- Project plans
- Project activities
- Legislation and standards
- Industry context
- Specialist wikis
Last edited 23 Nov 2020
How to install an underfloor safe
An underfloor safe is a common way to protect important documents, cash, data storage devices and other valuables in both homes and businesses. These robust safes do not take up any additional space in a room and may be concealed under a rug, floor panel or other feature.
In order for them to offer the maximum possible security, however, they have to be properly installed. The correct installation procedure varies depending on the model of safe and the floor in which it is being installed.
 Before installation
Although floor safes share the same purpose, they differ in their design and features. Each safe comes with an instruction manual that will outline the specific procedures required to install that particular safe. Failure to follow these instructions can result in voiding the manufacturer's warranty.
 Combination check
Homeowners and business proprietors often install safes as a result of insurance requirements for the secure storage of insured items. These guidelines can vary from insurer to insurer, making it important to check that the safe to be installed is in compliance with them. The insurer may have requirements not only for the type of safe but also for installation and record-keeping.
Proper location selection is an important feature of underfloor safe installation. Creating a space for the safe involves cutting into the floor or concrete foundation of the building, creating potential hazards.
Before installation, the installer should identify the location of power lines, water pipes, gas lines, data cables and other hazards that might be running under the floor. Damage to these features can lead to additional expense or danger.
In addition to these safety concerns, there are other factors to take into consideration when choosing a location for a safe. Properly-located safes are more secure. The best location will vary depending on the needs of the user and the features of the building.
A properly-installed safe will be flush with the floor level, avoiding a trip hazard, but many installers still prefer to keep safes out of areas which receive heavy foot traffic. Considering usage is also important: the safe should be fitted with the combination dial or keypad oriented relative to where the user will be kneeling to open it.
 Installation by contractors
Installing this kind of safe requires time, equipment and a moderate level of construction expertise. It can be done by home installers who have experience working with concrete, but others may choose to use a professional contractor to handle the installation.
Proper installation will require a range of tools and materials. The exact materials and tools required will vary depending on the type and location of the safe, but there are some common items. Some tools are used to install safes in concrete floors, while others are used to place safes in wooden floors. Many tools are useful for both types of installation.
 For all installations
Safe installation is ideally carried out by teams of two or more people. Safes can be heavy and bulky, and installation requires precise positioning to be successful. This task is much easier with assistance. Lowering the safe into the cut and adjusting its position will typically require more than one pair of hands.
- Pencil and ruler for marking cut locations.
- Tape measure.
- Spirit or digital level.
- Protective goggles and dust mask.
- Drop cloths or tarpaulins.
- Dust cover for safe.
- Plastic sheeting.
- Concrete mix.
- Concrete mixing tools and supplies.
- Waterproofing agent.
- Sand or gravel.
- Desiccant gel.
Installing a safe in an existing wooden floor requires some additional tools. The installer will need to create a concrete box around the safe to securely attach it; otherwise, a burglar might simply be able to detach the safe from the floorboards or joists and remove it completely.
 For existing concrete floors
Installing a safe in an existing concrete floor is the most demanding method in terms of the tools and equipment needed. The installer must cut a hole in the concrete slab to create a space for the safe; doing this quickly will require specialised tools, including:
 Preparing for installation
The installation process poses several risks to safes. Dust and moisture can interfere with the safe mechanism, while concrete seeping into the body can prevent the safe closing fully. Different safes require different types of preparation for installation, which will be reflected in their instructions.
In some cases, the installer will have to remove the safe door. When this happens, the inside of the safe should be filled with an absorbent material (such as crumpled newspaper) and a dust cover fitted over the opening. In other cases, the door will remain in place with a dust cover fitted over the outside of the safe.
Safe installation involves cutting into the existing floor, a process which can generate large quantities of dust and debris. Before installation, exposed surfaces should be covered with drop cloths or plastic sheeting to protect them. Installers should wear protective eyewear and dust masks.
Concrete used in safe installation should use a minimum of water to give the construction maximum strength. If damp is expected to be a problem, a suitable waterproofing agent can also be used. To improve durability, a steel reinforcement mesh may be used around the sides of the safe.
First, the installer has to remove any carpet or other floor covering and mark out the location in which the safe will be installed. Next, using a saw, the installer cuts a hole in the floorboards. This should be large enough to fit the safe into, with a small amount of extra room to create the concrete box.
The opening should be between 6 inches and 12 inches wider than the safe in every dimension. The exact size will vary depending on the dimensions of the safe, but some excess room is necessary for simple installation.
Once the hole is cut in the floor, the installer needs to build a form to pour the concrete. This form will support the concrete as it sets; it takes the shape of a box as wide as the hole and about 6 inches deeper than the safe. The sides of the form should be constructed of chicken wire lined with roofing paper.
After installing the form, the installer mixes a small amount of concrete and pours a thin floor into the bottom of the form. This should be thinner than the difference between the depth of the form and the depth of the safe. For instance, if the form is 6 inches deeper than the safe, the floor should be about 5 inches thick.
