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General: Single storey extension with EWI: what wall structure material?

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      CommentAuthorfostertom
    • CommentTimeJul 11th 2012 edited
     
    Posted By: an02ewOne of the great advantages of EPS is its ability to be shaped and planted on to create the look that you require
    Here's me as Architect trained with a keen eye for 'truth to material' and 'expressed structure', which have been the basic criterion for honest, serviceable, well designed buildings. Now I find myself carving buildings out of EPS, any style you like guv. But it's not so new - Brighton for instance is all beautifully done fake plasterwork applied to dumb masonry (called 'bungaroosh' - a terrible mixture of chalk lumps, bits of rubble and wood!). Those skills, incl fake brickwork if that's what you want, prob even convincing rubble stone soon I hope, are still alive and well amongst plasterers. Many modern city-centre commercial buildings are fake render over a steel frame.
    • CommentAuthorTimSmall
    • CommentTimeJul 11th 2012 edited
     
    Posted By: fostertomBrighton for instance is all beautifully done fake plasterwork applied to dumb masonry (called 'bungaroosh' - a terrible mixture of chalk lumps, bits of rubble and wood!).


    Bungaroosh is great - mainly lime (locally produced from chalk), bits of flint (waste product from local chalk quarying) and whatever else was handy at the time. Just don't IWI it, or apply portland-cement render over it, or let it stay damp, or get too dry either. Or look at it funny. I can't think why it didn't catch on anywhere else?
    • CommentAuthorseascape
    • CommentTimeJul 12th 2012
     
    Sorry to go back a few posts - Borpin:

    Both Kingspan K12 and NBT Pavaclad systems for timber frame (which have exterior wall insulation up against the frame, no cavity, have BBA certificates.

    If you look at the certificates you will see in both cases under NON REGULATORY INFORMATION:

    NHBC Standards 2008 accepts the use of ........., when installed and used in accordance with this certificate, in relation to NHBC Standards......

    The document you must have seen was NHBC Standard Extra 22 (Dec 2001) which highlighted "need for cavity between insulated render system and wall of light steel framing or timber frame..'.
    • CommentAuthorMikeRumney
    • CommentTimeJul 12th 2012
     
    anO2ew wrote:

    "Yes very nice, i love the corners, how are you cutting your EPS? i have recently came up with an EPS cutting machine but it only cuts straight lines in 8x4 sheets but will cut 200mm plus thick sheet, i would like to know how you cut such a nice curve.."

    (Can't seem to use the quote link if it's on an earlier page by the way ... Am I missing something?)

    First idea was to use a rig as in the pic, with a hot wire ... got a few wires types and transforners etc on "Freecycle" but realised I was moving away from what I knew.

    Next version was a kind of hinged coping saw made up from soldered 15mm copper left-overs.
    Too much play.

    Finally used a double profile to work against with a hand held saw made up from two large flat blades soldered together for extra length and screwed to a 2 by 2 batten ..... Think the pic may have to go in a separate post:
      corner block cutting diagram.jpg
    • CommentAuthorMikeRumney
    • CommentTimeJul 12th 2012
     
    ...
      CIMG1892 50%.jpg
    •  
      CommentAuthorfostertom
    • CommentTimeJul 13th 2012
     
    You're v adept with the SU, Mike. i couldn't get on with it.
    • CommentAuthorTimber
    • CommentTimeJul 13th 2012
     
    Posted By: seascapeSorry to go back a few posts - Borpin:

    Both Kingspan K12 and NBT Pavaclad systems for timber frame (which have exterior wall insulation up against the frame, no cavity, have BBA certificates.



    Sorry to keep going over the same points, but we are again talking at cross puproses. Both of those BBA certificates (and products) have a cavity between the insulation and the cladding.
    • CommentAuthorMikeRumney
    • CommentTimeJul 13th 2012
     
    Posted By: fostertomYou're v adept with the SU, Mike. i couldn't get on with it.


