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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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    • CommentAuthorCWatters
    • CommentTimeOct 30th 2012
     
    Every house (4) I've lived in has been wet plastered and all have had cracks where the walls meet the ceiling. It seems the ceiling shrinks and sometimes pulls upto 3" of plaster off the top of the walls. eg the crack frequently occurs not at the join but can be a few inches down the wall.

    If you were building a new house (I'm not) how would prevent this happening? Is it a secret ploy to boost sales of coving :-)
    • CommentAuthorRoger
    • CommentTimeOct 30th 2012
     
    Coving was traditionally used to accommodate this.
  1.  
    Cut through the skim at the internal corner with a Stanley knife and point with caulk...?

    J
  2.  
    CWatters,
    Funnily enough I have been thinking about this recently. My recent self build went up a coving free zone. My wife likes "clean lines" rather than dirty ones!
    I warned her that the cracks would soon ruin the whole clean line idea but after 1 year not a single crack has appeared. This may be down to the fact that I used Easi joists between floors as they shrink less (so they say) and transfer less sound. Upstairs I have no idea. Block and brick construction. Built slowly over 2 years around 3000sq ft. I am confused as I put my hand on my heart, not 1 crack around the ceilings at all. I think the plasterers used Skrim but nothing else.
    On a slightly different note but similar too my liquid floor screed covers the ground floor area. 65mm thick. 150mm boards beneath. I tiled through 3 doors and have no expansion gaps. I tiled through doors as we wanted a clean look. GSHP working a treat. No cracks at all. I just do not get it. I did let the screed dry properly before I sealed it though.
    The house does stay at a fairly constant temp though as we insulated well.
    Any ideas anyone or just lucky? I know houses dry over many years but so far so good,
    Gusty.:bigsmile:
    • CommentAuthorBeau
    • CommentTimeOct 30th 2012
     
    My guess is that us self builders are on the whole a bit slow this allows any wood used to dry thoroughly and reduce the risk of subsequent movement.
    • CommentAuthorCWatters
    • CommentTimeOct 30th 2012
     
    Our first floor is beam and block but we needed battens below itto form a void for cable runs in both directions and to fix plasterboard to.

    I was thinking that some form of slip membrane (Selotape?) might be enough to stop it happening. eg plaster ceiling then fit tape around the edge so the plaster on the wall doesn't stick to the ceiling. Something like that anyway.
    • CommentAuthortony
    • CommentTimeOct 30th 2012
     
    Easy way round the problem is to not nail the ceiling at the edges! start 150mm out qed TC
  3.  
    What I did (for both drywall walls and plaster-and-lath walls) at the junction between the wall and the ceiling (which was always drywall) was to use "internal steel angles" rather than paper tape. The internal steel angles are paper-covered so that they can be covered with jointing compound. I also used fibreglass mesh tape in some places too - neither has cracked and the paper-covered steel angles might be a bit faster to install, but cost more. Once the plaster/jointing compound has dried, a tip I learned from a pro-painter is to fill the 90 degree junction between the wall and ceiling with a bit of paintable caulking. This helps smooth out any inconsistencies and makes it easier to get a clean line when painting, plus will hide and tiny cracks that might develop (though the steel angle joints never crack). I didn't bother not screwing the ceiling right to the edge (don't use nails!) - but I have heard this can help if you suffer from "truss uplift". In my case, the ceilings were always below regular joists.

    Also, unlike UK practice, I only taped and jointed the drywall ceiling panels, no skimcoat. But this shouldn't make a difference if the junction technique I described is used. By the way, I do the same thing for the vertical 90 degree joints between perpendicular walls (which can also crack otherwise).

    Paul in Montreal.
  4.  
    I also used screws to fix my plasterboards and not too close to the edges. Fibreglass mesh tape and no cracks. One other benefit of the Easi joist is that there is less timber in them so shrinkage should be less. I am very pleased so far anyway and electrics and plumbing is much easier. Sound transfer is slightly higher than I hoped though with 2 kids running around upstairs! Very little deflection in the floor aswell.
    I am sure that the speed of the build must have an impact,
    Gusty.
    • CommentAuthorJulio
    • CommentTimeFeb 19th 2018
     
    Bringing up an old thread..

    We do a lot of projects with plasterboard scimmed ceilings and lime plastered walls on wood wool board, we often get from cracking (shrinkage) at the junction between the two.

    Has anyone had this problem?
    Has anyone used thin coat angle bead here successfully to avoid this problem?

