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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
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    Plasterer 1 and Plasterer 2 seemed quite happy to plaster onto Celcon blocks - but never followed through to actually do the work.

    Plasterer 3 advised to dry-line over the Celcon blocks, to avoid the emergence of "inevitable cracks". It is true, that there are a few hairline cracks across multiple courses already. The blocks were laid two years ago.
    ( I thought that the cracks were partially due to inadequate curing time between their manufacture and their laying. )

    Plasterer 3 will put my job in the queue and expect to do it in January.

    I gradually realised that I could have a go at dry-lining with fermacell boards. i.e. save on labour and put the money into the increased cost of the Fermacell boards.

    After all Fermacell boast that a DIYer can do it and make a reasonable job.

    Upon reading the Fermacell info I read that - for the dot & dab method :-
    " .. expect to place two mechanical fixings on each board."

    methinks : I've never read about anyone placing extra mechanical fixings on plasterboard. Why for Fermacell ?

    "For dot & dab . . .use tapered boards." OK but what about all the offcuts used in the door/window reveals - which will inevitably have cut edges ?

    Both edging techniques therefore necessary ??
    I did my shop using 'foamed on boards' and used 2 mechanical fixings per board. But with hindsight I would have drilled a hole or two in and squirted extra foam in that way. Can't see it going anywhere.
    Wet plaster is far superior from an airtightness point of view. Drylining doesn't seal the face of the block, leaves gaps in mortar perpends unfilled and provides a cavity for air circulation. We get a lot of cold air coming out of our mains sockets as a result.

    The recommended approach is to at least parge a wall with plaster or sand/cement before drylining.

    fermacell is a bit heavier and those Northern Europeans like doing things by the book :-)

    you can cut in your own taper with a rasp of old plane for off cuts
    you can scrim it straight on top then feather out with easyfill or premix

    parge it first with a brushed on thick slurry mix of sand and cement or hardwall

    foam or full board adhesive behind sockets or perimeters to stop air movement.

    or wood cladding :-) Swedish style
    • CommentAuthorcjard
    • CommentTimeNov 3rd 2016 edited
    Posted By: malakoffee

    I gradually realised that I could have a go at dry-lining with fermacell boards. i.e. save on labour and put the money into the increased cost of the Fermacell boards.

    Vivalda had the best value boards when I was looking - one man 1200x1200 were 4.50 each

    That said, of all the things I've done at my build myself, I think the boarding and skimming is the thing I've saved the least on. I cannot board fast enough to beat the cost of a team of monkeys doing it (if I assign my time a reasonable value that can be better spent doing other things like plumbing, electrics, second fix fittings and other high cost trades)
    The only thing that boarding my place out helped me do was catch all the places where I'd forgotten to do a bit of air tightness/insulating, or prevent wires getting buried etc.

    When I was talking to my father in laws plasterer about the difficulty of finding someone that would come from time to time and skim on a casual basis, I said all I wanted was to be able to ring someone up and say "right, I've got another 3 rooms ready, 4 quid a metre, come whenever you can and do a bit" he said "really? You couldn't get anyone to do that? Those are the jobs I dream of getting, perfect infill around the bread and butter ones"

    Got the impression he gets screwed for 2.50 a metre on big site.. it's only that he can get through 120 to 150 metres a day with a partner and a labourer that means he gets the 120-150 quid a day he's hoping for.. and when you think about it, ultimately he's working for a quid a metre by the time he's finished paying his lads

    So how does fermacell compare to regular board? If you can get em for 3 quid a metre you're possibly onto a winner.. normal plasterboard are about 1.30 a metre, board finish about 50p a metre so 2 quid covers your materials, 4 may cover your skimming so 6 quid done (screws are a penny each or less). I forget the cost of the joint filler, glue, special screws and fine surface finish but here's a chance Fermacell is still cheaper until you start throwing in the cost of havi to pay someone to do what you now don't have time for (sparky, plumber, tiler, decorator) because you're busy with the heavy physical job of boarding it out.

    Examine the two closely. I couldn't make fermacell work out for me
    I guess that the mechanical fixings are recommended/mandated BECAUSE the fermacell boards are capable of carrying significant loads.

    i.e. loading up the boards with cupboards, hangings, shelves, etc. might overwhelm the dot and dab bonding

    Parging :
    Point taken. Whatever happens I'll be applying dilute PVA to the Celcon blocks first, then parge it with something.
    Hopefully the "something" does not compromise the dot & dab bonding.

    I would actually prefer to plaster rather than board. A few hairline cracks don't seem like a terrible risk. == minor maintenance task.

    Cost & Time :
    Not really an issue as long as I don't choose an expensive AND inadequate solution. This is one of the benefits of retirement - loads of time!
    • CommentTimeNov 5th 2016
    I don't really know but ... lime can move a bit more without cracking, so maybe using lime plaster would work?

    Hopefully somebody who does know will correct my suggestion?!
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