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    I have a job coming up with 200 platinum EPS on a 225 solid brick wall (U value appr 0.16). It has been suggested I should use fixings with a countersunk head and an EPS plug which slots in to the countersink, to avoid the appearance of dry patches at the fixing points on dewy mornings, due to heat-loss through the fixings.

    Standard fixings, without the countersink, are less fiddly, and cheaper.

    My feeling is that I know that mech fixings (which I want, and *will* use!) are a cold bridge, whatever, and I'll live with that (without the fancy capped fixings) if the aesthetic effect is minimal.

    Anyone out there with 150+ EWI got experience of this issue?

    Thanks in advance!

    • CommentAuthortony
    • CommentTimeMay 18th 2017
    I have plenty of evidence with block work and mortar beds, ceiling joists with and without insulation.
    I'm thinking particularly of aesthetics, and the 'early-morning mottled effect'.

    Are you saying you see the 'ghosting' of, for example, joist-end thermal bridges on the external brickwork on moist days?
    • CommentAuthortony
    • CommentTimeMay 18th 2017
    Yes, see the mortar beds through rendered aircrete blockwork within mould on the paint, none were the mortar is thermal bridging.
    I've had ghosting on thinner jobs (70mm semi rural location) , not on my 200mm jobs.
    I think I'd be tempted to go for the plugs though in the future now theyre easier to get hold of.
    theres large area of my estate (urban) now EWI via council 90mm , thincoat and dash finish , not noticed any ghosting and they used 5 fixs a panel
    I've not seen any ghosting on my EWI, 100mm with plastic mushroom head fixings, however the fixings were well sunk into the EPS and the resultant dent filled with render (adhesive) as a separate exercise prior to the render and mesh being put on.

    I asked why the dents were filled separately first and not floated with the mesh render and I was told that if you try to do it all at once you will see the fixing points.
    You could just foam the Insulation onto the wall.
    • CommentTimeMay 20th 2017
    Posted By: Nick Parsonsmech fixings (which I want, and *will* use!)
    It's OK, it's OK - but why?
    ..because I am someone for whom adhesives often don't work! I like mechanical fixings as a back-up!
    • CommentAuthorgyrogear
    • CommentTimeMay 20th 2017
    adhesives held the tiles on the space shuttle

    (or most of them...)

    • CommentAuthorMikC
    • CommentTimeMay 21st 2017
    The phrase " belt and braces" springs to mind....
    • CommentTimeMay 21st 2017 edited
    It really does depend on the background you'd be glueing to - EWI regional rep will come to site and advise whether it makes the cementitious adhesive 100% safe, or not stable enough so needing mech fixings too.
    From experience I think it is not necessarily just down to the rep. I think some system suppliers just favour the belt and braces approach.
    • CommentTimeMay 21st 2017
    Are we saying that cases where we've trusted the Rep, will come unstuck in 15yrs time? Isn't there massive experience, giving confidence, amongst the suppliers?
    I'm not saying that, FT, just that in my case glues don't work as well for *me* as they are said to, hence generally Rawl-bolts rather than resin anchors (though Rawl-bolts can be a PITA!), and EWI/IWI adh *plus* mech fixings. Small c conservatism, belt and braces, call it what you will.
    • CommentAuthortony
    • CommentTimeMay 21st 2017
    • CommentAuthorrevor
    • CommentTimeJun 4th 2017 edited
    I had considered EWI for my renovation of an old farmhouse until I went to see some examples of EWI with render. I was not impressed I could see the joints in the EWI through the render and the render had stain marks. What I chose to do in the end was to EWI, and cedar cladding it painted with Owatrol paint and it looks great. added advantage is that there is an air gap between the insulation and the cladding which protects the insulation from any potential ingress of weather. Where I live there is an issue with algae in the air and render is prone to staining from it in particularly monocouche renders. I fixed the insulation with battens using stainless screws into previously fixed battens over a layer of insulation therefore having a thermal break to the exterior. i.e I had 2 layers of insulations of 50mm cross laid.
    • CommentTimeJun 5th 2017 edited
    100 (2x50) is about the max EWI thickness where you could get away with fixing the cladding like that - simple long screws, relying on the bending strength of lots of screws to carry the cladding weight, not positively suspending it from above or supporting it from below. Clamping friction doesn't work. Hope it doesn't slide down with time.

    The joint-pattern staining you saw is because either the joints are gappy, not foam filled as-you-go, or the gaps have (deliberately or accidentally, partly or fully) the cementitious adhesive in them - at any rate, lines of convective and/or conductive heat-leak which encourage different algal growth on the joint lines because they're warmer.

    Algae in the air - must be Devon? Famous for it - some lovely colours - rich pink, grass green ...
    • CommentAuthorMarkyP
    • CommentTimeJun 5th 2017
    I'm not a fan of modern renders. I'm doing DIY EWI and went on a week long training course to get my head around the whole process, especially renders. I just didnt like the render much. Either monocouche through coloured stuff which you scrape back to leave a texture finish or the thin coat which was almost a textured silicone paint, though you still trowel it on. Was working with some decent spreads on the course, while we got a good finish, no one liked the thin coat finish and mixed views on the scrape back.The course was worthwhile as got some much need practice at setting beads, mesh and applying various base coats, ruling off and so on with lime and cementitious products. But I'll be going with a lime render and mineral paint for my EWI. LIme green have a BBA for their lime render over EPS., two passes, mesh embedded, 15mm thick overall. I'll give it a float up and then I'll then use keim or similar mineral paint over that to finish. This is my own house, so I'm not constrained by the usual warranty and system installer methods, though I will be inline with the lime green BBA method which BCO will want to see.
    • CommentAuthorrevor
    • CommentTimeJun 5th 2017
    On the block work part of our extension we rendered with Alumasc render a 3 coat plus mesh system. Am very pleased with the material but not so with the contractor whose guys were not that careful. However he brought in some Hungarian guys for the finish coat who were absolutely brilliant and careful. I had put Weber render on the chimneys during the roofing work and that has become badly stained which is why I switched to Alumasc.
    The system is a German system and is designed for ewi also, you just miss out on the base coats. I think you have to have been on an alumasc course to buy the stuff.
    Posted By: revorHowever he brought in some Hungarian guys for the finish coat who were absolutely brilliant and careful.

    Roll on Brexit !!

    Posted By: revorThe system is a German system and is designed for ewi also, you just miss out on the base coats.

    Brexit will fix that !!
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