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Brent, London

SAP calculations in Brent

SAP calculations in Brent give building control the energy evidence for an extension, a conversion or a new home, prepared from your own drawings. We quote a fixed price after a free constraints check, VAT included.

Fixed quote after a free constraints check

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We use it to check conservation areas and constraints.
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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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    Red-brick English house with rows of solar panels on its tiled roof

    SAP calculations in Brent: three council documents to reconcile

    Brent publishes several design documents, and an energy calculation has to sit comfortably beside all of them. For house alterations the first document is the Residential Extensions and Alterations Supplementary Planning Document; for lower-ground work it is the Basement Supplementary Planning Document; and for the overall look of a scheme it is the Brent Design Guide Supplementary Planning Document (SPD1). All of them sit under the Brent Local Plan 2019-2041.

    Each document shapes the building envelope, and the envelope is what a SAP calculation measures. A basement adds a floor against the ground, a loft adds a roof, and a rear extension adds walls and glass. We take the dimensions that the guidance allows and test them against the energy limits before the layout is fixed.

    Conversions bring a fourth document, the Houses in Multiple Occupation SPD. A house turned into several units needs sound, fire and energy treatment between them, and the assessment has to cover each new dwelling separately.

    House extension under construction with scaffolding, new glazed doors and building materials

    Local figures for Brent

    Figures with their unit, period and source
    MeasureValuePeriodSource
    Article 4 directions39 Article 4 directions published by the council—planning.data.gov.uk
    Article 4 direction areas162 Article 4 direction area polygons published by the council—planning.data.gov.uk
    Conservation areas23 named conservation areas published by the council—planning.data.gov.uk
    Tree preservation orders1,229 tree preservation orders published by the council—planning.data.gov.uk
    Listed building entries93 list entries (Historic England, within the LPA boundary)—planning.data.gov.uk
    Larger home extension prior approvals refused79 decisions2025 Q2 to 2026 Q1 (1 Apr 2025 to 31 Mar 2026)assets.publishing.service.gov.uk
    Domestic gardens share of land (GLUD 2005)30.3 % 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 Brent
    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

    Energy limits for extensions in Brent

    For new elements in an existing house the elemental limits 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. A well-built cavity wall extension with sensible windows can reach them without a calculation.

    The glass cap applies as well: 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. On a narrow terrace plot the temptation is to glaze the whole back wall to bring in light. That is where we run the numbers early.

    The alternative routes are: Alternative routes: area-weighted U-value (para 10.9) or a SAP calculation against a notional extension (para 10.10). Of the two, the SAP comparison gives the most room, because it treats the extension as a whole and lets a strong roof offset more glass.

    Article 4, trees and heritage in Brent

    Brent has 39 Article 4 directions covering 162 mapped areas, together with 23 conservation areas. Where a direction removes permitted development, external changes need a planning application, and the materials in the SAP assumptions must match the ones consented.

    The council also holds 1,229 tree preservation orders. A protected tree near a rear extension affects foundations, and sometimes the size of glazing that shading allows, so we check the order map at the outset.

    Brent has 93 listed building entries. For those homes, any window or roof change needs consent beyond planning, and the energy upgrade is designed around what the conservation officer will accept.

    How Brent decides, and what that means for timing

    In its latest year Brent decided 879 householder applications, granting 86.6 per cent, with 97.2 per cent decided in time. Larger home extensions are another matter: the council granted 10 prior approvals and refused 79 in the latest national return.

    A refusal rate like that on the prior approval route means the submission has to be precise. We settle the energy route alongside the drawings, so there is no loose end to explain later. See planning drawings in Brent for the application options, and lawful development certificate in Brent for permitted development.

    Gardens cover 30.3 per cent of the borough's land, so rear extensions and garden buildings are common, and each carries its own energy question.

    New homes and the date that sets the rules

    A new dwelling is assessed differently. 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, and the start of the next edition is: AD L 2026 takes effect 24 Mar 2027 (24 Sep 2027 for higher-risk building work). The transition rule is: AD L/F 2021 continue where plans/notices are deposited before 24 Mar 2027 and work starts before 24 Mar 2028.

    We record the deposit date and the start date on the project programme, so the assessor works to the right edition. A new home also needs an energy certificate: An energy performance certificate is required on construction of a new dwelling.

    The result is a fixed quote after a free constraints check, VAT included, and figures that match the drawings. The same sheets support building regulations drawings in Brent; for everything else we do locally, start at architectural drawings in Brent.

    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.
    Pencil resting on a dimensioned technical drawing beside a scale rule
    Energy in
    Move the pointer up — the plug rises toward the socket.

    Other services in Brent

    SAP calculations nearby

    Questions

    Which Brent documents affect my extension?

    The Residential Extensions and Alterations Supplementary Planning Document for alterations, and the Brent Design Guide Supplementary Planning Document (SPD1) for design. Energy limits come from Approved Document L.

    Do protected trees affect the energy design?

    They can. A protected tree changes foundation design and may limit shading options. The council holds 1,229 orders, so we check early.

    Does a conversion need its own SAP assessment?

    Each new dwelling is assessed separately. The Houses in Multiple Occupation SPD applies alongside the energy rules.

    How much does a SAP calculation cost in Brent?

    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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