Could this building become homes?

How this check works

It is a desk check from public records — no site visit, no drawings. It reads what the radar knows about a building (or measures an OpenStreetMap outline in your browser), then runs three layers. Rules version 2026-10-10.1.

1 · Fit

Five parts, each scored 0–10 and weighted: floor plate 30%, daylight 30%, height and storeys 20%, services and structure 10% and location 10%. 70 and up is band A, 50 and up band B. The method follows the published office-conversion screens — Gensler's five categories (whose own scorecards weigh windows and daylight twice their brochure weight) and the TU Delft Transformation Meter's veto and gradual criteria — adapted to what public records hold in Europe.

• Floor plate. Depth façade to façade of 10–16 m is ideal, still workable to 20 m and worth nothing at 30 m (Basel study: up to 16 m good, from 20 m special concepts; Brussels Task Force Bureaux: 17 m takes dual-aspect flats, 20 m and more does not; Banque des Territoires' 2026 guide: under 15 m; BBSR Redevelopment: post-war offices are 12–17 m). A plate of about 750 m² is best.
• Daylight. The share of each floor within 7.5 m of a façade, measured on the outline. On this page the outline is measured again on the base map: walls shared with a neighbour are not façades, and the daylit band shrinks to 2.5 × the clear height where that is less (BDA Bayern, Office to Housing).
• Height. Floor-to-floor height (official height ÷ storeys) on a scale, with 0.4 m of slab and services (BDA): below the country's minimum clear room height it is a warning, below the 2.6 m clear the market expects it is capped (the Transformation Meter), 3.3–4 m earns a bonus and taller floors none. Homes above 4 storeys need a lift, which buildings not built as offices often lack.
• Services and structure. What the building was built for, and its age where a record has it: asbestos is likely from 1930 to 1993, slabs of the 1950s–70s often fail today's fire and sound rules, from 1985 they are sound (BDA; BBSR).
• Location. Steps at 300 / 500 / 800 / 1,200 / 1,700 m to rail or metro (BDA); road noise costs points from 55 dB (the Transformation Meter wants under 50); an industrial estate counts against it.
• Flags. A listed building goes to the challenging cost tier (heritage conversions cost the most); a co-ownership has every owner to win over (Brussels); the year built, listing and land use come from the record or OpenStreetMap.

2 · Programme

It starts from the economic model's site default — shared rooms, ground-floor businesses, furnished mid-term flats — and lets the floor plate move it: a dark core becomes the building co-op's shared rooms (up to 25% of the floor), the ground floor of a building of 3 storeys and up stays commercial, what is still dark is let as storage and workspace or cut out as a light well, and the band 7.5–10 m from a façade suits small furnished flats (up to 50% of the homes) — for awkward plates the Basel study recommends small flats and serviced shared flats run by an operator. The 3D model stacks the layers from the ground up — businesses, the shared rooms both groups use, furnished flats, long-term homes — on the building's own outline; only a dark core breaks the stack. A rough check of floor areas, not a design.

3 · Money

EHC's economic model — its own engine — runs the building on today's site default for Luxembourg City: its floor area and mix, a conversion cost and a purchase price. The conversion cost starts from the country's factor and the building's fit band (the model's good / typical / challenging tiers); a replaced façade adds 20 points of new-build cost (BDA: conversions cost 60–120% of new build, the façade being the biggest item; BBSR: 22–42% of works) and a light well 5. “Works” means the bank lends and the deal balances at the site default's own money, and the homes' fee for the same flat starts at or below the market. The most the building's co-op could pay is the highest price at which it still works. Public pages show it in bands so that a named building's ceiling is not printed for everyone; signed-in members see the figure. A ground lease is modelled as a yearly ground rent on the value, with nothing paid up front. The carbon line compares the materials of a new building (about 505 kg CO₂e per m²) with the conversion's ( ULI 2025, 24 US conversions; materials only), as a range.

