{ "name": "basementexcavationcost.co.uk UK Basement Price Index", "title": "UK Basement Price Index", "url": "https://basementexcavationcost.co.uk/datasets/uk-basement-price-index/", "csv": "https://basementexcavationcost.co.uk/datasets/uk-basement-price-index.csv", "markdown": "https://basementexcavationcost.co.uk/datasets/uk-basement-price-index/index.md", "computed_at": "2026-09-26", "license": "https://basementexcavationcost.co.uk/terms", "headline": "The median published figure in the UK Basement Price Index is 2,800 GBP across 13 figures from 10 sources' own pages (range 1,000 to 7,200 GBP), read 26 September 2026.", "quotes": [ "The median published figure in the UK Basement Price Index is 2,800 GBP across 13 figures from 10 sources' own pages (range 1,000 to 7,200 GBP), read 26 September 2026.", "10 of the 33 named sources read in full publish a figure; 23 publish none, read 26 September 2026.", "UK Basement Price Index, job type convert an existing cellar: median 1,140 GBP across 4 sources, read 26 September 2026.", "UK Basement Price Index, job type excavate a new basement: median 3,000 GBP across 9 sources, read 26 September 2026.", "The median is unchanged since 25 September 2026 (was 2,800 GBP across 13)." ], "citation": "\"basementexcavationcost.co.uk UK Basement Price Index\", updated 2026-09-26, https://basementexcavationcost.co.uk/datasets/uk-basement-price-index/.", "changed_since": { "since": "2026-09-25", "previous_median": 2800, "delta": 0, "direction": "unchanged", "sentence": "The median is unchanged since 25 September 2026 (was 2,800 GBP across 13)." }, "national": { "unit": "GBP", "n": 13, "median": 2800, "min": 1000, "max": 7200, "p25": 1350, "p75": 4000, "mean": 2971.5385, "units": { "GBP": 13 }, "published_sources": 10, "named_sources": 37, "read_sources": 33, "not_published": 23, "published_share": 0.303 }, "by_axis": { "job type": { "convert an existing cellar": { "GBP": { "n": 4, "median": 1140, "min": 1000, "max": 2800, "p25": 1020, "p75": 2400, "mean": 1520 } }, "excavate a new basement": { "GBP": { "n": 9, "median": 3000, "min": 1500, "max": 7200, "p25": 2500, "p75": 4675, "mean": 3616.6667 } } } }, "rows": [ { "source": "LCCL Construction basement conversion London", "url": "https://www.lcclconstruction.co.uk/post/basement-conversion-london-2026", "figure": "£2,800 ", "value": 2800, "unit": "GBP", "vat": null, "axis": { "job type": "convert an existing cellar" }, "retrieved_at": "2026-09-11", "quote": "Basement conversion costs in London typically range from £2,800 to £5,500 per square metre — significantly more per square metre than a rear or side extension because of the excavation, underpinning, waterproofing and structural complexity involved.", "source_class": "primary-provider-own-site", "text_sha256": "617c2336d717783bae6332085a52d2a06e43b1370093a23b6811686a30417470" }, { "source": "ALTER Architects basement cost guide", "url": "https://alterarchitects.co.uk/basement-conversion-cost-uk-what-to-expect-in-2025-architects-guide", "figure": "£2,500", "value": 2500, "unit": "GBP", "vat": null, "axis": { "job type": "excavate a new basement" }, "retrieved_at": "2026-09-11", "quote": "Central London:** £2,500-£4,000/m²", "source_class": "primary-provider-own-site", "text_sha256": "3fb5001f62b781acaedac95606d9d1b6179f1efbc7aedf9aedaee198bcb7b76e" }, { "source": "EMA Structures basement and underpinning cost", "url": "https://emastructures.com/blog/basement-underpinning-cost-london/", "figure": "£3,500 ", "value": 3500, "unit": "GBP", "vat": null, "axis": { "job type": "excavate a new basement" }, "retrieved_at": "2026-09-11", "quote": "Basement construction Labour and materials, excavation up to about 3.5 m deep, basements up to around 50 m² ~£3,500 per m² Basement construction, smaller footprint Below roughly 50 m², the fixed costs of set-up, propping and waterproofing spread over less area ~£4,200 per m²", "source_class": "primary-provider-own-site", "text_sha256": "4f57b85c191e8c4aef7795ee68532f861d39a181833906968ebe5232b41ba3ae" }, { "source": "Beams