How to fit an underfloor safe

How to fit an underfloor safe

An underfloor safe is a steel box with a secure safe door attached at the top. The body itself doesn’t offer much protection so it is encased in concrete to make it more secure. An underfloor safe is well hidden and is less likely to be found unless you know where to look for it.

Unlike floorboard safes, which is attached between floor joists, an underfloor safe is suitable for insurance purposes as it is properly secured by being embedded in concrete. Underfloor safes are available with either a very secure round screw-in door or with a larger rectangular lid to allow a wider range of valuables to be stored.

Underfloor deposit safes are great for small businesses who often handle in cash and are looking for an effective way to keep money or smaller high-value items secure. There are a variety of underfloor safes available in varying sizes, offering different insurance values.

Installing your underfloor safe

The body of an underfloor safe must be sunk into concrete on an existing and suitable solid floor (concrete or timber) and so to install one of these safes, the ground must be excavated to create enough depth if a cavity is not already present. The top opening of the safe should sit flush with the floor level.

Some types of underfloor safe can be secured on to a floor if they are encased in reinforced concrete, but this should only be considered where excavation is not possible.

It is key to remember that the concrete mix used to secure these safes is not standard and each manufacturer will have suggestions for the mix that would be best for securing the safe. Failure to install the safe correctly could invalidate any insurance, so it is best done by a professional builder.

If the safe is to be installed on a floor that is floorboards over joists and there is a sufficient void underneath, shuttering can be constructed to make a box that the safe sits in, with concrete poured around it. It is also possible to construct an above ground box, using shuttering, to the same effect.

Safes of £10,000 cash rating and above also come with a steel mesh, which is placed into the concrete around the neck of the safe to reinforce the floor and give extra resistance.


Key steps:

  • Remove safe door and keep clean
  • Protect safe from any sand and cement entering via neck
  • Remove floor covering to expose concrete floor
  • Ensure no drains, cables, pipes are located beneath this area
  • Mark out area at least 150mm wider than footprint of safe
  • Dig away until depth is at least 75mm deeper than height of safe
  • Fit a damp-proof membrane to resist corrosion from water damage
  • Add a water resisting additive before filling base of hole with 100mm of concrete mix
  • Lower safe into the excavated hole until safe is level with ground surface
  • Fit mesh if required
  • Check safe is level while filling with mix
  • Do not disturb or use safe within 7 days of installation


You can browse our full range of underfloor safes on our website, or for further assistance on choosing and installing an underfloor safe, contact the team at Safe Options today to see how we can help.