How to crush a can

Flush-mounted boxes for electrical installations


In the case of flush-mounted electrical installation, so-called switch boxes are used to install flush-mounted devices such as flush-mounted sockets, flush-mounted switches or flush-mounted telephone sockets, flush-mounted dimmers, flush-mounted thermostats and many more.

These switch boxes are available in different designs. The simplest form of the switch box is 40mm to 46mm deep and has a diameter of 60mm. The switch box is made of plastic and has 4 screw domes, to which the device insert will be attached later.

Normal switch boxes * are used if only, for example, a flush-type socket with a three-wire cable is to be connected. A maximum of two connection cables should be inserted into the normal switch box. If several cables are required, it is essential to use deep switch boxes or switch junction boxes.


Deep flush-mounted boxes for electrical installations

So if you want to put three to four cables in a flush-mounted box, use a deep switch box. This has the same diameter of 60mm, but it is 60mm deep and therefore has more space to clamp.

A deep switch box is also used for devices that naturally require a lot of space in the switch box. These devices are, for example: flush-mounted antenna socket, network socket, flush-mounted dimmer, or flush-mounted motion detectors.

When installing the electrical system, think carefully about which socket is needed where and how many cables have to be inserted into the respective socket. If in doubt, always prefer a deep switch box to install.


Flush-mounted boxes as device junction boxes

If you want to insert more than four cables into the switch box, use a device junction box. With this box you have a large terminal space and can thus jam entire circuits.

The device junction box can still be used as a switch box for devices (switches). If possible, I recommend that you do not use any additional junction boxes for jamming circuits, but always carry out the clamping work in the device junction box. This has the advantage that there are no ugly can lids to be seen on the finished plaster later.

If you prefer to do the clamping work in a separate box, use flush-mounted junction boxes *. These have a diameter of 70mm and a depth of 40mm. If this is still too small due to too many cables, use flush-mounted junction boxes *. These, in turn, are available in many different sizes.

There are special wall outlet boxes for wall outlets such as wall lamps.

How are the flush-mounted sockets attached in the shell?

It is advisable to set the flush-mounted boxes with a quick-assembly mortar. In the past, plaster of paris was often used, but this can later lead to cracks in the plaster, especially with lime plaster. It is therefore best to use quick-build mortar or similar, it also has the advantage that you can set many doses at once due to the longer setting time of the mortar.


Here are the guide heights of the device sockets in the middle (finished floor), so add your floor structure:

  • Sockets for devices 30 cm in the middle from the upper edge of the floor
  • Switches or sockets next to doors or windows 105 cm in the middle from the upper edge of the floor
  • Switches or sockets above work surfaces 115 cm in the middle from the upper edge of the floor
  • Wall outlets for workplace lights 135 cm in the middle from the upper edge of the floor
  • Junction boxes 30cm in the middle from the lower edge of the ceiling


Before you start setting the cans, they must be precisely marked. To do this, use the spirit level to draw a large cross with a pencil (cross is in the middle of the flush-mounted box) for the box height. This cross is used for precise orientation and makes placing the cans much easier for you.


Procedure for setting the cans

  1. Using the spirit level, mark the reference heights vertically and horizontally.
  2. With a can drill * drill out the cans
  3. Check whether the cans fit in and, if necessary, rework with the chisel
  4. Use a brush to slightly wet the masonry hole in the can
  5. Break out the required cable entries for the flush-mounted sockets
  6. Mix the quick construction mortar
  7. Use a spatula to spread an adequate amount of mortar into the hole provided
  8. Put the cans in at the exact height (pencil line) and put them exactly into the water with the spirit level.
  9. Let the cans look about 1cm out of the wall (plaster height)
  10. To be on the safe side, measure and correct again
  11. Let the mortar harden

Flush-mounted boxes for cavity wall installation

There are special switch and junction boxes for cavity walls such as plasterboard stud walls or wooden stud walls. these are called cavity wall boxes. The cavity wall boxes are attached using screw claws on the side of the box.

The holes for the cavity wall boxes must be made with a special cavity wall socket drill * (68mm) can be drilled. Also mark a cross for the middle of the can (note the guide heights) with the spirit level and then carefully drill it out.

The cavity wall boxes is also available in a windproof version. These are used in bare bones or in wooden houses.

Special tip: Are you looking for a suitable switch range at an acceptable price? I can recommend a provider without hesitation. It is the small switch range. I myself have installed it hundreds of times. My customers are extremely pleasantly surprised by the look and, above all, the price.

I can recommend it with a clear conscience that it is of high quality and so far there have been almost no complaints (that is also the reason why I decided to sell it myself).

It is, in my opinion, maybe not quite the quality of the programs presented above, but so far I have sold it to thousands of customers who are extremely satisfied with it. Here you can get an impression of it.

Filed Under: BasicsTagged With: flush box, flush box, flush switch box, set flush box, set switch box, junction box, device junction box, cavity wall box