A double storey extension can transform a property by creating valuable additional living space across both the ground and first floors. Whether you want a larger kitchen and family area downstairs, additional bedrooms and bathrooms upstairs, or a complete redesign of your home, iProTrades helps you find experienced double storey extension builders in Surrey and compare up to 3 quotes for your project.
Two-storey extensions are significant building projects and require careful planning, structural design and professional construction. From foundations and brickwork through to roofing, structural steelwork, plumbing, electrics and internal finishing, choosing a builder with suitable extension experience is an important part of achieving a successful result.
Through iProTrades, homeowners can describe their project, provide photographs or plans where available and compare quotes from tradespeople covering Surrey.
What Is a Double Storey Extension?
A double storey extension, also commonly called a two-storey extension, adds new accommodation across two floors of an existing property.
Unlike a single-storey extension, which increases ground-floor space only, a double storey extension can potentially increase both the living space downstairs and bedroom or bathroom accommodation upstairs.
Depending on the property and design, a two-storey extension might be constructed to the rear or side of a house or form part of a larger extension and refurbishment project.
Because much of the construction work — including foundations and roofing — serves both floors, extending over two storeys can sometimes provide an efficient way of creating substantial additional floor space.
Types of Double Storey Extensions
The most appropriate extension design will depend on the existing property, available land, planning considerations and what you want to achieve internally.
Rear Double Storey Extensions
A rear double storey extension extends both floors at the back of the property.
On the ground floor, this can provide space for a larger kitchen, dining area, family room or utility space. The first floor could potentially provide an additional bedroom, bathroom, dressing room or enlarged existing bedrooms.
The size and design will need to take account of neighbouring properties, boundaries, windows, daylight and applicable planning requirements.
Side Double Storey Extensions
Properties with sufficient space alongside the house may be suitable for a two-storey side extension.
These can substantially increase the internal floor area and may be particularly useful where homeowners want additional bedrooms upstairs while creating a larger kitchen, utility room, office or living space downstairs.
The design normally needs to complement the appearance and proportions of the existing property as well as satisfy relevant planning requirements.
Combined Side and Rear Extensions
Larger renovation projects can sometimes combine side and rear extensions to substantially alter the layout of a property.
This can create large open-plan kitchen and family areas downstairs while increasing bedroom and bathroom accommodation upstairs.
Projects of this scale usually require careful architectural and structural design because significant alterations may be made to the existing building.
What Rooms Can a Double Storey Extension Add?
One of the main advantages of extending over two floors is the flexibility it can provide when redesigning a home.
Ground-floor accommodation could include:
Larger kitchen
Kitchen and dining area
Family room
Utility room
Home office
Playroom
Downstairs WC or shower room
Additional living space
The first floor could potentially provide:
Additional bedrooms
En-suite bathrooms
Family bathroom
Dressing room
Larger existing bedrooms
Home office
Additional storage
The best layout will depend on the existing house and how your family intends to use the additional space.
How Much Does a Double Storey Extension Cost in Surrey?
There is no single price that accurately represents every double storey extension.
The overall cost will depend on the size, design, construction method, structural requirements and level of finish.
A relatively straightforward two-storey extension will have very different costs from a large project involving extensive structural alterations, premium glazing, bespoke kitchens, several bathrooms and complete refurbishment of the existing property.
For this reason, homeowners should be cautious about relying on simple online prices per square metre without considering what those figures actually include.
For an accurate indication of cost, builders need sufficient information about the proposed project and specification.
Through iProTrades, you can compare up to 3 quotes from builders covering Surrey.
What Affects the Cost of a Double Storey Extension?
Several factors can significantly affect the final price, including:
Overall floor area
Ground conditions
Foundation requirements
Drainage alterations
Structural steelwork
Brickwork and external finishes
Roof design and materials
Insulation specification
Windows and doors
Rooflights
Plumbing and heating
Electrical work
Number of bathrooms
Kitchen specification
Plastering and carpentry
Flooring and decoration
Scaffolding
Site access
Waste removal
Landscaping and making good
The amount of alteration required to the existing house can also have a major effect on cost.
When comparing quotations, make sure you're comparing the scope and specification, not simply the final price.
Do Double Storey Extensions Need Planning Permission?
Many double storey extensions will require careful consideration of planning rules, and some will require a planning application.
Whether permission is required depends on factors including the property's location, previous extensions and alterations, the proposed extension's dimensions and its relationship with boundaries and neighbouring properties.
Planning considerations can include the extension's height, depth, position, appearance and potential impact on neighbouring properties.
Don't assume that because another house nearby has a similar extension, the same development will automatically be acceptable on your property.
The planning position should be established during the design stage and before construction begins.
Can a Double Storey Extension Be Built Under Permitted Development?
Certain home extensions can potentially be carried out under permitted development rights, subject to specific limitations and conditions.
However, the rules for extensions over more than one storey are more restrictive than for many straightforward single-storey additions.
Permitted development rights can also be restricted or removed in certain circumstances.
Because every property and proposed design is different, homeowners considering a two-storey extension should establish the planning position for their individual project rather than assuming permitted development applies.
Building Regulations for Double Storey Extensions
Planning permission and Building Regulations are separate matters.
A double storey extension will generally involve work covered by Building Regulations.
Depending on the project, Building Regulations can address areas including:
Foundations
Structural stability
Structural steelwork
Floors
Walls
Roof construction
Insulation
Energy efficiency
Ventilation
Fire safety
Drainage
Electrical safety
Glazing
Staircases
Building control inspections may take place at different stages of construction.
Before appointing a contractor, establish who will be responsible for liaising with building control and arranging the necessary inspections.
Foundations for a Double Storey Extension
Foundations are one of the most important parts of any substantial extension.
