Guide · 25 October 2026

Building costs and house prices in Greenwich

Royal Greenwich runs along the south bank of the Thames from Deptford Creek to Thamesmead, and back up the hill to Blackheath, Shooters Hill and Eltham. It holds some of London’s grandest Georgian and Victorian streets, a lot of interwar suburb, large council and post-war estates, and a riverside that has filled up with new flats in the past twenty years, from Greenwich Peninsula to Royal Arsenal Riverside. Which of those you live in matters more than anything else in this guide.

The Census 2021 accommodation-type table (TS044, via Nomis) shows the split. Of Greenwich’s 114,054 households, 43.1% lived in a purpose-built flat, above the London share of 40.3%, and another 6.0% in a flat in a converted or shared house (London: 11.1%). 26.7% lived in a terrace (London: 21.3%), 17.6% in a semi (London: 18.6%) and just 4.1% in a detached house (London: 6.1%). That puts about 48% of households in a house, a little above the London figure of 46%. So roughly half of Greenwich homeowners have a house that permitted development rights can apply to, and most of those houses share at least one wall.

Greenwich house prices in August 2026

The UK House Price Index from HM Land Registry and the ONS, published on 21 October 2026, covers August 2026 (provisional). It puts Greenwich’s average price at £462,868, 2.2% lower than a year earlier and 0.4% down on July. That is the same annual fall as London as a whole, where the average is £554,430, so Greenwich sits about £91,600 below the capital’s average and ranks 26th of London’s 33 local authority areas on price. Its peak was £494,314 in August 2022, and this August’s figure is about 6.4% below that. First-time buyers paid £409,131 on average, and buyers who had owned before paid £573,288.

Houses in Greenwich have held their value over the year, while flats have not: the average flat fell 3.9%, and with flats making up so much of the borough that drags the overall figure down. A Greenwich terrace averages about £100,000 less than the London terrace average and a flat about £77,000 less, but the average semi is only about £16,000 below the London semi. These are borough-wide averages from the HPI full data file and the ONS local house prices page for Greenwich. They mix a Blackheath villa with an Abbey Wood terrace, rest on a modest number of sales (Land Registry recorded 157 Greenwich sales for June 2026), will be revised, and can’t value any particular home.

Is it cheaper to move or to extend?

On August’s averages, swapping a Greenwich terrace for a semi meant finding about £166,000 more, and moving from a semi to a detached house about £297,000 more. Stepping up from a flat to a terrace, the move many Greenwich owners will be weighing, meant about £198,000. Stamp duty, legal fees, a survey and removals come on top of all of these.

No one publishes building costs for Greenwich alone, so these are national ballparks. Checkatrade’s house extension cost guide, last updated in June 2026 and checked by estimators who are members of RICS and the CIOB, gives these UK ranges, excluding VAT:

• £1,800–£3,000 per m² for a finished single-storey extension, so roughly £40,000–£56,000 for 20m² or £60,000–£84,000 for 30m²
• £30,000–£42,000 for a small (15m²) rear extension to a mid-terrace house
• £108,000–£180,000 for a 60m² two-storey extension
• £50,000–£95,000 for a 30m² loft conversion
• £100,000–£160,000 for a 40m² basement
• £8,500–£20,000 for a 15m² garage conversion

Checkatrade says its figures aren’t location-based and that builders in London and the South East usually charge more, so expect Greenwich quotes above these ranges, plus VAT. Even so, a loft or a rear extension on a terrace usually costs well under the £166,000 terrace-to-semi gap. If you own a flat, the comparison doesn’t really work: flats don’t have permitted development rights, and most extensions need the freeholder’s consent as well as planning permission, so moving is often the only realistic way to get more space. Nobody can promise what an extension will add when you sell, so treat this as a budget test rather than an investment forecast.

What you can build without planning permission

National permitted development rules, explained on the Planning Portal, usually allow a single-storey rear extension of up to 3 metres beyond the original back wall of a semi or terrace, or 4 metres for a detached house, without a planning application. Under the prior approval scheme, where the council notifies neighbours and considers their objections, those limits rise to 6 and 8 metres. A single-storey side extension can be up to 4 metres high and no wider than half the original house, and an extension of more than one storey can go back 3 metres if it stays at least 7 metres from the rear boundary. The loft conversion guidance allows up to 40 cubic metres of extra roof space on a terrace and 50 cubic metres on a semi or detached house, with nothing projecting beyond the front roof slope.

These rights don’t apply to flats or maisonettes, and they are narrower in conservation areas or where an Article 4 direction applies (see below). If you think your project qualifies, a Lawful Development Certificate from the council is the proof a future buyer’s solicitor will ask for. All extensions and loft conversions also need building regulations approval.

Greenwich’s own rules for extensions

When a project does need planning permission, Royal Greenwich decides it against the London Plan and its adopted Local Plan, the Core Strategy with Detailed Policies adopted on 30 July 2014. Its design policies ask that extensions are of a scale and design that suits both the house and the area around it.

