• Extra Room Garage Conversions

    Relocate Your Car

    Make use of the garage by converting it from storage to a living space.

Garage Conversions

A well designed garage conversion could add as much as 10% to the value of your property as well as additional living space within your home and is one of the most lucrative ways to increase your property’s resale value.

In addition to adding 10% to the value of your property a garage conversion could increase your living space considerably without the inconvenience of moving home.


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.

An example of a garage to kitchen conversion


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.


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.

An example of a Velux installation within a garage conversion

Windows & Doors:

Should you wish to proceed with a second room, this will require ventilation to meet building regulations. These regulations require a window 1/20 the floor area of the room, whilst fire regulations require a window with a 600mm base opening and a total area of not less than 0.45m². The window would also require trickle vents and windows that meet these requirements are obtainable in a metal frame or UPVC, although metal frame windows must have a ‘thermal break’ (due to the conductivity of metal) to meet insulation requirements. Wood framed windows can also meet requirements but they must be of a satisfactory depth to accommodate a 24mm double glazed unit. Commonly a wood effect UPVC is used or a metal frame with block and wood cladding.

Extra Room Limited is accredited by FENSA (FENestration-Self Assessment) for the installation of windows.

Doors also require the same requirements as windows in terms of their u value and in addition to UPVC doors with double glazed windows; wooden doors are also a good choice.

Reinforcement may be essential to the original garage walls when installing doors or windows in the walls of the garage. This would be in the form of a concrete lintel or a Rolled Steel Joist (RSJ) depending on the dimension of the new aperture. A lintel would be required to overhang the edges of the window gap by 100-150mm.

With regards to Standalone garages, footings are frequently omitted or insufficient which makes adding a window and panelling a more appealing proposal than excavating new footings and building an infill wall. The front opening of most garages however, are not a standard dimension for windows so further building works may be necessary. A block or brick wall filling some of the opening can bring the space to a standard size without requiring additional footings, due to the reduced weight when compared to a full infill wall. Extra Room Ltd would consult the Building Inspector for his thoughts on this at the planning stage.

Completion Certificate:

Any project that requires a Building Notice will require a Completion Certificate. The Completion Certificate is purely proof that when the work was completed, it met regulations. Possessing a Completion Certificate will make a difference to the value added to your property by the garage conversion and Estate Agents and prospective buyers will value your Completion Certificate highly in view of the fact that items like an under floor damp proof course cannot be proven without this.

When the Building Inspector attends to make his final inspection, he must be provided with documentation proving that building regulations were met during the construction and installation of the parts he has not visually inspected and of course Extra Room Ltd would make this available. These documents would include the following:

  • Corgi Certificate for the boiler
  • NIC or EIC for electrical installations
  • Documents for insulation and damp proofing
  • FENSA or other certification for the installation of the windows

Once the Building Inspector is satisfied, the Completion Certificate should follow within 28 days but is often much sooner.

Garage Conversion Pros & Cons:


  • Design Control: Converting a garage provides you with the means to maintain control of every step of the design process, subject to technical and legal restrictions.
  • Added Value: Moving home is expensive and are costs that cannot be recouped but converting a garage in habitable room will add more value to your home than it costs in the majority cases.
  • Local Amenities: Relocating children in schools, moving families from commute routes, sports and leisure facilities and places of worship can be problematic and expensive. Remaining at your current property while acquiring additional living space is a better option for many.
  • Contract Control: When works commence and who carries out the work are all your decisions. Many house sales fall through due to one party changing their mind and if you chose a conversion, you are the sole decision maker.
  • Council Tax: Moving from a 3 to a 4 bedroom home could increase your council tax band, whereas a garage conversion leaves your council tax band unchanged.


  • Disruption: During the process of a garage conversion, one or more existing rooms may be rendered unusable. Rooms adjoining the garage, garden or yard space will be most affected. Workmen will be present in your home during working hours to carry out direct works on the conversion. Electricians and plumbers will require access to the mains supplies inside and outside of the property. Extra Room Ltd are committed to providing the best service possible, which includes a full time Project Manager to ensure works progress smoothly and as much as possible your home remains your home.
  • Control of Work: You will be responsible the legality of works carried out on your property, however Extra Room Ltd will be present at all times to supervise works and provide you all the support and advice require to complete your conversion to the highest standard.
  • Impact on Existing Buildings: Extending the garage will consume garden space and possibly access to the property. With the assistance of Extra Room Ltd, we would look design your conversion to the best possible potential.
  • Planning Uncertainty: Projects which require planning permission at a cost of £150.00 which is non-refundable on rejection of an application. Extra Room Ltd, however are extremely experienced in these matters and would not advise you to apply and pay the fee unless we were confident of a positive outcome. This fee maybe higher if your property is a listed building or you reside in a conservation area.
  • Cost Uncertainty: As investigations commence on your property, you may be required to pay for additional improvements. Extra Room Ltd would thoroughly discuss any extra costs that may arise and a separate quotation would be presented for these, with your full agreement before any alterations are made.

Why Choose Extra Room?

Our Staff

This is exactly what it means; our staff are the only people who are involved in your project. Extra Room Ltd does not sub-contract your project out to other contractors.

All operatives are employed by Extra Room Ltd we are always contactable by phone and email to deal with any queries or questions that may arise. All of our operatives have an Extra Room Ltd uniform and identification badge so that they are instantly recognisable.

Site Rules

We have very strict guide lines for all projects, all staff must wear the Extra Room Ltd uniform and personal protection whilst at work i.e. boots, high visibility jackets and safety helmets where necessary.

There is a no smoking policy at work and where possible we will provide a discrete portable toilet facility so that your home stays your home with no intrusion. No radios are to be played on your project. We understand that whilst your project is being completed this should not intrude upon your neighbours who are already being submitted to the noise of building works.


Extra Room Ltd provides a full time Project Manager who will be involved from the very start of the project until completion, he will provide all certificates and completion certificates which will then be held in a project file and presented to you at the end. They will also ensure that all site rules are followed and report directly to the Director of the company.

Unrivalled Guarantee

All structural works come with a 10 year no quibble guarantee, of which upon completion of your project you will receive a certificate of guarantee. All other works i.e. plumbing and electrics will come with a standard 2 year guarantee.

No Hidden Costs

Once we have surveyed your project, a quotation with a complete breakdown of costs will be presented to you. This break down will be individually priced so that you can clearly see where your budget will be spent and if at any time you would like to remove an item you will instantly know what the saving will be.

In the event that you decide that you would like to add additional works, these additions will be separately quoted and an instruction sheet issued that yourself and the Project Manager will both sign so that there is no hidden costs and you are in control of your budget at all times.

Peace of Mind

Before any works commence, Extra Room Ltd will provide you with a break down sheet of all the works to be completed within your project. This includes an empty box at the end of the description, yourself and the Project Manager will go through this sheet and check that you are completely satisfied with the completed works and then tick the box together. At this point you will only have ever paid for works that are fully completed and you will not be asked to pay any monies upfront or before the works are complete.

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