I am planning an extension to my kitchen and have found that new regulations call for a wider cavity wall than in my 1988 build. I need to align the outside so this will mean there is a step in the inner wall which will cause a headache with kitchen units. Is there any way around the requirement for a thicker wall - perhaps by using better insualtion materials?
The BCO may well allow you to do it to the same standard as the current. Failing that, there are ways of meeting the insulation requirement in other ways. (e.g. stud wall and insulation - which could work if the outside was rendered)
Considering the whole kitchen is being bashed about, I don't think moving a doorframe an inch or two is going to break the bank
It's fairly certain that he will, in which case the existing walls will need thicker adhesive behind the boards to bring them out to suit, like I said, an irrelevance
It depends what other critical dimensions there are. When we converted a built-in garage into a kitchen, the BCO wanted me to dry-line the outside wall - which would have made it just too narrow to get the planned equipment across the end. I managed to persuade him to let us plaster direct to brickwork, to match the other end of the room which had previously been plastered and used as a utility room. That way, we managed to get everything in.
Exactly. We have an extension to the kitchen where one wall is in line with the existing interior wall and the other is just far enough away to fit washing machine, tumble dryer and dishwasher in. Reducing that space at all would prevent all three fitting and moving the outer wall a couple of inches would prevent access to the garage (yes it is that tight - I can get my kit-car in okay, but the normal day to day car only goes through to be worked on and will only go through with the door mirrors folded and someone watching and directing from the front; there's less than an inch free each side).
Similarly my parents have solid walls and may well insulate internally (outside is brick and would not fit in if rendered), but the boxroom will not be able to have the thickness required by current building regs or a standard bed will no longer fit across the end wall!
SteveW
About the thinnest cavity wall construction possible is 275mm consisting of a 100mm brick outer leaf, a 100mm inner leaf of an aerated block (such as Thermalite Turbo or Celcon Solar) with a cavity of 50mm PIR (such as Kingspan or Celotex) and a 25mm clear cavity. The last bit can only be achieved in walls up to 4.5m high in sheltered locations, otherwise it would need a 50mm clear cavity.
You may be able to achieve a solid 200mm blockwork wall if you can render the outside, and dry-line the inside with 50mm Kingspan, but you'd need to check the figures for that; I'm just going from my sieve-like memory.
As others have pointed out, if the wall in question isn't very large in comparison to the rest of the extension, you could try an average U-value calculation, with a 50mm full-fill or 25mm + 25mm PIR/clear cavity. This would give you a U-value of something in the order of
0.45W/m^2K (again, from memory, so check the figures) to offset against lower (better) values on the other walls and/or floor or roof.Hugo Nebula wrote in news: snipped-for-privacy@4ax.com:
The BCO is going to allow me to continue with the same thickness due to the extension being less than a certain volume.
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