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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
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    • CommentAuthortony
    • CommentTimeMay 1st 2022
    How would you support tile hanging over 100mm of EPS

    I am thinking of hanging vertical 47x50 battens from the roof rafter feet long fixings at 1.4m c/c recessed into green EPS, membrane and horizontal barrens at 120mm c/c for plain tiles.

    Will that work?
    What to at the bottom?
    Sounds like a plan. At the bottom I would fix the vert. battens into galvanised shoes of the type to hold the bottom of the battens off the ground (rot prevention) and the foot fixings should be load bearing. I would also fix the vert. battens through to the wall every 2m. Rather than recess the vert. battens into the EPS I would surface mount and infill between the battens with more EPS, (a bit more insulation and (for me) easier to do). This assumes you have the depth of overhang to accommodate the extra thickness.
    I'm thinking that vert. battens at 1.4m spacing would allow the horiz. tile battens to sag over time. I would go for 1m spacing.
    • CommentTimeMay 1st 2022
    What is "green EPS"? Do you mean grey?

    I'd suspect 1.4 m separation for the vertical counterbattens was a bit large. What support is required for the weight of your chosen battens and tiles? Maybe you need a larger section cross piece between the rafters to enable a closer spacing?

    Also why bother embedding the counterbattens? Isn't it simpler to just put them on top of the EPS?

    At the bottom it depends what you've got underneath! Assuming it's rigid and not damp (e.g. brick plinth with a DPC) I'd be tempted to land the counterbattens on the plinth to provide extra support. If there's any sort of gap at the bottom then you'll want a rodent screen (wire mesh) although insects will still be able to get in through the tiles.
    Any fire break requirements with the 'chimney' behind the tiles filled with battens and EPS?

    How will water drain past the horiz battens?

    Why EPS and not mineral wool, it isn't supporting the cladding layer?

    Otherwise, what the others said.
    • CommentAuthortony
    • CommentTimeMay 1st 2022
    Thanks all

    Re 1.4m that was the centres for the fixings in the vertical bearers

    I agree with not rebating, I would do 100mm and 50mm between

    Vertical centres to match rafter feet so likely to be 16”, 400, 450 or 600mm

    I like shoes but in my opinion would need to carry load into the external leaf of the wall.

    EPS breathable, no void, no water, any condensation on the back of tiles will drain outwards. No plinth as this is retrofit/replacement of tile hanging.
    • CommentAuthorphiledge
    • CommentTimeMay 2nd 2022
    Theres likely a fair weigh in the tiles which would be quite a weight for the rafter ends to carry if theres no support at the bottom. You could fit one end of metre long straps to the external wall, bend them out a a shallow angle then bolt the other end to the vertical battens. Fit long thin triangluar slivers of EPS either side of the straps. The straps should transfer the bulk of the weight back to the original wall.
    • CommentAuthoran02ew
    • CommentTimeMay 2nd 2022 edited
    Lot of weight for hanging tiles at 60/m2 probably need to check with SE for fixings, I would a vertices fixed to the side of every rafter so more like 600/400 centres

    Also consider:
    Vermin and insect ingress at base?
    Where will membrane sit?
    Lots of changes to BR regarding “cladding” following Grenfell tower, I understand that the normal method of ventilation behind cladding is discouraged unless fire broken at junctions on with expensive breathable intumescent closures?
    • CommentTimeMay 3rd 2022 edited
    Everything needed has been said above.

    Ideal is for the considerable weight to be entirely 'hung' from above, with rafter-end reinforcement if nec, esp as EWI inherently moves the 'skin' face outboard of any existing structure that could support the vertical battens' bottoms. Supporting such skinny compression members at bottom will create large buckling effect (added to wind buffeting/suction), both pulling outward and crushing/abrading back against the EPS, so their 1.4m restraints should be carefully considered.

    Would tilehanging be airtight enough to create a chimney effect?
    If the tiles are all hung on a timber batten that is fixed at the top, will that timber batten expand/contract differentially with the seasons and humidity (vs the masonry wall beneath the insulation), so a gap opens/closes at the bottom? If the batten is restrained at both top and bottom, would it be forced into and out of compression when it tries to expand/contact?

    In practice the 1.4m restraints might be what's resisting the tendency of the timber to expand, so might need to be closer together.

    Edit: Tom, I'd possibly misunderstood that the battens and counterbattens were to create a drainage cavity behind the tiles, which might need cavity fire barriers because it is a wall not a roof. Tony's comment suggests no cavity and no drainage are intended. Cavities don't have to be airtight to give a chimney effect, but cavity barriers do have to be fairly airtight to work correctly, as far as I understand it.
    • CommentAuthortony
    • CommentTimeMay 3rd 2022
    Thanks all for all the very helpful comments - loved them 🙂
    • CommentAuthormuddy
    • CommentTimeMay 3rd 2022
    Could you fix them directly to the render with adhesive? Are there any brick slips that give the same look as tile hung?
    • CommentTimeMay 3rd 2022
    Posted By: muddyCould you fix them directly to the render with adhesive?
    I don't think there is any render?
    Posted By: djh
    Posted By: muddyCould you fix them directly to the render with adhesive?
    I don't think there is any render?

    There should be - if only to keep the mice out !
    • CommentAuthormuddy
    • CommentTimeMay 4th 2022
    Wasps can make a lovely home in the void behind any cladding. EPS doesn't offer any resistance to wasp jaws. I have watched queen wasps investigating holes for nesting sites, with trepidation.
    I've got to decide how to finish some EPS exterior wall insulation in the near future, so I'll try using render to fix the tiles, and some slate as well.
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