How Much Do House Extensions Cost?

Extension expenses in the UK can vary significantly, influenced by the project’s scale, the materials you select, and the complexity of the design. Industry data shows that a single-storey rear extension may start at £1,500 per square metre for a simpler plan, while most typical configurations sit in the £1,800–£2,500 per square metre band. If your vision involves custom steel beams, premium glazing, or very high-end finishes, expect costs to surpass £3,000 per square metre.

In Havering, which sits on the eastern edge of Greater London, labour charges often run somewhat below central London rates, providing room in your budget for upgraded fixtures or specialised finishes. However, older Victorian or Edwardian houses, as found in certain Havering neighbourhoods like Romford or Hornchurch, might need additional structural reinforcement, raising the overall outlay. Broader expansions frequently range between £40,000 and £100,000+, whereas smaller side-return projects may be less expensive, and two-storey or lavish schemes can surpass normal ranges if advanced engineering or top-quality materials are involved. Kitchens and bathrooms push prices upward because of plumbing, wiring, and waterproofing requirements.

When gathering quotes, ensure each bid includes foundation digging, the structural envelope, roofing, fittings, finishing, plus labour and overhead. Also confirm if VAT—commonly 20%—is calculated in the total or listed separately. Though home-improvement publications and renovation sites offer general cost references, to get a precise estimate, you should acquire multiple quotes from dependable builders and compare them meticulously.

Different Types Of Extensions

There are also different requirements for different extensions. Under is a list of the different types of house extensions:

Side extensions
Single storey extensions
Extensions more than one storey

They each have their own specific limits concerning such as rear extensions requirements, height, roofing and windows. For extensions of more than one storey, there is for example a requirement that roof pitch must match the existing house as far as practicable.

Havering

Havering, one of the easternmost London boroughs, encompasses areas like Romford, Hornchurch, Upminster, and Rainham. Many dwellings here are semi-detached houses from the mid-20th century, though some older Victorian-era terraces also dot the borough, especially near Romford’s historic centre. Single-storey extensions are common to enlarge kitchens or create open-plan living areas. Homeowners in Upminster might add side expansions if the plot configuration allows it, and loft conversions are frequent for extra bedrooms or home offices—particularly in suburban neighbourhoods with pitched roofs. Certain prime roads near Romford might see basement construction, but these remain less typical in Havering than in older central boroughs.

Local contractors point out that Havering roads can experience congestion, especially around Romford town centre or along the A127, so scheduling skip deliveries outside busy times helps. Labour costs usually sit below the highest London rates, allowing families to invest in better finishing details. The borough features some conservation areas—like parts of Gidea Park—where planning might be more strict. Overall, a well-planned extension can boost everyday comfort and property value, particularly if you’re close to well-regarded schools or transport links like Romford station. Letting neighbours know early about any boundary walls or shared fences can help you avoid party-wall disputes later.

Whether your plan is a single-storey design to enlarge your existing kitchen or a more elaborate scheme adding bedrooms upstairs, shaping your extension to match Havering’s suburban identity and council requirements is often the quickest route to smooth approvals.

Getting Started

Before construction starts, choose the type of extension that best suits your property. A single-storey rear addition might integrate a dining area and living space, while a two-storey plan can add both ground-floor living room plus upstairs bedrooms. Some owners reclaim a side alley for a side-return or wrap-around design, whereas a loft or basement might be feasible if outward expansions aren’t practical. Basements in Havering are less widespread but occasionally appear in higher-value roads or where land space is restricted.

Well-thought-out planning upfront typically averts mid-build delays. Form a thorough budget, referencing average labour costs and standard materials, and allocate a contingency for structural or finishing surprises. If your plan includes major structural changes, think about hiring an architect or qualified designer. A number of building companies provide design-and-build, but they commonly want early sketches or partial permission for accurate quotes. Plenty of Havering homeowners consult an architect first, then approach builders with preliminary plans.

Also, secure a contractor early—leading teams often have packed schedules. By soliciting quotes sooner, you can compare cost breakdowns, check references, and finalise a builder who fits your budget and timeline. A knowledgeable firm may further refine your layout—for instance, adding a skylight in your extension’s roof to brighten the interior or subdividing a large space to include a utility cupboard.