They need to safely support the additional structure while taking account of the ground conditions and surrounding property.
The appropriate foundation design can be influenced by soil conditions, nearby trees, drains, existing structures and the loads created by the proposed extension.
Excavations may also need to be inspected by building control before concrete is placed.
Where unusual ground conditions are encountered, additional professional advice or an alternative foundation design may be required.
Structural Engineering and Steelwork
Double storey extensions frequently involve structural alterations to the existing property.
Creating large openings between the original house and new extension may require structural steel beams or other supporting elements.
A structural engineer may therefore be required to calculate loads and specify appropriate steelwork, padstones, columns or other structural components.
Structural design is particularly important where large open-plan spaces are being created or substantial sections of existing load-bearing walls are being removed.
Can You Build Above an Existing Single-Storey Extension?
Sometimes, but the existing structure needs to be assessed first.
A common question from homeowners is whether an existing ground-floor extension can simply have another storey added above it.
One of the most important considerations is whether the existing foundations and structure were designed to support the additional load.
Investigations may be required to establish the size, depth and condition of existing foundations.
A structural engineer may also need to assess the walls, foundations and overall structure.
If the existing construction isn't suitable, strengthening or more substantial structural alterations may be required.
Roof Construction
The roof is an important part of the extension's appearance and weather protection.
Depending on the design, a double storey extension could incorporate a pitched roof, hipped roof, gable roof or another roof arrangement designed to integrate with the existing property.
Roof construction may include:
Timber roof structure
Breathable roofing membrane
Roofing battens
Tiles or slates
Leadwork
Roof ventilation
Insulation
Fascias and soffits
Gutters and rainwater systems
Rooflights where required
The roof should be designed to work with both the existing building and the architectural appearance of the extension.
Matching the Existing Property
A well-designed extension should usually appear considered in relation to the original house.
Depending on the planning and architectural approach, this can involve matching or carefully complementing existing:
Brickwork
Render
Roof tiles or slates
Windows
Doors
Fascias and soffits
Gutters
Architectural details
Matching older bricks and roofing materials can sometimes be challenging, so material selection should be considered during the design and quotation stages.
Party Wall Considerations
Some double storey extension projects may fall within the scope of the Party Wall etc. Act 1996.
This can potentially apply where work involves certain shared walls or excavation close to neighbouring buildings.
Whether the Act applies depends on the proposed work and the relationship between the extension, boundaries and neighbouring structures.
If you believe your project may be affected, obtain appropriate advice early enough to deal with any necessary notices before construction is due to begin.
How Long Does a Double Storey Extension Take to Build?
Construction times vary significantly depending on the project's size and complexity.
A straightforward extension will have a different programme from a project that includes extensive structural alterations, complete internal refurbishment, a new kitchen and several bathrooms.
Factors affecting timescales can include:
Groundworks
Structural complexity
Weather
Material availability
Specialist subcontractors
Building control inspections
Kitchen and bathroom lead times
Changes made during construction
Unexpected conditions discovered after work starts
Ask builders for an estimated programme before appointing them and establish whether other renovation work is included within that timescale.
Can I Stay in My Home During Construction?
It may be possible to remain in the property during some double storey extension projects, but this depends heavily on the work involved.
There can be periods involving substantial noise, dust and disruption, particularly when the new extension is connected to the existing house.
Temporary interruptions to water, heating or electricity may also be required.
Where a project involves extensive refurbishment of the existing property alongside the extension, temporary accommodation may sometimes be more practical.
Discuss this with your builder during the planning stage so you understand how the construction programme is likely to affect the occupied parts of the house.
What Should a Double Storey Extension Quote Include?
For a substantial project, the quotation should provide enough detail for you to understand what you're paying for.
Depending on the project, it could include:
Site setup
Demolition
Excavation
Foundations
Drainage
Brickwork and blockwork
Structural steelwork
Floors
Roof construction
Roofing materials
Insulation
Windows and external doors
Plumbing and heating
Electrical installation
Plastering
Carpentry
Kitchens and bathrooms
Flooring
Decoration
Scaffolding
Waste removal
It should also identify significant exclusions.
This is particularly important when comparing several quotations because a lower price may simply include less work.
Choosing a Double Storey Extension Builder in Surrey
A two-storey extension represents a significant investment, so don't choose a contractor based on price alone.
When comparing builders, consider:
Experience with double storey extensions
Examples of similar completed projects
Reviews and references
Appropriate insurance
Quality of the quotation
Proposed start date
Estimated construction programme
Project management arrangements
Payment structure
How variations will be handled
Guarantees where applicable
Ask who will manage the project day-to-day and whether specialist trades will be directly employed or subcontracted.
Clear communication before construction begins can help prevent misunderstandings later.
Double Storey Extension Builders Across Surrey
iProTrades helps homeowners find tradespeople covering locations throughout Surrey, including Guildford, Woking, Weybridge, Epsom, Reigate, Redhill, Farnham, Camberley, Walton-on-Thames, Esher, Leatherhead, Dorking, Staines-upon-Thames, Chertsey, Addlestone and surrounding areas.
As individual contractors have different working areas, provide your postcode when submitting your project so suitable tradespeople can determine whether they cover your location.
Compare Double Storey Extension Quotes in Surrey
Whether you're considering a rear double storey extension, side extension, two-storey addition or a larger extension and renovation project, iProTrades can help you find tradespeople covering your area.
Tell us about your project, provide your Surrey postcode and upload photographs or plans where available.
For projects that already have architectural drawings, structural calculations or a detailed specification, providing this information can help contractors understand the proposed work.
You can then compare up to 3 quotes from tradespeople covering Surrey and decide which contractor is suitable for your double storey extension project.