House extensions · Balham

— LMDEC · South & West London · Since 2014

House extensions in Balham.

A better kitchen starts with the right decisions about your house.

Rear extensions, side returns and whole-ground-floor transformations, coordinated by our director and project manager. Before pricing the build, we establish the scope with you: the planning route, structural openings, drainage, access and the rooms that need to work together.

£2M Public Liability insurance · Best of Houzz 2026 · Two-year workmanship warranty

— First check: the actual property

Balham is not one planning rulebook.

Hyde Farm Conservation Area is in Lambeth. The Heaver Estate is in Wandsworth. Start with the full address, the council’s boundary map and whether the property is a house, flat or maisonette. A garden and a private front door do not establish householder permitted development rights.

Documented examples — check the individual plot; these are not whole-street permission decisions.
Address or locality	Council record	What to check before drawing
Heaver Estate: Bedford Hill, including the groups numbered 138–166, 168–172 and 176–210	Wandsworth appraisal, section 5.9	Match the house to the conservation map and Article 4 schedule; the estate includes different building types.
Haverhill Road, Hyde Farm	Lambeth appraisal, section 2.24	Only the southern end is described as within this conservation area.
Midmoor Road, Hyde Farm	Lambeth appraisal, section 2.27	The appraisal identifies the eastern end at Radbourne Road, rather than the entire road.
A flat or maisonette anywhere in Balham	National householder guidance	Householder permitted development rights do not apply; establish the planning route and any lease or freeholder consent separately.

Sources: Heaver Estate appraisal · Hyde Farm appraisal and boundary map · Householder permitted development guidance.

— The local detail that changes the design

Hyde Farm: filling the side gap is different from extending the rear return.

Lambeth’s November 2023 appraisal, paragraphs 3.18–3.20, resists extensions behind the original rear returns. It supports single-storey side infill that is lightweight, largely glazed and set back from the return’s end. Corner properties need particular care; a successful mid-terrace solution is not automatically suitable at an exposed end.

Read the design guidance, printed pages 27–28.

Our practical starting point: ask your designer to show the existing return, the proposed setback, retained garden, neighbouring windows and rainwater route on the same drawing. Resolve these before turning a preferred kitchen layout into a structural opening.

— A route to check, not a promise of consent

Does your Balham extension need planning permission?

Confirm the lawful property type. Establish whether you are extending a house or a flat, then check previous approvals and conditions.
Check designation and the actual Article 4 direction. Conservation-area controls and Article 4 restrictions are separate checks. Read the schedule for the proposed work.
Measure against the original house. Existing additions count. Side-return and wraparound proposals must satisfy the relevant side and rear limits together.
Record the route before setting the start date. This may be a planning application, a qualifying prior-approval process, or evidence of permitted development supported by a Lawful Development Certificate.

A standard rear extension

The usual single-storey rear depth limit is 3m for an attached house or 4m for a detached house, subject to all other Class A limits and conditions. Eligible larger rear extensions use a separate prior-approval route; its 6m/8m limits do not apply in conservation areas.

A side return in a conservation area

An extension beyond an original side wall is excluded from Class A permitted development on conservation-area land. A short projection into the garden does not remove that restriction.

Sources: GOV.UK: Class A, original house and larger rear extensions · GPDO Schedule 2, Part 1.

— Heaver Estate & neighbouring streets

Read the direction, not just the words “Article 4”.

Wandsworth’s Heaver Estate appraisal records directions made on 20 June and 20 December 1996 for different property categories. Its current council summary identifies controls including street-visible alterations, roofs, porches and front-boundary works. That is a reason to inspect the specific schedule, not to assume every alteration has the same restriction.

For Wandsworth applications, check LP5 — Residential Extensions and Alterations alongside the Housing SPD and the relevant conservation appraisal. The council’s March 2026 partial review replaces six other policies; it does not replace LP5. For Lambeth properties, use its 2023 Design Guide, Part 4, alongside the local conservation guidance.

Heaver Estate controls · Appraisal, section 3.9 · Wandsworth’s adopted plan · Lambeth Design Guide.

— Construction decisions before kitchen decisions

Four details to resolve before you place orders.

1. The drain under the footprint

Locate chambers, pipe routes, depth and ownership. Thames Water says works within 3m of a public sewer or 1m of a public lateral drain are likely to need a build-over application. Planning permission does not authorise that work. Confirm the required agreement before construction, then coordinate foundations, access and drainage design.

Thames Water: build-over requirements

2. The wall opening and floor levels

Coordinate the structural design, temporary support, beam depth and finished floor build-up. A larger opening can affect headroom, kitchen elevations and the threshold to the garden. Ask for those junctions to be resolved together, rather than ordering doors from an early planning drawing.

3. Light, privacy and the roof edge

A rooflight is not a substitute for checking the effect on neighbouring rooms. Wandsworth’s Housing SPD, paragraphs 4.22–4.24, considers daylight, height, bulk and privacy. Discuss glazing, shading, rainwater falls and the boundary edge together with your designer.

