INTERIOR DESIGN FROM LONDON House Extensions
Design, Planning, Tendering and Builders
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Plan your house extension properly before choosing a builder
A house extension can create the space your home is missing.
You may want a larger kitchen, an additional bedroom, more living space, a home office or a better connection with the garden.
Whatever your goal, the project needs to be clearly defined before a builder can price and construct it properly.
Tholos helps homeowners develop house extension projects to the point where suitable contractors can be identified, vetted and invited to tender.
If you are only at the idea stage, we can help establish what may be possible.
If you already have drawings or planning permission, we can review the information and identify what is still needed before builders are approached.
Once the project is ready, we can help manage the tender process, compare contractors and prepare the building contract.
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What type of house extension are you planning?
There is no single type of extension that works for every property.
The right solution depends on the existing house, available space, planning context, budget and your ideal goals for the property.
Rear extensions
A rear extension can create valuable additional space at the back of a property.
It is often used to enlarge a kitchen, create a dining area, form a family room or improve the relationship between the house and garden.
The design should consider more than additional floor area.
Natural light, circulation, views, storage, structure and the relationship between new and existing spaces all influence whether the extension works well.
Side extensions
A side extension can make use of underused space beside a property.
Depending on the house, this may create room for a larger kitchen, utility area, office, bedroom or a substantial change to the ground floor layout.
Side return extensions
Side return extensions are common in terraced and semi detached properties where a narrow strip of external space exists alongside the original rear part of the house.
Extending into this area can increase the width of the ground floor and create a much more usable kitchen and living space without necessarily taking a large area from the garden.
Wraparound extensions
A wraparound extension combines rear and side development.
This can create a much larger transformation and often allows the entire ground floor layout to be reconsidered.
Because the scale of the project is greater, planning, structure, drainage, natural light and relationships with neighbouring properties need careful consideration.
Kitchen extensions
A kitchen extension is one of the most common reasons homeowners decide to extend.
The goal is often not simply to create a larger kitchen, but to improve how the whole ground floor functions.
A well planned kitchen extension can create space for cooking, dining, storage, entertaining and everyday family life while improving light and access to the garden.
Single storey extensions
Single storey extensions can provide additional living space without adding another floor to the property.
They may be used for kitchens, living rooms, bedrooms, utility spaces, accessible accommodation, offices or combinations of several uses.
Double storey extensions
A double storey extension can add substantial additional accommodation across two floors.
It may provide space for additional bedrooms, bathrooms and ground floor living areas within one coordinated project.
Because the proposal is larger, the planning and structural implications can be more significant.
Extensions over garages
Where a house has an attached garage, it may sometimes be possible to create additional accommodation above it.
This can provide useful bedroom, bathroom or office space without increasing the footprint of the house.
The existing garage structure must first be assessed to determine whether it is suitable for the additional load or requires alteration.
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How do you start planning a house extension?
The starting point should be your goals rather than the size of the extension.
It is easy to begin with a question such as, “How many square metres can we add?”
A better starting point is:
What do you want the home to do better?
We normally look at:
- your ideal goals for the property
- how the house currently works
- what is missing
- how rooms connect
- natural light
- views
- access to the garden
- privacy
- storage
- circulation
- existing structure
- neighbouring properties
- planning constraints
- how to establish a realistic project budget
The extension can then be designed around those requirements rather than simply adding floor area.
When should you start looking for an extension builder?
You can speak to builders at an early stage to understand general availability and experience.
However, asking contractors for a final price before the project is sufficiently defined can create problems.
If several builders are pricing different assumptions, their quotations are not genuinely comparable.
One contractor may include work that another has excluded.
Another may have allowed a different structural solution, specification or level of finish.
The most useful tender process begins once there is enough information for each builder to price the same scope of works.
Tholos can help establish when the project has reached that point.
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Do you need planning permission for a house extension?
Not every house extension requires a full planning application.
Some extensions may fall within permitted development rights if the property and proposed work meet the relevant requirements.
Other extensions require planning permission.
Factors that may affect the planning route include:
- the size of the extension
- its height
- how far it projects from the existing property
- its position
- the type of house
- previous extensions
- proximity to boundaries
- conservation area restrictions
- listed building status
- local planning restrictions
Permitted development rights may also have been limited or removed from a particular property.
The planning route should therefore be assessed specifically for the project rather than assumed.
