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Housing - New Build: Dot and dab plasterboard

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  1.  
    After reading another thread on things to be avoided when doing a self build dot and dab plasterboard was highlighted as a No,No.

    Can anyone please explain why this is ??

    We are currently in the process of building a self build property and the internal walls are all constructed using 100mm concrete blocks, what would be the best process to bring it to a finished wall??
  2.  
    10-12mm Sand/Cement/lime render 3mm gypsum plaster finish.

    Dot and Dab not liked by most due to air circulation behind. Hence more heat loss
  3.  
    ''....dot and dab plasterboard was highlighted as a No,No.

    Can anyone please explain why this is ??''


    Air movement behind. If the block walls are finished as most are (i.e. not 'finished'), you risk cold air movement between the block and plasterboard. I had to strip out and completely re-fit a 1990s extension which was almost uninhabitable having been dot 'n' dabbed.

    Hard plaster everything, using that as an air-tightness layer.
    • CommentAuthorowlman
    • CommentTimeOct 5th 2014
     
    Posted By: Mike George.............Dot and Dab not liked by most due to air circulation behind. Hence more heat loss</blockquote>


    But these are internal walls where is the "loss"?
  5.  
    I think that what is meant by internal walls is the internal face of the exterior walls.
  6.  
    That's how I read it, but I accept I could have been wrong. CL, can you clarify?
    • CommentAuthorMike George
    • CommentTimeOct 5th 2014 edited
     
    Posted By: owlmanPosted By: Mike George.............Dot and Dab not liked by most due to air circulation behind. Hence more heat loss



    But these are internal walls where is the "loss"?


    Ah, I assumed internal face of external walls as Bot suggests..If they are completely internal and do not link up with dot and dab on external walls then there would be no extra heat loss as you suggest. Can't see anyone dot and dabbing internal walls only though can you?
    • CommentAuthortony
    • CommentTimeOct 5th 2014
     
    http://readinguk.org/draughtbusters/?page_id=45

    read this lot and internal wall voids behind dot and dab are connected to those of the outside wall ones causing draughts to come out behind architraves!
    • CommentAuthortony
    • CommentTimeOct 5th 2014
     
    It is not so much the cold behind the lining boards but it escaping into rooms through sockets, under skirtings, into floor voids, pipe casings, behind internal wall linings, under window boards, round service penetrations.

    Then worry about the walls being cold http://readinguk.org/draughtbusters/wp-content/uploads/2014/05/IR_0600.jpg
    • CommentAuthorowlman
    • CommentTimeOct 6th 2014
     
    Posted By: tonyhttp://readinguk.org/draughtbusters/?page_id=45" rel="nofollow" >http://readinguk.org/draughtbusters/?page_id=45

    read this lot and internal wall voids behind dot and dab are connected to those of the outside wall ones causing draughts to come out behind architraves!



    Not if it's done correctly, AFAIK the correct way to apply adhesive is a continuous bead around the perimeter. "DOT & DAB" in literal terms is a little bit of a misnomer.
  11.  
    But why would you Dot and Dab if you could wet plaster sraight on blocks? It just more cost and work, unless the walls are bad?
    It's easier for hanging pics and mirrors etc on block to.
    • CommentAuthorowlman
    • CommentTimeOct 6th 2014
     
    Maybe because you can easily DIY it, and with FE boards make an even better job than most plasterers.
  13.  
    Hmm maybe.

    You need to police your contractors more :bigsmile:
    • CommentAuthorowlman
    • CommentTimeOct 6th 2014
     
    Maybe I'm just unlucky with plasterers Steve, but I've contracted several over the years for interior jobs and I've never felt I got top notch work, for any of them. They rarely use a Darby believing they can shove stuff straight from the hawk and get a nice even finish with a 10" trowel.
    Try this test next time you encounter a finished plastering job; close your eyes and walk along a wall running you hand along the plaster and 10 to1 you'll find its up and down like the waves of the ocean.

    They really do need policing:sad:
    •  
      CommentAuthorjoe90
    • CommentTimeOct 6th 2014
     
    Perhaps I am lucky but I have a really top rate plasterer, young chap, tought old school methods and although I am retired I still recommend him to old clients. He is even willing to travel to Devon next year to plaster my new build. He is in the Bristol area and I can whisper his details if you require.
    • CommentAuthortony
    • CommentTimeOct 6th 2014
     
    I disagree about continuous beads, a) never seen them done (thermal imaging would pick them up), b) still get wind coming out of sockets and other places, c) parging is essential,
  17.  
    The way I look at it is that if the Picture frame method is good enough for EWI then its good enough for dot and dab....
    • CommentAuthortony
    • CommentTimeOct 6th 2014
     
    Does EWI have socket outlets in it?
  19.  
    Nope, but it has base rails; End of system rails; Verge and eaves and cill trims; All of which are generally fixed prior to insulation to walls whether straight or not..... Also numerous pipe and electrical penetrations.

    Fantastic recipe for heat loss by air circulation from bottom to top.
    • CommentAuthorgravelld
    • CommentTimeOct 6th 2014
     
    What is the best way of diagnosing and fixing these problems? Is it easy to do when there is a loft space above, or pitched roof? I have some plasterboard walls in a ground floor extension I'd like to check.
    • CommentAuthorringi
    • CommentTimeOct 6th 2014
     
    What about leaving a small gap at the top and bottom of each board, then using expanding foam?
    Likewise foaming behind the board after cutting for sockets…
  22.  
    <blockquote><cite>Posted By: Nick Parsons</cite>That's how I read it, but I accept I could have been wrong. CL, can you clarify?</blockquote>

    Yes Nick you are correct, I mean the inner leaf of block work on all outside walls.
  23.  
    I understand the idea now behind what you guys are suggesting, what do you do with the exposed walls between floors?? I.e. The space in between floor joist on outer walls.
  24.  
    Parge coat (I'd say lime, Mike George would say sand/cement lime - both are valid), leave to dry, then air-tightness tape round the end of the joists to the parge coat. I think Cwatters had a pic for this.
    • CommentAuthortony
    • CommentTimeOct 6th 2014
     
    http://readinguk.org/draughtbusters/?page_id=284

    There is a lot on there about rectifications
    • CommentAuthorgravelld
    • CommentTimeOct 7th 2014
     
    Thanks Tony. With regards the polystyrene, what about cabling? I thought EPS and electrical cable were never to meet.
    • CommentAuthortony
    • CommentTimeOct 7th 2014
     
    They work well behind radiators where ther tend to be no wires.

    It not so much never meet as a possible problem, some de plasticisation of the cables can take place, there has never been a problem with this as yet.
  28.  
    Just like to say that's an excellent read, Tony. In fact it only occurred to me to rip off my window reveal to check the fitting after I went through the articles on that site... see parallel discussion topic. Boy, was there ever a lot of air leakage in a house!
    • CommentAuthorgravelld
    • CommentTimeOct 7th 2014
     
    Tony do you have any tips on how to "get at" the tops and bottoms of plasterboard? If it's a ground floor extension with pitched roof above (no access to this though) is it possible to take the tiles off, the roofing battens, then the sarking and look straight down for any void? Then fill with those EPS beads?
  30.  
    Silly question, but why are you adding lime to the sand & cement mixture?

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