Project Management

Extensions typically follow two main organisational methods:

• Single contract (design-and-build or main-contractor)
  You sign one agreement with a main building firm that handles everything—structural tasks, plumbing, electrics, roofing, finishing—subcontracting specialists as needed, plus around 10–15% markup. This approach centralises scheduling, providing one key contact for you.
• Multi-trade or split contract
  You handle the project yourself, hiring separate groundworkers, carpenters, roofers, electricians, plumbers, and so on. Although you might avoid a main contractor’s overhead, you shoulder coordination burdens. If one trade is delayed, subsequent tasks might idle. You need plenty of time and a decent grasp of construction processes.

For extensive or complex builds in Havering, many owners prefer single-contractor setups to avoid micromanaging daily schedules. If you attempt multi-trade, confirm you can check progress regularly and oversee deliveries without disruption.

Do I Need Planning Permission?

Whether planning permission is required depends on your extension’s scale, height, and location within your property. Under Permitted Development Rights, you can sometimes expand without filing a formal planning application if you remain within certain size and positioning bounds. If your design exceeds these, you typically must submit a householder planning permission request.

Under are the general rules that apply to all extensions:
Only half the area of land around the "original house" can be covered by extensions or other buildings.
Extensions cannot be higher than the highest part of the existing roof; or higher at the eaves than the existing eaves.
Where the extension comes within two metres of the boundary the height at the eaves cannot exceed three metres.
Extension cannot be built forward of the ‘principal elevation’ or, where it fronts a highway, the ‘side elevation’.
The work cannot include:
verandas, balconies or raised platforms.
a microwave antenna (e.g. TV aerial or satellite dish).
a chimney, flue or soil and vent pipe.
any alteration to the roof of the existing house.
On Article 2(3) designated land the work cannot include cladding of the exterior.
The materials used in any exterior work must be of a similar appearance to those on the exterior of the existing house.
Source: Planning Portal.

Because Havering has areas of special designation, such as conservation spots near Gidea Park, you should confirm if local restrictions apply. Early contact with the borough’s planning authority indicates if you qualify under PD or must apply formally.

Do I Need Planning Permission For A New Storey?

Loft extensions that add dormers or increase roof height generally demand planning permission. Nonetheless, you may be able to add a new storey under permitted development if you comply with certain requirements and submit a prior approval form to the local authority. Otherwise, Householder/Full Planning Permission will be necessary. If your home fits these criteria, the bullet points below outline the main restrictions:

Number of additional storeys:
One storey can be added to a single storey house
Two storeys can be added if the house has more than one storey.

Height increases:
The house cannot exceed 18 metres in total height
Each added storey cannot add more than 3.5 metres to the total height
If not detached (e.g. terrace or semi) the total height cannot be more than 3.5 metres higher than the next highest building that the house is attached to, adjoins, or is in the same row as.
The additional storeys must be constructed on the principal part of the house*
The additional storeys must not exceed 3 metres in height or the height of any existing storey in the principal part of the house (measured internally from floor to ceiling)
Engineering operations must only include works within the existing curtilage of the house to strengthen existing walls and foundations
The materials used must be of a similar appearance to those used in the construction of the exterior of the current house
Windows must not be placed in any wall or roof slope forming a side elevation of the house.

There may be more conditions after completion. Checking with Havering’s planning office helps confirm that your additional storey doesn’t disrupt the borough’s local building patterns or overshadow neighbours.

Do I Need Planning Permission For A New Basement?

Usually, adding a basement needs planning permission, and excavating below ground is similarly prone to requiring planning permission given its substantial nature. It’s best to consult your local planning authority early, clarifying their rules. Basement works are inherently large-scale projects, so even if official planning permission might not always apply, Building Regulations definitely do—encompassing structural stability, safe escape routes, ventilation, fire safety, and so forth.

Always see if local constraints override normal PD expansions. Some areas of Havering—especially near older roads or historical sites—might impose stricter guidelines. Checking council directives or speaking to a planning consultant provides clarity.

Basements are less frequent in suburban Havering, though a few roads with higher property values or limited outward room may adopt them. However, expect higher costs if advanced engineering is required, plus potential party-wall matters with neighbours.

Remember Building Regulations Application

Regardless of the size and shape of your extension, it must meet building regulations requirements. This is also regardless of whether you need planning permission or not.

You will need to submit a building regulations application. For smaller projects you can submit a Building notice but for larger extensions you’ll probably need a Full Plans Application. In this case full details of the proposed work will be submitted for approval before the work begins. With a Building Notice an inspector will inspect and approve the work as it is performed.

A Full Plans Application can detect design or safety flaws beforehand, whereas a Building Notice may suffice for a straightforward single-storey. Either way, final building control approval is mandatory to ensure compliance with code standards.

What’s The Difference Between Planning Permission And Building Regulations Application?

