Thu, 21 May 2026 21:30:10 +0100 https://www.greenbuildingforum.co.uk/newforum/ Lussumo Vanilla 1.0.3 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10263&Focus=169600#Comment_169600 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10263&Focus=169600#Comment_169600 Fri, 08 Mar 2013 11:03:23 +0000 Mike George
I'm particularly interested in establishing physical properties and how these justify liquid/vapour permeability ; *breathability* etc.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10263&Focus=169601#Comment_169601 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10263&Focus=169601#Comment_169601 Fri, 08 Mar 2013 11:58:34 +0000 Shevek https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10263&Focus=169679#Comment_169679 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10263&Focus=169679#Comment_169679 Fri, 08 Mar 2013 16:39:38 +0000 Mike George Posted By: ShevekDo any of these (or any other options) avoid the formation of cracks? What are elastomeric coatings, for instance, and can they be applied to EPS?

Hi Shevek, exactly the kind of things which need to be discussed. We could do with experts in product/coating/ mortar type putting forward the case for each.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10263&Focus=169737#Comment_169737 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10263&Focus=169737#Comment_169737 Sat, 09 Mar 2013 10:55:06 +0000 jamesingram From BS12524 Building materials and Products,Hygrothermal properties, Tabulated design values.

Renders / water vapour resistance factor /DRY/WET
gypsum sand /10/6
lime sand /10/6
cement sand /10/6

So no difference there.
In practice many poorly informed plaster/renderers add water proofer additive to sand/cement render (often 4/1 in my experiance) which no doubt changes things.
6/1/1, sand/cement/lime without additive , I beleive is the correct/better mix, perhaps weaker ?]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10263&Focus=169739#Comment_169739 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10263&Focus=169739#Comment_169739 Sat, 09 Mar 2013 11:04:21 +0000 jamesingram http://www.natural-building.co.uk/images/downloads/Breathability_in_buildings.pdf

Vapour Permeability (r) is offered ( unsure how this relates to water vapour resistance factor in BS12524)
cement plaster 100
lime plaster 75
clay plaster 40]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10263&Focus=169750#Comment_169750 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10263&Focus=169750#Comment_169750 Sat, 09 Mar 2013 12:04:21 +0000 Mike George
Edited

The conversion is actually quite simple if you look at the excellent illustration here http://builddesk.co.uk/wp-content/uploads/2013/01/vapourResistances.pdf
It's the raw data such as that in the NBT Table that is hard to come by . .

Regarding the data given by NBT, the numbers do not tally (See images below)with data in BS12524 (unless my maths are wrong) The NBT sorces of these data is unclear from the paper.

Right or wrong they are in the same ballpark however and when you consider the range of these values I see no justification for any argument that one kind of render is significantly different to another in terms of vapour permeability What we don't have is numbers for the acrylic/mineral renders in order to be able to make a comparison...]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10263&Focus=169754#Comment_169754 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10263&Focus=169754#Comment_169754 Sat, 09 Mar 2013 12:21:23 +0000 fostertom Posted By: Mike GeorgeIts the raw data such as that in the NBT Table that is hard to come byHas anyone asked NBT Neil for his raw sources?]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10263&Focus=169759#Comment_169759 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10263&Focus=169759#Comment_169759 Sat, 09 Mar 2013 13:22:36 +0000 Mike George
These are the sources listed under the NBT table

sources: Bablick, Federl (1997): Fachwissen für Maler und Lackierer, Stamm Verlag, Köln
CIBSE 1999 Guide A: Environmental Design
Product technical sheets: Various

Googling them yields nothing. Though the Guide A will be easy to find when I can grab my copy]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10263&Focus=169764#Comment_169764 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10263&Focus=169764#Comment_169764 Sat, 09 Mar 2013 15:32:33 +0000 Henry Sears https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10263&Focus=169766#Comment_169766 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10263&Focus=169766#Comment_169766 Sat, 09 Mar 2013 16:16:59 +0000 SteamyTea Posted By: Henry Searshas just dissolved benignly into the landscape leaving nothing but a pile of native stone.Is it really benign, bit on the alkaline side isn't it]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10263&Focus=169772#Comment_169772 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10263&Focus=169772#Comment_169772 Sat, 09 Mar 2013 17:53:15 +0000 Triassic Posted By: SteamyTeaIs it really benign, bit on the alkaline side isn't it
But dosn't nature naturally buffer the alkalinity, will an acrylic resin break down naturally? Probably not!]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10263&Focus=169777#Comment_169777 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10263&Focus=169777#Comment_169777 Sat, 09 Mar 2013 18:53:14 +0000 djh Posted By: SteamyTeaIs it really benign, bit on the alkaline side isn't it
Not especially once its carbonated - but that's the point really, acid rain needs to be neutralised.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10263&Focus=169778#Comment_169778 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10263&Focus=169778#Comment_169778 Sat, 09 Mar 2013 18:54:29 +0000 djh Posted By: fostertomHas anyone asked NBT Neil for his raw sources?
Stable door, 600 mm bolt, horse. I guess Ecobuild would have been a good place to ask many questions like this of the great and good.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10263&Focus=169803#Comment_169803 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10263&Focus=169803#Comment_169803 Sun, 10 Mar 2013 01:01:58 +0000 Henry Sears Posted By: SteamyTeaIs it really benign, bit on the alkaline side isn't it

That's welcome round here, where the pH is seriously on the low side...]]>