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Scratch Coating for airtightness

  • 21-07-2010 12:35pm
    #1
    Registered Users, Registered Users 2 Posts: 22,255 ✭✭✭✭


    Quick question folks, if I am getting the plasterer to put a scratch coat on the walls of my house for airtightness, should I only get him to scratch coat the outer walls of the house? e.g. there's no need to scratch coat any inside walls between rooms, just the outside shell of the house needs to be scratchcoated.


Comments

  • Subscribers Posts: 42,170 ✭✭✭✭sydthebeat


    Lemlin wrote: »
    Quick question folks, if I am getting the plasterer to put a scratch coat on the walls of my house for airtightness, should I only get him to scratch coat the outer walls of the house? e.g. there's no need to scratch coat any inside walls between rooms, just the outside shell of the house needs to be scratchcoated.

    i assume you are asking because you intend using insulated plasterboards internally???

    if so then only the external walls will be plasterboarded....

    all walls will be scratch coated, as internal walls will be finished in a plaster skim.


  • Registered Users, Registered Users 2 Posts: 22,255 ✭✭✭✭Lemlin


    sydthebeat wrote: »
    i assume you are asking because you intend using insulated plasterboards internally???

    if so then only the external walls will be plasterboarded....

    all walls will be scratch coated, as internal walls will be finished in a plaster skim.

    Is scratch coating not different to skimming?


  • Subscribers Posts: 42,170 ✭✭✭✭sydthebeat


    Lemlin wrote: »
    Is scratch coating not different to skimming?

    it is.. :confused:

    all walls internally should be scratched and skimmed.....


  • Registered Users, Registered Users 2 Posts: 22,255 ✭✭✭✭Lemlin


    sydthebeat wrote: »
    it is.. :confused:

    all walls internally should be scratched and skimmed.....

    Why the need to scratch all internal walls? Plasterer had mentioned to me just scratch coating the external inside walls and leaving any between rooms free of a scratch coat.


  • Registered Users, Registered Users 2 Posts: 12,902 ✭✭✭✭mfceiling


    Most plasterers will scratch a block wall to give the skim coat something to grip.
    Most plasterers will put on a sand and cement base then "comb" it and use a long straight edge to take out any roughness in the blockwork so as to leave a good surface for the skim coat.


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  • Subscribers Posts: 42,170 ✭✭✭✭sydthebeat


    Lemlin wrote: »
    Why the need to scratch all internal walls? Plasterer had mentioned to me just scratch coating the external inside walls and leaving any between rooms free of a scratch coat.

    bad workmanship...

    a decent scratch coat has many advantages including:

    1. forms a superior protection against impact damage. plaster on a trowel "thrown" coat will fall off in lumps.

    2. its allows for great ability of the plaster to shrink on drying and prevention of crazing and cracking.

    3. more economical... building up thicker layers using plaster is more costly, obviously.


  • Registered Users, Registered Users 2 Posts: 22,255 ✭✭✭✭Lemlin


    sydthebeat wrote: »
    bad workmanship...

    a decent scratch coat has many advantages including:

    1. forms a superior protection against impact damage. plaster on a trowel "thrown" coat will fall off in lumps.

    2. its allows for great ability of the plaster to shrink on drying and prevention of crazing and cracking.

    3. more economical... building up thicker layers using plaster is more costly, obviously.

    How much of a price difference would I be looking at though? House is 3800 square foot.
    The architect also reckons there's only a need to scratch coat the outer internal walls.


  • Subscribers Posts: 42,170 ✭✭✭✭sydthebeat


    Lemlin wrote: »
    How much of a price difference would I be looking at though? House is 3800 square foot.
    The architect also reckons there's only a need to scratch coat the outer internal walls.

    dont know about price.... i usually specify the scratch coat and let them price accordingly....


  • Registered Users, Registered Users 2 Posts: 2,489 ✭✭✭No6


    You need a scratch coat on blockwork walls, you only need a gypsum skim on plasterboard partitions so if the internal walls are plasterbaord partitions then the don't need one!!


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