Garage Conversions | C.R Design Services

Garage Conversions



Garage Conversion

Due to the size of modern cars, garages in the UK are rarely used as a place to park a car. Instead, they end up being used for storage. Converting a garage into a usable room, such as a bedroom or a study, is a great way to make better use of the space and add value to your house. The cost of converting a garage into a bedroom costs on average £6,500. Planning permission for a garage conversion usually isn't required, but a Building Control application will be required. A Building Control package is a set of technical drawings and construction details that is submitted to your local council for approval. The package needs to show that the proposed garage conversion will be built correctly, safely and that it will meet (or exceed) the national minimum requirements. Your builder (or you, if taking on the building work of the conversion yourself) will use the contents of the Building Control package to quote and build from.

To discuss the design of your garage conversion project, contact us today.


Garage conversion design package

Our garage conversion package includes the design of your proposed conversion, a review and validation of the planning permission requirements that would apply to your house, the preparation of all relevant drawings, and the preparation and submission of the planning application (if required) and building control application. The package is also suitable for sending to builders, both for quotations and for them to build from. For additional information contact us.

Garage Plan

The process

The first stage of a garage conversion project is to prepare a measured survey sketch of your existing hoause. You can provide your own survey sketch, or to make the process easier have a look at our Architect in a Box kit. For most garage conversion projects, a survey sketch of just the ground floor plan would be sufficient.

We take your survey sketch, along with a few photos of the house, and discuss your requirements with you and explain the design options available. We'll will check the planning requirements for your area. Your permitted development rights may have been removed, if you live in a conservation area for example. If a planning application if required, we will prepare and submit all the necessary information to the council.

We then prepare a set of technical drawings of your house and write a construction specification. One of our Structural Engineers will review the project and provide design input where needed. We then prepare the Building Control application and submit everything on your behalf to your local council.

We'll act as your agent throughout the whole process, dealing with queries from the council and your builder.

Things to consider

There are a few things to consider when designing a garage conversion.

The floor construction

The existing garage floor will most likely be a concrete slab slightly higher than external ground level (there should be a small step up into your garage to stop rain water running into the garage or being blown in on a windy day). The first design choice we consider is the new floor type. The options will be dictated partly by the level difference between the internal floor level of the garage vs. the internal ground floor level of the house. In most cases the garage floor level will be about 150mm lower than the house ground floor level, or maybe at the same level as the house. In other cases the garage may be much lower than the level of the internal ground floor of the house. An easy way to estimate the level difference is to follow the mortar lines between the bricks and count the number of brick courses between the bottom of the front door and the bottom of the garage door.

  1. If the garage floor is the same level as the internal ground floor level of the house you have two options.
  2. 1) Apply rigid insulation boards and flooring over the existing garage slab, raising the level of the floor and creating a step up into the garage at the new internal door from the house. In this scenario the floor will have a slight slope that matches the slope of the existing garage floor slab, but this is usually unnoticeable and common practice. If you were concerned about the slope, there are ways to remove the slope, such as applying a self-leveling compound to the existing garage slab before adding the floor buildup.
  3. Step up
    Step up into garage conversion
  4. 2) Break out and remove the existing garage concrete floor slab and build a new slab at a lower level, so once insulation and flooring has been installed the level of the new floor matches the internal ground floor level of the house, eliminating the need for a step up into the garage.
  5. Screed floor
    New insulated floor slab
  1. If the garage floor level is below the level of the internal ground floor of the house you have two options depending on the level difference.
  2. 1) Apply rigid insulation boards and flooring over the existing garage slab, using an insulation thickness to suit the level difference and therefore create a new floor that is level with the internal ground floor level of the house. In this scenario the floor will have a slight slope that matches the slope of the existing garage floor slab, but this is usually unnoticeable and common practice. If you were concerned about the slope, there are ways to remove the slope, such as applying a self-leveling compound to the existing garage slab before adding the floor buildup.
  3. Rigid floor
    Insulation over existing slab
  4. 2) If there is sufficient level difference you could install timber joists to create a new suspended floor, with insulation between the joists, therefore creating a new floor that is level with the internal ground floor level of the house.
  5. Suspended floor
    Suspended timber floor

Insulating the walls

The existing external walls of the garage may need to be insulated. Whether the existing garage walls are single leaf brickwork, or a 300mm cavity wall, it's usually safe to assume they're not currently insulated and a new layer of insulation material will be require. The most practical way to do this is to add a new layer of insulation to the internal face of the wall. Failure to insulate adequately could mean the room is cold, damp and may fail to comply with Building Control requirements. We would design the wall insulation to suit the size and conditions of the garage.

Insulated wall
Insulation against existing walls

Insulating the ceiling

If there is a room above the existing garage then there is no need to insulate the ceiling. If there is a roof above the existing garage it is unlikely to be insulated and therefore some form of insulation would be required. We would review the existing ceiling and calculate the insulation required. The specification of the insulation would depend on the existing roof type.

Creating an opening into the garage

When converting a garage there would usually be a new door created from the house. Depending on the type of wall the door will be installed in, you may require a new lintel over the door. You may decide to take out a wall to join the garage with an existing room, this may also require a lintel or steel beam. This would be something that one of our Structural Engineers would check during the design of your project.

Replacing the garage door with a window

When replacing the existing garage door with a window, it is common to install a new window the same width as the original garage door opening. This means that you would only need new brickwork under the new window, and avoid needing new brickwork up the sides of the window. The style of the new window should be in keeping with the other existing windows.

Replacing door
Existing garage door replaced with window

Only converting part of your garage

You could decide to convert the rear part of the garage, and keep the front part (including the existing garage door) as it is. This has the benefit of keeping some storage space for bikes and a lawnmower, whilst also maintaining an unchanged appearance at the front of the house (useful in conservation areas, for example).

Working from home

If you plan to convert your garage into a home office, it is unlikely that you will need planning permission. However, you may require planning permission if you intend to run your own business from home. If a 'change of use' application is required, we will apply to the council on your behalf.

Working from home
Garage converted into home office

Contact us

We can help you plan and design your next project. We prepare planning application drawings, building control packages, and structural design calculations for all types of house extension, renovation and self-build projects. Contact us today for further information and to request a quotation. Contact us