Choosing an extension system involves more than establishing the required footprint. The existing property, available space, structural requirements, roof design, glazing, thermal performance, external finish and Building Control requirements all need to be considered before the construction system is specified.
For installers and trade professionals, establishing these requirements at the start of a project can help determine the most appropriate construction method and avoid unnecessary changes during installation.
What Type of Extension Suits the Property?
The position and configuration of an extension will be influenced by the existing building, available footprint and proposed connection to the property.
Rear Extensions
A rear extension increases the footprint of the property and creates a new connection between the existing building and the extension.
The available footprint, existing wall construction, structural openings and proposed roof arrangement all need to be assessed before the extension system is specified.
Side Extensions
A side extension makes use of available space alongside the existing property.
The width available between the building and boundary, existing foundations and proposed openings can all influence the construction approach. These factors should be established before the wall and roof systems are selected.
Wraparound Extensions
A wraparound extension combines rear and side elements to create a larger footprint.
The junctions between the existing building and new structure can be more complex, making coordination between the wall construction, roof system and structural openings particularly important.
Conservatory Conversions
Where an existing conservatory is being upgraded or incorporated into a larger extension project, the existing structure needs to be assessed before new components are specified.
This is particularly important where an insulated roof, new structural openings or other components are being introduced to the existing structure.
Which Roof Design Is Right for the Extension?
The roof system affects the structural design, internal ceiling height, external appearance and available natural light.
The roof should therefore be considered alongside the wall construction, glazing and intended extension footprint rather than specified separately.
Flat Roof Extensions
A flat roof can provide a low-profile solution where the extension needs to work beneath existing windows, rooflines or other features of the property.
For installers, the specification needs to account for the structural span, insulation build-up, roof covering, drainage and connection to the existing building.
An insulated flat roof system can also incorporate a roof lantern where additional roof-level glazing is required.
Pitched Roof Extensions
A pitched roof can be specified where the extension needs to work with the existing roofline or where additional roof volume forms part of the design.
The pitch, span, roof covering, structural loading and connection to the existing building all need to be established as part of the roof specification.
For trade installers, using a pre-engineered pitched roof system can help reduce the amount of roof construction that needs to be developed and fabricated on site.
Lantern Roof Extensions
A roof lantern can be incorporated into a flat roof system where additional natural light is required from above.
The size and position of the lantern need to be coordinated with the roof structure, insulation, internal layout and surrounding glazing.
For installers, the lantern should therefore be treated as part of the roof specification rather than an isolated glazing component.
How Will the Extension Connect to the Existing Property?
The connection between the new extension and existing building is a key part of the specification.
The existing foundations, wall construction, structural openings and proposed loads need to be established before the new system is selected.
Large openings for bifold doors or other glazing can introduce additional structural requirements. The wall and structural system therefore needs to accommodate the required spans and loads without compromising the overall design.
A pre-engineered extension system can help simplify this process by bringing the structural components together as a coordinated system rather than requiring individual elements to be developed independently on site.
For installers, this can make the construction process more predictable and reduce site-based structural and material coordination.
How Much Natural Light Does the Extension Need?
Glazing should be considered alongside the extension footprint, wall configuration and roof design.
Large areas of vertical glazing can be incorporated into external walls, while roof glazing can introduce additional daylight where wall openings are limited.
Depending on the project specification, options can include:
- Aluminium bifold doors
- Fixed glass panels
- Roof lanterns
- Roof windows
- Large glazed openings
The position of each element needs to work with the structural and thermal requirements of the extension.
For trade installers, coordinating the glazing with the wall and roof systems from the outset can help avoid conflicts between structural openings, insulation and finishing requirements.
What Thermal Performance Should Be Considered?
An extension needs to be specified as a complete building envelope, with the walls, roof, floor and glazing considered together.
The insulation specification and structural construction can influence both thermal performance and the amount of internal space available.
For installers, a coordinated extension system can make it easier to establish how the individual components work together and identify the supporting technical information required for Building Control.
The roof is particularly important where a significant proportion of the extension envelope is above the occupied space. Insulation, roof construction, glazing and internal finishes should therefore be considered as part of the same specification.
What External Finish Will Work With the Property?
The external finish needs to be considered alongside the wall construction and overall system specification.
Traditional brickwork may be appropriate where a direct material match is required, while a brick-slip system can provide a brick finish as part of a pre-engineered construction method.
For installers, a brick-slip system can allow the external finish to be incorporated into the wall specification rather than treated as a separate construction process.
This can provide a more coordinated approach where a traditional brick appearance is required from a modern extension system.
What Building Control Requirements Need to Be Considered?
Building Control requirements should be established during specification rather than once construction is underway.
Depending on the project, structural calculations, thermal performance, condensation risk and supporting technical documentation may all form part of the approval process.
Where an extension system has undergone independent assessment, the available technical information can help support the Building Control process.
Warmer Roof’s system has been independently tested and certified by LABC, with assessment covering structural calculations, thermal performance and condensation risk. Warmer Roof also operates an in-house Building Control department specialising in Warmer Roof applications.
For installers using the system, this provides a dedicated point of contact for applications, technical queries and inspections, keeping the Building Control process connected to the system being installed.
Applications need to be made before works have started, and Warmer Roof advises allowing at least five days’ notice to register an application.
Why the Extension System Matters
Once the project requirements have been established, the construction system can be selected around the specific application.
For installers, this means looking beyond individual components and considering how the structural walls, insulation, roof, glazing and external finish will work together. A pre-engineered house extension system can bring these elements together as a coordinated package, reducing the amount of site-based fabrication and structural coordination required during installation.
The system should also provide the technical information needed to support specification and Building Control, particularly where structural calculations, thermal performance and other compliance requirements need to be demonstrated.
For trade installers, having these elements coordinated from the outset can make the build process more predictable and simplify project administration from quotation through to installation.