Here’s a guide as to what’s involved with a basement or cellar conversion

A complete basement or cellar conversion will most likely encompass the removal of the existing floor, some excavation of the ground, (how much will depend on the depth of the existing foundations), a full waterproofing system using a cavity drainage membrane system, drainage and sump pump, a new floor (usually concrete or screed), insulation to the walls and floor, dry lining plastering, new electrical installation, joinery and plumbing.

A new internal staircase may be installed or sometimes the existing flight can be left in place and incorporated into the waterproofing system. Removal of internal wall/s to create larger open plan spaces are commonplace or creating a new external access via a set of steps maybe an option if desired. Most things are possible and only limited by your imagination.

Windows

Replacement or additional basement windows are commonly installed to provide additional natural daylight. If there’s no external door access to the basement and the area is to be classed as' habitable space' at least one or more windows within the basement must conform to part B (fire safety) of the building regulations. This provides an alternate means of escape in the event of a fire and is normally created using a tilt and turn window that opens inwardly.

Plumbing and Heating

Heating may come in the form of radiators fitted with thermostatic radiator valves (TRVs), electric convectors or increasingly popular, under floor heating. The size and capacity of the existing heating system will be assessed to provide advice on the best system to install. Most conversions will require the relocation of some or all of the existing heating, gas, water and waste pipes which may be attached to the timber joists or walls .Our heating engineer with many years’ experience, has advanced City and Guilds qualifications and is ' gas safe registered.

Sometimes, waste water may be disposed of directly to the outside drains, but will depend on the level of the external pipework. Most conversions incorporating a kitchen, utility or bathroom will require some form of pump to remove the waste water, either a macerator, shower pump or mini pumping station.

Joinery

Joinery works may include new internal and external doors, skirting boards, purpose made cupboards around boilers and gas/electric meters, shelving etc. Due to access restrictions and unusual dimensions found within some basements, internal staircases are generally custom built on site together with hand rails or balustrades.

We are able to offer a full bespoke joinery service which may include the supply and/or fitting of kitchen and utility units if required. We are more than happy to discuss your specific requirements.

Our joiners are fully qualified at level 1 / 2 / 3 NVQ and advanced construction.

Electrical Works

All new electrical installations (17th addition) must comply with Part P of the building regulations. All new circuits should be protected by a residual current device (RCD) and we will therefore generally install a separate dedicated consumer unit to provide an electrical supply for the basement conversion. A smoke alarm or heat sensor will normally be required within the basement (sometimes linked to a ground floor alarm) along with your choice and position of 13a sockets, light fittings normally LED down lighters and any other requirements you may have. Most projects will require a certain amount of alteration/ relocation to the existing wiring, we can install cabling for your TVs, Sky connection, home cinema speakers and technology cables etc on request. These can be installed in your selected positions before the installation of the dry lining.

Ventilation

Natural ventilation will normally be provided by means of an opening window/s. Extractor fans are generally required if there is a utility or bathroom area within the project. For additional ventilation and air change we often install a positive input ventilation unit (PIV). This provides a constant supply of fresh air from outside the property.

Process of Waterproofing

Modern innovation and technology has provided a range of ‘Cavity Drainage Membranes' (CDM) that are now widely accepted as a means of effectively waterproofing basements. Coupled with the installation of a water management system including sump pumps and drainage channels, CDMs are installed quickly and with minimum of wall preparation.

Cavity drainage membrane systems (CDM) are particularly suited to waterproofing basements commonly encountered in the UK, as it does not rely on the soundness of the underlying substrate for its effectiveness. The membrane is attached to the wall by means of sealed fixing plugs, whilst on the floor there is normally no need for any form of fixing.

CDMs can be covered with plasterboard using timber battens, a metal dry lining system or dot and dabbed plasterboard may be applied directly to membrane with a suitably attached mesh. Membrane over the floor area may be screeded, concreted or covered with a floating timber floor. Insulation is incorporated into the dry lining before the application of plasterboards and also before the laying of concrete/screed to the floor area. A drainage facility, incorporating a sump, pump and high water level alarm will are included as an important part of every system.

Pump Systems

A cavity drainage membrane system is designed to provide dry decorative surfaces to the basement wall and floor. Any water that may enter the area behind the cdm needs to be collected in a sump chamber and pumped to an external drain as and when it is required to do so. This normally takes the form of a single or double pump system, fitted with a high water level alarm that will sound in the unlikely event of a pump failure. In cases where flooding is a known to have taken place in the past, a battery backup system may be considered to provide additional cover should the mains electricity power supply be lost temporarily. A quality sump pump system is an essential part of any basement conversion.

Building Regulations

The majority of basement conversions will be subject to compliance with building regulations.

You should be cautious if any contractor offers to convert your basement or cellar without the involvement of the local authority or independent building control department. Please call us for further help and advice regarding building regulations. Unless otherwise stated, all our quotations include a building notice application.

We will project manage the building control visits during the contract, arranging for periodic inspections from the building inspector throughout the process. A certificate of completion will be provided thereafter.

New Basement Creation and Underpinning

Sometimes an existing basement may lack sufficient head room to be used for everyday living. Occasionally the existing foundations of the building may be deep enough to allow us to excavate downwards to create more ceiling height, but very often, significant extra head room can only be created by underpinning the basement walls. Underpinning is a method of construction that sees the depth of the foundations to a building being increased. The soil beneath the existing foundation is excavated and is replaced with foundation material, normally concrete, in phases. A structural engineer would be engaged to design an underpinning project and the work will be overseen by the building inspector involved with the project.

This process can be used expand an existing basement into an under floor 'void' area or to create a new basement from scratch. Please contact us for more information about underpinning.