Most cellars are set either partially, or completely within the ground , which means they tend to suffer from problems with damp. Whilst your cellar may never have experienced flooding, with the area being underground there is always a high possibility that this could occur in the future. Principally there are two types of systems that are available for damp proofing cellars. 1) Cementitious – Waterproofing. This is where cementitious slurry’s are applied to the walls and the floors to stop any water entering into the cellar. 2) Cavity Drainage Systems – Water management. This is where plastic dimpled membranes are installed in the walls and floors. A drainage channel is installed to the perimeter of the room that leads to a sump where a pump(s) discharge the water out of the cellar. Protecting your cellar from damp is an important part of the cellar conversion process. Building Control will need to approve the details of the system that it is intended to be installed prior to installation.
Lowering the Cellar Floor
If there is not sufficient headroom in your cellar it is sometimes possible to lower the cellar floor. However, this is not a simple operation and careful consideration needs to be given to whether lowering the floor will undermine the house or the neighbour’s house foundations, whether the floor will end up below the water table and make the property more vulnerable to flooding.
Some cellars already have good stepped access to them, whether the existing stairs will provide suitable access to a habitable room is a matter of judgment and our Building Control. If there are no steps, or if the existing steps are inadequate, a new stair will need to be installed.
Careful consideration should be given to the best location for the stair and this will be influenced by a number of factors, including the layout of the existing house and cellar, the headroom available and whether a secondary means of escape can be provided from the cellar area.
Wherever the stair is installed it should be designed in accordance with the following guidance;
The maximum pitch for the stair should not exceed 42 degrees.
Rise and Going
The maximum rise of each tread of a domestic stair should not exceed 220mm and the going should be at least 220mm.
The clear headroom over the stair should be at least 2m, for some loft conversions the Building Regulations allow a reduced headroom of 1.9m over the centre of the stair and 1.8m on the outside edge.
Handrails and Balustrades
The stair should be provided with a handrail at least 900mm high. Any exposed edges of stairs or landings should be provided with a balustrade that is at least 900mm high.
The cellar will need to be provided with suitable escape routes in case of a fire. If your cellar has a porthole type window to the outside for to provide light and ventilation, it may be possible to upgrade this. Doing this not only provides light and ventilation to the room but also a secondary fire escape. To be considered as a secondary fire escape it would need to be fitted with a door or window which has a clear area of at least 0.33m2 and 450mm wide. To form a room suitable for habitation, then an escape route has to be installed. Special fire escape hinges should be fitted to this window or door to ensure that it can be fully opened if you ever need it and you should be able to easily climb up from the light well to ground level.
When converting a cellar mains operated smoke detection will need to be installed, and these detection units will have to be installed to other floor levels if there are no such devices.
Fire doors and frames will be required to seal the cellar either at the top or the bottom of the stairs. In older properties there may be a featured door at the top of the cellar, in this case the fire door can be installed at the bottom of the stairs.
Depending on the use of the room you may wish to install a sink, bathroom, shower room or even a washing machine in your conversion. Therefore, it is important that you consider drainage at an early stage. As the drains are usually above the level of the appliances that you wish to install you are likely to need to install a pumped drainage system and various package systems are available.
Unless your existing cellar has an adequate ceiling you will need to provide one as part of your conversion. Plasterboard is the most common material used for ceilings as it offers good fire resistance and flame spread properties. Ceilings will need to offer 1 hour fire protection.
If either your cellar or the room above is to be used as a bedroom you will need to install 100mm of acoustic quilt within the floor void between the rooms.
To maximize the usability of the room you will probably want to install heating, in most instances the most effective way of doing this is to extend the existing central heating system. You will need to check with your plumber or heating engineer to ensure that your existing boiler and pump has sufficient capacity to serve any additional radiators. Any new radiators should be fitted with thermostatic valves to control the room temperature.
If it is not possible to extend the existing system, or, if you prefer an alternative method of heating, e.g. electric panel heaters, careful consideration should be given as to how these can be switched and controlled to ensure that they function efficiently.
Any new habitable rooms will need to be ventilated and this can sometimes present a problem for cellar conversions. Where the cellar contains a light well this can sometimes be adapted to include an opening window equivalent to 1/20th of the floor area of the room with a trickle vent at high level. In any bath or shower rooms an extract fan should be fitted and if they do not have opening windows extract fans should be fitted that are triggered by the light switch with overrun timers that allow the fan to remain on after the light is turned out.
Where natural ventilation through windows is not practical a mechanical ventilation system will need to be installed and various package systems are available on the market. Ventilation should be considered early in the design stage as, if mechanical ventilation is required, the duct work will need to be accommodated.
CO2 emissions are a major concern in today’s environment and you will need to provide a high level of insulation within your conversion. Your cellar should provide an insulated envelope so that the amount of heat escaping is minimised. The walls and floor of your cellar are generally lined with insulating boards and the windows should include 24mm double glazing units incorporating low emissivity glass. As well as insulating your extension you will need to consider the efficiency of any services you put into it. Low energy light fittings should be used where possible and any new heating systems should work to high levels of efficiency and have suitable thermostats and controls.
You are likely to require some electrical alterations as part of your conversion. Depending on the age and condition of your existing electrical system it is sometimes possible to extend existing circuits, but sometimes new circuits and even a new distribution board will be required. It is a good idea to get advice from a competent electrician at an early stage. When appointing an electrician please ensure that they are able to issue you with BS7671 test certificates when they have completed their installation as these will be required before your Building Regulations Completion Certificate can be issued and you will incur additional costs if the test certificates have not been provided.
A well converted cellar can be an interesting space and can be a great way of getting extra room in your house. In the first instance, see what you want out of the cellar that you intend to create.
We arrive at many potential clients properties that intend to have a conversion carried out to their cellars and contact three to four contractors to call and provide them with an estimate. Whilst obtaining various quotations is a good idea, we would recommend that plans are drawn up and a system designed with the type of materials used to obtain a ‘like for like’ quotation. Sadly clients have gone on the price only, and many are not experts in cellar conversions, so they do not know until a problem arises if they have got a cellar designed for damp, and or suitable to Building Regulations.
Damp Nation offers a design service where we will design and specify materials required for your conversion where we are more than happy for you to use to obtain further quotations.