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Fixing Plasterboard

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  • 24-05-2019 2:34pm
    #1
    randombar
    Registered Users Posts: 3,361 ✭✭✭


    Hi All,

    Going to start putting insulated plasterboard up in my garage (upstairs and dnow been there over a year now. Going to do the straightforward parts myself. Few questions:

    1) Top down approach? Ceilings first, sides second?

    2) Cavity block wall, I'm told I should "dab" or glue?

    3) Sloped upstairs rafters. Do I cut the edges so it fits neatly, if so any tips/tool recommendations?

    4) Anything else to be mindful of?

    Thanks for any advice.

    // Gary


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    #2
    Sleeper12
    Registered Users Posts: 16,882 ✭✭✭✭Sleeper12


    GaryCocs wrote:
    2) Cavity block wall, I'm told I should "dab" or glue?


    Neither. Use the mushroom fixings designed for the job. You need 12 for each 12x4 slab. With insulated plasterboard it needs to be tight against the wall. Dabbing it on leaves air pockets & reduces the insulation effect.


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    #3
    randombar
    Registered Users Posts: 3,361 ✭✭✭randombar


    Sleeper12 wrote: »
    Neither. Use the mushroom fixings designed for the job. You need 12 for each 12x4 slab. With insulated plasterboard it needs to be tight against the wall. Dabbing it on leaves air pockets & reduces the insulation effect.

    Nice one. Would prefer that to be honest.

    Any idea about the wall meeting slope edges? Do I just scrape away 45 degrees at the back with a Stanley or are there better options?


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    #4
    Sleeper12
    Registered Users Posts: 16,882 ✭✭✭✭Sleeper12


    GaryCocs wrote:
    Any idea about the wall meeting slope edges? Do I just scrape away 45 degrees at the back with a Stanley or are there better options?


    That I don't know. I'm sure there are plenty of posters that have experience with that


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    #5
    policarp
    Registered Users Posts: 3,658 ✭✭✭policarp


    Sleeper12 wrote: »
    That I don't know. I'm sure there are plenty of posters that have experience with that

    Have you a two storey garage?
    For the joints, use expanding foam.
    Ceilings first.


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    #6
    randombar
    Registered Users Posts: 3,361 ✭✭✭randombar


    policarp wrote: »
    Have you a two storey garage?
    For the joints, use expanding foam.
    Ceilings first.

    Story and a half.


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    #7
    randombar
    Registered Users Posts: 3,361 ✭✭✭randombar


    Going to try and borrow a screwgun for slabs will help not drive screws through.

    Also saw that the boards on the wall go landscape. That right?

    Still can't find a video on how to cut an insulated board at an angle for the slopes


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    #8
    dodzy
    Registered Users Posts: 9,927 ✭✭✭dodzy


    GaryCocs wrote: »
    Going to try and borrow a screwgun for slabs will help not drive screws through.

    Also saw that the boards on the wall go landscape. That right?

    Still can't find a video on how to cut an insulated board at an angle for the slopes

    Grab a skillsaw and adjust the mitre to suit your required angle.


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    #9
    HappyAsLarE
    Closed Accounts Posts: 771 ✭✭✭HappyAsLarE


    Will you not be taping/filling the joints? If so no point trying to cut your angle, just slop your filler in and try profile it with round edge.


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    #10
    randombar
    Registered Users Posts: 3,361 ✭✭✭randombar


    HappyAsLarE wrote: »
    Will you not be taping/filling the joints? If so no point trying to cut your angle, just slop your filler in and try profile it with round edge.

    Taping all right, so probably over thinking it.


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    #11
    Lumen
    Registered Users Posts: 31,010 ✭✭✭✭Lumen


    HappyAsLarE wrote: »
    Will you not be taping/filling the joints? If so no point trying to cut your angle, just slop your filler in and try profile it with round edge.
    Yeah, but then you're going to get cold spots.

    Worth doing properly for the few seconds it takes to mitre a board.


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    #12
    randombar
    Registered Users Posts: 3,361 ✭✭✭randombar


    Lumen wrote: »
    Yeah, but then you're going to get cold spots.

    Worth doing properly for the few seconds it takes to mitre a board.

    Using a skill saw?


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    #13
    GreeBo
    Registered Users Posts: 27,039 ✭✭✭✭GreeBo


    Sleeper12 wrote: »
    Neither. Use the mushroom fixings designed for the job. You need 12 for each 12x4 slab. With insulated plasterboard it needs to be tight against the wall. Dabbing it on leaves air pockets & reduces the insulation effect.

    Dabbing is ok assuming you put a perimeter of mud around the edges...its a messy job and I would use mushrooms where I can. But if the wall is not true then dabbing can help counter this.


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    #14
    randombar
    Registered Users Posts: 3,361 ✭✭✭randombar


    GreeBo wrote: »
    Dabbing is ok assuming you put a perimeter of mud around the edges...its a messy job and I would use mushrooms where I can. But if the wall is not true then dabbing can help counter this.

    What type of mushrooms should I use to drill into cavity block?


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    #15
    GreeBo
    Registered Users Posts: 27,039 ✭✭✭✭GreeBo


    GaryCocs wrote: »
    What type of mushrooms should I use to drill into cavity block?

    I've always used these without any issues on 9" cavity walls
    5391504705900.jpg?width=497&height=497

    Btw, if you are going to dab, you need to use some mushrooms for fire regs anyway (so prevent the board falling off the wall)

    so whether you need to do both depends on the shape of the wall.