basement and cellar conversion cost", "url": "https://beamsrenovation.com/blog/how-much-does-a-basement-conversion-cost-in-the-uk", "figure": "£1,080 ", "value": 1080, "unit": "GBP", "vat": null, "axis": { "job type": "convert an existing cellar" }, "retrieved_at": "2026-09-11", "quote": "Planning and budgetingBasement conversionsCosts Converting a cellar you already have costs £1,080 to £1,680 per square metre including VAT, or around £32,400 to £50,400 for a 30 square metre cellar.", "source_class": "primary-provider-own-site", "text_sha256": "19213791904ff2a91b77d6a24186d271b9f4b467f641e141def061e3dac679d3" }, { "source": "Beams basement and cellar conversion cost", "url": "https://beamsrenovation.com/blog/how-much-does-a-basement-conversion-cost-in-the-uk", "figure": "£7,200 ", "value": 7200, "unit": "GBP", "vat": null, "axis": { "job type": "excavate a new basement" }, "retrieved_at": "2026-09-11", "quote": "Digging a new basement under a London house is a different order of project: £7,200 to £12,000 per square metre including VAT, which is £288,000 to £480,000 for 40 square metres.", "source_class": "primary-provider-own-site", "text_sha256": "19213791904ff2a91b77d6a24186d271b9f4b467f641e141def061e3dac679d3" }, { "source": "Harper Latter Architects basement cost guide", "url": "https://www.harperlatterarchitects.co.uk/post/uk-cost-of-a-basement-conversion-essential-guide-2024", "figure": "£3,000 ", "value": 3000, "unit": "GBP", "vat": null, "axis": { "job type": "excavate a new basement" }, "retrieved_at": "2026-09-11", "quote": "A new excavation, however, starts at a much higher price point—often from £3,000 per square metre and climbing steeply based on the project's complexity and your location.", "source_class": "primary-provider-own-site", "text_sha256": "955c5500cd20029655c9e8960d5d0314d69adacd43e579747bed2a68d35d1f42" }, { "source": "Rise Design Studio London basement costs", "url": "https://www.risedesignstudio.co.uk/blog/building-down-to-rise-up-understanding-basement-costs-in-london-2025", "figure": "£4,850 ", "value": 4850, "unit": "GBP", "vat": null, "axis": { "job type": "excavate a new basement" }, "retrieved_at": "2026-09-11", "quote": "As a 2025 benchmark, basement construction in London starts around £4,850 per m² plus VAT, and rises to about £8,400 per m² plus VAT on more complex or high-spec sites.", "source_class": "primary-provider-own-site", "text_sha256": "51f337a33b954c9e576df1cd3ea10e7ba2e4140b7db51885e81e0d79b0d4527d" }, { "source": "The Premier Loft Company basement conversions", "url": "https://www.thepremierloftcompany.co.uk/basement-conversions/", "figure": "£2,500", "value": 2500, "unit": "GBP", "vat": null, "axis": { "job type": "excavate a new basement" }, "retrieved_at": "2026-09-11", "quote": "constructing a subterranean storey from scratch): even without waterproofing, will cost around £2,500/m2.", "source_class": "primary-provider-own-site", "text_sha256": "92feb068b90d0d234bbecc00d7ddb9c3f47cf96eeb6e57e61f5b0289fcbb47e5" }, { "source": "HXL Construction London basement costs", "url": "https://hxlbuild.co.uk/journal/london-basement-construction-costs", "figure": "£4,500 ", "value": 4500, "unit": "GBP", "vat": null, "axis": { "job type": "excavate a new basement" }, "retrieved_at": "2026-09-11", "quote": "For a single-storey basement under the existing footprint of a Victorian or Edwardian terrace, 2026 all-in build costs run from £4,500 to £7,500 per square metre of net usable basement area.", "source_class": "primary-provider-own-site", "text_sha256": "f187f6440f1e4c1fbd749a15c93edb8e7a4ec26075d9ec47b0eb45fda09e0132" }, { "source": "HouseUp basement conversion cost", "url": "https://www.houseup.co.uk/news/basement-conversion-cost", "figure": "£1200 ", "value": 1200, "unit": "GBP", "vat": null, "axis": { "job type": "convert an existing cellar" }, "retrieved_at": "2026-09-11", "quote": "When considering a basement conversion, one of the first questions that comes to mind is, “How much will it cost per square metre?” For