Timber storeys on top

Where a building stands lower than its street — measured on satellite heights of it and its neighbours — the check offers to build the missing storeys on top in serial timber, at most 3 and never past a 25 m roof or 8 storeys. It is off until you switch it on: it needs the city's consent and a structural survey, which no desk check knows. The new floor (90% of the footprint a storey, the rest set back) joins the building's: the shared rooms keep their share of all of it, and the homes go up top. It adds no land. It costs 110% of new build a m² (95–130% in the sources: the TU Darmstadt Deutschlandstudie, a Dutch top-up business case and ARGE Kiel: about what new build costs, a little more for small projects), blended with the conversion's cost by floor area; storeys that take the homes above 4 storeys need a lift, a new one about €150,000. The timber's own carbon, 200–400 kg CO₂e a m² of materials, is counted apart from what the conversion saves, the carbon the wood stores not subtracted (timber against concrete, SBUF 2018, on the new-build figure above). The price stays per m² of the building as it stands.

Tested on buildings that were converted

Does the check turn down buildings that real projects did convert? We ran the fit layer on 294 buildings in Paris that received a permit to turn them into homes (Ville de Paris — autorisations d’urbanisme with a change of use to housing (person export, 6 Oct 2026); outlines IGN BD TOPO): 65% scored A, 33% B and 2% C; their median depth is 12 m. Location, services and use are not on the permits, so those parts sat at the middle. It cannot show the reverse — that a low band is right — because nobody publishes the conversions that failed. A C is not a no; it is where cost and compromise pile up.

The rules in Luxembourg (Ville de Luxembourg)