    You've said this before :shamed: ... ... I couldn't have designed our build without it.
    I've found it invaluable for working through alternatives by saving a file and then developing it on some new tangents.
    Maybe it's better suited to someone like me who's had to work it up from first principles,
    as opposed to having been formally trained in either building design or 3D software?
    (I use Sketchup "my way" so not to its full potential by a long shot)

    Is there a niche for offering relatively low cost modelling to "smaller" clients, or the Architects working on their project?
    Sketchup is improving all the time.
    I'm looking for new ways of working when I've finished this self-build ... "Chronic Fatigue Syndrome" is stopping me from continuing to do any meaningful work in my "day job" (Craniosacral Osteopath)

    Any offers?! :wink:
    • CommentAuthorborpin
    • CommentTimeJul 14th 2012 edited
     
    Posted By: Timber
    Posted By: seascapeSorry to go back a few posts - Borpin:
    Both Kingspan K12 and NBT Pavaclad systems for timber frame (which have exterior wall insulation up against the frame, no cavity, have BBA certificates.
    Sorry to keep going over the same points, but we are again talking at cross puproses. Both of those BBA certificates (and products) have a cavity between the insulation and the cladding.
    I've had a look at the BBA 08/4615 (for K12) and quote "This Certificate relates to Kingspan Kooltherm K12 Framing Board Insulation for use between studding and/or as sheathing over walls of normal timber-frame or steel-frame buildings with a ventilated and drained cavity between the outer leaf and the timber frame." This is somewhat confusing as the insulation is between the 'outer leaf' and TF!!! Later it does imply that it can be placed against the TF but on the detailed product information it only shows timber cladding or block/brick.

    If you then go to render BBAs, they don't then tie up with the insulation BBAs as they show a cavity between the insulation and the TF.

    I still think the ideal (and probably cheapest) way is a standard 89mm TF, OSB as the airtight layer, 200mm EPS on outside, small cavity and render coat just like VH has. Unfortunately, I have yet to find BBA certificates to back this up to satisfy the BCO (and architect) and I do not have the time or inclination to enter into a long drawn out discussion with them.
    •  
      CommentAuthorfostertom
    • CommentTimeJul 15th 2012 edited
     
    Posted By: MikeRumneySketchup is improving all the time
    Interesting - I abandoned SU somewhere between V6 and v7 because it was just adding more bells and whistles without fundamental improvement. The unreliability of coincident lines merging properly, its fussiness about coincidence, exacerbated by reluctant/inaccurate snapping, the impossibility of tracing faults, and above all the lack of extend/trim and other aids to dimensional input/accuracy.

    Posted By: MikeRumneyIs there a niche for offering relatively low cost modelling to "smaller" clients, or the Architects working on their project?
    I did have some guys build me a model in SU but couldn't make much use of it. Once the model's built (I couldn't) it's OK as is - for visualisation as you use it, and presentation. But for wider use as basis working drawings, or thermal modelling, SU models don't import well - or at all really - into e.g. Autocad, despite SU's .dwg compatibility claims.
    • CommentAuthorMikeRumney
    • CommentTimeJul 15th 2012
     
    Posted By: fostertom
    Posted By: MikeRumneySketchup is improving all the time
    Interesting - I abandoned SU somewhere between V6 and v7 because it was just adding more bells and whistles without fundamental improvement. The unreliability of coincident lines merging properly, its fussiness about coincidence, exacerbated by reluctant/inaccurate snapping, the impossibility of tracing faults, and above all the lack of extend/trim and other aids to dimensional input/accuracy.

    Posted By: MikeRumneyIs there a niche for offering relatively low cost modelling to "smaller" clients, or the Architects working on their project?
    I did have some guys build me a model in SU but couldn't make much use of it. Once the model's built (I couldn't) it's OK as is - for visualisation as you use it, and presentation. But for wider use as basis working drawings, or thermal modelling, SU models don't import well - or at all really - into e.g. Autocad, despite SU's .dwg compatibility claims.



    Yes actually I know what you mean ...
    Being an amateur I've been able to afford the luxury of putting time into compensating for those problems.
    I enjoyed the hands-on initial surveying required too ... so it became a little project/test/training exercise.