Housing SPD: neighbourliness, printed pages 41–42

4. Access and life during the build

Agree how materials and waste will move through a terraced property, where they can be stored, how occupied rooms will be protected and whether a temporary kitchen is needed. Put delivery restrictions and proposed working arrangements into the programme before work starts.

— Keep the approvals separate

Planning, building control and party wall are different jobs.

Building Regulations approval is separate from planning permission. The construction package needs to address the structure, thermal performance, ventilation, drainage and applicable fire-safety requirements, with inspection stages agreed with building control.

Check the Party Wall etc. Act 1996 where the work involves a party structure, a new wall at the boundary or qualifying excavation near a neighbour. Party-structure notices normally require at least two months; relevant boundary-wall and excavation notices normally require at least one month. Written consent can avoid an award at that stage; a dispute triggers the Act’s surveyor procedure.

Ask who prepares notices and who coordinates with the appointed surveyor. Separate professional fees from the construction price and do not confuse neighbour consultation for planning with party wall consent.

Building Regulations approval · Government party wall guidance.

— Balham extension costs

Price the finished scope, not just the extra square metres.

LMDEC’s indicative extension budget is £70,000–£160,000 excluding VAT, with complex or higher-specification projects above that range. This is an initial guide, not a Balham price-per-square-metre promise. A combined extension and full refurbishment needs its own coordinated scope.

Package	What the written quotation should clarify
Groundworks & drainage	Known foundation assumptions, drain surveys, diversions, chamber changes and responsibility for approvals.
Structure & weatherproofing	Steelwork and temporary support; roof build-up, insulation, rainwater disposal and junctions with the existing house.
Kitchen, glazing & finishes	Who supplies and installs each item; specification, allowances, flooring transitions and making good.
Heating, plumbing & electrics	System capacity, proposed alterations, lighting and controls, testing and the relevant completion documentation.
Fees, VAT & contingency	Professional and statutory fees, party wall costs and VAT shown separately; a client contingency outside the agreed construction scope.

We follow up within 48 hours of our site visit to confirm the next steps. The timescale for a detailed fixed-price quotation is agreed once the drawings, specification and scope are complete. The written quotation records the agreed scope, assumptions and exclusions; changes to that scope are priced and agreed before proceeding.

— Managed by LMDEC

One point of contact. A project you can follow.

Our director and project manager coordinate the in-house team and specialist trades. Gas work is carried out by our regular Gas Safe registered subcontractors, and electrical work by our regular NICEIC registered subcontractors.

Your Client Portal brings the programme, drawings and progress photographs together. Use it to follow decisions and progress alongside your regular project communication.

£2 million Public Liability insurance and a two-year workmanship warranty. Over fifty verified five-star reviews on Google, Trustindex and Yell, and Best of Houzz 2026.

Explore house extensions across South London, compare our Wandsworth extension guide, or consider a loft conversion in Balham. For a combined project, see our full house refurbishment service.

— Common questions

Balham extensions — your questions.

Which council deals with a house extension in Balham?

Check the full address. Balham includes properties in Wandsworth and Lambeth; Hyde Farm Conservation Area is in Lambeth. The SW12 postcode or a neighbourhood name alone does not establish the planning authority or conservation-area boundary.

Can I build a side-return extension in a Balham conservation area?

A side extension to a house in a conservation area is not permitted development under Class A. That does not mean it cannot be built: it needs a planning application and a design that responds to the relevant conservation guidance.

What makes a Hyde Farm extension different?

Lambeth’s November 2023 appraisal distinguishes rear-return extensions from side infill. Its guidance supports carefully designed single-storey infill while resisting extensions to the back of the original rear returns. Check the full guidance and property boundary before developing the design.

Does planning permission cover building over a sewer?

No. Thames Water has a separate build-over process. Building within 3 metres of a public sewer or 1 metre of a public lateral drain is likely to need an application. Confirm the drain’s position, ownership and applicable route before construction.

How much does a house extension in Balham cost?

LMDEC’s indicative extension budget is £70,000–£160,000 excluding VAT, with complex or higher-specification projects above that range. It is not a fixed Balham rate. Access, structure, drainage, glazing and the kitchen specification determine the quotation; inclusions, allowances and exclusions must be written down.

Can you quote from approved drawings?

Yes. Send your full address, approved drawings, decision notice, structural information and intended finishes. Our director and project manager review the scope and coordinate the project. We follow up within 48 hours of our site visit to confirm the next steps. The timescale for a detailed fixed-price quotation is agreed once the drawings, specification and scope are complete. The quotation records the scope, assumptions and exclusions.

— Your next step

Bring the address. Bring the ideas.

Send your full address, photographs and drawings if you have them. Tell us what is missing from your current home, your preferred start date and whether your budget includes VAT, kitchen supply and professional fees.

We follow up within 48 hours of our site visit to confirm the next steps. The timescale for a detailed fixed-price quotation is agreed once the drawings, specification and scope are complete.

Discuss your Balham extension 0204 577 2001

— Sources & review

The documents behind the advice.

Prepared by LMDEC Ltd. Sources checked 2 November 2026. This guide identifies checks to make; the council records, property history and proposed design determine the route for an individual address.