Garage Conversions

Design:

The internal area of most garages is not a layout that most people would be keen on. To attain a more innate feel in the conversion, you could consider using stud or block walling to adapt the garage into two rooms. The additional room is often used as a WC or shower, or maybe a storeroom would suit better. Consideration needs to be taken during the planning stage as to how you plan to put the rooms to good use and Extra Room Limited would be happy to assist you with this.

Planning & Building Regulations:

Planning permission is only necessary if you plan to alter the structure of the building. The alteration of use from a garage to a habitable room means compliance with building regulations, including delivery of a building notice to your council. Should you reside in a listed building or conservation area, planning permission may be required for even the most minor of alterations. Properties in newly built housing estates can sometimes require planning permission. Standalone garages are more probable to need “change of use” planning permission when converted to habitable rooms. Extra Room Ltd would check with your local planning department by phone and if the answer is positive, we would write without delay to ask for written permission.

Building regulations apply to ventilation, moisture proofing, insulation, fireproofing, escape routes and structural soundness. Consequently, most design decisions must take these into account.

When a garage area is divided up, a new room is formed and this room is also subject to a set of building regulations that require an escape route and ventilation separate from the main room. Modifications such as an infill wall replacing the original garage door will also be subject to building regulations with regards to the foundations. A Building Inspector will want to visually inspect windows, doors, fireproofing and foundations prior to proving a Certificate of Completion.

Insulation & Damp Proofing:

Insulation is assessed in terms of a ‘u’ value: the measure if the rate of heat escape, in watts, from a square metre of the material in an hour. Walls must achieve a u value of 0.35W/m2/K and roofs a u value of 0.16W/m2/K if pitched or 0.25W/m2/K if flat and the floor 0.25W/m2K. The floor will need to be 0.25W/m2K. Windows should be 0.18W/m2K and window manufacturers will provide the u value as part of their specification.

Damp proofing will be essential to the walls and floor. A damp proofing membrane is required to lay in the wall and would be laid between two layers of bricks to avoid moisture rising up the wall by capillary attraction and rotting the brickwork. The membrane is typically polyethylene or bitumen polymer. Many garages already have a damp course laid in the walls but this needs to be checked. The floor requires being damp proofed by laying a Damp Proof Membrane at the same time the floor is remade.

Plumbing & Wiring:

Extra Room Ltd would provide thorough survey of the plumbing and wiring in the house and garage as any wall you plan to pierce for doorways or windows requires special awareness. We would locate the main water outflows for water and if you plan to install a WC, the soil outflow.

Inspections of the garage for wiring in the walls as ceilings would also be carried out prior to works commencing. Additional lighting and electric radiators will be an additional strain on the household mains, which is fused at 100 amps. A further mains supply can be installed but the cost can be extremely variable, between £500.00 & £20,000.00 and this also requires the installation of a separate consumer unit or alternatively locates the garage on the current consumer unit. If its own MCB (Miniature Circuit Breaker) is not present, consider replacing the consumer unit or upgrading it. Should you wish the garage to be an additional habitable room in your house (which is the most common idea), its own MCB in all probability will be enough and adding at least one new 20-amp circuit. Wiring with in a detached garage can be run through an underground conduit and if it is to be a separate residence, a new connection may be required depending on expected power usage. Extra Room Ltd can provide a qualified electrician for these works.

Flooring:

The floor of the existing garage will be adequately robust but will require additional damp proofing and insulation to meet building regulations.

A concrete floor can be formed and a Damp Proof Membrane added between the two layers. Insulation will also be added under the new floor; however a separation layer is occasionally required to avert a chemical reaction with the damp proofing. Concrete floors would be finished with a screed of 75mm depth and sealed prior to painting.

A raised timber floor can be constructed over the existing floor and this requires a gap of 150mm between the joists and the existing floor. Wide or long raised timber floors may possibly require a small supporting wall and damp proofing would be laid under the timber and insulation between the joists and the timbers of the floor. Fire regulations may require a step to be installed in a raised timber floor at doorways to prevent fire spreading under fire doors by burning of the floor timbers.

Walls:

External walls are covered by building regulations and are required to meet requirements in terms of moisture-proofing and insulation. Should the garage be integral to the house, the exterior walls will ordinarily meet building regulations but should this not be the case, we would ask you to consider a second block wall or stud wall inside the existing exterior wall. Insulation, power and water lines can be put behind this wall but this would decrease the interior dimensions of the area.

Interior walls between rooms within the alteration must meet building regulations’ requirements for fire proofing and this can be provided by installing one or two layers of fireproof plasterboard on stud walls, for block walls this is unwarranted. Doors through interior walls require being fireproof with a 30min rating and building regulations may require a step to be installed in the floor at the doorway to avert fire spreading along the floorboards.

Additional insulation should be considered if the garage is to be used frequently, particularly if it is external to the property as this will reduce costs in the long term. Insulation requirements for buildings have been and will continue to rise so over-insulating now will make your property more marketable later when building regulations may require it and it’s also most cost effective to add whilst the walls are under construction.

Should you wish to replace the garage door with an infill wall, this would require investigating the foundations to verify their depth and shallow fill foundations may require enhancement to sustain the additional weight. Extra Room Ltd would be happy to assist you with these decisions with ideas such as replacing the door with a large window and panelling. The adjoining room to the door can be a store room or the window could be the ‘front’ of the conversion. When saving on the expenditure of reworking the foundations, these options can be significantly cheaper. Previous clients have requested an interior-style block wall behind the existing garage door and insulating this, leaving the exterior appearance of the garage unchanged.