converting an existing cellar, you can expect prices to range from £1200 to £2,250 per square metre.", "source_class": "secondary", "text_sha256": "2f7871e2b95acecc43f751e25792da33e154a0cc8a812c9cd5650a5446905a6a" }, { "source": "HouseUp basement conversion cost", "url": "https://www.houseup.co.uk/news/basement-conversion-cost", "figure": "£3,000 ", "value": 3000, "unit": "GBP", "vat": null, "axis": { "job type": "excavate a new basement" }, "retrieved_at": "2026-09-11", "quote": "On the other hand, creating a new basement space from scratch is a more intensive and costly endeavor, with prices ranging from £3,000 to £4,650 per square metre.", "source_class": "secondary", "text_sha256": "2f7871e2b95acecc43f751e25792da33e154a0cc8a812c9cd5650a5446905a6a" }, { "source": "Refurbb basement conversion cost", "url": "https://refurbb.co.uk/household/basement-conversion-cost/", "figure": "£1,000 ", "value": 1000, "unit": "GBP", "vat": null, "axis": { "job type": "convert an existing cellar" }, "retrieved_at": "2026-09-11", "quote": "UK average basement conversion prices range from £1,000 to £1,800 per square metre for the conversion work (excluding excavations), but so much depends on the age of the property.", "source_class": "secondary", "text_sha256": "fde427545bfb6bb4dc414d5760c3043c8941fb85a91ae2975705c8a41b1ddc12" }, { "source": "Refurbb basement conversion cost", "url": "https://refurbb.co.uk/household/basement-conversion-cost/", "figure": "£1,500 ", "value": 1500, "unit": "GBP", "vat": null, "axis": { "job type": "excavate a new basement" }, "retrieved_at": "2026-09-11", "quote": "Digging new basement spaces – usually between £1,500 and £3,000 per square metre, including labour and equipment hire.", "source_class": "secondary", "text_sha256": "fde427545bfb6bb4dc414d5760c3043c8941fb85a91ae2975705c8a41b1ddc12" } ], "not_published": [ { "source": "Architecture for London basement costs", "url": "https://architectureforlondon.com/news/basement-costs-in-london/", "retrieved_at": "2026-09-11", "reason": "every candidate on the page was refused" }, { "source": "LCCL Construction basement cost London 2026", "url": "https://www.lcclconstruction.co.uk/post/basement-conversion-cost-london-2026", "retrieved_at": "2026-09-11", "reason": "every candidate on the page was refused" }, { "source": "The Page basement conversion cost London", "url": "https://www.the-page.co.uk/blog/how-much-a-basement-conversion-costs-in-london/", "retrieved_at": "2026-09-11", "reason": "every candidate on the page was refused" }, { "source": "NU Projects basement costs London", "url": "https://www.nuprojects.co/single-post/basement-costs-london-nu-projects", "retrieved_at": "2026-09-11", "reason": "read in full and no accepted figure on the page" }, { "source": "Berati Construction basement cost London", "url": "https://www.beraticonstruction.co.uk/post/basement-cost-london-2026-guide", "retrieved_at": "2026-09-11", "reason": "every candidate on the page was refused" }, { "source": "Myrmex Group basement cost per square foot", "url": "https://myrmexgroup.co.uk/journal/basement-cost-per-square-foot-london", "retrieved_at": "2026-09-11", "reason": "every candidate on the page was refused" }, { "source": "Dry Basements UK conversion cost", "url": "https://drybasements.uk/blog/basement-conversion-cost-uk-2026.html", "retrieved_at": "2026-09-11", "reason": "every candidate on the page was refused" }, { "source": "Space Conversions basement conversions (Manchester)", "url": "https://www.spaceconversions.co.uk/basement-conversions", "retrieved_at": "2026-09-11", "reason": "every candidate on the page was refused" }, { "source": "Basements North West cost FAQ", "url": "https://basementsnorthwest.co.uk/faqs/how-much-does-a-basement-conversion-cost-in-the-uk/", "retrieved_at": "2026-09-11", "reason": "read in full and no accepted figure on the page" }, { "source": "Up and Under basement conversions Manchester", "url": "https://www.upandunda.co.uk/basement-conversions-manchester/", "retrieved_at": "2026-09-11", "reason": "read