Professional Building Extension Services

Professional Building Extensions Across London for Homes, Landlords & Businesses

From rear and side extensions to wraparound, single-storey and double-storey projects, Benjamin Services helps homeowners, landlords and businesses create practical new space around the existing property. We review the site, layout, structure, foundations, drainage, roof design, services, access and approval requirements, then coordinate the project from early assessment and planning through groundworks, structural construction, installation, finishing and final handover.

Request an Extension Assessment Call 07405 440644
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Why Extension Planning Matters FAQs
🏗️ Professional Building Extensions Across London

Add Space That Works with the Existing Property, Structure and Services

A well-planned extension should feel like a natural part of the property rather than a separate addition. Benjamin Services helps coordinate rear, side, wraparound, single-storey and double-storey projects around the existing layout, foundations, structural openings, drainage, roofing, insulation, glazing and building services. We review the design and site conditions early, then organise the work from groundworks and structural construction through to first fix, finishes and handover.

Site, foundations, structure and drainage reviewed before construction begins Planning, building regulations, party-wall and access requirements considered early Groundworks, shell, services, finishes and handover coordinated in one programme
Your building extension at a glance
Assess Review site, layout, boundaries, drainage, structure, access and intended use
Plan Confirm drawings, approvals, foundations, structure, roof, services and materials
Build Coordinate groundworks, shell, first fix, finishes, testing and handover

Pricing depends on extension type, drawings, foundations, steelwork, drainage, roofing, glazing, services, access, specification and finish required.

01 SITE Feasibility & Site Conditions

Understand What the Property and Plot Can Realistically Support

Boundaries, levels, drainage, trees, access and the existing building all affect the extension route before any ground is opened.

  • Available footprint and relationship to neighbouring properties reviewed
  • Ground levels, access routes and storage space considered
  • Existing drainage, manholes and service routes identified where possible
  • Intended room use, layout and connection to the house discussed
02 BASE Foundations & Structure

Support New Loads and Open the Existing Building Safely

Foundations, walls, floors, beams and roof structures must work together with the existing property and any large new openings.

  • Foundation type and depth informed by design and ground conditions
  • Structural openings and steelwork coordinated carefully
  • Temporary support considered before walls are altered
  • New roof and floor loads connected into the existing structure
03 FLOW Services, Comfort & Finish

Plan Drainage, Heating, Electrics and Internal Flow as One Design

A successful extension needs practical services, comfortable temperatures and a clear relationship with the original property.

  • Kitchen, bathroom or utility drainage routes considered early
  • Heating capacity, lighting, sockets and ventilation reviewed
  • Insulation, glazing and overheating risk considered
  • Floor levels, doors, finishes and circulation coordinated
Different properties and plots suit different extension approaches

Building Extension Types We Can Help Deliver

The most suitable option depends on the property, site, planning position, internal layout and required floor area. We review how each extension affects structure, light, drainage, access and the rooms next to it.

01

Rear Extension

Adds space behind the property for kitchens, dining areas, living rooms or utility space.

02

Side Return Extension

Uses the narrow side area often found beside kitchens in London properties.

03

Wraparound Extension

Combines rear and side extension space to create a wider, more flexible layout.

04

Single-Storey Extension

Creates additional ground-floor space with coordinated roof, glazing and service design.

05

Double-Storey Extension

Adds space on two levels and requires more detailed structure, access and planning coordination.

06

Kitchen, Living or Utility Extension

Internal layout, glazing, storage, services and finishes shaped around the intended use.

Good extensions are resolved before excavation begins

Layout, Foundations, Structure, Approvals and Services Need to Agree with Each Other

The extension footprint, structural openings, drainage, roof form, glazing, floor levels and internal services all affect one another. Early coordination helps reduce redesign, delays and expensive changes during construction.

PLAN

Planning & Neighbours

Size, position, appearance, boundaries and local restrictions shape the design route.

BASE

Ground & Structure

Foundations, drainage, steelwork and load paths must suit the site and existing building.

FLOW

Light, Services & Layout

Glazing, circulation, heating, ventilation and utilities need to support the new space.

Important decisions before construction starts

Early Site and Design Decisions Can Change the Entire Project

Foundation strategy, drainage position, structural openings, roof design, glazing and service routes can all affect cost, approvals and the construction programme.

Planning Route
Confirm Whether the Extension Needs Planning Permission
ReviewSize, height, position and relationship to boundaries
Possible RoutePermitted development or planning application
DesignMaterials, windows, roof form and neighbour impact considered
LimitFinal approval remains with the relevant authority

The planning route should be clear before the external design and programme are fixed.

