flush-mounted socket
Standards-compliant, precision-fit, installer-friendly
Flush-mounted boxes are the invisible foundation of every electrical installation: they house switches, socket inserts, dimmers and control components, disappear flush into the wall and provide code-compliant support – in new builds as well as renovations. Whether a standard device box, an airtight version for low-energy construction or an electronic box for deep smart home inserts – at WATT24 you'll find flush-mounted boxes and matching accessories such as plaster compensation rings from Kaiser, OBO Bettermann, Busch-Jaeger and Fränkische.
As an electrician or installer, you benefit from a range that covers all common installation scenarios: solid masonry, timber frame construction, airtight assemblies to blower door requirements and gang installations for multi-gang frames. Distance spacers, plaster compensation rings and signal covers round off the programme.
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What is a flush-mounted box?
A flush-mounted box (also known as a switch box or device box) is set into a recess in the masonry and serves as the carrier for switches, socket inserts, dimmers or other installation components. After installation, the box is plastered or bonded in place – only the design element remains visible at the wall surface.
Standard flush-mounted boxes have an outer diameter of 68 mm with an installation dimension of 60 mm, complying with DIN 49073. The installation depth varies by type between 45 mm and 66 mm – relevant for example in confined spaces within thin walls or when accommodating deep dimmer inserts.
Types at a glance
| Type | Characteristic | Typical application |
|---|---|---|
| Standard device box | Open, no seal | New build, masonry, interior fit-out |
| Airtight / draught-proof box | Compatible with airtightness membranes or collars | KfW efficiency house, passive house, timber frame |
| Electronic box | Greater installation depth, more terminal space | Dimmers, wireless inserts, smart home components |
| Double device box | For two side-by-side inserts | Double sockets, switch/socket combinations |
| Junction switch box | With side terminal compartment or screw domes | Cable distribution directly inside the box |
Plaster compensation rings and accessories
If the plaster thickness was not calculated precisely, the flush-mounted box may end up sitting too deep. Plaster compensation rings are screwed onto the box and bring it to the correct level – so that switches and sockets sit flush once installed. OBO Bettermann offers rings with 12 mm (ZU 12-PR) and 24 mm (ZU 24-PR) height for boxes with a 60 mm diameter.
| Accessory | Function | Application |
|---|---|---|
| Plaster compensation ring 12 mm | Raises the box by 12 mm | When the box sits slightly too deep |
| Plaster compensation ring 24 mm | Raises the box by 24 mm | With heavier plaster application |
| Signal cover | Protects the box during plastering | Shell construction – prevents contamination, remains visible |
| Distance spacer | Connects boxes at exact 71 mm centre spacing | Gang installation for multi-gang frames |
| Quick-Fix | Clamp fixing instead of plastering | Fast installation during renovation or in cavities |
Choosing the right flush-mounted box
For the flush-mounted box to fit perfectly, a few parameters need to match:
1. Wall material and installation situation
Solid masonry, concrete or timber stud construction with boarding – the installation method differs depending on the substrate. In masonry, the box is plastered or bonded in place; in timber construction, it is fastened or combined with an airtight membrane.
2. Airtightness
In new builds to KfW or passive house standard, airtight installation is mandatory. Only specifically designed boxes – such as the Kaiser 1068-26 or the Fränkische ReMo – can be permanently integrated into the airtightness layer.
3. Installation depth
Standard device boxes have a depth of 45–50 mm. Dimmers, smart home inserts or wireless modules often require 60–66 mm. Always check the insert's datasheet before selecting the box.
4. Number of inserts
Is a single insert needed or several side by side? For multi-gang frames, individual boxes are connected using distance spacers. Alternatively, double device boxes accommodate two inserts in a single housing.
| Criterion | What to look for |
|---|---|
| Wall material | Masonry, concrete, timber frame – determines installation method |
| Airtightness | Standard or airtight (KfW, passive house) |
| Installation depth | 45–50 mm standard, 60–66 mm for deep inserts |
| Number of inserts | Single box, double box or gang with distance spacers |
| Accessories required | Plaster compensation ring, signal cover, Quick-Fix needed? |
| Manufacturer | Kaiser, OBO Bettermann, Busch-Jaeger, Fränkische |
Frequently asked questions about flush-mounted boxes
The terms are often used interchangeably. Strictly speaking, the device box is the generic term – it accommodates insert units for sockets, switches or dimmers. Switch box means the same thing but is often used specifically for switch inserts. A junction switch box additionally features a terminal compartment for distributing cables directly inside the box.
In Germany, the standard dimension according to DIN 49073 is widely used: the installation diameter is 60 mm, and the outer diameter of the box is approximately 68 mm. Almost all switch programmes from major manufacturers (Gira, Busch-Jaeger, Merten, Jung) are designed for this dimension and can be combined without issue.
Wherever an airtight building envelope is required: in timber frame construction, KfW efficiency houses or passive house standard. Standard boxes break the airtightness layer. Airtight boxes such as the Kaiser 1068-26 or the Fränkische ReMo can be permanently sealed with acrylic films or special adhesive tapes and will pass the blower door test.
A plaster compensation ring is a plastic adapter that is screwed onto a flush-mounted box that sits too deep. It raises the edge of the box by 12 or 24 mm so that switches and sockets can later be mounted flush with the wall surface. It is needed whenever the applied plaster thickness exceeds the original plan.
For gang installations, a centre-to-centre spacing of 71 mm is maintained. Distance spacers – such as the OBO ZU 20-AS with bayonet lock – connect the boxes stably and automatically maintain the correct spacing, without the need to measure each box individually.
In principle yes – thanks to the standardised installation dimension of 60 mm, inserts from most manufacturers fit into any standard flush-mounted box. Exceptions include deep dimmer or smart home inserts that require an electronic box with an installation depth of 60–66 mm. When in doubt, check the insert's datasheet.
No – hollow walls and drylining walls require special cavity wall boxes that are fastened from the front using expansion screws or toggle clamps. The flush-mounted boxes listed here are intended for solid masonry or timber stud construction, into which they are plastered or bonded.
The signal cover (e.g. OBO ZU 60-SD) protects the installed box from dirt and plaster during the plastering process. Its red signal bristles remain visible even under a thin layer of plaster, ensuring the box is not lost during plastering.
Buy flush-mounted boxes at WATT24
At WATT24 you'll find a well-thought-out range of flush-mounted boxes for every installation scenario – from the affordable standard device box for solid masonry to the airtight electronic box for passive house applications. Plus the complete range of accessories: plaster compensation rings, signal covers, distance spacers and Quick-Fix systems.
Why WATT24?
- Comprehensive range: All common types from Kaiser, OBO Bettermann, Busch-Jaeger and Fränkische
- Fast delivery: Dispatch within 24 hours for items in stock
- Expert advice: Our specialists help you select the right box and matching accessories
- Fair pricing: Competitive rates for electricians and trade customers
Typical applications for flush-mounted boxes
- Residential new build: Standard device boxes for switches and sockets in masonry
- KfW efficiency house / passive house: Airtight boxes for blower door-compliant installation
- Timber frame construction: Draught-proof boxes compatible with vapour barriers and acrylic films
- Renovation and conversion: Quick-Fix system for fast installation without plastering
- Smart home installation: Electronic boxes for wireless inserts, KNX panels and touch controls
- Commercial interior fit-out: Robust junction switch boxes with terminal compartment for clean cable management
Do you have further questions about flush-mounted boxes or need help with your selection? Contact our team – we're happy to help!