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About kxi

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  1. kxi

    Precast Floor Slabs - Cost

    We had quotes from Leroc and Bison on 300m2 of 150mm hollowcore, max 6m spans. Roughly £50/m2 and £57/m2, supply and fix, including passive fall arrest. Price does not include structural topping (to be supplied by others).
  2. @TerryE Isn't the conversion of a barn to dwelling likely to be at least in part 5%, as per VAT notice 708? (I hope it is) https://www.gov.uk/government/publications/vat-notice-708-buildings-and-construction/vat-notice-708-buildings-and-construction Summarised: https://www.charltonbaker.co.uk/news-blog/detail/reduced-rate-of-vat-and-barn-conversions Also, if the barn conversion is under Class Q Permitted development (which I assume it is unless you go for full planning) then one would need to make a 'prior approval' application to the council. Whether one then needs to also get a certificate of lawful development in addition is debatable. Our council never suggested this was necessary and our planning consultant didn't think it necessary either, however a planning lawyer did later suggest there was in theory a case for one, though AFAIK not one that has ever actually applied to any class Q conversion in reality (but don't take my word for it). I would be surprised if anyone getting Class Q barn conversions also got an LDC, but it would be interesting to hear from others using Class Q.
  3. Hello, could you provide more details about your existing barn and the nature of the conversion? Esp. are you allowed to extend the envelope or not. This will help with more specific advice. The main reason for asking is steel frame may require a slightly different solution to most of those discussed on the forum.
  4. kxi

    Modern Portal Frame Barn Conversion

    It was IanR who had the conversion with the insulation layer inside the existing steel frame: https://forum.buildhub.org.uk/topic/1111-touchwood-homes-experiences/?tab=comments#comment-14294 Our conversion has no existing steel, so I've not thought through the pros and cons of insulating entirely inside vs external / straddling, but I would suppose it's conceptually simpler to build everything inside, but you then lose some floor space and head height to accommodate thick insulation (I'm sure plenty of other pros and cons each way). Also, if your steel is say 180mm deep, then the purlins 130mm, the windows will be deeply inset if the insulation layer is fully inside. This could be seen as a design feature though. Some of our windows will probably end up being inset over 500mm!
  5. kxi

    Modern Portal Frame Barn Conversion

    I assume maximising the internal space is a concern, so @Tosh 's straddling ICF route neatly gets half of your insulation layer outside of the steel, with probably enough room left to fit some cladding support within your 4-5 inches currently used by the purlins - thus no footprint extension so staying within your Class Q. I don't know what you had in mind for the party walls, but I would guess block is the easiest and thinnest way to meet the desired standard for noise, vibration & fire? Using the ICF for that as well would seem to add unnecessary width. For the roof, do you have the same 4-5 inches of purlins on top of the frame? It would be nice to get the insulation layer above the steel (in contrast to the current plan), especially if it can be continuous with an outer face of the wall's ICF. For that to be feasible you'd probably need something like the quadcore foam used in Kingspan's Benchmark panels, or the full insulated roof panels like the KS1000. I don't know if your planning requires you to retain/replicate the exact corrugations of the existing roof? @Tosh how are you planning to do the roof in your conversion? It may be relevant that our LPA were surprisingly relaxed about Non Material Amendments to the original Permitted Development design, once we got over the small hurdle that they insisted no changes were supported under the legislation. They are, but it's not well-known it seems. But I suspect you'd rather just avoid going back to them for any reason.
  6. kxi

    Modern Portal Frame Barn Conversion

    Hello, congratulations on the planning. Quick initial questions. Is the current plan to have the insulation layer (e.g. sips panels) on the inside of the existing steel frame? The plan implies so and I assuming planning will not allow the footprint extension of an insulation layer outside of the existing frame? There is another barn conversion on the forum where I believe the existing steel frame was outside the envelope (apologies can't find it right now as on phone). Have you got any 'cladding space' to have at least some of the insulation layer external to the steel? The plans say timber cladding, but I assume the metal cladding you describe above was a later planning condition? My initial thought was the panels don't necessarily need to be structural and one could use something like the probably cheaper steel faced kingspan insulated panels. But it may be that the idea is to support the new first floor on the sips? Is the existing steel not ok to support a first floor (I assume not). Building an internal facing wall (+ service zone?) Might be easier against sips than steel faced panels. But perhaps worth looking in to.
  7. kxi

    Non Material Amendment NMA

    @Jilly Hello, if it's a stable conversion did you get this under full planning permission or under permitted development e.g. conversion from agricultural to residential? Dealing with an NMA is different if done under PD (and I can explain more if so).
  8. kxi