    The only real issue arose when the Architect,
    who was asked to draw up and "give credibility to" the plans from my models for the application,
    instead of telling me they were having unforeseen problems getting DWG files from SU to their software,
    printed off something like 32 A3 colour sheets and tried to charge me for them.
    Poor communication I'd say ... maybe they didn't want to concede defeat on the file transfer issue, but still :angry:
    So, yes, not for the pro's out their maybe, and yes, I was only really thinking of it as a visualisation tool off the back of a detailed survey.
    • CommentAuthorTimSmall
    • CommentTimeOct 14th 2012
     
    Posted By: borpin

    "I still think the ideal (and probably cheapest) way is a standard 89mm TF, OSB as the airtight layer, 200mm EPS on outside, small cavity and render coat just like VH has."


    Interesting article from on the topic of foam-over-OSB etc.:

    http://www.buildingscience.com/documents/insights/bsi-038-mind-the-gap-eh

    ... wish I'd seen it earlier, specifically on the topic of the "small cavity" - perhaps I could have talked my BCO into omitting some of those daft 50mm ventilated cavities that the BBA and the regs seem so keen on - the article says ~10mm is conservative:

    "This 3/8-inch gap is very, very conservative. It can be smaller. Just how much smaller most of us are not sure about. But with a 3/8-inch gap I have never, ever, anywhere, known of anyone to have a problem related to drying if nothing else fundamentally stupid was not also happening. How do I define fundamentally stupid? How about a missing flashing"
    • CommentAuthorCav8andrew
    • CommentTimeOct 14th 2012
     
    Tim, Thanks for this link, it seems to me incredibly helpful. I presume the construction method described is equally relevant to the construction of warm roofs, in the sense that it is possible to have OSB clad joists and still cover with vapour resistant/semi resistant insulation. Due to the parallel discussion thread re. dew points I am becoming concerned that my roof build up may suffer from interstatial condensation and am wondering if I should also face externally with EPS (As per Viking House). Having said that apart from understanding the basic principal of dewpoint calcs. most of the issues in the thread are slightly lost on me but I was struck by the apparent formation of condensation/mould on the back face of the OSB as shown in the photo and am concerned that this is a situation that could occur in our chosen build up
    •  
      CommentAuthorfostertom
    • CommentTimeOct 16th 2012
     
    Mike, about SU, I found this http://sketchupdate.blogspot.co.uk/2012/07/telling-full-story-with-sketchup-pro.html eye-opening - can't imagine how he does it.
    •  
      CommentAuthorfostertom
    • CommentTimeOct 16th 2012 edited
     
    Posted By: TimSmallhttp://www.buildingscience.com/documents/insights/bsi-038-mind-the-gap-eh" >http://www.buildingscience.com/documents/insights/bsi-038-mind-the-gap-eh
    You need to download the .pdf version to get vital content, which doesn't show on the web version.

    Very interesting - but the differences between what he's describing and assuming, and what I guess we UK greenie builders are looking at today, are many. Just a few:
    To him 'stucco' is unbreatheable (so we'd all agree a vented cavity wd be reqd behind it) - but the patent renders on European EWI are well breatheable.
    To him 'foam sheathing' means XPS, PIR etc and are non-breatheable - but EPS (as EWI) is reasonably breatheable.
    To him, the new breed of blown-in tween-stud insulations are non-breatheable - but blown-in (or wet sprayed) Warmcel (cellulose fibre) insulation is highly breatheable. So in fact are nearly all blown- or sprayed-in insulations except polyurethane foam (tho Icynene PU is very breatheable) - but we wouldn't use the latter anyway for shrinkage and eco-nasty reasons anyway (except Icynene).

    So I'm not convinced this is gd advice for UK greenie builders - let's go thro that article with a tooth-comb.

    One v interesting mention was plasterboard as sheathing - Brit Gypsum used to offer that back in the late 80s and I specified/used it, but no longer documented or offered in UK AFAIK.

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