    If I am dabbing I wait until its dry and then add some mushrooms


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    #16
    randombar
    Registered Users Posts: 3,361 ✭✭✭randombar


    GreeBo wrote: »
    I've always used these without any issues on 9" cavity walls
    5391504705900.jpg?width=497&height=497

    Btw, if you are going to dab, you need to use some mushrooms for fire regs anyway (so prevent the board falling off the wall)

    so whether you need to do both depends on the shape of the wall.

    If I am dabbing I wait until its dry and then add some mushrooms

    Wall is fairly plumb so I reckon mushrooms are the way to go.

    Looking at those, looks like hammer in ones, i.e. drill hole and belt them in with a hammer.


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    #17
    GreeBo
    Registered Users Posts: 27,039 ✭✭✭✭GreeBo


    GaryCocs wrote: »
    Wall is fairly plumb so I reckon mushrooms are the way to go.

    Looking at those, looks like hammer in ones, i.e. drill hole and belt them in with a hammer.

    Yep, exactly.


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    #18
    chris445
    Registered Users Posts: 237 ✭✭chris445


    GaryCocs wrote: »
    Using a skill saw?

    Just use a handsaw. They are very easy to cut and takes a few seconds per board.


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    #19
    Lumen
    Registered Users Posts: 31,010 ✭✭✭✭Lumen


    GaryCocs wrote: »
    Using a skill saw?
    I'd use a tracksaw because I have one and it's handy, but you don't need joinery-level precision so a circular saw run by hand is fine. I'd try to close the gap behind the junction to <10mm or so and then fill the rest with good quality (PU) expanding foam.

    Otherwise you'll have a cold line running all the way along your ceiling junction which is just asking for condensation.
    chris445 wrote: »
    Just use a handsaw. They are very easy to cut and takes a few seconds per board.
    Yeah, or that!


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    #20
    GreeBo
    Registered Users Posts: 27,039 ✭✭✭✭GreeBo


    I used to cut the insulation with a hand saw or old kitchen knife and then just score & snap the plasterboard as normal from the front.
    As above, you dont need perfect joints, in fact a small gap that would allow you to run a bead of window/door foam wouldnt hurt to ensure you have a good thermal barrier behind the board and then just trim the excess and tape/scrim/skim.


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    #21
    randombar
    Registered Users Posts: 3,361 ✭✭✭randombar


    GreeBo wrote: »
    I used to cut the insulation with a hand saw or old kitchen knife and then just score & snap the plasterboard as normal from the front.
    As above, you dont need perfect joints, in fact a small gap that would allow you to run a bead of window/door foam wouldnt hurt to ensure you have a good thermal barrier behind the board and then just trim the excess and tape/scrim/skim.

    Will foam where the wall meets the roof all right but I'm not sure if I can foam where the sloped roof meets the ceiling as there's nothing behind it only joists, if that makes sense.


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    #22
    lgk
    Registered Users Posts: 589 ✭✭✭lgk


    GaryCocs wrote: »
    Going to try and borrow a screwgun for slabs will help not drive screws through.

    Could use a drywall bit...


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    #23
    mfceiling
    Registered Users Posts: 12,774 ✭✭✭✭mfceiling


    Make sure to use washers when you're using screws for the ceiling joists.


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    #24
    randombar
    Registered Users Posts: 3,361 ✭✭✭randombar


    mfceiling wrote: »
    Make sure to use washers when you're using screws for the ceiling joists.

    Nice one, ya have a tonne of them left over from the build 8 years ago :D


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    #25
    sheff the ref
    Registered Users Posts: 617 ✭✭✭sheff the ref


    Do any of ye have experience of using these twist fixings? How do they compare to using the mushroom fixings pictured above? There is an SDS drill attachment that can be used and you can set the countersink depth

    general.jpg


    Also, I have a wall less than 3m wide x 2.4m high approx that does not require insulated plasterboard as it is an internal wall that once had tongued and grooved sheeting. I do not really want to dot and dab. Nor do I want to plaster. I would just prefer to put the 12.5mm plasterboard on it using mechanical fixings. Wall is very level and I have touched up a small hollow

    Is there any reason why I cannot directly fix it with mechanical fixings?


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    #26
    whizbang
    Registered Users Posts: 1,924 ✭✭✭whizbang


    No reason at all, except...! Isnt it so much more work ?

    Foam adhesives can get the boards fairly close to the blockwork, and just about as solid as direct plastering.

    Other question?
    No fixings needed on an internal block wall for fire regs ? Im fairly sure you dont need 12 either.


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    #27
    sheff the ref
    Registered Users Posts: 617 ✭✭✭sheff the ref


    whizbang wrote: »
    No reason at all, except...! Isnt it so much more work ?

    Foam adhesives can get the boards fairly close to the blockwork, and just about as solid as direct plastering.

    Other question?
    No fixings needed on an internal block wall for fire regs ? Im fairly sure you dont need 12 either.

    The wall in question will be used to hang a number of large photo frames, plus there will be sideboard in front of it that will move from time to time.

    Even allowing for modern fixings like Corefix which would handle the photos, I am concerned with the sideboard being pushed into the plasterboard. I feel that if the plasterboard is fixed directly to the wall, it will take more punishment, whereas if a foam/adhesive leaves a void, it then provides a space for plasterboard to pop into upon impact from the sideboard, whereas it will only mark the plasterboard if directly and mechanically fixed to the wall.


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