The detail is in the Urban Design Guide, a supplementary planning document the council’s cabinet agreed to adopt on 18 October 2023, replacing the older guidance on residential extensions, basements and conversions. Officers quote it in decisions such as this 2025 report on a house in Shooters Hill, and a few points are worth knowing before you brief a designer:

• Rear extensions. They should respond to the scale of the house and the size of the garden, and a projection of about 3.6 metres is described as typically appropriate. Flat roofs are generally preferred, kept about 300mm below the sill of the first-floor window above.
• Dormers. Rear dormers are generally acceptable if they sit about 0.5 metres below the ridge, 0.5 metres in from each party wall and 0.5 metres above the eaves. Full-width box dormers are discouraged.
• Hip-to-gable and raised roofs. The council says it does not support hip-to-gable conversions when they need planning permission, and expects loft conversions to find enough headroom without raising the ridge. That matters if you own a semi or end-of-terrace with a hipped roof. Where permitted development applies the rules are different, so check which route your loft is on before you commit to a design.

A new Royal Greenwich Local Plan 2025–2040 is on its way. Its final (Regulation 19) consultation ran from 27 July to 6 September 2026, and the council’s answer to a public question at its October 2026 meeting says submission to the government for examination is due to go to Full Council on 11 November 2026, with submission before the end of the year and an examination in 2027. Until it is adopted, householder applications are decided under the 2014 plan and the Urban Design Guide, though the emerging plan can carry some weight.

Conservation areas and Article 4 directions

The council’s conservation area maps and appraisals page lists 23 conservation areas. They include Blackheath and West Greenwich (both designated in 1968), Greenwich Park, East Greenwich, the Ashburnham Triangle, Westcombe Park, Blackheath Park, Charlton Village, Eltham Palace, Eltham Green, Well Hall Pleasaunce, the Progress Estate, Shrewsbury Park Estate, Plumstead Common, Woolwich, Woolwich Common and the Royal Arsenal. Each has a map, and most have a character appraisal or management strategy that spells out what the council wants protected.

On its areas with extra planning restrictions page, the council says most of its Article 4 directions are in conservation areas and can mean you need permission to replace windows and doors or re-roof. The Ashburnham Triangle direction, confirmed in May 2014, is one example, and there is separate design guidance for East Greenwich, the Progress Estate, Rectory Field, Shrewsbury Park and West Greenwich. Check what applies to your street before you order new windows or plan a roof extension.

The council’s current and proposed Article 4 directions page also covers a borough-wide direction for houses in multiple occupation, in force since 27 September 2018. Turning a family home (use class C3) into a small HMO (C4) needs planning permission anywhere in Greenwich, and HMO licensing applies as well. So an extension designed to let rooms individually is a planning and licensing matter as well as a building one.

Basements, the river and flood risk

The Planning Portal says a new basement is likely to need planning permission, and digging close to a neighbour’s foundations brings in the party wall process. Much of Greenwich’s riverside, from Deptford Creek and the Peninsula to Charlton, Woolwich and Thamesmead, is low-lying ground protected by the Thames Barrier and river walls, while Blackheath, Shooters Hill and Eltham sit much higher. Before planning work below ground, or a large extension on a riverside plot, check your address on the government flood map for planning and ask your designer about groundwater and surface water.

Party walls

Most Greenwich houses are terraces or semis, so most extensions and lofts here touch a party wall. Cutting beams into it, building a new wall on the boundary or digging foundations within a few metres of next door can all need notice under the Party Wall etc. Act 1996, and the excavation rules can catch detached houses too. GOV.UK’s guidance explains the different notices and includes example letters. If a neighbour doesn’t agree, surveyors prepare an award that sets out how the work will be done. A conversation over the fence before the notice arrives usually saves time and fees.

Checking a builder

Be wary of anyone who knocks on the door offering work, asks for a large cash deposit or quotes a single round figure. A reputable builder will give you a written, itemised quote and a contract, tie payments to completed stages, show proof of insurance and recent jobs you can visit, and tell you who will sign off the building regulations, whether that’s the council or a registered building control approver.

You can find registered tradespeople through TrustMark, work through Citizens Advice’s checklist before building work, and report a rogue trader to your local Trading Standards office.

Figures change: get quotes before you decide

House prices here are UK HPI averages for August 2026. They are provisional and will be revised, and the September 2026 figures are due on 18 November 2026. Building costs are Checkatrade’s national figures, last updated in June 2026. They are not Greenwich quotes, and London work often costs more. Household figures come from Census 2021 (census day was 21 March 2021). Planning details come from Royal Greenwich’s pages and documents as they stood when we checked them, and the new Local Plan could change some policies once it is adopted. Check the rules for your own address, and get at least three itemised quotes based on proper drawings before you decide whether to build or move.

Sources: UK House Price Index England: August 2026 (GOV.UK); UK HPI data downloads, August 2026 (full file, Greenwich E09000011); ONS local house prices: Greenwich; Census 2021 TS044 accommodation type (Nomis); Checkatrade: house extension costs; Planning Portal: extensions; Planning Portal: loft conversions; Planning Portal: basements; Royal Greenwich: Local Plan; Royal Greenwich cabinet: adoption of the Urban Design Guide SPD (October 2023); Royal Greenwich planning report 25/3983/F, 61 Shooters Hill; Royal Greenwich: Local Plan Regulation 19 consultation; Royal Greenwich Council: public question responses (October 2026); Royal Greenwich: conservation area maps and appraisals; Royal Greenwich: areas with extra planning restrictions; Royal Greenwich: current and proposed Article 4 directions; GOV.UK flood map for planning; GOV.UK: Party Wall etc. Act guidance; TrustMark; Citizens Advice: before building work; GOV.UK: find local Trading Standards. Data checked 25 October 2026.