Filling plasterboard

Discussion in 'Electricians' Talk' started by Jako202196, Aug 4, 2022.

  1. Jako202196

    Jako202196 Member

    Hi guys when filling the chases in dot and dab walls what filler do you use? I’ve been told it needs to have the same fire rating as the plaster board but don’t know how easy this would be to find?
     
  2. chesterw

    chesterw Well-Known Member

    You don't chase in dot and dab, you install the wiring and box/boxes before the plasterboard, cut out pb to fit round box/boxes and then fix it.
     
  3. Bazza

    Bazza Screwfix Select

    Also, is there’s a sheet of plasterboard dot & dabbed on a brick wall then the fire resistance is the brick wall!
    The plasterboard is not a fire barrier so and repair does not require any fire-resistant properties.

    PS use Easyfill to repair holes
     
    Jako202196 likes this.
  4. Wayners

    Wayners Screwfix Select

    Fire rated plasterboard? The pink one?
    Doubt that
    Standard 12.5mm

    I'd cut chase tidy with vertical cuts. Pva edges. Cut new strips of 12.5mm plasterboard and stick with board adhesive.
    Seal the the new strips along cut edges and mix the powdered board adhesive and dot and dab in.
    Won't need tapes or anything if you have adhesive along edges as you go. Fill and sand off smooth.

    Wet sponge as you go to clean surfaces. Don't let it set proud
     
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  5. Tony Goddard

    Tony Goddard Screwfix Select

    Sometimes you do have to chase dot and dab if they have gone overboard with the dots!!

    I do as Wayners suggests, and use Gyproc Easifil 60 (B&Q have it) to fill in, its a fast setting plaster very similar to the plaster that the board itself is made from, and is made for the job.
     
    BGL likes this.
  6. Jako202196

    Jako202196 Member

    Thanks guys just was on the 18th edition course Thursday and the guy taking it was telling me that even in back boxes where the plaster board has been penetrated the cable entering the box needs a fire seal round it. Something that I’ve never seen hence why I thought I’d ask you guys. Thanks for Your kind replies
     
  7. Bazza

    Bazza Screwfix Select

    As above it is only needed if the plasterboard is a fire barrier. Which it hardly ever is in a wall.

    standard single thickness gypsum plasterboard is not fire rated and this means it will not meet the stringent fire performance requirements of current UK building regulations in any case. For it to be a fire barrier it would have to be two sheets of 12.5mm plasterboard or a single sheet of the pink jobby.

    Also, I assume that you are talking about metal back boxes? Drywall boxes tend to be plastic, so no fire resistance there either.

    Ask him(her) for clarification.
     
    Last edited: Aug 6, 2022
  8. BGL

    BGL Member

    You can get fire rated & acoustic Metal back boxes, fire putty pads & intumescent sealer.
    I have always thought that one layer of plasterboard had a 30-minute rating unless I am wrong.
     
    Last edited: Aug 6, 2022
    Jako202196 likes this.
  9. Jako202196

    Jako202196 Member

    I think this is where I was getting it from, if this is the case surly the metal back box needs fire putty. Just not something I’ve not seen done .
     
  10. jimbobby

    jimbobby Screwfix Select

    So, steel back boxes on a block wall surrounded by plasterboard needs fire putty ?
    Can anyone show any building regs for this specification in domestic premises ?
     
  11. BGL

    BGL Member

    Back boxes are covered on the outside with intumescent material. Mainly for timber stud / dry lined walls.
    In Part B of the Building Regulations, section 11.12 states:

    ‘All openings for pipes, ducts, conduits, or cables to pass through any part of a fire separating element should be fire stopped. It goes on to say: ‘Proprietary fire stopping and sealing systems (including those designed for service penetrations) which have been shown by test to maintain the fire resistance of the wall or other element, are available and should be used’.

    The IET Guidance note 4. Protection against fire 6.2.4. says:

    ‘Where knockouts have been removed to allow the access of cables. These should be fire stopped to prevent the spread of hot gases into the structure in the event of the accessory sealing the box failing. This is also applicable if there are gaps between the electrical accessory box and plasterboard wall.
     
  12. Bazza

    Bazza Screwfix Select

    Yes, BUT the essential words in Part B:

    through any part of a fire separating element

    In most domestic premises there are NO fire separating elements.

    None of the ceilings in the usual house are designed and built to be a fire barrier. The exceptions are usually the ceilings of integrated garages.
    there are differences where a building has a number of separate dwellings. Here each dwelling is a separate fire-compartment.

    That’s why your standard gypsum plasterboard doesn’t have a rated fire resistance. It doesn’t need to have one!

    so, unless the wall or ceiling is actually a fire barrier, then there is no need for intumescent boxes, fire stop putty or anything of the like.
     
    jimbobby likes this.
  13. jimbobby

    jimbobby Screwfix Select

    So ALL ceiling roses and switches need to be fire stopped ?
    (including around the cables as they pass thr into a void ?)
    lol
     
  14. Bazza

    Bazza Screwfix Select

    If they penetrate a fire barrier, yes.

    When did you last come across a plasterboard wall that was a fire barrier?
    Brick is the usual way.
     
  15. BGL

    BGL Member

    Why not? We seal the cable back entries in new consumer units, I know to contain the spread of fire, but ceiling roses yes especially. My view is if you penetrate a wall of whatever construction you are reducing the fire rating capability & the rating should be equal to that before you carried out the work. In general domestic dwellings must have some fire rating & compartmental design to reduce the spread of fire to aid evacuation, even just plasterboard must have some form of resistance to fire.
     
  16. Bazza

    Bazza Screwfix Select

    We don’t seal back entries to consumer units. It’s spaces on top that matter, and thats not for fire, it's to stop your child from putting their pinkies in the gap.

    And they do not anything of the sort. If you look at your house, there is a big thing that makes any sort of other fire resistance pointless....

    ....it is that great big fire corridor that connects the various floors. The STAIRCASE.

    Houses are not built with fire doors on each floor. A substantial fire on the ground floor can take only a few minutes to roar upstairs. Certainly it will get to your bedroom faster than through a (non fire-rated) Gypsum plasterboard ceiling, even with a few pendants installed.

    So there is little point in plugging a ceiling rose, a back box, or anything else.
     
    Last edited: Aug 9, 2022
    Ind spark likes this.
  17. jimbobby

    jimbobby Screwfix Select

    How about sealing all the led light 'cans' which penetrate the ceilings below the loft spaces.
     
  18. Bazza

    Bazza Screwfix Select

    What about the plastic loft hatch cover?. How you gonna seal that?
    [​IMG]
    May be better to install a water sprinkler system throughout your house.
     
    jimbobby and Ind spark like this.
  19. BGL

    BGL Member

    It is my own particular way of working & I do seal, back entries in consumer units/ceiling roses & cableways penetrating walls. Just because materials have not been officially Fire rated, does not mean they do not have some form of resistance.
     
  20. Ind spark

    Ind spark Screwfix Select

    Denis6482 likes this.

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