in full and no accepted figure on the page" }, { "source": "MyJobQuote basement conversion cost guide", "url": "https://www.myjobquote.co.uk/costs/basement-conversion", "retrieved_at": "2026-09-11", "reason": "every candidate on the page was refused" }, { "source": "PriceYourJob basement cost guide", "url": "https://www.priceyourjob.co.uk/convert-basement-cost/", "retrieved_at": "2026-09-11", "reason": "every candidate on the page was refused" }, { "source": "HomeHow basement conversion costs", "url": "https://www.homehow.co.uk/costs/basement-conversion", "retrieved_at": "2026-09-11", "reason": "every candidate on the page was refused" }, { "source": "BuildSafe basement conversion costs", "url": "https://buildsafe.co.uk/basement-conversion-costs/", "retrieved_at": "2026-09-11", "reason": "every candidate on the page was refused" }, { "source": "Homebuilding & Renovating basement costs", "url": "https://www.homebuilding.co.uk/advice/basement-conversion-costs", "retrieved_at": "2026-09-11", "reason": "every candidate on the page was refused" }, { "source": "MyBuilder excavation price guide", "url": "https://www.mybuilder.com/groundwork-foundations/price-guides/excavation-cost", "retrieved_at": "2026-09-11", "reason": "every candidate on the page was refused" }, { "source": "BookaBuilder basement conversion cost", "url": "https://www.bookabuilderuk.com/blog/basement-conversion-cost-2026", "retrieved_at": "2026-09-11", "reason": "every candidate on the page was refused" }, { "source": "Bark cellar and basement conversion", "url": "https://www.bark.com/en/gb/cellar-basement-conversion/", "retrieved_at": "2026-09-11", "reason": "every candidate on the page was refused" }, { "source": "TrustBuilt Projects basement conversion cost London", "url": "https://trustbuiltprojects.com/blog/basement-conversion-cost-london/", "retrieved_at": "2026-09-11", "reason": "every candidate on the page was refused" }, { "source": "NU Projects the real cost of a London basement", "url": "https://www.nuprojects.co/single-post/the-real-cost-of-a-london-basement-what-homeowners-need-to-know-before-starting", "retrieved_at": "2026-09-11", "reason": "every candidate on the page was refused" }, { "source": "LABS cellar conversion cost (Sheffield)", "url": "https://l-a-b-s.co.uk/cellar-conversion-cost/", "retrieved_at": "2026-09-11", "reason": "every candidate on the page was refused" }, { "source": "MyBuilder cost to build a basement", "url": "https://www.mybuilder.com/extensions/price-guides/cost-to-build-a-basement", "retrieved_at": "2026-09-11", "reason": "every candidate on the page was refused" }, { "source": "MyBuilder basement conversion price guide", "url": "https://www.mybuilder.com/conversions/price-guides/basement-conversion-cost", "retrieved_at": "2026-09-11", "reason": "every candidate on the page was refused" } ], "sources": [ { "url": "https://architectureforlondon.com/news/basement-costs-in-london/", "label": "Architecture for London basement costs", "license": "the publisher's own terms; quoted for reporting and comment" }, { "url": "https://www.lcclconstruction.co.uk/post/basement-conversion-cost-london-2026", "label": "LCCL Construction basement cost London 2026", "license": "the publisher's own terms; quoted for reporting and comment" }, { "url": "https://www.lcclconstruction.co.uk/post/basement-conversion-london-2026", "label": "LCCL Construction basement conversion London", "license": "the publisher's own terms; quoted for reporting and comment" }, { "url": "https://alterarchitects.co.uk/basement-conversion-cost-uk-what-to-expect-in-2025-architects-guide", "label": "ALTER Architects basement cost guide", "license": "the publisher's own terms; quoted for reporting and comment" }, { "url": "https://emastructures.com/blog/basement-underpinning-cost-london/", "label": "EMA Structures basement and underpinning cost", "license": "the publisher's own terms; quoted for reporting and comment" }, { "url": "https://beamsrenovation.com/blog/how-much-does-a-basement-conversion-cost-in-the-uk", "label": "Beams