    I would rather not use coving.
    •  
      CommentAuthordjh
    • CommentTimeFeb 19th 2018
     
    I have lime-plastered walls and skimmed plasterboard ceilings. I have some cracking but not too bad - I'll wait until it's five years old-ish so most of the movement has finished and then fill the cracks with paintable caulk and do an initial touch-up of all the paintwork. The cracks haven't pulled any wall plaster off, probably because the walls were plastered first and were pretty much dry and hard before the skim went on the ceilings.

    I think in any building that is going to continue to experience occasional movement (i.e. timber and in my case straw), paintable caulk after the event is the only sensible course.
  5.  
    Posted By: JulioHas anyone used thin coat angle bead here successfully to avoid this problem?


    Yes I used to use this - the angle bead that is paper-covered steel. It works well. See my post further up from 2012. Even with angle bead I still put paintable caulk as it gives and easier line for painting if your ceiling and walls are different colours. If also used just fibreglass mesh tape and joint compound plus the paintable caulking. No cracks in my case with either method. If you're using drywall, there's really no need to skim the whole surface - you just do the joints and that's it.

    Paul in Montreal.
    • CommentAuthordelprado
    • CommentTimeFeb 19th 2018 edited
     
    you can also scrim over the ceiling to wall junction, or use expanding wire bent at 90 degrees
    • CommentAuthortony
    • CommentTimeFeb 19th 2018
     
    Or miss out the nails to the plasterboard for the edge 200mm :)
    • CommentAuthorgoodevans
    • CommentTimeFeb 20th 2018
     
    So are we saying the trick is to allow the border of the ceiling to flex a little by not nailing too close to the edge, and to reinforce the junction between the ceiling and the wall so that should there be a change of height of the ceiling either due to shrinkage or deflection there is a good change the junction will hold.

    I can see this working - and counter to first impressions of making sure the ceiling plasterboard is tightly fixed to the joists right up to the edge.
    • CommentAuthortony
    • CommentTimeFeb 20th 2018
     
    The problem with that is that the timber shrinks and moves

    Another secret comes out -- I never used edge noggins! ( don't push up too hard with the roller! )
    • CommentAuthorgoodevans
    • CommentTimeFeb 20th 2018 edited
     
    Will anyone complain without the edge noggins (bco, plasterer etc).

    So two basic techniques here - let the border of the ceiling plasterboard flex and bond the ceiling to the wall with scrim etc
    or
    create a slip joint with caulk and let the ceiling move slightly at the wall.

    Worst case is ceiling bonded to the wall with no flex- meaning that wall plaster can be forced off the wall near the top in the worst cases.
    • CommentAuthortony
    • CommentTimeFeb 20th 2018
     
    Or coving?

    Never got caught in 30 yrs with no noggins or had any problems
    • CommentAuthorgoodevans
    • CommentTimeFeb 20th 2018
     
    I shall instruct my builders and inform my plasterer accordingly. Thankyou.
    • CommentAuthorJulio
    • CommentTimeFeb 21st 2018
     
    Thanks for this, although it feels a bit strange, Ill try not fixing the last 200mm of plasterboard around all edges and warn the decorators. But I think that I might use a thin coat corner bead to strengthen the junction between the two as well.

    Thanks
    • CommentAuthortony
    • CommentTimeFeb 21st 2018
     
    The problem with the thincoat bead is that they are intended for external corners and don’t work for internal corners.

    Most people scrim the internal corners, some use paper tapes or caulk.
  6.  
    <blockquote><cite>Posted By: tony</cite>The problem with the thincoat bead is that they are intended for external corners and don’t work for internal corners.</blockquote>

    Not true at all Tony - at least, not over here where there are beads for internal and external corners, though the external corner ones don't have paper tape on them usually unless they're curved.

    This is what I used for wall to ceiling junctions:

    https://www.homedepot.ca/en/home/p.sheetrock-paper-faced-metal-inside-corner-bead-b2-38-in-x-38-in-90-degree-8-ft.1000109090.html

    Paul in Montreal.
    • CommentAuthorJulio
    • CommentTimeFeb 25th 2018
     
    <blockquote><cite>Posted By: tony</cite>The problem with the thincoat bead is that they are intended for external corners and don’t work for internal corners.

    Most people scrim the internal corners, some use paper tapes or caulk.</blockquote>

    I was figuring that because the purpose of the bed was just to make better that junction between the different plasters that the thin coat bead may work well. The difficulty with using scrim is that it doesn't stick to either the wood wool board or the lime base coat very well, which would make plastering difficult and the potential junction less strong.

    Also what do you mean by paper tapes, we have been using caulk formerly just to cover up the cracks that seem to emerge.
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