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Bromley, London

SAP calculations in Bromley

SAP calculations in Bromley prove that an extension or a new home meets the energy rules, and in a borough this large and varied the right route depends on the site. Fixed quote after a free constraints check, VAT included.

Fixed quote after a free constraints check

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  • Fixed fees, VAT included

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    Architectural model of a four-storey London stucco townhouse in its terrace, with a portico, area railings, sash windows, a cornice and chimney stacks
    The house as it stands: four storeys over a lower ground floor.Existing Proposed worksAn illustrative model, built for this page.

    How we work on sap calculations

    Five steps from first call to approval.

    The same model cut through the middle: every floor, the stair, the chimney breasts, the new mansard, rear extension and basement in section
    Section through the model: every floor on one datum.

    1. Enquiry and constraints check

      We check the property against conservation areas, listed status, Article 4 directions, tree preservation orders, flood zone and planning history. We choose the right route and send a fixed quote.

    2. Measured survey

      We survey the house on one datum: rooms, levels, boundaries, drains, trees and the neighbours' windows that the 45° and 25° tests depend on.

    3. Independent check

      A second chartered technologist checks every sheet against the council's validation checklist and the policy. A senior review signs it off before anything is submitted.

    4. Building regulations

      Technical drawings are coordinated with the structural engineer's calculations, the drainage and the planning conditions.

    5. Approval and hand-over

      Building control approval, then a next-steps pack covering the commencement notice, party wall timing and CIL.

    Free redraws until approval. Every drawing set is checked independently, and the checker is never the person who drew it.

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    Pencil resting on a dimensioned technical drawing beside a scale rule

    SAP calculations in Bromley across town and Green Belt

    Bromley covers a great deal of ground, and the planning context changes street by street. Half of the borough, 51 per cent of its area, is Green Belt, and there are 47 conservation areas. A SAP calculation is the same national method everywhere, but what it has to accommodate is not.

    The council's design guidance is the Urban Design Guide SPD, supporting the Bromley Local Plan. On Green Belt land, extensions are judged against openness, which tends to keep them modest, and a modest building usually has a low ratio of glass to floor area, easing the energy question.

    In the built-up suburbs, the opposite applies. Domestic gardens make up 23.4 per cent of the borough's land, and long plots can take deep rear extensions with the large glass walls those invite. The energy route then needs real thought, because the glazing cap is quickly reached and the roof has to do more of the work.

    Red-brick English house with rows of solar panels on its tiled roof

    Local figures for Bromley

    Figures with their unit, period and source
    MeasureValuePeriodSource
    Green Belt share of the council area51 % of council area covered by green-belt polygons—planning.data.gov.uk
    Conservation areas47 named conservation areas published by the council—planning.data.gov.uk
    Article 4 directions108 Article 4 directions published by the council—planning.data.gov.uk
    Listed building entries412 list entries (Historic England, within the LPA boundary)—planning.data.gov.uk
    Householder applications granted78.6 %1 July 2025 - 30 June 2026assets.publishing.service.gov.uk
    Householder appeals allowed37.6 % of householder appeals alloweddecision dates 1 Jul 2021 to 30 Jun 2026assets.publishing.service.gov.uk
    Domestic gardens share of land (GLUD 2005)23.4 % of land that is domestic garden (GLUD 2005)2005data.london.gov.uk
    Approved Document L Vol 1 2021 incl. 2023 amendments, Table 4.2New elements in existing dwellings, limiting U-values W/(m²·K): roof 0.15, wall 0.18, floor 0.18, windows 1.4 (or WER Band B), doors 1.4—gov.uk
    Approved Document L Vol 1 2021, para 10.7(d)Windows, roof windows, rooflights and doors in an extension should not exceed 25% of the extension floor area plus the area of openings removed or covered—gov.uk

    A blank value means the figure has not been published, not that there are none. Check your own address with the council.

    Councils bordering Bromley
    Building regulations, layer by layerPart A: structure: Approved Document A: Structure, 2004 edition incorporating 2004, 2010 and 2013 amendments. Part B: fire safety: All dwellings: fire detection and alarm system minimum Grade D2 Category LD3 (BS 5839-6), mains-operated smoke alarms to BS EN 14604. Part L: insulation: New elements in existing dwellings, limiting U-values W/(m²·K): roof 0.15, wall 0.18, floor 0.18, windows 1.4 (or WER Band B), doors 1.4. Part K: stairs: 2.0 m clear headroom over stairs. Full plans application: Building control body must decide a full plans application within 5 weeks, or longer if agreed in writingPart A: structurePart B: fire safetyPart L: insulationPart K: stairsFull plans applicationABCDE

    Building regulations, layer by layer

    The Approved Documents that shape most house projects, from structure to the application itself.

