House Extensions
Project-Specific Scope
Explore rear, side, double-storey and wrap-around extension options. Scope, access, planning route, specialist responsibilities and geographic coverage remain project-specific.
The Most Popular Way to
Add Space & Value
A house extension is a permanent structure added to an existing residential property to increase its floor area. Unlike a loft conversion or basement conversion, a house extension typically extends the footprint of the property outwards — to the rear, side, or both — creating new ground-floor or multi-storey living space.
For homeowners in London and Hertfordshire, a house extension is often the most practical alternative to moving — avoiding stamp duty, estate agent fees, and the upheaval of relocation, while creating a home that is precisely tailored to your family's needs.
TCM can manage building work directly and, where appropriate, coordinate the specialist contractors and professional disciplines required for the project. The delivery arrangements depend on the individual scope.
Which Extension Is Right for You?
Rear House Extensions
A rear extension enlarges the property into the rear garden or yard. It can create kitchen, dining, living or other space, but the permitted-development or planning route depends on the exact property, existing additions, dimensions, designations and current rules. Check the actual proposal before assuming a planning application is unnecessary.
Side Return Extensions
A side return extension fills in the narrow alley that runs alongside many Victorian and Edwardian terraced houses. Often combined with a rear extension, this creates a substantial L-shaped addition that dramatically transforms the ground floor. The result is typically a wide, open-plan kitchen-diner that feels like a completely different home.
Double Storey Extensions
A more-than-one-storey extension can add space on two levels, but its budget and feasibility cannot be inferred from a percentage uplift over a single-storey scheme. Structure, foundations, roof, services, access, design and planning constraints should be assessed for the actual proposal.
Wrap-Around Extensions
A wrap-around extension combines rear and side enlargement. The achievable footprint, layout and openings depend on the site, neighbours, structure, drainage, access and planning context; the design should be based on the actual property rather than a maximum-footprint assumption.
How We Deliver Your Extension
Project Enquiry
Record the property, proposed scope, access and any known planning or specialist requirements before work is arranged.
Design & Planning
The design and planning route depends on the property and scope. Appropriate professional input may be required.
Structural Engineering
Structural alterations require appropriate competent professional input and the relevant regulatory route.
Scope and Commercial Terms
Confirm the agreed scope, inclusions, exclusions, VAT, allowances and change process before work begins.
Construction
TCM can deliver building work directly and coordinate specialist contractors and professional disciplines where appropriate.
Finishing & Handover
Agree inspection points, handover information and any remaining specialist requirements for the project.
Do You Need Planning
Permission?
Many house extensions in England can be built under Permitted Development rights, meaning no formal planning application is required. However, the rules are complex and depend on your property type, location, and the size of the proposed extension.
Some two-storey rear extensions qualify for permitted development when all applicable conditions are met. The route depends on the property, previous additions, design and any local restrictions. Check the proposal with the local planning authority and read the Planning Portal extension guidance. Planning permission and Building Regulations are separate requirements.
House Extension Scope Guide
The appropriate scope depends on the property, proposed work, access, design, ground conditions, planning route and specialist requirements.
| Extension Type | Property and Access | Scope | Programme | Planning |
|---|---|---|---|---|
| Single-Storey Rear | Confirm site conditions | Scope-dependent | Project-dependent | Confirm route |
| Side Return | Confirm access | Scope-dependent | Project-dependent | Confirm route |
| Double Storey | Confirm structural input | Scope-dependent | Project-dependent | Confirm route |
| Wrap-Around | Confirm planning requirements | Scope-dependent | Project-dependent | Confirm route |
Establish the applicable planning route, scope, inclusions, exclusions, VAT, allowances and change process for the individual project.
Questions to Resolve Before Work Begins
Establish the scope, access, design information, planning route, structural requirements and commercial terms before building work is arranged.
| Extension Type | Property | Scope | Programme | Specialist Input |
|---|---|---|---|---|
| Single-Storey Rear | Access and ground conditions | Define inclusions | Agree milestones | Planning and trades |
| Side Return | Neighbouring property considerations | Define inclusions | Agree milestones | Planning and trades |
| Double Storey | Structural requirements | Define inclusions | Agree milestones | Structural professional |
| Wrap-Around | Planning and access considerations | Define inclusions | Agree milestones | Planning and trades |
Scope Details Matter
Ground conditions, drainage, trees, neighbouring structures, access and the required foundations can affect the proposed scope. Identify the relevant surveys, investigations and professional input before the work is arranged.
Party-wall and planning requirements should be considered early where they may apply. Obtain the appropriate independent professional advice for the individual property and proposed work.
