Back Boxes - How Deep

Discussion in 'Electricians' Talk' started by Jube, Dec 11, 2004.

  1. Jube

    Jube New Member

    When setting backing boxes into a wall that is going to be plastered at what depth should they be set - I am assuming that as long as they are not proud of the expected finish level then they are ok ?

    Thanks Justin
     
  2. seylectric

    seylectric New Member

    They should be flush, ideally. Some brands of sockets and switches have a bit of a "lip" on them, so the sockets will still be flush even if the boxes are 2-3mm proud.

    More importantly, don't sink them too deep. You will leave a gap between the socket and the box and debris (bits of plaster etc.) may fall into the backbox.

    When chasing out your hole for the backbox, have a box handy for checking the depth every so often.

    Boxes for sockets are 25mm deep, and typically 16mm deep for lightswitches.
     
  3. tellondon

    tellondon New Member

    I would suggest using 25mm deep boxes for light switches and 35mm deep for sockets
    16mm is usually ok for light switches unless you decide to use a dimmer
    and 25mm is usually ok for sockets unless you decide to change the socket to a flush plate type socket
     
  4. seylectric

    seylectric New Member

    Agreed, I was just trying to "keep it simple" for the purposes of the thread, those I quoted being the most common sizes, but it's a fair point.
     
  5. plugwash

    plugwash New Member

    i would think you probablly wan't to aim for about a mm or so below the finish level.

    a 16mm box is considered plaster depth so i would screw those direct to the surface to be plastered and recess other sizes of box to leave about 16mm sticking out.

    if you are using normal sockets/switches you can get away with them slightly proud but with flat plate units you won't.

    on the other hand you don't really want to leaev a big gap as that kind of defeats the perpose of a backbox.

    the normal way seems to be to plaster over the boxes (which are padded out with cardboard and/or tape) with the finishing coat and then to break away the plaster from over the boxes after its set.
     
  6. andyspark

    andyspark Active Member

    telllondon

    Does this mean you cannot retro fit flat plate sockets in a house with 25mm back boxes unless you change all the boxes for 35mm ones.
     
  7. tellondon

    tellondon New Member

    I think it depends what make you use,sorry but im not sure which makes will fit and which wont
     

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