A simple but effective process…

1) Check suitability for cellar conversion

Is the cellar or basement suitable for conversion? Consider the following:

• Has the cellar previously flooded?
• What access is there?
• Is a staircase in place, or does one need installing?
• What is the cellar or basement headroom? Note that ceiling and floor treatments will reduce the headroom.
• What will you use the new rooms for?
• Is there another escape route, excluding the staircase?
• Does the cellar have ventilation, or could it be provided?

If these questions can be answered without creating further problems then your cellar or basement conversion is feasible.

2) Technical Issues

Waterproofing

Most cellars are partially, or completely within the ground. Therefore, there is always the risk of damp issues. Basements tend to be partially below ground but still have the same issue with possible damp. Even if your cellar or basement has never been flooded, there is always the potential for it to happen in the future. There are mainly two ways of damp proofing cellars or basements.

• Cementitious Waterproofing. Cementitious slurries are applied to walls and floors to prevent water from entering into the cellar.

• Cavity Drainage Systems and Water Management. Dimpled plastic membranes are attached to walls and floors. A drainage channel is added to the room’s border and goes to a sump to enable a pump(s) to eliminate water from the cellar. Obviously, any cellar conversion project needs to be protected from damp, otherwise, your new furnishings and decorations remain at risk.

Building control approval for the system to be used is required before any work is carried out. This is vital as it ensures that the project is set up correctly from the beginning.

3) Cellar Floor

When there is insufficient cellar or basement headroom it may be possible to lower the cellar floor. This needs to be approached cautiously as you need to consider your own home and neighbours. The following questions must be answered:

• Will lowering the floor undermine your house or a neighbour’s foundations?
• Will the new floor be lower than the water table, making your home more vulnerable to flooding?

4) Entry/Exit

Cellars and basements usually already have some way of accessing them. However, we involve Building Control to ensure that the access is acceptable for a habitable room. Then if Building Control says the steps are inadequate (or don’t exist) we would need to include new steps to ensure safe entry and exit to the conversion.

It is important that the exact location of the stairs is considered with regard to the existing layout, the proposed changes, the headroom that will be available and whether another means of escape is required by planning law.

Any  new or existing stairs must have the following elements:

4.1) Stair Pitch

A stair’s maximum pitch must not exceed 42 degrees.

4.2) Tread Rise and Going

The rise of each tread of domestic stairs must not exceed 220mm. The going must be at least 220mm.

4.3) Headroom

The headroom over the stair must be a minimum of 2m. Unlike loft conversions, where Building Regs allow a reduced headroom of 1.9m over the stair centre and 1.8m on its outside edge.

4.4) Handrails and Balustrades

The stair should have a handrail which is at least 900mm high. Any exposed stair edges or landings should have a balustrade that is at least the same height.

5) Fire Precautions

Your cellar or basement needs suitable escape routes in case of a fire. It might possible to upgrade cellars that have a porthole-type window to the outside. Doing this provides light and ventilation to the room and a secondary fire escape. A secondary fire escape must be fitted with a door or window with a clear area of at least 0.33m2 and 450mm wide. To create a habitable room, an escape route must be installed. Special fire escape hinges must be fitted to this secondary escape to ensure it can be fully opened if you ever need it so that you can easily climb up the light well to ground level.

Mains-operated smoke detection equipment must be installed in a cellar conversion. They will also need to be installed on other floors if there are no such devices there.

Fire doors and frames must be used to seal the cellar either at the top or the bottom of the stairs. The fire door can be installed at the bottom of the stairs if the cellar has a feature door at the top of the cellar stairs.

6) Drainage

You need to consider drainage at an early stage if you intend to install a wet room, bathroom, sink or giant aquarium. This is because any drains will usually be higher than the appliances you install. That means you are probably going to need a pumped drainage system.

7) Cellar Conversion Ceiling

Unless your cellar or basement already has the right ceiling installed you need to have one as part of the conversion. Ceilings must be able to provide an hour of fire protection, which is why plasterboard is commonly used for ceilings because it provides good fire resistance and flame spread properties.

If your cellar or the room above is to be a bedroom, 100mm of acoustic quilt will need to be installed within the floor void between the rooms.

8) Cellar Heating

It is likely that heating will need to be installed in your cellar or basement. Usually, the best approach to this is to extend your current heating system. However, it’s important that a plumber or heating engineer checks that your existing boiler and pump can serve your cellar conversion radiators. Thermostatic valves should be fitted to these new radiators to control the different rooms’ temperatures.

If it is impossible to use the existing system, or, you want a different type of heating, e.g. electric heaters, it’s important that consideration is given to ensuring that they function efficiently.

9) Cellar Ventilation

Habitable cellar or basement rooms require ventilation. Sometimes this can be an issue in cellar conversions. Sometimes, where there is a light well, this can be adapted to have an opening window equivalent to 1/20th of the room’s floor area with a trickle vent at a high level. Bath or wet rooms must have an extractor fan. If they don’t have opening windows the fans must be triggered by the light switch with overrun timers so that the fan stays on after turning the light off.

If natural ventilation through windows is impractical a mechanical ventilation system will need to be installed. Like drainage, ventilation should be looked at in the design stage, as duct work will be needed if mechanical ventilation is used.

10) Thermal Insulation

A high level of insulation is needed within your conversion to reduce emissions and reduce heating costs. Your cellar should have an insulated envelope to minimise the heat escaping. Your cellar or basement is usually lined with insulating boards, and any windows should have 24mm double-glazed units with low emissivity glass. You also need to consider the efficiency of any services you put in the cellar. Wherever possible, low-energy light fittings should be used. The heating system should work efficiently with suitable thermostats and controls.

11) Electrics

A cellar conversion means that there will be some electrical changes. Sometimes it may be possible to extend existing circuits. However, if these are too old, a new circuit and even a new board will be needed. Again at the planning stage, consult with a competent electrician. Please ensure that any electrician you use issues you with BS7671 test certificates when they finish their installation.  These are necessary to enable your Building Regulations Completion Certificate to be issued. Extra costs will be incurred if these certificates are not provided.

Conclusion

A properly planned cellar or basement conversion makes an interesting space and is a great way of getting more room. However, remember, think about what you want from your cellar before converting it.

We arrive at many potential clients’ properties that want a cellar conversion. They contact three to four contractors for estimates. Of course, obtaining various quotations is a good idea, and we recommend that plans are drawn up and a system designed with the type of materials used to obtain a “like for like” quotation. Unfortunately, cellar conversions require expertise that experience brings, so if clients go on price alone, their cellar conversion “experts” may not realise there is a problem until it hits them in the face. That could be at the design stage, the planning stage or when the building starts and, worse, when something has to be torn down because it doesn’t meet Building Regulations – like stairs, ventilation, or drainage.

Simply Cellars offers a design service where we design and specify materials required for your conversion, which we are more than happy for you to use to obtain further quotations.