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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
These two books are the perfect starting place to help you get to grips with one of the most vitally important aspects of our society - our homes and living environment.

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    • CommentAuthoran02ew
    • CommentTimeFeb 17th 2016
     
    Has anyone had experience of either natural stone slips or natural stone cladding? To be fixed direct to EWI or to cement board on battens.
    • CommentAuthortony
    • CommentTimeFeb 17th 2016
     
    Done brick slips
    • CommentAuthoran02ew
    • CommentTimeFeb 18th 2016
     
    what? if any issues? how did it all finish around corners and into windows? did you have to arrange windows and doors to work to a bond?
    • CommentAuthortony
    • CommentTimeFeb 18th 2016
     
    pistol bricks on corners and cuts in work same as normal brickwork. not see pistols with stone but the may well exist
    •  
      CommentAuthorfostertom
    • CommentTimeFeb 18th 2016
     
    What are you up to Andy - EWI-ing a Bath stone mansion?
    • CommentAuthoran02ew
    • CommentTimeFeb 22nd 2016
     
    Planning restriction on our next project will mean we have to use a lot of stone work some brickwork and a little render. Recently our work has been generated from self builders who are using planning consultant to attain permission in awkward areas, they are designing what the planners want to see but not necessarily what is easy to adapt to a low energy construction method, it then passed over to me to try and make it work!
    This particular project is in a village of beautiful Ham stone houses and cottages, so i am looking at stone slips and /or stone panels, the latter laid on counter battens over EPS to allow for the annoying air gap insisted by LABC,
    •  
      CommentAuthorfostertom
    • CommentTimeFeb 22nd 2016
     
    You need some WUFI modelling mate!
    • CommentAuthoran02ew
    • CommentTimeFeb 25th 2016
     
    there is definitely a potential for a moisture issues with these build methods, so when we decide on a wall make up i will give you a call.
  1.  
    We are in a similar situation - previous owner of the land made an application for a mix of stone cladding and timber.

    Don't want to do anything that counts as advertising but I have found a manufacturer of a stone slip system who we may resort to if our planning amendment (showing all timber) is rejected. The system consists of a concrete backing board with real stone embedded in the front. Each unit is then hung from mechanical fixings (not great thermally) or adhered to insulation (not feasible for us due to Rockwool). Cost last year was around £45 (+VAT) per sqm. End result looks like a dry stone wall so won't be a perfect visual match for ashlared stone but there were a range of stone types on offer so the colour will be right.

    I think the system acts essentially like a rainscreen so if you could fix to battens in front of the insulation it should be possible to ventilate without compromising your thermal performance. I fear from what you say above though that this is the dreaded NHBC 'ventilate behind the insulation' clause - although I thought I heard somewhere that they have now relented on this requirement. (doesn't mean the LABC will see sense though)

    Ham stone is also fairly soft and absorbent from what I recall. No chance you can use terracotta instead?
    • CommentAuthorringi
    • CommentTimeFeb 25th 2016
     
    If you are forced to use stone, maybe copy http://www.greenbuildingstore.co.uk/technical-resource/denby-dale-passivhaus/ see for overview http://www.building.co.uk/passivhaus-diaries-part-two-why-we-chose-cavity-walls/3141714.article
    • CommentAuthoran02ew
    • CommentTimeFeb 25th 2016
     
    Interesting DT i have done some research into something similar which is one half of my OP when vs stone (albeit fake) slips. My chief concern is the o/a weight of slips adhered to EPS and would the EPS fail leaving everything on the lawn?

    Ringi
    i have not ruled the cavity method- but not convinced of the extra work needed at foundations to support outer skin would counter the work involved in stone clad EWI. not too mention the wall thickness would be painfull
    •  
      CommentAuthorfostertom
    • CommentTimeFeb 26th 2016
     
    If it's smooth cut fine jointed (ashlar) stone rather than rough knobbly 'rubble' stone then it's got to be thin stone slips glued direct on the EPS, just like brick slips.

    I'd say get natural stone sawn to 15mm thick or whatever - fragile while loose but strong once full-bed glued with suitable cementitious adhesive (but must be breatheable - vapour permeable) to the impact-distributing EPS. But I'm not sure of the freeze-thaw resistance of natural stone in such thickness.

    100% convincing ashlar can be faked in render - long tradition - half of Cheltenham and all of clasic Brighton is done that way. But only a conservation-grade craftsman will get it right - your average plasterer won't get the scored-in joint layout and profile right and and will make it look like DIY stikabrik.

    For rubble, a glued-on slip solution may become possible - tony brilliantly suggested 3D printing thin stones of infinite variation, after scanning a real wall, which would have to be installed in correct numbered location/layout.
    • CommentAuthoran02ew
    • CommentTimeFeb 26th 2016
     
    Some interesting points Tom, both the breath-ability of the final covering and the freeze-thaw resistance haven't figured in my (long)list of potential issues till now. The planning App states a "natural stone finish" so i dont think would get away with stone impressions in render?

