Double Storey Extension Cost in Rugby: 2026

What the 2026 double storey figures cover

The published ranges describe national construction benchmarks, and they do not include every room, service or professional cost needed for a finished Rugby project.

Checkatrade's double storey extension guide, updated in August 2026, gives £1,650 to £2,150 per square metre for standard quality, £1,830 to £2,350 for good quality and £2,150 to £3,000 for excellent quality. Its table labels these figures as cost plus VAT, so VAT must be added where applicable. The guide also says the construction figures exclude internal fixtures and fittings such as plumbing and electrical work.

The Federation of Master Builders gives a broader £1,000 to £2,500 per square metre range for a two-floor extension. Its page does not clearly state VAT treatment beside that range. It also warns that planning fees, drawings and alterations to the existing structure need separate budget attention. The difference between the two guides shows why a benchmark must be read with its scope and tax basis, rather than treated as a local rate.

Checkatrade also lists £66,000 to £100,000 plus VAT for a 5m by 4m double storey side, front or wraparound extension. It describes these as ballpark national averages. The footprint, total floor area, quality level and excluded fit-out must match your proposal before that example is useful. It is not evidence that a particular Rugby project will cost the same.

Check the guidance: Checkatrade double storey extension cost guide, Federation of Master Builders two-storey extension guide.

Every figure above is an attributed national benchmark. None is a Belmax quotation or a claimed Rugby average.

Bottom line: Keep the guide range, VAT treatment and excluded work visible when testing an early budget.

Decide whether two floors solve the right problem

A second floor is useful only when the ground-floor plan, upper-floor plan and connection to the existing house work together.

Start with the rooms and relationships you need, not the largest footprint that appears possible. A two-floor rear addition might create a kitchen or family room below and a bedroom or bathroom above. A side addition might improve circulation and add rooms while preserving more rear garden. Each choice changes the planning route, roof form, structural connection and the amount of existing space that must be altered.

Test the upper floor early. A new bedroom needs a sensible route from the landing, workable furniture space, windows, heating and fire-safety coordination. A bathroom adds hot and cold water, drainage, ventilation and waterproofing. If the extension makes an existing bedroom into a corridor or creates awkward level changes, the extra area may not deliver the useful layout expected.

Then test the ground floor. Large openings can help connect a new room, but they also affect temporary support, permanent steelwork, services and making good. The lowest construction rate is not good value if the finished plan leaves dark internal rooms, poor circulation or a kitchen that cannot be arranged properly.

Bottom line: Choose the footprint only after both floors and the rooms they connect to have been tested.

Structure and ground conditions shape the quotation

A double storey extension needs a continuous load path from the roof and upper floor through the walls, beams and foundations to the ground.

The proposed structure must work with the existing house. Foundations need a design suited to the ground, nearby trees, drains and the loads above. Openings through the existing external walls may need beams, bearings, posts and temporary works. The roof connection must manage structure, weathering, insulation and drainage without relying on a generic detail that ignores the existing building.

A quotation prepared before structural information exists should state its assumptions. Ask what foundation type and depth, steelwork allowance, temporary support and drainage work have been included. If investigations or calculations are outstanding, identify which figures are provisional and how any change will be agreed. A fixed-looking total built on hidden assumptions is not the same as a fixed scope.

Building above an existing garage or extension needs its own assessment. Existing walls and foundations should not be assumed capable of carrying another storey. A structural review may find they are suitable, need strengthening or should be replaced. The apparent saving from reusing a structure is only real after that condition and capacity have been checked.

Bottom line: Make the structural basis and unresolved assumptions visible before comparing prices.

Stack rooms and services deliberately

Putting related rooms and service routes above one another can reduce complexity, while a disconnected layout can add drainage, ventilation and coordination work.

A bathroom above a kitchen or utility can create shorter service routes, but it still needs a workable soil connection, falls, ventilation, water supply, electrical zones and access for maintenance. A bedroom above a living room may have fewer drainage demands, but acoustic separation, heating, sockets, lighting and the arrangement of windows still need a specification.

List the intended use of every new and altered room. For the ground floor, include the kitchen, utility, cloakroom, storage, glazing, heating and flooring. For the first floor, include bedrooms, bathrooms, wardrobes, doors and landing changes. Then add work inside the existing house, such as moving radiators, changing ceilings, upgrading doors or redecorating affected rooms.

Check whether products are supplied by the contractor, homeowner or a separate specialist. A kitchen allowance without appliances and worktops is different from a complete fitted room. The same applies to sanitaryware, tiles, wardrobes and floor finishes. Product decisions also affect first-fix locations, so late changes can move both cost and programme.

