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Tower Hamlets, London

Plumbing and drainage drawings in Tower Hamlets

Tower Hamlets sets a greenfield run-off target in critical drainage areas and wants a flood risk assessment for basement or ground-floor extensions in the higher-risk flood zones. Our MCIAT chartered architectural technologists prepare plumbing and drainage drawings for Tower Hamlets flats and houses on a fixed quote after a free constraints check.

Fixed quote after a free constraints check

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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 plumbing and drainage drawings

    Four 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. Building regulations

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

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

    Plumbing and drainage drawings in Tower Hamlets: the local rules

    The Tower Hamlets Local Plan 2031: Managing Growth and Sharing the Benefits carries the drainage rule that matters. Major development has to submit a drainage strategy. The run-off target is Greenfield (CDA); 50% attenuation minimum elsewhere, so a site in a critical drainage area must reach the greenfield rate and volume, and other sites should aim for it, with attenuation of at least half the pre-development peak as the minimum.

    The second rule is narrower but catches many small jobs: FZ2/3 basement or ground-floor extensions. A householder flood risk assessment has to cover SuDS and safe access. If the house sits near the river, a lower-ground or ground-floor extension can need one even though the work is small.

    We read the council's flood and critical-drainage mapping first, then decide how much the drawing has to carry. On a flat refurbishment inside an existing envelope, the drawing is a clean soil and waste layout. On an extension in a flood zone, it also shows floor levels, a non-return valve on the outlet and how surface water leaves the plot.

    The same evidence goes to the building control officer, so the drawing is prepared alongside our building regulations drawings rather than as a separate exercise.

    Brick house being extended, with a wide new opening supported over the ground floor

    Local figures for Tower Hamlets

    Figures with their unit, period and source
    MeasureValuePeriodSource
    Households living in a house12 % of households living in a house or bungalow (detached, semi-detached or terraced)Census 2021nomisweb.co.uk
    Owner-occupied households23.1 % of households owner-occupied (owned outright or with mortgage/loan)Census 2021nomisweb.co.uk
    Domestic gardens share of land (GLUD 2005)7.4 % of land that is domestic garden (GLUD 2005)2005data.london.gov.uk
    Conservation areas59 named conservation areas published by the council—planning.data.gov.uk
    Article 4 directions64 Article 4 directions published by the council—planning.data.gov.uk
    Listed building entries916 list entries (Historic England, within the LPA boundary)—planning.data.gov.uk
    Policy D.ES5: major development must submit a drainage strategy; new development in critical drainage areas must achieve greenfield run-off rate and volume; other development should seek greenfield rate, with minimum 50% attenuation of pre-development peak run-off.Greenfield (CDA); 50% attenuation minimum elsewhere—towerhamlets.gov.uk, Tower Hamlets Local Plan 2031 (adopted 15 January 2020), Policy D.ES5 parts 2-3, PDF p.165
    Householder FRA required in Flood Zone 2 or 3 for basement or ground floor extensions, including SuDS and safe access.FZ2/3 basement or ground-floor extensions—towerhamlets.gov.uk, Tower Hamlets Householder Planning Application Checklist (September 2020, V5), p.8
    AD H (2015) para 2.34 and Table 6, PDF p.18 (printed p.16)1 in 80—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 Tower Hamlets
    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

    A borough of flats

    Only 12 per cent of Tower Hamlets' 120,539 households live in a house or bungalow, and just 23.1 per cent own their home. Most plumbing questions are therefore about a flat: moving a kitchen, adding a shower room or connecting into a stack that serves floors above and below.

    In a block the first question is permission from the freeholder, because the stack and the drain run are often communal. The second is ground-floor drainage, since a basement or lower flat can sit below the sewer level and need a pumped outlet. The drawing shows the pump, its discharge point and the non-return valve.

    Gardens are scarce, at only 7.4 per cent of the land, so soakaways are rarely an option. Roof water usually reaches the sewer by a controlled outlet, and the attenuation sits in a roof tank, a blue roof or a below-slab crate.

    Heritage and the High Density Living guidance

    The borough has 59 conservation areas, 64 Article 4 directions and 916 listed entries, with 39 on the Heritage at Risk Register. In streets of Georgian and Victorian terraces, a new external soil pipe is exactly the kind of alteration an officer notices.

    A larger conversion may also be read against the High Density Living SPD. We keep plant, vents and risers inside the building line wherever the plan allows and draw any external element in elevation.

    If the house is listed, the pipe route needs to be justified in a heritage statement and is drawn to avoid cutting historic fabric.

    The figures we check each sheet against

    Approved Document H sets the fall of a seventy-five-millimetre foul drain carrying above one litre per second at 1 in 80. Hot water delivered to a new bath is limited to 48 degrees Celsius, which we note on the schematic for any new bathroom.

    Where a new basement or lightwell is dug near a neighbour, the Party Wall etc. Act applies to excavation within 3 metres of a neighbouring structure that goes below its foundations, so we hand the surveyor the depths and distances. Our party wall notices service picks up from there.

    Quote and scope

    The set includes a foul and surface-water plan, a section through the deepest run with falls marked, a schedule of chambers and invert levels, and a short note answering the council's drainage question in plain words. Your builder can price from it and the building control officer can inspect against it.

    No starting price is published. We run a free constraints check on your address and send a fixed quote. We draw and specify; installers install. Each Tower Hamlets set is checked by a second technologist before issue. Read more in our plumbing and drainage drawings guide, or see architectural drawings in Tower Hamlets.

    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
    Every layer specified
    Move across to open the layers; move down to pick one.

    Other services in Tower Hamlets

    Questions

    When does a Tower Hamlets extension need a flood risk assessment?

    The council asks for a householder one in these cases: FZ2/3 basement or ground-floor extensions. We check the flood zone before quoting.

    Can I use a soakaway in Tower Hamlets?

    Rarely. Gardens cover only 7.4 per cent of the land, and many sites are paved. We usually draw a controlled outlet with attenuation instead.

    Does my flat need drainage drawings for a new shower room?

    Often yes, because building control wants to see the waste route, its fall and the connection to the stack. The drawing is short and usually part of the wider building regulations set.

    Sources and dates

    City of London skyline glowing at dusk across the Thames under a dramatic orange sky

    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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