    I was concerned about the long-term durability of standard steel rebar, so looked into alternatives a bit. My layperson's summary below. However, I'm now just going to use standard steel in our own Reinforced Concrete parts. While steel corrosion seems a major problem for structures like bridges, dams, etc, my SE has assured me any RC with standard rebar kept protected from; the elements, unusual chemicals, and cyclical loading should be fine for over 150 years. I.e. ours will be fine, and I'd guess anything inside ICF also fine. As below, all the alternatives have some disadvantages. But if you are building something with exposed RC and care about it lasting more than 50 years, the lifecycle costs seem to suggest everything is more cost-effective than using standard steel. Some evidence of standard steel / iron reinforcement durability: The first RC house ever built 1852 is still standing https://en.wikipedia.org/wiki/François_Coignet The first one in the US 1876 is apparently fine https://en.wikipedia.org/wiki/William_E._Ward_House The first RC skyscraper 1903 is also apparently fine https://en.wikipedia.org/wiki/Ingalls_Building Alternatives: (Some comparison here https://www.usbr.gov/research/projects/download_product.cfm?id=2493 ) Stainless steel A fairly straightforward replacement for normal rebar (though apparently, you need to use a bit more to get the stiffness) and used for many years. Main issue is the cost, which might be 3 or more times the cost of normal rebar. I didn't check the specific price. Glass Fibre Reinforced Polymer GFRP Proposed as a corrosion-free alternative to steel and much lighter, with higher tensile strength. Has been well studied and increasingly in use in some structures worldwide, and has building codes that govern its safe use. Unfortunately, it's not without problems: Fire - while the glass withstands very high temperature, it's in resin that softens at over 150 C. For this reason, the Institution of Structural Engineers do not recommend it for situations in which fire is a concern. Unknown long term behaviour in concrete - glass doesn't like alkali i.e. concrete, or moisture, and as per one of the suppliers' own descriptions "At this time, there is no consensus as to what would be an accurate service life prediction model for the use of GFRP bars". http://www.aslanfrp.com/media/aslan100.pdf Creep - This same supplier also notes that GFRP has creep rupture with sustained high utilization. Though these are AFAIK accounted for in the building codes that apply to GFRP. My SE also noted its long term creep is not good. Elasticity - much more elastic than steel and so requires more reinforcement or more concrete depth to compensate. Perhaps of note Owens Corning recently bought the manufacturer of Aslan GFRP, so presumably they think it has long term potential. Carbon Fibre Reinforced Polymer CFRP Really good, really expensive, doesn't like fire. Basalt Fibre Reinforced Polymer BFRP A new contender that has only been in use for a few years, and the subject of much current research especially in China. Similar properties to GFRP (light, high tensile strength) but may address some of the issues with GFRP and appears to be able to be produced more cheaply e.g. in the US you can get rolls at $6.60 a metre, and Gatorbar claim cost parity with standard steel. https://www.neuvokascorp.com/sites/all/themes/theme923/pdf/GatorBar_data_20160907_HIGH.pdf BUT it shares GFRP's disadvantages in that The resin doesn't like fire Still elastic The major drawback is that it's so new, people seem nervous about doing anything structural with it: There's almost no example of it being used in house construction other than floors & shallow foundations Gatorbar currently limit use to slab on grade and low walls/foundations (confirmed this with them) UK suppliers of Galen's Rockbar (Magmatech) said it hadn't been used structurally and any structural use of it would have to be approved by an SE Various BFRP references: http://www.thestructuralengineer.info/onlinelibrary/pdfs/SustainabilityMasterBuilder_Sep10.pdf https://www.ripublication.com/ijaer18/ijaerv13n8_37.pdf https://livrepository.liverpool.ac.uk/16333/4/SalhLuna_Feb2014_16333.pdf http://www.carnationconstruction.com/Materials/01-Materials-Rebar.html https://www.sciencedirect.com/science/article/pii/S187661021730022X https://www.monolithic.org/link-to/basalt-fiber-rebar https://smarter-building-systems.com/smarter-building-basalt-faqs/ https://www.researchgate.net/publication/315642749_Investigation_of_Structural_Members_with_Basalt_Rebar_Reinforcement_as_an_Effective_Alternative_of_Standard_Steel_Rebar https://pure.qub.ac.uk/portal/files/154263432/180620_polymers_10_00678_paper_accepted_in_J_of_Polymer.pdf BFRP durability: https://www.sciencedirect.com/science/article/pii/S0264127518308724 https://www.researchgate.net/publication/319943787_A_refined_prediction_method_for_the_long-term_performance_of_BFRP_bars_serviced_in_field_environments https://ascelibrary.org/doi/pdf/10.1061/(ASCE)CC.1943-5614.0000497 Some BFRP suppliers: https://www.neuvokascorp.com/sites/all/themes/theme923/pdf/GatorBar_data_20160907_HIGH.pdf http://magmatech.co.uk/products/rockbar/ http://orlimex.co.uk/composites/ https://www.monolithicmarketplace.com/collections/basalt-rebar-products/products/rebar-12mm-diameter http://galencomposite.com/products/composite-reinforcement-rockbar/
  9. kxi

    Insulated roofing sheets

    @Simon Brooke Ok, good luck.
  10. kxi

    Lignacite block

    @Russell griffiths I suspect it's a question of the market you are catering for. The Shard used 140,000 of them, presumably because in the context of a project like that, being able to say the blocks were carbon neutral was worth more to them than an extra £140k (or whatever it was). http://www.lignacite.co.uk/project-library/the-shard-2.html The blocks also seem to have a slightly better acoustic reduction than standard medium weight, but perhaps not a big factor in most cases.
  11. kxi

    Insulated roofing sheets

    @Simon Brooke Have you had an airtightness test yet to see how the taped kingspan panels perform?
  12. kxi

    Lignacite block

    Does anyone have experience with / opinions on the Lignacite block from Lignacite? http://www.lignacite.co.uk/concrete-and-facing-masonry-blocks/concrete-blocks/medium-dense/lignacite.html Data sheet http://lignacite.co.uk/component/edocman/?task=document.viewdoc&id=128&Itemid= Medium weight concrete block with 48% recycled aggregate including recycled wood, allowing them to claim the block's carbon footprint is -2kg per tonne. Used extensively at The Shard and London Olympic stadium (among other places).
  13. kxi

    Bungalow Barn - update

    @Snowbeetle excellent, thanks very much.
  14. kxi

    Bungalow Barn - update

    @Snowbeetle How did you find installing the geocell? Any tips / things you would do differently if doing again?
  15. From an initial look appears superior to stainless - thanks very much.