• Coordinate soil, waste, water, heating, ventilation and electrical routes across both floors.
• Name every altered room outside the extension footprint.
• Record exact product allowances and who supplies each item.
• Include fire, acoustic, insulation and ventilation requirements in the technical design.
• Agree how late layout or product changes will be priced.

Bottom line: A room schedule makes the fit-out boundary clearer than a broad price per square metre.

Check the Rugby planning route early

Some rear extensions of more than one storey can use permitted development, but side extensions of more than one storey require householder planning permission.

Planning Portal says a rear extension of more than one storey under permitted development must project no more than three metres beyond the original rear wall and remain at least seven metres from the boundary opposite that wall. The roof pitch should match the existing house as far as practicable, and upper-floor side windows must be obscure-glazed and normally non-opening below 1.7 metres from floor level. The proposal must also meet the general extension limits.

The same official guidance says all side extensions of more than one storey require householder planning permission. Rear extensions of more than one storey on Article 2(3) designated land also require it. Previous additions count against some limits, and the original house means the building as first built or as it stood on 1 July 1948 if older.

Rugby Borough Council warns that permitted development rights may have been removed from a property. Its formal householder pre-application advice costs £115 inclusive of VAT from 1 April 2026, and it points homeowners to a Certificate of Lawfulness when formal confirmation is needed. Advice or a certificate has a different purpose from a planning application, so confirm the correct route for the actual property and design.

Check the guidance: Planning Portal extension planning rules, Rugby Borough Council pre-application advice.

Bottom line: Confirm the Rugby planning route before treating the footprint, windows or roof as settled.

Budget separately for technical approvals and neighbour duties

Planning permission, building regulations approval and party wall duties are separate processes, and one approval does not replace another.

GOV.UK says building regulations approval is normally needed for a new building or an extension. The technical work can cover structure, fire safety, ventilation, drainage, energy performance, electrical safety and glazing. Agree who prepares the drawings and calculations, submits the application, responds to queries, arranges inspections and provides completion information.

Party wall duties are separate. GOV.UK says notice may be required for work on an existing party wall or shared structure, building on or at the boundary, or excavation below and near a neighbour's foundations. Whether the Act applies depends on the design and neighbouring buildings. Check early because the process can affect information, professional fees and the intended start date.

Keep professional and statutory costs visible beside the construction budget. Possible items include measured surveys, design work, structural engineering, planning or lawful development submissions, building control charges, drainage information, specialist reports and party wall advice. Include VAT treatment against each figure. A contingency should remain under the homeowner's control and should not replace a defined scope.

Check the guidance: GOV.UK building regulations approval, GOV.UK party wall guidance.

Bottom line: Assign every submission, notice, inspection and completion document to a named party and budget line.

Compare complete two-floor quotations

Two totals can be compared only when they use the same drawings, room schedule, specification, approvals and VAT basis.

Give each contractor the same Rugby postcode, photographs, surveys, drawings, structural information and room schedule. Identify access limits, known drains, intended openings, the kitchen or bathroom requirements and the finish expected in every affected room. If design work is incomplete, ask each contractor to list assumptions and exclusions rather than hiding uncertainty inside one total.

Compare groundworks, drainage, structure, temporary support, external walls, roof, scaffolding, windows, doors, services, plastering, joinery, decoration, flooring and external making good line by line. Include work inside the existing house, professional responsibilities, applications, inspections, waste, welfare, protection and cleaning. Check whether VAT is included, excluded or not applicable for every price.

Review allowances carefully. A provisional sum should state what it covers and how it will be adjusted. A product allowance should identify quantity, quality and whether delivery and fitting are included. Changes should be described and priced before extra work proceeds. Payment stages should follow defined work or orders, not vague dates.

For an initial conversation with Belmax, send the postcode, photographs, the rooms required on each floor and any drawings or decisions already received. That information helps identify the survey, design and technical questions still needed. A project-specific quotation follows a sufficiently developed scope, not the national figures in this guide.

• Design basis: surveys, drawings, calculations and room schedule.
• Construction: foundations, drainage, frame, openings, roof and weathering.
• Fit-out: services, kitchen or bathroom, joinery, plastering and finishes.
• Project costs: approvals, professional work, access, protection and waste.
• Commercial detail: VAT, exclusions, allowances, changes and payment stages.
• Handover: inspections, certificates, product information and completion records.

Bottom line: Normalise the scope and tax basis before deciding which quotation offers better value.