    A · Part A: structure
    Approved Document A: Structure, 2004 edition incorporating 2004, 2010 and 2013 amendments
    B · Part B: fire safety
    All dwellings: fire detection and alarm system minimum Grade D2 Category LD3 (BS 5839-6), mains-operated smoke alarms to BS EN 14604
    C · Part L: insulation
    New elements in existing dwellings, limiting U-values W/(m²·K): roof 0.15, wall 0.18, floor 0.18, windows 1.4 (or WER Band B), doors 1.4
    D · Part K: stairs
    2.0 m clear headroom over stairs
    E · Full plans application
    Building control body must decide a full plans application within 5 weeks, or longer if agreed in writing

    Meeting the limits on a Bromley extension

    The starting point is the elemental table: New elements in existing dwellings, limiting U-values W/(m²·K): roof 0.15, wall 0.18, floor 0.18, windows 1.4 (or WER Band B), doors 1.4. We specify wall, roof and floor build-ups that meet it, and show the thickness on the sections.

    Glazing is capped on this route: Windows, roof windows, rooflights and doors in an extension should not exceed 25% of the extension floor area plus the area of openings removed or covered. Bromley's larger detached and semi-detached houses often receive extensions with generous glass, and the cap is quickly reached.

    The alternatives are laid out as: Alternative routes: area-weighted U-value (para 10.9) or a SAP calculation against a notional extension (para 10.10). We usually propose the area-weighted route when only one element falls short, and SAP when the design is glass-led.

    Heritage, Article 4 and appeals in Bromley

    The borough has 108 Article 4 directions, plus 412 listed building entries. Where permitted development is removed, a window or door replacement can need an application of its own, and energy upgrades must be planned around that.

    Bromley decided 1,609 householder applications in its latest year, granting 78.6 per cent, with 89.1 per cent in time. At appeal, 37.6 per cent of 502 decided householder cases were allowed over five years.

    Those figures call for a well-prepared submission, with the heritage and energy decisions made together rather than one after the other, because a window changed late for energy reasons can undo a consent already won. Our planning drawings in Bromley set out the route, and a lawful development certificate in Bromley can settle permitted development where it applies.

    New homes, plots and the rule dates

    Newly built homes are assessed on a different footing from extensions. The guidance says: For new dwellings AD L 2026 names two methods: the Home Energy Model (HEM) and SAP; validity dates are in the Notice of Approval. Which edition applies depends on dates: AD L 2026 takes effect 24 Mar 2027 (24 Sep 2027 for higher-risk building work).

    The transition arrangement is: AD L/F 2021 continue where plans/notices are deposited before 24 Mar 2027 and work starts before 24 Mar 2028. For a replacement house on a larger Bromley plot we set both dates out at the first meeting, so the assessor works to the right edition from the start.

    A new home is also subject to overheating rules: Approved Document O (overheating) applies to new residential buildings. On a south-facing plot with large windows, that shapes the shading and the openable areas.

    What it costs and how it fits with the rest

    The price is a fixed quote after a free constraints check, VAT included, agreed before work begins, with no hourly meter running. The assessor uses our model, so the dimensions match your drawings, and the output feeds the submission covered in building regulations drawings in Bromley.

    The borough's levy schedule is the Bromley Community Infrastructure Levy charging schedule, with a residential rate of £120.12/m² (Residential development excluding residential development which delivers additional care and support services). We note the added floor area on the drawings, which helps you plan the levy.

    Average prices in the borough are £511,670. See architectural drawings in Bromley for the full range of drawings we prepare locally.

    What you receive

    Building regulations section drawing showing the construction build-up
    Sample drawing. Building regulations section showing construction build-up for a building control check.
    House extension under construction with scaffolding, new glazed doors and building materials
    Energy in
    Move the pointer up — the plug rises toward the socket.

    Other services in Bromley

    SAP calculations nearby

    Questions

    Does the Green Belt change the energy rules in Bromley?

    No. The energy rules are national. Green Belt policy limits the size of extensions, which can keep glazing modest.

    Which Bromley guide covers design?

    The Urban Design Guide SPD, under the Bromley Local Plan.

    What are the U-value limits for an extension?

    They are: New elements in existing dwellings, limiting U-values W/(m²·K): roof 0.15, wall 0.18, floor 0.18, windows 1.4 (or WER Band B), doors 1.4.

    How much does it cost?

    Fixed quote after a free constraints check, VAT included.

    Sources and dates

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    Tell us about your property.

    We check the constraints, then send a fixed fee. Messages before 3pm get a reply the same working day.

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