• Minimum clear room height for homes: 2.5 m — Luxembourg has no national building code for room heights: each commune sets them in its building regulation (règlement sur les bâtisses, RBVS). Ville de Luxembourg RBVS (coordinated text 07/2018, the version the City still publishes) art. 9.1: every full storey must have a clear height under the ceiling of at least 2.50 m; art. 9.2: rooms for prolonged stay in the roof only directly above the last full storey and 2.50 m over at least two thirds of their area; art. 9.3: utility rooms 2.20 m. The national rental-fitness rules (loi et règlement grand-ducal du 20 décembre 2019, art. 11) set 2.20 m for a dwelling or room let or made available for living (attic rooms 2.00 m over two thirds) — that is the floor below which an EXISTING rented home is unfit, not a conversion standard, so it is not entered as minClearHeightExistingM: a change of use that creates homes in the City needs a building permit and the RBVS 2.50 m applies. Other communes' RBVS differ (not checked). (Ville de Luxembourg — Règlement sur les bâtisses, les voies publiques et les sites (texte coordonné 07/2018), art. 9)
• Daylight: Ville de Luxembourg RBVS art. 34.1: every room for prolonged stay needs light at a 45° angle across the whole window, light and air directly from outside through vertical windows, and a gross window opening of at least 1/8 of the room's floor area (1/10 in the roof storey); offices, workshops and shops may derogate (34.2); habitable rooms and bedrooms at least 8 m² and 2.50 m wide (34.3); no dwellings below ground (floor more than 50 cm under the adjoining ground, 34.5). Nationally (RGD 20 Dec 2019 art. 5 and 14(2)), bedrooms and living rooms in let homes need a window with a direct view outside, and each bedroom a window of at least 0.85 × 1.10 m or 0.95 × 0.95 m.
• A second escape route or stair from about 22 m — Fire rules (ITM/CGDIS prescriptions, now applied by the CGDIS): buildings are classed by the floor level of the highest usable storey above the reference level — low up to 7 m, medium over 7 m up to 22 m, high over 22 m (ITM-SST 1500.4, 19 Dec 2024). In high buildings (ITM-SST 1503.5, 19 Dec 2024: type A 22–30 m, B 30–60 m, C 60–200 m) every person on every storey must reach at least two independent regulatory escape routes (art. 8.2.3) and the building needs one or more firefighter lifts (art. 11.12.1). In medium buildings housing normally works with one protected stair plus an accessory escape (windows or balconies reachable by the fire service), the CGDIS residential guide PRV 1.2 (Feb 2026) noting that two regulatory routes avoid the need for accessory ones. CITY RULE THAT BITES FIRST: Ville de Luxembourg RBVS art. 25.2 requires one stair per 500 m² of usable floor area on each storey and no point of a habitable room more than 35 m from the nearest stair (20 m from a dead end) — so a deep office plate over 500 m² needs a second stair whatever its height.
• Affordable-housing quota: Art. 29bis (loi du 27 juin 2025): 15% / 20% / 30% (PSL priority zone) of the housing gross floor area in every new-quarter plan of 10 homes or more, ceded to the commune, the State or a public developer, with a 10% density bonus. No quota found for a conversion of a single building inside an existing quarter. The City buys all affordable homes created in its new-quarter plans and owns land in most of them (PAL 2023).
• Building permit for a change of use within the PAG (autorisation de bâtir): No national office-to-housing fast track was found. A conversion is an ordinary building permit from the mayor where the City's PAG zone admits housing: HAB-1/HAB-2 (HAB-2 also admits offices), and the mixed zones MIX-cen and MIX-c, where at least 25% of the gross floor area must be housing. Where the zone does not fit, the City reclassifies or raises density by a one-off PAG modification (MOPO), as it did for Porte de Hollerich, Villeroy & Boch and the former Luxemburger Wort site. The RBVS applies to transformations: average usable area of the new homes at least 52 m² (art. 7.3), 2.50 m clear storeys (art. 9), window opening ≥ 1/8 of floor (art. 34), one stair per 500 m² per storey (art. 25.2). City PAG approved 5 Oct 2017, modified since. (source)
• Art. 29bis loi ACDU as amended by the loi du 27 juin 2025 — affordable share in every new-quarter plan: Every PAP 'nouveau quartier' with 10 homes or more reserves 15% of the housing gross floor area for affordable homes (zones HAB/MIX from a PAG procedure begun before 18 Feb 2022), 20% (procedure begun from 18 Feb 2022) or 30% in a priority housing zone of the plan directeur sectoriel « logement »; the land or homes go free (homes at capped amounts) to the commune, else the State, else another public developer, and the plan's density rises by 10%. The PAG's dwelling-density cap no longer applies to these affordable homes. Applies to PAP NQ (new-quarter plans), not to a single building converted inside an existing quarter (PAP QE). Porte de Hollerich, Kirchberg-Kuebebierg, Kennedy Sud and Cessange are PSL priority zones, so 30%. (source)
• State capital aid for affordable rental homes (loi du 7 août 2023 relative au logement abordable): A promoteur social can receive up to 75% of the eligible costs of building or converting homes for affordable rent, if a social landlord manages them and rents follow tenants' net disposable income. Approval as promoteur social / bailleur social; tenants meet the law's eligibility and allocation criteria. Whether a housing co-operative can be approved is not stated on the ministry page (unknown). Bill 8535 (filed 2025) amends the law. (source)
• Public land on emphyteosis / surface right (City, Fonds Kirchberg): The City sells affordable homes on its own land by emphyteosis (Baulücken I–III: 75, 58 and 66 homes) and grants surface rights (Caritas, 13 intergenerational homes); the Fonds Kirchberg tenders lots to developer-architect teams on emphyteosis or surface right with capped sale prices (Réimerwee lot 20, 2021–22). Luxembourg's first housing co-op, Adhoc, was promised Fonds Kirchberg land at Réimerwee for 35 homes, then sent to a public tender in June 2020. Allocation by call or negotiation; no co-op-specific procedure exists. The City stated in 2023 that it had no experience with housing co-operatives and was studying them for Porte de Hollerich and Wunnquartier Stade. (source)

What it cannot tell you

The façade, the structure, pollutants, heritage listing, whether the owner would sell, and what a planning office will accept. It is a first sort, to decide which buildings deserve a feasibility study — not the study.