Tholos can review the proposal and advise on the appropriate route.
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What drawings are needed for a house extension?
Different drawings serve different purposes.
Early design drawings establish the proposed layout, scale and relationship with the existing property.
Planning drawings explain the proposed development for the planning process.
Technical and Building Regulations drawings provide the more detailed information required to coordinate compliance, obtain appropriate approvals and construct the extension.
Depending on the project, the information may include:
- existing floor plans
- proposed floor plans
- existing elevations
- proposed elevations
- sections
- roof plans
- site plans
- technical construction details
- Building Regulations information
- structural design
- drainage information
- material and performance specifications
The precise package depends on the complexity of the extension.
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Planning drawings are rarely enough to build from
Planning permission does not automatically mean that the project is ready for construction.
Planning drawings are prepared primarily to explain the appearance, scale and arrangement of a proposal.
They rarely provide all of the technical information required during construction.
A builder may still require:
- Building Regulations drawings
- structural design
- construction details
- insulation specifications
- drainage information
- fire safety information
- ventilation requirements
- material specifications
This information helps establish exactly what contractors are being asked to price and build.
If you already have planning approval, Tholos can review the drawings and identify what is still required before tender.
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Who is responsible for Building Regulations compliance?
Building Regulations compliance is not simply the responsibility of Building Control.
Building Control checks relevant information and construction work, but it does not design the project or coordinate the design team.
The relevant project dutyholders have responsibilities for ensuring that the work complies with Building Regulations.
Where more than one designer is involved, a competent Principal Designer may need to be appointed to plan, manage and monitor the design work.
For a house extension, this can include coordinating architectural design, structural design and other technical information so that compliance responsibilities are clearly managed.
Tholos can help establish what professional appointments are required and coordinate the project accordingly.
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Building Regulations for house extensions
Most house extensions need to comply with Building Regulations, even where planning permission is not required.
Building Regulations cover technical requirements including:
- structural safety
- fire safety
- insulation
- ventilation
- drainage
- electrical safety
- glazing
- access
- energy performance
The technical design stage establishes how the extension will meet the relevant requirements.
Structural design will also be required where the project introduces new beams, removes walls, creates significant openings or alters existing structural elements.
Tholos can coordinate the architectural information with the structural engineer and other relevant designers.
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How does the tender process work for a house extension?
Once the extension has been sufficiently defined, suitable builders can be invited to tender.
A structured tender process gives contractors the same project information and asks them to price the same scope of works.
Depending on the project, Tholos can help:
- prepare the tender package
- define the scope of works
- identify suitable contractors
- vet contractor experience and references
- review accreditations and relevant information
- issue tender documents
- respond to contractor questions
- receive returned tenders
- compare pricing
- identify exclusions and assumptions
- clarify tender differences
- support contractor selection
This provides a much stronger basis for choosing a builder than comparing informal estimates prepared from different information.
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How do you choose the right extension builder?
The cheapest quotation is not automatically the best option.
Sometimes a lower price represents a genuine saving.
Sometimes it reflects missing work, optimistic assumptions or a contractor intending to fit the extension around other projects.
Contractor selection should consider:
- extension experience
- relevant previous projects
- references
- accreditations
- insurance
- quality of tender
- communication
- availability
- proposed construction programme
- exclusions
- payment terms
- approach to changes
- who will actually carry out the work
Where appropriate, Tholos can identify and vet extension builders whose experience and references fit the project.
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Preparing the building contract
Once a preferred builder has been selected, the scope, price and responsibilities should be clearly recorded before work begins.
A building contract can establish matters including:
- the agreed scope of works
- contract price
- start date
- construction programme
- payment arrangements
- responsibilities
- procedures for variations
- extensions of time
- completion
- defects
Tholos can help prepare the appropriate building contract and, where appointed, provide contract administration during construction.
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How Tholos helps you find a builder
Our role is not simply to pass you a contractor name.
The process begins with understanding the project.
First, we review where the project stands
We look at what you are planning, what information already exists and whether the project is ready to be priced.
Next, we identify any missing information
If drawings, approvals or technical details are still required, we can explain what needs to happen before builders are approached.
Then, where suitable, we introduce relevant builders
If the project is ready and falls within the areas covered by our current builder network, we can identify contractors whose experience may be suitable for the work.