    The breath-abilty issue is less if i use a vented cavity behind the cement board (sub-strait to stone slips or stone cladding) but in-front of the eps, this create another problem at eaves and plinth.
    •  
      CommentAuthorfostertom
    • CommentTimeFeb 26th 2016
     
    Posted By: an02ewThe breath-abilty issue is less if i use a vented cavity behind the cement board (sub-strait to stone slips or stone cladding) but in-front of the eps
    That's true - there will be freeze-thaw, like anything relatively thin (only moderate thermal inertia) exposed (both sides) during a sub-zero overnight or a longer cold snap.

    But when glued to a EWI'd breatheable wall, there will be lots of water vapour traffic in and out, which WUFI shows fluctuatingly condensing, for extended periods in winter, intersitially within the very outermost part of the EPS and within its finish, whether render or slips. This doesn't matter with EPS and EWI renders, but slips need to be up to such treatment.

    Note that all these - the EPS, the render and the slips/pointing may be proof against liquid water, but need to be well permeable to water vapour. Any thought of silicone surface treatment etc must have same effect - improve liquid run-off and reduce liquid capillarity, without degrading water vapour permeability.

    Think of it that the surface may be sluiced with liquid water and quite immune to it, but its wetness is a major source of water vapour, which freely penetrates back thro the surface - in both directions e.g. when the sun comes out.

    The water content in a wall is a constant in-out traffic, from both inside and outside - not just from inside as popularly supposed and embodied in building regs e.g. the notion of internal VCL.

    Even if the surface isn't entirely impermeable to liquid water, it def needs to be vapour permeable, as its survival absolutely depends on max re-drying at the slightest opportunity.
    • CommentAuthoran02ew
    • CommentTimeFeb 26th 2016
     
    Very interesting. i was always leaning towards a vented cavity with cement board outer layer to fix/glue stone facade, also the stone panels i`m considering are dry(un-pointed) so less of an issue as far as freeze-thaw for mortars.there are still adhered to outer cement board with fixing above 2M. the system seams within my skill set and allows for on-site tinkering of panels to get the best fit.

    what do think of the propose wall make-up

    140mm concrete block (rendered internally for airtightness)
    350mm Steico beam fixed externally as spacer skeleton for
    12 permavent board over i beams to create cavity to be filled with Diamond grafite bonded EPS bead
    breather memebrane
    25mm vertical batten for vented space
    12mm super E board as substrate for stone panels
    •  
      CommentAuthordjh
    • CommentTimeFeb 26th 2016
     
    Posted By: an02ew
    12 permavent board
    12mm super E board

    Isn't permavent a membrane?
    And what is super E board?
    • CommentAuthorEd Davies
    • CommentTimeFeb 26th 2016
     
    13mm Panelvent DHF?
    • CommentAuthoran02ew
    • CommentTimeFeb 26th 2016
     
    Sorry. Your right I mean panel vent or timber vent
    Super E or E board is 8x4 sheets of 12mm cement board
    •  
      CommentAuthordjh
    • CommentTimeFeb 26th 2016
     
    Thanks guys. In which case I don't see any problems but it seems a little odd. With a structural block wall, I'd expect to see rigid EPS glued to the outside, and then a separate carrier for heavy cladding tied back to the block wall for stiffness. With timber beams containing an insulant, I'd not expect to see blocks inside and I'd maybe expect cellulose rather than EPS beads as the insulant. But maybe that's just my preconceptions.

    I don't know how EPS beads behave as compared to cellulose but cellulose bulges out if it is only constrained by a membrane, so it would need more than 25 mm battens to guarantee an airspace. But perhaps EPS beads aren't pressurised in the same way?
    • CommentAuthoran02ew
    • CommentTimeFeb 26th 2016
     
    Blockwork inner for thermal mass and clients negative opinion on "timber frame" ibeams provide very stronge cantilever out from blocks for heavier cladding

    12 mm panel vent has more resistance than membrane. So almost zero bulging, but I would, if readily available as treated, like to use a little wider batten.

    EPS over cellulose as this area is outside of DPM and in contact with foundation insulation. My concern is wicking and moister
    •  
      CommentAuthordjh
    • CommentTimeFeb 27th 2016
     
    Posted By: an02ew12 mm panel vent has more resistance than membrane.

    Oops, sorry, I misread that when I replied. Yes panelvent will be fine, that's what we used.

    very stronge cantilever out from blocks for heavier cladding

    I think I'd be trying to support the cladding separately, but I'm sure you've thought it through.

    EPS over cellulose as this area is outside of DPM and in contact with foundation insulation. My concern is wicking and moister

    I suppose that given there's a block wall inside it, the choice doesn't much matter for cellulose's usual advantages.
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