Building Regulations
Design the Extension Around Safety, Structure and Performance
StructureFoundations, walls, floors, beams and roof reviewed
ThermalInsulation, glazing and ventilation considered
DrainageFoul and rainwater routes coordinated
InspectionKey stages made available where required

Compliance affects the hidden build-up as much as the visible finish.

Foundations & Groundworks
Match the Foundation Strategy to the Site and New Loads
GroundSoil, levels, trees and nearby structures considered
DepthFoundation design confirmed from project information
ServicesDrainage and buried utilities reviewed before excavation
InspectionExcavation stages made available where required

Foundations should not be treated as a generic depth without regard to the site.

Structural Openings
Connect the New Space to the Existing Property Safely
OpeningWidth, load above and support conditions reviewed
SteelBeams, columns and connections detailed where required
TemporaryPropping and sequence considered before demolition
FinishFloor, ceiling and wall junctions planned carefully

Large openings can transform the layout, but they also change how the building carries load.

Drainage, Roofing & Services
Coordinate the Hidden Systems Before Walls and Floors Are Closed
DrainageFoul, rainwater and manhole routes reviewed
RoofFalls, outlets, coverings and junctions considered
ElectricalLighting, sockets, circuits and controls planned
HeatingCapacity, emitters and ventilation coordinated

Late service changes can affect floors, walls, cabinets, ceilings and external finishes.

Architectural drawings, structural calculations, planning submissions, building-control fees, party-wall services, drainage surveys and specialist reports may need to be provided separately depending on the property and extension design.

Clear Building Extension boundaries

What Is Not Automatically Included in a Building Extension Quote?

The quotation covers the listed works, assumptions and agreed specification. Professional fees, approvals, hidden conditions and additional client choices remain separate unless specifically included.

  • Architectural design, structural calculations or specialist consultant fees unless listed
  • Planning, building-control, party-wall or freeholder application charges
  • Asbestos surveys, removal or specialist hazardous-material work
  • Unexpected ground conditions, buried structures or hidden drainage defects
  • Utility-provider upgrades, diversions or network charges beyond the agreed scope
  • Loose furniture, specialist interior design, landscaping or temporary accommodation unless listed
From site assessment to a completed new part of the property

A Four-Stage Building Extension Process

The exact sequence depends on the design, but the work should move through controlled groundworks, structure, weatherproofing, services and finishing stages.

  1. 01

    Survey & Feasibility

    We review the site, property, access, boundaries, layout and available project information.

  2. 02

    Design & Prepare

    Drawings, structure, approvals, materials, logistics and programme are coordinated.

  3. 03

    Groundworks & Structure

    Excavation, foundations, drainage, walls, steelwork, floors and roof are completed in sequence.

  4. 04

    Services, Finish & Handover

    First fix, insulation, plastering, second fix, decoration, testing and completion checks are carried out.

Before the assessment

Information That Helps Us Understand the Extension

Photos, drawings and site details help us prepare for a useful first visit.

  • Send the postcode, property type and intended use of the new space
  • Describe the preferred extension size, layout and connection to existing rooms
  • Share drawings, surveys, approvals or structural information already available
  • Provide photos of the rear, side access, boundaries, drainage and internal connection area
  • Confirm occupancy, parking, storage, neighbour restrictions and working-hour limits
  • Explain budget priorities, finish level and target completion date
A completed extension should feel integrated, weatherproof and ready to use

Handover Means More Than Finishing the Decoration

We review the agreed scope, inspect the finished areas and explain controls, drainage, maintenance needs, certification and any outstanding work outside the completed package.

BASE

Structure & Openings Completed

Agreed foundation, wall, steelwork and structural connection items are checked.

SEAL

Roof & Weatherproofing Reviewed

Visible roof, flashing, glazing, drainage and external completion items are checked.

FIN

Services & Finishes Completed

Plastering, joinery, fixtures, electrics, heating and decoration are reviewed against the scope.

HAND

Handover Information Provided

Care advice, controls, outstanding items and relevant documents are explained.

When excavation or opening up reveals a different condition

What Happens if the Extension Needs More Work Than Expected?

Unexpected ground, buried structures, damaged drainage, unsuitable masonry, additional steelwork or design conflicts can change the scope. We explain what was found and confirm the cost and programme impact before additional work proceeds.

STOP

Pause the Affected Area

Work is not covered up where an unexpected structural, drainage or safety issue needs review.

SHOW

Record What Was Found

Photos and a clear description are provided where practical.

SPEC

Review the Design

Structural, drainage, architectural or building-control input is arranged where needed.

COST

Price the Variation

Additional labour, materials, plant and professional input are shown separately.

TIME

Update the Programme

Lead times and the effect on dependent trades are explained.

SYNC

Resequence the Work

Groundworks, structure, services and finishes are adjusted around the revised scope.