basement and cellar conversion cost", "license": "the publisher's own terms; quoted for reporting and comment" }, { "url": "https://www.the-page.co.uk/blog/how-much-a-basement-conversion-costs-in-london/", "label": "The Page basement conversion cost London", "license": "the publisher's own terms; quoted for reporting and comment" }, { "url": "https://www.harperlatterarchitects.co.uk/post/uk-cost-of-a-basement-conversion-essential-guide-2024", "label": "Harper Latter Architects basement cost guide", "license": "the publisher's own terms; quoted for reporting and comment" }, { "url": "https://www.risedesignstudio.co.uk/blog/building-down-to-rise-up-understanding-basement-costs-in-london-2025", "label": "Rise Design Studio London basement costs", "license": "the publisher's own terms; quoted for reporting and comment" }, { "url": "https://www.nuprojects.co/single-post/basement-costs-london-nu-projects", "label": "NU Projects basement costs London", "license": "the publisher's own terms; quoted for reporting and comment" }, { "url": "https://www.beraticonstruction.co.uk/post/basement-cost-london-2026-guide", "label": "Berati Construction basement cost London", "license": "the publisher's own terms; quoted for reporting and comment" }, { "url": "https://myrmexgroup.co.uk/journal/basement-cost-per-square-foot-london", "label": "Myrmex Group basement cost per square foot", "license": "the publisher's own terms; quoted for reporting and comment" }, { "url": "https://www.thepremierloftcompany.co.uk/basement-conversions/", "label": "The Premier Loft Company basement conversions", "license": "the publisher's own terms; quoted for reporting and comment" }, { "url": "https://drybasements.uk/blog/basement-conversion-cost-uk-2026.html", "label": "Dry Basements UK conversion cost", "license": "the publisher's own terms; quoted for reporting and comment" }, { "url": "https://www.spaceconversions.co.uk/basement-conversions", "label": "Space Conversions basement conversions (Manchester)", "license": "the publisher's own terms; quoted for reporting and comment" }, { "url": "https://basementsnorthwest.co.uk/faqs/how-much-does-a-basement-conversion-cost-in-the-uk/", "label": "Basements North West cost FAQ", "license": "the publisher's own terms; quoted for reporting and comment" }, { "url": "https://www.upandunda.co.uk/basement-conversions-manchester/", "label": "Up and Under basement conversions Manchester", "license": "the publisher's own terms; quoted for reporting and comment" }, { "url": "https://hxlbuild.co.uk/journal/london-basement-construction-costs", "label": "HXL Construction London basement costs", "license": "the publisher's own terms; quoted for reporting and comment" }, { "url": "https://www.mjrooney.co.uk/basehub/cost-to-build-a-basement-london", "label": "MJ Rooney basement cost London", "license": "the publisher's own terms; quoted for reporting and comment" }, { "url": "https://www.myjobquote.co.uk/costs/basement-conversion", "label": "MyJobQuote basement conversion cost guide", "license": "the publisher's own terms; quoted for reporting and comment" }, { "url": "https://www.priceyourjob.co.uk/convert-basement-cost/", "label": "PriceYourJob basement cost guide", "license": "the publisher's own terms; quoted for reporting and comment" }, { "url": "https://www.homehow.co.uk/costs/basement-conversion", "label": "HomeHow basement conversion costs", "license": "the publisher's own terms; quoted for reporting and comment" }, { "url": "https://www.houseup.co.uk/news/basement-conversion-cost", "label": "HouseUp basement conversion cost", "license": "the publisher's own terms; quoted for reporting and comment" }, { "url": "https://refurbb.co.uk/household/basement-conversion-cost/", "label": "Refurbb basement conversion cost", "license": "the publisher's own terms; quoted for reporting and comment" }, { "url": "https://buildsafe.co.uk/basement-conversion-costs/", "label": "BuildSafe basement conversion costs", "license": "the publisher's own terms; quoted for reporting and