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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
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    We are planning to clad in either Hardieplank or cedar in panels between rendered areas of our external blockwork.

    Since getting the render done, my other half has decided that whatever cladding we use, she would now like it to run vertically not horizontally.

    That creates an issue with the battening as the extra space taken up by counter-battens would look odd with a large step to the render.

    Any way to ensure drainage and ventilation while still only having a batten of 25mm?

    I have seen chamfered battens used to allow the water to drain away from the blockwork, but that wouldn't help with airflow.


    • CommentTimeSep 5th 2018
    You don't need much of a gap for drainage so very thin vertical counterbattens should be OK for that purpose. The need for back ventilation depends on both the material and the style of cladding. But I think 21 mm is the recommended minimum for ventilation of timber. You could use a plank on edge at the sides of the clad areas to tidy them up if required.

    One reason I went for horizontal cladding was so I only have to replace one or two complete boards if I ever get rotting from splashback. But the upstand and the gravel below should hopefully reduce the amount of splashback.
    • CommentAuthorowlman
    • CommentTimeSep 5th 2018
    If the original (vertical ) battens are not already in place, could you not use (horizontal) battens with, eg. nylon spacers behind to create a thin air/drainage gap?
    • CommentTimeSep 5th 2018
    The gap can be very thin for drainage, but not as thin for ventilation.
    • CommentAuthorowlman
    • CommentTimeSep 5th 2018
    I assume that cladding area is set below the adjacent walls and that the end result needs to be flush, although a little bit proud with chamfered vertical edges left and right wouldn't be noticeable.
    Perhaps an 8mm drainage spacer behind a 22mm batten? That would give 30mm of ventilation behind the vast majority of the area. It all depends on the rebate depth and the cladding thickness.
    Has anyone tried battens fixed at 45degrees to the horizontal? Short-ish lengths, overlapping loosely to allow airflow and drainage paths between them, no counterbattens.

    Has anyone on here used rot-proof battens eg made of plastic?

    What are views on potential for fire spread in the gap behind the cladding? How to exclude mice/rats/birds/bats/wasps?
    Something like this looks interesting, but I would have to fix the cladding through the batten and into the blockwork.

    • CommentAuthorgyrogear
    • CommentTimeSep 6th 2018
    "Cladding fixings must be installed through the cavity batten onto the studs and dwangs in accordance with the instructions of the cladding manufacturer."

    which leaves me trying to figure out why they should be incompatible with a blockwork wall... ?

    There is also this product here


    But I suspect my building Control Officer will look at it and say "Not seen that used in that way before"

    I would have to secure the boards through the steel batten into the blockwork, which would mean fixings of around 90-100 mm, with ugly masonry screws, etc. Suspect the blocks will not hold a screw well (3.6N Fenlite)

    The rest of the wall has a 10m render, so this way the cladding would only stick out by either 37mm (single layer of vertical cladding) or 47mm (if I went with overlapping vertical boards)

    If I come out too far, I will have problems with the gap to the edge of the window sills.

    The original plan was to have 25mm battens and then the 16mm boards horizontally. = 31mm past the render.

    Tending towards Owlman's suggestion of 25mm batten and some nylon spacers, that could work, I could also alter the nailing pattern and stagger the battens to provide a bit more airflow.


    • CommentAuthorskyewright
    • CommentTimeSep 7th 2018 edited
    Posted By: OracsRevenge...alter the nailing pattern and stagger the battens to provide a bit more airflow.

    Might combining the staggering with battens of shorter than usual length help?

    i.e. (exaggerating)

    ----  ----  ----
       ----  ----

    rather than

    -------     -------

    Just a thought from someone who hasn't tried it out...

    Edited to play with the formatting of the illustration ('non breaking space' is a handy thing!)
    Yes, that could add a bit more airflow.

    I suppose they can't be too precious about the air gap as they insist on insect mesh at the top and bottom, some of which is just steel sheet with drilled holes. They seem to accept this ok even though it restricts the air flow by a fair amount.
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