Kitchen Extension Cost Guide 2026: What to Budget in Hertfordshire

A kitchen extension adds or reconfigures ground-floor space so the kitchen and related living areas can be enlarged or reorganised. Common forms include rear, side and wrap-around extensions, but the appropriate footprint depends on the existing property, plot, planning context, structure and household brief.

A rear extension creates additional space behind the existing house. A side extension can use space beside the existing building where the plot and planning position allow it. A wrap-around extension combines rear and side enlargement. None of these labels determines the final floor area, cost or planning route by itself.

For budgeting, separate the structural shell from the kitchen fit-out. The building work can include groundworks, structure, roof, glazing, openings, insulation and services interfaces; the kitchen package can include cabinetry, worktops, appliances, lighting, plumbing/electrical connections and finishes. Whether those items sit in one contract or separate appointments is project-specific.

A kitchen extension can improve how a home functions, but TCM does not guarantee a percentage property-value uplift or financial return. If resale value is material, use current independent valuation evidence for the individual property.

A useful kitchen-extension quotation identifies the structural build and internal fit-out it actually prices. That can include groundworks, foundations, walls, roof, glazing, structural openings, plastering, electrical/plumbing interfaces, floor build-up and decoration, but no item should be assumed merely because it is common on another project.

Kitchen units, worktops, appliances, heating, large glazed doors, specialist lighting, structural-professional work, design services and statutory fees may sit inside or outside the builder's quotation depending on the procurement route. Ask each bidder to identify the same inclusions, exclusions, allowances and client-supplied items.

VAT treatment must be stated in the actual quotation. Compare prices only after confirming whether each amount is inclusive or exclusive of VAT and whether professional, statutory and specialist costs are included.

The words budget, mid-specification and premium are not reliable price bands unless the actual products and workmanship requirements are defined. Two quotations can use the same label while pricing different glazing, roof systems, kitchen packages, flooring, heating, lighting or joinery.

For comparison, specify the same structural scope, external envelope, window/door systems, services, kitchen package and finish level. If one contractor includes cabinetry, appliances or specialist glazing and another does not, their headline totals are not like-for-like.

The current Experience Inputs Register contains no approved TCM kitchen-extension cohort from which to publish a Hertfordshire £/m² range or a preferred specification tier. Use current project-specific quotations based on the actual design.

Ground and structural conditions can materially change scope, but foundation depth, temporary works and structural solutions must come from the individual property and responsible design rather than a generic Hertfordshire or “London Clay” rule.

Party Wall etc. Act matters depend on the actual work, party structures, boundaries and relevant excavation geometry. Surveyor appointments, fees and programme effects are therefore project-specific rather than triggered by one simple distance test.

Roof and glazing design can change structure, weathering, thermal design and procurement. Flat, pitched and glazed roof elements each require product- and project-specific detailing; none carries a universal £/m² rate, lifespan or “best value” ranking on this page.

Connection to the existing house can involve structural openings, changes in floor level, services and temporary works. The responsible structural professional should define any structural design needed, and the quotation should state what making good and service alterations are included.

Planning permission and permitted development are separate routes. Some house extensions can fall within permitted-development rights when every relevant Class A limitation and condition is met; other proposals require a planning application or additional consent.

Qualifying larger rear extensions can use the statutory prior-approval route, but the applicable limits, neighbour-consultation process and current application requirements should be checked for the actual proposal rather than inferred from an old fee or generic timeline.

Side, rear and wrap-around extensions can have different planning implications, and designated land, Article 4 directions, planning conditions, listed-building status or previous development can change the position. Check current planning records for the specific property before relying on permitted development.

TCM Building & Maintenance can undertake kitchen-extension building work and coordinate specialist contractors or professional disciplines where the agreed project requires them.

The current Experience Inputs Register contains no approved Borehamwood kitchen-extension case, structural opening detail, programme outcome, valuation uplift or TCM kitchen-extension cost cohort for publication. Those claims should only be added when the source, methodology, permission and page assignment are approved.

For a project-specific budget, the design, structural scope, kitchen package, glazing, services, professional/statutory costs, VAT, allowances and exclusions should be defined before quotations are compared. See the House Extension Cost Guide for the wider extension-budget framework.