The installer then smoothens the floor and leaves it to partly set. The floor should be firm enough to support the weight of the safe but not so completely set that it doesn't allow the safe to move when placed in the form.
Once the floor has set to this level, the next step is to lay down a thin layer of sand or gravel. Once this is in place, the safe is ready to be inserted into the form. The installer carefully lowers the safe into the form, adjusting its position in the layer of sand with small movements until it is flush with the floor and in the correct orientation.
At this stage, it is critical to ensure that the safe is level, flush with the floor and orientated correctly; after the concrete is poured, it will be impossible to move. Once the safe is in the correct position, any excess sand or gravel should be removed.
With the safe in place, the installer now carefully pours concrete into the form around the safe. For maximum strength, each individual layer of 4 inches should be fully compacted and carefully worked into the previous layer. When the concrete level is nearly flush with the floor, the safe door should be reattached if necessary. Finally, the installer pours in the last layer, smoothens the top of the concrete with the trowel and allows it to set.
 Installing a safe in a concrete floor
Like installation in a wood floor, installing a safe in a concrete floor involves cutting out a space for the safe, positioning it and surrounding it with concrete. Cutting into the concrete floor requires special equipment.
Before beginning to cut, the installer must locate the correct location for the safe and mark out the dimensions of the cut. Using a jackhammer, concrete saw or similar tool, the installer then cuts out a recess for the safe.
The space needs to be larger than the safe in every dimension; exact dimensions vary depending on the safe, but a margin of 6 inches on each side of the safe is common. The space also needs to be deeper than the safe to allow for precise positioning. Concrete fragments will need to be periodically removed from the area.
Once the hole has been cut, the installer then pours and smoothens a concrete floor at its base. The base should be thin enough to allow the safe to be placed atop it without protruding from the recess; for instance, if the hole is 6 inches deeper than the depth of the safe, the floor should be 5 inches thick.
After smoothing, the installer leaves the floor to partly set. The desired consistency is firm but not yet completely hard; when the safe is placed on top of this layer, it will need to be adjusted slightly without pushing down all the way to the bottom of the cut.
Once the floor has set to the desired level of firmness, the installer places a thin layer of sand or gravel on top of the floor and positions the safe on top of it. This layer should be slightly more than an inch thick. During this phase, the position of the safe is finalised. The safe should be level and centred within the cut. The door of the safe should be level with the floor. Multiple fine adjustments will need to be made before the next step.
Once the safe is in its final position, the installer pours concrete in successive layers around the sides of the safe as it sits in place. Each layer should be firmly tamped down and worked into the layer beneath for maximum strength.
Before the final layer of concrete is poured and smoothed, the installer reattaches the safe door if necessary. Once the final layer is in place, the concrete should be level with the existing floor. Any excess concrete on the dust cover should be carefully cleaned up before it sets.
 Installing a safe in a new concrete floor
In some cases, a safe is not inserted into an existing floor but installed while the foundation is being poured. Typically, the builder creates a form around the space where the safe will be positioned and fills it with concrete in the same way as would be done for a safe installed under a wood floor.
Putting an underfloor safe into a new concrete floor may require additional measurement. If the concrete foundation will be covered with a wooden floor or other covering, the installer needs to take the thickness of this flooring into consideration so that the safe will be flush with the finished floor and not just with the concrete foundation.
Additionally, installation in a new foundation raises a new security concern: since construction sites are relatively open environments with workers coming and going, it becomes much more difficult to keep the location of the safe a secret.
 Post-installation care
Once the concrete around the safe has set for 48 hours, it should be ready for use. Some basic maintenance after this period will help protect the safe and its contents. Painting the concrete surface with linoleum paint can help prevent small grit particles coming loose from the surface.
Preventing water damage to the safe is a high priority; when floors are washed or mopped, cleaners should avoid the safe if possible. The locking mechanism should be regularly cleaned, oiled and maintained. Spraying the door hinges with lubricant immediately after installation will help keep the door moving smoothly.
Despite user precautions, floor safes can be vulnerable to damp and moisture. Silica gel desiccant packets can help reduce the risk of moisture damage. Damp-sensitive items such as documents can be stored in sealed plastic bags to minimise the risk.
Installing a safe in a floor, whether a wooden or concrete one, can be a challenging process for beginners, who may want to call on the services of a contractor with the required tools and experience.
Once installed, however, these safes provide effective protection and theft deterrence without taking up excess space. If properly installed and routinely maintained, they can protect valuables for many years.
--PRobert 15:16, 22 Feb 2017 (BST)
 Find out more
 Related articles on Designing Buildings Wiki
Featured articles and news
CIAT commentary after the first meeting.
Who is to blame?
Research recommends focussing on portfolio success rather than project success.
The revised standard for mapping underground utilities.
Cross-industry steering group seeks support in delivery.
Help us update process pieces from your field.
APM report explores existing practice.
COVID-19 and the importance of mental wellbeing.
As Professionally Qualified Person (PQP).
In order of relevance and with industry responses.
Raising awareness of the impacts of loneliness.
The list is growing, and in more ways than one.
We shouldn’t build new, If we can’t maintain what's built.
Timber Accelerator Hub phase 1 report