No responsible extension quotation can guarantee that every hidden ground, drainage or structural condition is known before excavation and opening up. Variations are discussed and agreed before they are added to the working scope.

No meaningful fixed figure before the site and design information are understood

Building Extension Quotes Reflect the Site, Foundations, Structure, Services and Finish

A compact side return is not the same as a wraparound or double-storey extension. We price the actual design, groundworks, structure, services and specification rather than using one generic extension rate.

Rear Extension
Based on footprint, structure and finishAssessment-Based
Additional kitchen, dining or living space
  • Foundations, roof and structural opening reviewed
  • Glazing, drainage and services considered
  • Specification and finishes confirmed separately
Request an Assessment
Most common scope Side Return Extension
Access, drainage and neighbouring walls consideredTailored Quote
Wider kitchen and improved ground-floor layout
  • Boundary and party-wall factors reviewed
  • Drainage, roof and structural opening coordinated
  • Specification and exclusions shown clearly
Request a Side Return Quote
Wraparound Extension
Depends on footprint and structural designProject Review
Combined side and rear extension space
  • Planning, foundations and steelwork assessed
  • Complex roof, drainage and glazing considered
  • Kitchen and service layouts coordinated
Book a Project Review
Double-Storey Extension
Design and approval requirements drive the scopeCombined Programme
Additional space across two levels
  • Structure, planning and neighbour factors reviewed
  • Access, roof and service changes considered
  • Phased construction and finishes mapped clearly
Send Extension Details
Homeowners, Landlords, Developers and Property Investors Building extensions can be planned around occupancy, tenant access, investment goals, business use and handover dates. Pricing is prepared from the drawings, site condition, specification and agreed working arrangements. Request an Extension Quote
Site factors Footprint, boundaries, levels, access, trees, drainage and existing condition.
Design factors Extension type, layout, roof, glazing, structure and intended use.
Build factors Foundations, steelwork, scaffolding, services, finishes and programme.
VAT & extras Benjamin Services is not currently VAT registered. Professional fees, permits and specialist access are confirmed separately.
Why one fixed Building Extension price would be misleading Two similar properties can have different ground conditions, drainage routes, structural openings, access restrictions and specifications. The quotation is confirmed after the site, drawings, approvals and expected finish are reviewed.

The final quotation is confirmed after reviewing the site, drawings, approvals, structure, access, services and specification. Additional conditions found during excavation or opening up are explained and priced before they are added to the agreed scope.

Building Extensions across London

Send Us the Extension Details. We Will Help Identify the Most Practical Next Step.

Include the postcode, property type, proposed extension, drawings, approvals, site photos, access details, preferred finish and timescale.

Request Your Extension Quote Call 07405 440644
Why Building Extensions Matter

Good Extension Planning Helps Protect the Structure, Budget and Final Result

A building extension changes the footprint, foundations, structure, drainage, roof, services and relationship with the existing property. Careful planning helps create useful new space without introducing avoidable structural, access or coordination problems.

Not every extension design is automatically ready to build. We review the site, boundaries, access, foundations, drainage, structure, services and approval requirements before confirming the construction route.

Understand the site properly Site Conditions and Layout Shape the Whole Extension

The available footprint, ground levels, boundaries, drainage and connection to the existing rooms determine what the extension can realistically achieve.

  • Available footprint must work with boundaries, access and the existing layout.
  • Ground levels affect floor heights, drainage and external access.
  • Early site checks help avoid poor layouts and costly redesign.
Coordinate foundations and structure Foundations and Structural Openings Need Proper Design

Foundations, walls, beams, large openings, floors and roof construction all need to be sequenced correctly.

  • Foundation design should reflect the site, loads and ground conditions.
  • Temporary support protects the property while structural openings are formed.
  • Coordinated structure helps connect the new extension safely to the existing building.
Services before finishes Drainage, Services and Weatherproofing Cannot Be Added as an Afterthought

A practical extension needs coordinated drainage, heating, electrics, ventilation, insulation, glazing and weatherproofing.

  • Drainage planning helps avoid conflicts with foundations, floors and external levels.
  • Thermal design helps keep the extension comfortable throughout the year.
  • Service coordination helps avoid late changes to walls, ceilings, floors and cabinetry.
Resolve approvals and neighbours early Planning, Building Regulations and Party-Wall Matters Can Shape the Design

Rear, side, wraparound and double-storey extensions may need different approval routes, structural information and neighbour coordination.

  • Planning checks help confirm the acceptable size, position and external appearance.
  • Building regulations cover foundations, structure, drainage, insulation, ventilation and glazing.
  • Party-wall and boundary checks can help reduce neighbour disputes and programme delays.
Assess the Site Before Fixing the Extension Design

Tell Us About the Property, Site and Intended New Space

Send the postcode, property type, proposed extension, available drawings, access details and clear photos of the site and connection area. We will confirm the right assessment and quotation.