The TCM Difference
A house extension requires an agreed scope, clear responsibilities and the appropriate professional and specialist input.
TCM can manage building work directly and coordinate specialist contractors and professional disciplines where appropriate.
Confirm inclusions, exclusions, VAT, allowances and the change process before work begins.
Agree roles, communication arrangements, inspection points and handover information for the project.
Establish the appropriate planning, Building Regulations and party-wall route for the property and proposed work.
Structural and other regulated work must follow the appropriate competent, registered or licensed specialist route.
Before You Commit
Check the proposed scope, relevant approvals, specialist responsibilities, access arrangements and commercial terms before building work begins.
Contact TCM
Contact TCM by telephone, email or the enquiry form.Scope and specialist requirements remain project-specific.
A house extension adds new floor area to an existing property. Depending on the building and brief, that can include a rear, side-return, wrap-around or more-than-one-storey addition. The appropriate form depends on the available site, planning context, structure, access, services and intended use. TCM can undertake house-extension building work and coordinate specialist contractors or professional disciplines where the agreed project requires them. Design, structural, planning, Building Regulations and party-wall responsibilities should be confirmed for the individual project rather than assumed from a generic extension type. The value of an extension is the additional space and function it creates for the household. Any effect on market value is property- and market-specific and should be assessed independently rather than promised by the builder.
You're starting to feel the squeeze at home, aren't you? Maybe the kids need more space, or you're dreaming of a bigger kitchen for entertaining. You know something needs to change to make your home work better for you, but you're not quite sure what the best path forward is yet.
What You Need to Know
Design and Planning
The design and planning route depends on the property, proposed scope and relevant local requirements. Appropriate professional input may be required.
Structural Requirements
Structural alterations require the appropriate competent professional input and the relevant regulatory route.
Project Scope
Confirm the proposed work, inclusions, exclusions, VAT, allowances and change process before work begins.
Project Coordination
TCM can manage building work directly and coordinate specialist contractors and professional disciplines where appropriate.
Everything Else You Should Know
Understanding House Extension Costs
Extension cost depends on size, design, structure, access, services, specification, professional input, VAT basis, allowances and exclusions. A quotation should state those assumptions clearly; no universal free or fixed-price promise is approved.
Navigating Planning & Regulations
Do you need planning permission, or does your project fall under Permitted Development? Understanding the rules can feel overwhelming. We're experts in local regulations for Borehamwood and Hertfordshire, guiding you through the entire process to ensure your extension complies with all legal requirements.
Extension vs. Moving: What's Right for You?
You're weighing up your options: extend or move? Extending your home can save you stamp duty, solicitor fees, and the stress of finding a new property. It allows you to create a bespoke space tailored to your exact needs, often at a lower overall cost than relocating.
Common Extension Mistakes to Avoid
Building an extension is a big undertaking, and it's easy to overlook crucial details. We help you avoid common pitfalls like underestimating budgets, neglecting proper planning, or choosing the wrong builder. Our expertise ensures a smooth process and a high-quality finish.
House Extension FAQs
Not always. Some house extensions can use permitted-development rights when every applicable condition and limitation is met, while other proposals require planning permission or another planning route. Property type, previous additions, conservation or listed status, Article 4 directions and planning conditions can affect the answer, so check the exact property and design before work starts.
The programme depends on the proposed scope, approvals, design information, access, materials, specialist requirements and any changes. Discuss the project-specific programme before work is arranged.
Extension costs depend on the property, proposed scope, access, design, ground conditions, materials, professional input and agreed commercial terms. Confirm inclusions, exclusions, VAT, allowances and the change process before work begins.
Living arrangements and disruption depend on the scope, access, structural alterations, services and safety requirements. Discuss the project-specific arrangements before work begins.
The effect of any work on property value depends on the property, local market, design, condition and buyer demand. Obtain independent professional advice for a value assessment.
Discuss Your Extension Project
Contact TCM by telephone, email or the enquiry form.Property, access and specialist requirements remain project-specific.
Explore House Extensions Location Pages
TCM Building & Maintenance is based in Borehamwood, Hertfordshire. The individual location pages provide project information for each place. Geographic coverage, availability, scope and access remain project-specific and should be checked through a verified contact route.
TCM Building & Maintenance is based in Borehamwood, Hertfordshire.
Explore the Radlett location page.
Explore the Bushey location page.
Explore the Potters Bar location page.
Explore the Watford location page.
Explore the St Albans location page.
Explore the Hatfield location page.
Explore the Welwyn Garden City location page.
Explore the Barnet location page.
Explore the Edgware location page.
Explore the Stanmore location page.
Contact TCM by telephone, email or the enquiry form. Contact TCM.