ChrisJ

@Nick Laslett Your drawing makes sense to me, couldn't tell from your photo I don't agree with the DPM between the top of the slab and the wall, may as well just slather some butter on there as the bond will be the same @SteamyTea Yes rebar can help during catastrophic failure, I've seen it and allows time to safely secure and repair rather then no notice and someone die

Is that DPM on top of the concrete slab separating the wall concrete from the slab, or placed prior to the slab concrete and just run over the top edge of the KORE?

Sure we do, rebar on the perimeter where the structure sits and then typically mesh across the top of everything

How we get away without rebar throughout amazes me actually Understanding what the rebar does would make you question - does the engineer understand it The theory of we don't use it in block walls why would we put it in concrete walls then - is like comparing an engine on a 1992 Ford Escort and a 2025 BMW X5 Concrete shrinks as it cures, the larger the concrete mass the more its pulling on itself and more chance of cracking. now granted its within the ICF form, the perfect cure environment as moisture is trapped, a typical concrete test is done at 28 days to ensure design strength has been achieved, in ICF I have had it fail many times at 28 days as the cure is so slow based on moisture being trapped, however at 56 days not only met the design strength but exceeded by 50% or more Back to the rebar, the horizontal bar is to help with cracking, that's it, nothing more, nothing less, I'm referring to the horizontal in the main open part of the walls, above lintels is different. vertical rebar deals with loading, not just wind or backfill loads, but also point loads from above. how we set a steel beam into a pocket of the wall without vertical bar directly below amazes me as well Does no one question why we do slabs and have mass amounts of rebar cages throughout and then the walls above have no rebar? This post is to make you think and question nothing more

I don't know the product you are using but any that I have used all requiring rasping The block maybe clean but its also got too smooth a surface so the base coat will not adhere and be loose and potentially fall off And even tho only 6 months old I can assure you there is some UV damage and a light film on it, rub your hand across it and you will see it on your hand but maybe not visible to see

There is a product called Insuldeck it is from America, but I understand there is also a manufacturer in Italy and can arrive in the UK in about a 2 week turnaround. I have used the product in Canada and if you are after a concrete decking system I would recommend it. It is similar to Amdeck, however it is one piece length rather then small panels as Amdeck is. Amdeck is not available here, shipping from Canada is possible but costly unless you require an entire container

Is your balcony proposed to be concrete or wood? Both are possible, personally I’d do concrete for long term. Based on your picture with columns from foundation to underside of roof this will all be quite simple for the engineer to design connection and support details price - you’ll need design first and then go for pricing

https://www.framemax.com Not part of the UK, but a company I have dealt with during my time in the US a long time ago, they have done well with pre fab walls for steel frame construction

Can you post some pics of these corner blocks failing?

Natural Stone for an ICF house is no different then conventional masonry, you can use a Brick Ledge (4.5" sculpted ICF form) form at the bottom to carry the stone, usually placed 150mm above finish grade or use an ICF form 4" wider (i.e. 10" below grade to 150mm above then switch to 6" ICF) the Brick Ledge form with proper rebar stirrups is designed to carry 27' (roughly 8.5m) of standard masonry bricks, I don't know that weight value but if you get that and your stone weight you can sort how high the stone can go There are ways to allow you to go higher, I've done 6 storey buildings all masonry and we used an angle iron every 2nd floor to help break the weight load to the brick ledge form at the bottom Brick Ties can be screwed directly into the ICF webs, most are rated for 450lb pull out depending on the screw fastener used (Sorry don't know the metric conversion for that). There is a 2 part brick tie that you embed part of it prior to placing concrete, it goes thru the polystyrene into the concrete void, probably have to import from North America and if I recall fairly expensive and not sure how well it would work since natural stone is various sizes. I did do a project in Los Gatos, California almost 20 years ago and the owner had very thick tie wire (think what was used for T-bar ceilings) cut in 800mm lengths, folded in half and then pushed though the foam into the cavity prior to concrete placement, this was engineer designed for the stone facade which exceeded 30' (9m+) in many areas

Unless you're planning to purchase the expensive structural screws I would just use 90mm nails in my nail gun to secure the joists down. a little trick it to also use a dap of GripFill or even spray foam between the joist and the ledger, this will help prevent any potential squeaks as the floor will flex and move slightly. May not be a big issue with wood on wood, but if you had joist hangers it makes a huge difference, lets put it this way for the few pence it costs I'd be doing it, same with your filler piece (47x50) that will be used as solid blocking for a fully nailed diaphragm of the floor, don't forget to use GripFill or spray foam when you place your sheathing down either - makes the floor a bit more solid and prevents squeaks

Curious as to why the design calls for a steel beam within the ICF cavity instead of a concrete beam with rebar and stirrups In your detail, you may need to clear out the webs in order for the steel beam to fit, prop it with some timber or acrows, prefer acrows as f any settling occurs from the block during the pour you can adjust the height of the beam, shouldn't be an issue with Nudura tho with solid webs connecting vertically. After the pour is done and acrows removed, use spray foam and attach the polystyrene cap below. Be careful if you have to cut webs out to make beam fit, you may need to do a bit of additional temporary forming to prevent the block from flaring out during the concrete placement as concrete pressures are high and without the webs, nothing to hold it in place

Like I say, maybe not a code requirement in the UK, but keep in mind wood is organic and a sponge it will suck the moisture from the concrete and good potential for rot to occur. This is why I prefer the Simpson ICF hangers for my rim boards, but when doing exposed connections I would use peel & stick membrane on the backside of the rim board to separate the 2 products

Nudura XR35 will run you about £100 per block (Incl VAT) for 1.1 m2, others are slightly less expensive but do not have the accessories available that Nudura provides as well the increased block size reduces on site labour substantially - figure close to 20% savings U value I believe is 0.16

Concrete and wood should not Wood and Concrete should not touch, even once concrete has cured. May not be a code issue or requirement here in the UK, but I have seen wood rot sooner rather then later from touching concrete, even Green Treated lumber will start to fail