Request an Extension Assessment Call 07405 440644

The right extension plan depends on the site, boundaries, foundations, structure, drainage, approvals, services, access and finish expected.

Extension Design, Structure & Coordinated Construction

Professional Building Extensions Across London

From rear and side-return extensions to wraparound, single-storey and double-storey projects, each extension needs careful planning around the site, foundations, structure, drainage, roofing, glazing and services. We assess the property, review the intended use and coordinate the work from feasibility and design through groundworks, structural construction, first fix, finishing and handover.

Site Feasibility & Layout

We review the available footprint, boundaries, levels, access and the most practical extension route.

Foundations & Structure

Foundations, drainage, structural openings, steelwork and roof construction are coordinated in the right order.

Approvals & Site Requirements

Planning, building regulations, party-wall, drainage, insulation and ventilation requirements are reviewed where relevant.

Construction & Handover

Groundworks, structure, roofing, services, plastering, joinery, testing, snagging and final handover are managed clearly.

Get an Extension Quote Call 07405 440644
Benjamin Services team carrying out a professional Building Extension in London Building Extensions Professional Building Extensions Rear, side-return and structural extension work London
Benjamin Services Building Extension Guidance

Building Extension Questions, Answered Clearly

Straight answers about extension types, foundations, structure, drainage, approvals, party walls, timescales and how quotations are prepared.

We assess the property and site before confirming the extension scope

A practical building extension depends on the site, foundations, structure, drainage, access, services, approvals and intended use working together.

01 What types of building extension do you undertake?

Benjamin Services can help with rear, side-return, wraparound, single-storey and double-storey extensions. The most suitable option depends on the property, available footprint, planning position, structure, access and intended use.

02 How do I know whether my property is suitable for an extension?

Suitability depends on boundaries, site levels, access, drainage, trees, existing structure, neighbouring properties and how the new space will connect to the house. A site assessment helps confirm what is practical before design work is finalised.

03 Do building extensions need planning permission?

Some extensions may fall within permitted development, while larger, taller, double-storey or more complex projects may need planning permission. Flats, listed buildings and properties in restricted areas usually need additional checks.

04 Do building extensions need building regulations approval?

Yes, building extensions normally need building regulations approval. The work may be reviewed for foundations, structure, insulation, ventilation, drainage, glazing, fire safety and electrical installations.

05 What is the difference between a rear, side-return and wraparound extension?

A rear extension projects behind the property, a side-return extension uses the side passage, and a wraparound extension combines both. Each option affects light, access, drainage, structure and planning in a different way.

06 How are foundations designed for an extension?

Foundation design depends on the new loads, ground conditions, trees, nearby structures, drainage and the existing property. Depth and type should be based on the project information rather than treated as one standard solution.

07 Can a large opening be created between the house and the extension?

Yes, where the structure is properly designed. Large openings may need steel beams, columns, padstones and temporary support, together with careful sequencing before walls are removed.

08 How are drainage and manholes handled?

Existing foul and rainwater drainage should be identified before excavation. Manholes may need to remain accessible, be relocated or be redesigned around the extension, subject to the agreed drainage strategy and approvals.

09 Do I need a party-wall agreement for an extension?

A party-wall process may be relevant where work affects a shared wall, boundary structure or excavation near a neighbouring building. The requirement depends on the design and relationship to adjoining properties.

10 Can we stay in the property during the extension work?

Often yes, although noise, dust, temporary service interruptions and restricted access should be expected. The programme may be phased to keep essential rooms usable, but some stages can be easier when affected areas are empty.

11 How long does a building extension take?

Timescales depend on the extension type, design, approvals, foundations, structural work, weather, access, material lead times and internal specification. Smaller single-storey projects may be shorter, while wraparound or double-storey extensions usually require a longer programme.

12 How is the building extension price calculated?

Pricing is based on the drawings, footprint, groundworks, foundations, drainage, steelwork, roof, glazing, services, access, scaffolding and finish. Professional fees and approval charges are shown separately unless included.

13 What should I send before booking an extension assessment?

Send the postcode, property type, proposed extension, intended use and any drawings or surveys already available. Photos of the rear or side of the property, boundaries, access and the internal connection area are especially useful.

14 What is not automatically included in a building extension quotation?

Architectural design, structural calculations, planning fees, building-control charges, party-wall services, asbestos work, utility-provider charges, unexpected ground conditions and items not listed in the quotation are not automatically included.

The right building extension plan depends on the site, boundaries, foundations, structure, drainage, approvals, access, services and finish expected.

Not Sure Which Building Extension Route Suits the Property?

Send the postcode, property type, proposed extension and a few clear photos.

Request an Extension Quote Call 07405 440644