Whereas planning permission assesses whether the extensions meets local and national requirements, building control concerns structural safety and regulations compliance.

Even if your Havering extension fits PD thresholds, building regulations remain essential for stable foundations, adequate insulation, and safe modifications. For older suburban houses in Romford or Hornchurch, verifying load-bearing capacity is often critical.

DIY Contribution

Homeowners sometimes consider tackling parts of an extension themselves. Painting, decorating, or landscaping can be good DIY tasks if you’re confident in your skill level. Doing your own demolition, in a limited capacity, may also be viable—if you understand which walls are structurally significant and follow proper safety rules.

However, tasks such as installing gas lines, electrical systems, or major structural supports typically require licensed professionals. Mistakes can become serious safety hazards or cause expensive corrections. Being realistic about your abilities is pivotal; overcommitting could slow down the project. Builders may wait for you to finish certain tasks, increasing final costs. If you do want some DIY involvement, consider hiring an expert for an initial consultation to help you sidestep major mistakes.

In Havering, partial DIY usually concentrates on interior décor or garden landscaping after the shell is finished, letting professionals manage core mechanical or structural responsibilities. This approach avoids stalling official inspection checkpoints.

Do I Need An Architect?

If your layout changes are modest, a structural engineer or building designer may suffice. Yet for larger or more sophisticated expansions, an architect can deliver significant advantages. Skilled architects unify aesthetic appeal, daylight considerations, and functional flow so your new spaces merge neatly with existing ones.

They can also advise if your plan remains within PD or necessitates a planning application. Although an architect’s fee ups your front-end outlay, it typically prevents layout errors that might balloon into bigger costs later.

Havering is a varied borough, hosting 1930s estates, Victorian terraces in Romford, and modern developments near Rainham. An architect can propose consistent design themes that blend older exteriors with modern additions, possibly suggesting foldable glass panels or partial roof lanterns for a bright, contemporary vibe.

How Long Does It Take To Build An Extension?

Establishing a clear schedule helps keep you on track. A smaller single-storey rear extension—particularly if straightforward, using standard materials, and under PD—might complete within weeks of on-site work beginning. Larger expansions with multiple rooms or floors can stretch from several months to half a year or longer, reflecting design complexity and the number of trades involved.

In some cases, you might relocate briefly if crucial walls are dismantled or vital utilities disconnected. Even if you remain, you’ll likely see dust, noise, and limited access to certain parts of the home.

Provide a buffer in your timeline. Bad weather can delay exterior building tasks; inspectors might demand tweaks; deliveries can arrive late. Crafting a realistic plan with your contractor lowers stress, and if you finish early, so much the better. A financial reserve is similarly recommended to cover any unplanned tasks that emerge mid-project.

Havering roads experience rush-hour congestion, particularly along main routes like the A12 or near Romford town centre, so skip drop-offs often happen midmorning to avoid peak travel times. Changing finishes or structural details once building commences can also nudge your completion date further away.

House Extensions Step By Step

Though expanding a house is a major undertaking, with comprehensive planning, reputable trades, and a practical budget, you can succeed. Whether you desire an open-plan lounge-kitchen, upper-floor bedrooms, or a small basement level, carefully handle each stage while anticipating potential problems.

1. Start by confirming what you want to achieve—more natural light, a larger social area, or additional bedrooms.
2. Then decide how best to organise the project.
3. Check if you need planning permission and what kind of building regulations application you need to send in.
4. Gather quotes from at least three builders if possible, ensuring each has a solid track record and good references.
5. Check that their quotes are like-for-like in terms of scope.
6. Factor in the cost of planning applications, building control fees, and professional services such as architectural drawings or structural engineering.
7. Then develop a realistic schedule, communicate frequently with your chosen contractor, and keep a close eye on both time and budget.
8. Finally, as the build nears completion, consider a thorough inspection—often called a snagging survey—conducted alongside your main contractor or an independent professional. Any incomplete tasks should be resolved prior to final payment. Keep compliance papers, including building control certificates and warranties, safe for potential future sales or mortgage applications.

Once your extension secures final clearance, you can relish a more spacious home in Havering. Whether you created a sun-filled ground-floor expansion for your kitchen or introduced a new storey, the finished work usually boosts comfort and resale prospects. A snagging survey helps detect small flaws—like hairline cracks or poorly aligned doors—so your builder fixes them. Holding onto building control approvals and warranties proves the work followed regulations, calming the doubts of prospective buyers or lenders. With that, your newly expanded Havering residence is set to accommodate your evolving lifestyle for years to come.