comment" }, { "url": "https://www.homebuilding.co.uk/advice/basement-conversion-costs", "label": "Homebuilding & Renovating basement costs", "license": "the publisher's own terms; quoted for reporting and comment" }, { "url": "https://www.mybuilder.com/groundwork-foundations/price-guides/excavation-cost", "label": "MyBuilder excavation price guide", "license": "the publisher's own terms; quoted for reporting and comment" }, { "url": "https://www.bookabuilderuk.com/blog/basement-conversion-cost-2026", "label": "BookaBuilder basement conversion cost", "license": "the publisher's own terms; quoted for reporting and comment" }, { "url": "https://www.bark.com/en/gb/cellar-basement-conversion/", "label": "Bark cellar and basement conversion", "license": "the publisher's own terms; quoted for reporting and comment" }, { "url": "https://www.checkatrade.com/blog/cost-guides/cost-build-basement/", "label": "Checkatrade cost to build a basement", "license": "the publisher's own terms; quoted for reporting and comment" }, { "url": "https://www.hamuch.com/cost/basement-conversion", "label": "Hamuch basement conversion costs by town", "license": "the publisher's own terms; quoted for reporting and comment" }, { "url": "https://trustbuiltprojects.com/blog/basement-conversion-cost-london/", "label": "TrustBuilt Projects basement conversion cost London", "license": "the publisher's own terms; quoted for reporting and comment" }, { "url": "https://www.nuprojects.co/single-post/the-real-cost-of-a-london-basement-what-homeowners-need-to-know-before-starting", "label": "NU Projects the real cost of a London basement", "license": "the publisher's own terms; quoted for reporting and comment" }, { "url": "https://l-a-b-s.co.uk/cellar-conversion-cost/", "label": "LABS cellar conversion cost (Sheffield)", "license": "the publisher's own terms; quoted for reporting and comment" }, { "url": "https://www.mybuilder.com/extensions/price-guides/cost-to-build-a-basement", "label": "MyBuilder cost to build a basement", "license": "the publisher's own terms; quoted for reporting and comment" }, { "url": "https://www.mybuilder.com/conversions/price-guides/basement-conversion-cost", "label": "MyBuilder basement conversion price guide", "license": "the publisher's own terms; quoted for reporting and comment" }, { "url": "https://www.google.com/search?q=basement+conversion+cost+per+square+metre+uk", "label": "the UK basement contractor universe", "license": "the publisher's own terms; quoted for reporting and comment" } ], "methodology": "Every row is a verbatim sentence read from the named source's own page through the estate's fetch service on the date shown, hash-pinned to the stored read (the sha of the page's visible text; the raw page is mirrored to R2). 10 of the 33 named sources that could be read published a usable figure; 23 published none and are recorded as not published, never filled in; 4 could not be read (blocked, dead or unreachable) and count nowhere. The headline figures (median, minimum, maximum, quartiles) are over ONE figure per source in GBP (a source's median where its page yielded several accepted sentences), so N counts sources, never sentences; 256 candidate sentence(s) were refused by a reviewer with the reason recorded. Derivation as chartered: the median, minimum and maximum PUBLISHED £/m2 across every contractor, architect and engineer that states one, split three ways by job type - convert an existing cellar, underpin and lower an existing cellar, excavate a new basement - and by region; the London-to-North spread as a measured ratio rather than an assertion; the share of firms that publish any figure at all against the share that are quote-only; each figure normalised to a single date with the ONS construction output price index so a 2025 quote and a 2026 quote can be compared; changed-since the previous read", "embed": "

2,800 GBP

median published figure, UK Basement Price Index, across 10 sources, read 26 September 2026

Source: basementexcavationcost.co.uk UK Basement Price Index
" }