it. Report results here.

Have a look at how crib walls are constructed. Plenty info on the net. Don't push your luck and try and retain a big embankment, but for a modest garden retaiing wall well away from the house it may be the thing for you. Also you could look at gabion baskets. With the right choice of stone they can look great and provide the right habitat for wild flowers etc.

@the_r_sole My thoughts on this "There's a bit of confusion here, the architect would act as a contract administrator whilst the work is on site - not a project manager " Good point as there is a big difference between the two. For all you can find stuff on the net about this but simplistically an administrator handles the paper work.. on a small domestic project it is usually the builder that organises the day to day sequencing of trades, running of the job and standard of workmanship. "(a QS might also do this role which is why they'll be advising to ditch the architect)" Food for thought. Any construction professional that makes such recommendations should only take this course of action when it can be backed up by evidence of failure to perform. Unless of course they wish to commit professional suicide or attract a legal response. "If you're at the stage of nearly building and you haven't got enough trust in your architect that they're not acting in your best interest then don't go any further - contrary to popular belief I've never worked with any architect who would deliberately inflate costs to get more fees, they also should have zero financial incentive to steer you to their "preferred" contractors - that would be contrary to the code of conduct (and pointless)" Agree with the Sole. In any profession you get the odd bad apple but consider that Architect's, SE's, QS's often spend between 4 -5 years at uni, another 3 - 5 years training post graduation and another 3 -5 years becoming modestly competant. Even then they still have to continually train and complete CPD. Basically it can take you 12 - 15 years to get to a level where you can practice competantly. There is absolutely no incentive to bend the rules for some short term financial gain. "As mentioned, building control drawings are not construction drawings and won't have enough information to build from, so you're much more at the mercy of a contractor making assumptions if that's what you use as a basis for a contract, also if you're borrowing money to do the work you may find that a mortgage provider requires details of the contract being used and details of the contract administrator... " Well articulated by the sole. "But as I said earlier, if you've got this far any you don't trust the architect there's something very wrong in the relationship so probably not worth continuing with them - if one of my clients told me they were worried I would inflate costs for my own gain on their project that would be a red flag which would end my involvement. " Yes agree with the sole..but I would always explore why they think this way. Often it's just nerves that get the better of folk and they say daft things. A good professional who is used to dealing with domestic clients will appreciate that you may be nervous and seek to resolve this trust issue. If any advisor / designer fails to address your concerns then part company with them before you start spending big sums of money.

Hi Dragster Driver. @DragsterDriver "waiting on planning permission and then turnaround time on a slab design and delivery could be financially crippling- I really do need to ‘hit the ground running’. I have easy access to plant and groundworkers/bricklayers who owe me favours" Is there more to this? just had a scan at your drawing. Seems like you have a simple raft but a suspended floor over. What do you know about the ground? It may be that your SE does not know that you have these construction contacts and this may have swayed them towards the raft as the most economic based on the info available to them. It could be that if you can call in favours that suit, you can excavate deep strips, get the muck away cheep, do a trench fill strip found all over and cart on?