Finally, we can help with quotations
Where appropriate, Tholos can support the quotation process and help identify differences in scope, assumptions and exclusions.
The aim is to make the builder selection process clearer and more informed.
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House extension builders in Nottingham
Tholos can help homeowners planning extensions in Nottingham and surrounding areas prepare their project for tender and identify suitable contractors.
Our services can include architectural design, planning, Building Regulations coordination, structural design coordination, tender preparation, builder vetting and building contract support.
House extension builders in Derby
For house extensions in Derby and surrounding areas, Tholos can help take the project from early definition through design, approvals and tender.
Where suitable contractors are available, we can identify and vet builders whose experience fits the scope of works.
House extension builders in Durham
Tholos supports homeowners planning house extensions in Durham and surrounding areas.
We can help define the project, coordinate the design and technical stages and prepare the work for suitable builders to tender.
House extension builders in London
London house extensions can involve additional planning, design and construction constraints.
Property type, conservation areas, neighbouring buildings, access and site logistics can all influence the project.
Tholos can help homeowners in selected parts of London develop extension projects and identify suitable contractors where available.
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Can you live in your house during an extension?
Sometimes.
Whether this is practical depends on the scale of the work and which parts of the house are affected.
A relatively contained extension may allow parts of the property to remain usable.
A project involving major structural work, kitchen removal, extensive service alterations or substantial internal remodelling may make remaining in the house more difficult.
The practical arrangements should be discussed with tendering contractors and reflected in the construction planning.
How long does a house extension take?
The complete project programme includes much more than the construction period.
Depending on the extension, stages may include:
- initial consultation
- measured survey
- concept design
- planning assessment
- planning application where required
- technical design
- structural design
- Building Regulations coordination
- tender preparation
- contractor vetting
- tender period
- contractor selection
- building contract preparation
- construction
The overall timescale therefore depends on the size and complexity of the project, approval requirements and contractor availability.
Start planning your house extension
You do not need to know exactly what type of extension you want before speaking to us.
Start with your goals.
Tell us what is not working in your current home and what you want the property to do better.
Tholos can help define the project, establish what approvals and technical information are required and bring it to the point where suitable builders can tender for the work.
Once the project is ready, we can help identify and vet contractors, compare tenders and prepare the building contract.
Client experience
"
Lorem ipsum dolor sit amet, consectetur adipiscing elit. We had a vision for our home but no idea how to realise it. Tholos Interiors took complete ownership of the project — every detail was considered, every decision explained. The result exceeded everything we had imagined.
– Lawrence Ipsum, Homeowner · London –
Frequently Asked Questions
Do I need an architect for a house extension?
Not every extension requires the same architectural service. Professional design input is particularly valuable where the project involves planning, structural alterations, Building Regulations requirements or significant changes to the layout of the home.
Do all house extensions need planning permission?
No. Some extensions may fall within permitted development rights. Whether this applies depends on the property, the proposed extension and any local restrictions.
Do house extensions need Building Regulations approval?
Most house extensions need to comply with Building Regulations, even where a full planning application is not required.
Who is responsible for Building Regulations compliance?
Building Control checks compliance but does not design or coordinate the project. Responsibility sits with the relevant project dutyholders. Where required, a Principal Designer must plan, manage and monitor the design work for compliance.
Are planning drawings enough for an extension builder?
Usually not. Planning drawings rarely provide all of the technical information required for construction. Builders may also need Building Regulations drawings, structural design and detailed construction information.
When should I ask builders to quote for an extension?
You can speak to contractors early, but detailed tenders are more useful once the design, technical requirements and scope of works are sufficiently clear for each builder to price the same project.
How much does a house extension cost?
The cost depends on location, size, structure, materials, specification, site conditions and contractor availability. A project specific budget developed around the actual design is more useful than relying only on a generic cost per square metre.
Can Tholos help find an extension builder?
Relevant experience, project type, location, availability, insurance, references, quotation quality and communication are all important factors. Tholos can help assess suitability in the context of your particular project.
Can Tholos manage the tender process?
Yes. We can help prepare tender information, identify contractors, issue documents, respond to queries, compare returned tenders and support contractor selection.
Can Tholos take over a house extension that already has planning permission?
Yes. We can review the planning approval and drawings and establish what additional technical information, structural design, compliance coordination or tender documentation is required before construction.
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