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Vanilla 1.0.3 is a product of Lussumo. More Information: Documentation, Community Support.
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Posted By: CWattersIf you replace every other block with an eps one (is that the proposal?) the blocks that are left will need to carry at least twice the load so will need to be denser increasing the U-value. There is also a problem with the brick bond as far as I can see.
Posted By: davidfreeboroughnot a single person I've spoken to has said that EWI is cheaper than cavity wall for new buildFair enough, but hard to believe - I think you've provided figures on this in the past? As the inner skin and the EPS is basically same either way, we're saying that all the extra dig/muck away, extra found width - footprint in fact - plus the masonry outer skin and expensive wall ties, all add up to cost less than the render coat on EWI.
Posted By: davidfreeboroughusing well known & understood materials & construction techniquesIMHO, cavity walling pushed to these wide-cav extremes is a new and far-from-familiar animal.
Posted By: fostertomPosted By: davidfreeboroughusing well known & understood materials & construction techniquesIMHO, cavity walling pushed to these wide-cav extremes is a new and far-from-familiar animal.
Posted By: davidfreeboroughWhy not just put insulation inside & outside the foundation walls? Below is what I'm planning.
Posted By: TimSmallThermal resistance ~30% higher (need to run a calc - that's a guess)One part in 4 = 25%, max.
Posted By: TimSmallFor my case, as I'm building off chalk, I can do a block-width foundation using the info directly from England+Wales Building Regs Approved Document A (page 35). So 150mm wide concrete strip.You can't build up to the edge of a concrete strip foundation; you'll need 100-150mm concrete either side of the blockwork. You'll also need to dig out sufficient earth to allow the EWI to continue down to strip foundation level & to face it with 50mm of paving stone or similar. So there'll be around 200-300mm less concrete width due to absence of outer leaf & around 50mm less trench width due to using paving stone in place of outer leaf.
With a wide cavity, with 2x 100mm leaves, and 200mm insulation this would go up to a 400mm wide foundation.
Posted By: fostertomAs the inner skin and the EPS is basically same either way, we're saying that all the extra dig/muck away, extra found width - footprint in fact - plus the masonry outer skin and expensive wall ties, all add up to cost less than the render coat on EWI.The inner skin is likely to be wider for an EWI design as the main structure will be 190mm minimum rather than the 100mm common in cavity wall inner leaves. I'm using 100mm above slab, but 140mm below slab due to the weight of two cast in-situ concrete floors.
Posted By: fostertomU/ground 440x440 piers on pads down to reqd soil loadbearing level, shallow ground beams between, mainly avoids the problem - u/floor insul can come out under the ground beams and join the EWI. To avoid great reinf, the ground beams can be precast, or long railway ('crossing') sleepers on edge.
Posted By: davidfreeboroughPosted By: TimSmallFor my case, as I'm building off chalk, I can do a block-width foundation using the info directly from England+Wales Building Regs Approved Document A (page 35). So 150mm wide concrete strip.You can't build up to the edge of a concrete strip foundation; you'll need 100-150mm concrete either side of the blockwork.
With a wide cavity, with 2x 100mm leaves, and 200mm insulation this would go up to a 400mm wide foundation.
around 50mm less trench width due to using paving stone in place of outer leaf.
Posted By: davidfreeboroughthe main structure will be 190mm minimum rather than the 100mm common in cavity wall inner leaves.
Posted By: TimSmallApproved document A, page 35 says "Type of Ground" -> "1 Rock" -> "Not inferior to sandstone, limestone or firm chalk" -> "minimum width of strip foundations (mm)" -> "[...]equal to the width of wall".Good point, but this assumes you can lay out the house with pin-point accuracy. I've seen a lot of foundation walls get very close to the edge of a much wider concrete strip due to the tolerances of the ground workers trenches & the bricklayer's laying out.
Posted By: davidfreeboroughthis assumes you can lay out the house with pin-point accuracy.
Posted By: davidfreeboroughThe inner skin is likely to be wider for an EWI designAs TimSmall says, can be as narrow as calcs allow. With wide cavity, load is no longer shared onto the outer skin, and its lateral stabilisation is also more tenuous, so you may need thicker inner skin anyway.
Posted By: davidfreeboroughfootprint in terms of dig/muck removal will be similarWell, the extra is outer leaf plus found overhang - at least 250, assuming EWI down to found, which is something only we on GBF do, it seems!. But then we have that trench anyway, for french drain, Leca wing etc. I've not bothered with paving slab, just bare EPS - but am now looking to dob on a rodent-proof mesh where buried.
Posted By: davidfreeboroughlow cost mineral wool insulation, rather than rigid boards approved for EWI useTrue
Posted By: davidfreeboroughEWI wall fixingsNo longer necessary with some systems
Posted By: davidfreeboroughrender finish is quite technical and consists of a number of componentsBut shop around for plasterers - such render is common, cheap-option stuff on commercial buildings etc.
Posted By: fostertom[EPS] but am now looking to dob on a rodent-proof mesh where buried.
Posted By: fostertomam now looking to dob on a rodent-proof mesh where buriedWonder if the standard glassfibre mesh which reinforces the render anyway wd be sufficiently rodent proof, underground (roughly dobbed on with the standard adhesive, without the render). What think, anyone?
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