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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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    • CommentAuthorTriassic
    • CommentTimeNov 5th 2014
    The gable ends of our build will be constructed using local stone to meet a planning condition. The architect has suggested the use of Surecav units rather than blockwork. Has anyone got any experience of using Surecav, pros and cons etc?

    • CommentAuthorDarylP
    • CommentTimeNov 6th 2014
    SureCav are to keep the cavities 'clear' behind random stonework. They do not preclude the use of block inner leaf?
    Are you sure your arch didn't mean SureCav AND blockwork?

    Cheers :smile:
    • CommentAuthorTriassic
    • CommentTimeNov 6th 2014
    I'm sure he said local stone, SureCav, insulation, then block work, service void and plasterboard.

    Does that sound right?
    • CommentAuthorDarylP
    • CommentTimeNov 6th 2014
    Yep, the SureCav keeps the insulation up against the blockwork inner leaf, and the cavity clear from mortar snots from the stone work.
    I have seen it used on an exposed N Wales hillside to good effect.

    • CommentAuthortony
    • CommentTimeNov 6th 2014
    Can't see the point of the special stuff in the cavity, build it nicely with lime mortar = no probs
    • CommentAuthorDarylP
    • CommentTimeNov 6th 2014

    You must know better 'brickies' than me...:bigsmile:
    No one under 60 IMO could/would attempt that without BC picking them up on the bridged cavities....:cry:
    I looked into this product for our build and would have used it if we'd gone timber frame to benefit from the 100mm it would save compared to a cavity + block skin to support the stonework.

    Twice the cost of the block wall though (based on NI rates) so depends how much the extra space or speed of construction is worth to you.

    It can replace the outer leaf in a masonry build, but will probably dictate that the inner leaf is thicker to compensate structurally. Although you will need to use rigid board insulation, at least you will be able to ensure the inner leaf is clean and have good access to tape joints/make good around wall ties before fitting the Surecav and stone.
    • CommentAuthorTriassic
    • CommentTimeNov 6th 2014
    Posted By: slidersx200Twice the cost of the block wall though (based on NI rates)
    Wow I' hadn't realised that, I thought it was nothing more than a bit of extruded plastic.

    Are there any other products available that achieve the same end point at a more competitive price?
    • CommentAuthortony
    • CommentTimeNov 6th 2014
    Careful workmanship?
    • CommentAuthorTriassic
    • CommentTimeNov 6th 2014 edited
    Posted By: tonyCareful workmanship?
    I wanted to get away from using block work to support the natural stone.

    With careful workmanship can I build a wall made up of natural stone external skin, a cavity (with insulation) and internal block work?

    My architect thinks natural stone requires support of some sort?!
    I'm not aware of any alternative products that perform the same purpose, but I would expect building a typical ~200mm thick stone skin with a clear cavity would be difficult and expensive without something to back it up to.

    There are veneers available in Ireland now that are cut from real stone in roughly 30-50mm thick pieces and crucially, there are "L" shaped pieces to wrap around corners and avoid the stuck on tile like appearance that let more traditional veneers down. Can be combined with brick slips if brick quoins are in keeping with the area. Cost should end up fairly close to a natural stone wall if the stone had to be bought.

    Might be worth seeing if the veneers are available in a suitable stone for your locality and comparing the cost of a cavity wall clad in this to the other approach. It all depends on the area of stonework you're looking to build...
    • CommentAuthorDarylP
    • CommentTimeNov 7th 2014

    There are other 'egg box' systems other than SureCav. Arch's specifiy them because they know the system, not because it is the cheapest or best?
    You can SBR the external face of the inner leaf, insulation, and then tie the outer stone leaf back with ties; if your BCO will accept it?
    Exposure rating?:neutral:
    Posted By: TriassicMy architect thinks natural stone requires support of some sort?!

    This depends on his assumption of the thickness of the stone. 250mm done properly shouldn't need support. Thinner than that - well this depends on the stone and the stone mason.

    An architect will always err on the side of caution because it's too expensive for him not to.

    Building a stone wall can be much quicker if you are building to a flat vertical backing of some sort so some labour savings will help defray the cost of the backing. Much could depend on the skill set of the builder.
    I was quite impressed with this Deco Pierre video: https://www.youtube.com/watch?v=yrx1qPN6PK8 has anyone used this spray on lime rendering technique which simulates real stone?

    I would be concerned about longevity but it might be a way of applying a thin layer of something which looks like stone to board, reducing the thickness you might add to a wall if you were looking at going down the block and stone route? I am guessing because of its quickness of application it would be a lot cheaper than stone? They seem, by mixing colours in with the render to be able to simulate different types of stone: http://tinyurl.com/paccf79

    It is a challenge I am trying to deal with on a Passivhaus design, how if you are in a conservation area do you attach rubblestone to the outside of a wall without adding too much to its thickness and weight? It seems difficult to get away with anything less than 200mm, for something which doesn't add much to the thermal performance of the wall.
    • CommentAuthorslidersx200
    • CommentTimeNov 7th 2014 edited
    One property the stone does add to the build up is the ability to smooth out temperature swings when bright, hot days are followed by cool, cloudless nights.

    The big challenge we found on our build (wide cavity) was minimising thermal bridging at the openings with 200mm stone facing as the windows are in the same plane as the outer block skin. This is partly because there are limited options for depth of granite cills and partly because the windows would look odd and be overly shaded if placed too far back.

    My solution was to enlarge the opening size in the outer block skin by 100mm at the top and sides and inserting strips of PIR around the frame. This still left a slight pinch point in the insulation, but with a bit more thought I found a way to improve that by a factor of three.

    Using Surecav, or an equivalent product, would place the front of the window in the cavity and it may be possible to insulate around this.
    • CommentAuthorTriassic
    • CommentTimeNov 10th 2014 edited
    Having looked at SurCav and other similar bits of plastic I've realised I have no idea why they are used or what exactly is their purpose (other than provide a waterproof backing to stonework)?

    Could someone educate me!

    ps. just a thought, if I can build a house off a raft of EPS, why can't I use EPS behind the stonework instead of the SurCav?
    • CommentAuthorDarylP
    • CommentTimeNov 10th 2014
    SureCav (& similar) are designed to provide a level background for the stonework to be built up against and at the same time, keep the cavity clear, so that no mortar snots bridge it, and also keep the insulation tight back to the inner leaf.
    Does that make sense..?
    • CommentAuthortony
    • CommentTimeNov 10th 2014
    And allow water to drain down without saturating insulation
    • CommentAuthorTriassic
    • CommentTimeNov 10th 2014 edited
    So if I have natural stone I have though a cavity?

    Edit.. So how come EWI does not have a cavity, is it because the rendering is waterproof?
    • CommentAuthorringi
    • CommentTimeNov 11th 2014
    Or consider using Rockwool insulation so you don’t need a clear gap between the insulation and the stone. See http://www.building.co.uk/passivhaus-diaries-part-seven-the-walls/3146658.article
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