Mansard drawings for Hounslow terraces — the rebuilt roof with a steep, near-vertical rear slope that adds a full storey of loft, drawn to Hounslow Council's roofline and streetscape rules, delivered in days and revised free until your decision, with a free approval-odds check first.
Hounslow Council granted 86% of the householder planning decisions it made in its latest published year — 1 point below the 87% England-wide householder average. Side-return and mansard schemes dominate in Chiswick, where officers weigh roof bulk against a strongly uniform terrace roofscape, which is where a policy-literate drawing pack earns its keep. Its dominant Georgian (1714–1837), Victorian (1837–1901), Edwardian (1901–1910), interwar (1918–1939) and postwar (1945–1970) housing stock sets the design brief on most streets.
The permitted-development ceilings are fixed: 40m³ of new roof volume for a terraced loft and 50m³ for a semi or detached house under Class B, plus a 3m single-storey rear extension on a terrace or 4m on a detached house under Class A. Hounslow carries at least one Article 4 direction, and conservation areas including Bedford Park, Old Chiswick and Strand-on-the-Green remove those rights outright, so we confirm your exact address before a line is drawn. A validated householder application in Hounslow is determined against an 8-week statutory target.
Chiswick (Victorian and Edwardian terraces wrapped around the Bedford Park garden suburb), Brentford (older riverside terraces alongside recent waterfront redevelopment), Isleworth (the Old Isleworth riverside conservation area and Georgian frontages), Osterley (interwar semis on the fringe of Osterley Park), Feltham (postwar and interwar suburban estates to the south-west) and Hounslow (the town centre with mixed terraces and converted flats) — these are the Hounslow pockets our drawings cover most. Heritage designations here include Bedford Park, Old Chiswick, Strand-on-the-Green, Wellesley Road and Old Isleworth. Hounslow Council weighs each proposal against Hounslow Local Plan and the Residential Extension Guidelines SPD, where the borough's western edge sits under Heathrow flight paths, so glazing, ventilation and noise mitigation surface on larger schemes. Converted terraces are common through central Chiswick and Brentford, and flats and maisonettes carry no householder permitted-development rights.. On roofs the borough is London butterfly and valley roofs on the Chiswick terraces and hipped roofs on the interwar semis, over Victorian and Edwardian terraces across Chiswick, interwar semi-detached houses around Osterley and Hounslow and converted period flats and maisonettes.
The mansard is the maximum-volume loft, and Hounslow's stock is where it belongs — the borough runs to Victorian and Edwardian terraces across Chiswick, interwar semi-detached houses around Osterley and Hounslow and converted period flats and maisonettes, and on a period terrace a mansard rebuilds the roof at roughly seventy degrees to create almost a full new floor rather than the part-height room a dormer returns. Hounslow Council assesses it against Hounslow Local Plan and the Residential Extension Guidelines SPD, and because the whole roof changes shape the test is the street: whether the new profile continues the terrace or breaks it.
That is what the drawings have to settle. We set the mansard behind the original parapet or eaves, hold it to the ridge height of neighbouring mansards where the terrace already has them, and detail the slate face, the dormer windows within it and the party walls to both sides so the addition reads as part of the row. Side-return and mansard schemes dominate in Chiswick, where officers weigh roof bulk against a strongly uniform terrace roofscape, and on a roof this prominent that is the argument that has to be won on the page.
Much of Hounslow's terraced stock is designated — Bedford Park, Old Chiswick, Strand-on-the-Green, Wellesley Road and Old Isleworth among the areas — and there a mansard is judged on whether it restores or respects the historic roofline. Bedford Park — the pioneering garden suburb shared with Ealing — carries a long-standing Article 4 direction, and the Chiswick and Old Isleworth conservation areas remove permitted-development rights on many of their period streets. Some terraces already have a consistent mansard line an addition can follow; others do not, and we establish which before drawing.
A mansard in Hounslow always needs a full application to Hounslow Council — rebuilding the roof puts it well outside permitted development. These are the points the council weighs:
We draw the new roof behind the parapet, the slope and ridge matched to the terrace, the slate face and dormer windows, and the party walls to both neighbours — the roofline and streetscape relationships Hounslow Council's officers check first — and submit a validation-complete householder application.
Below is Hounslow Council's real householder decision record, drawn from official planning statistics and refreshed as new data lands. Hounslow grants a fair share of householder applications, with terrace roofscape in the Chiswick conservation areas the dominant constraint on loft and rear schemes. A mansard is decided on roofline and streetscape, so a scheme drawn to continue the terrace is cleared faster and refused less often than one that fights it.
Source: MHCLG planning application statistics (householder decisions, rolling year). Compare every borough on our London approval-rate league table.
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Across Chiswick, Brentford and Isleworth, the mansard that goes through is the one that disappears into the row: set behind the parapet, its ridge matched to neighbouring mansards, the front slope in natural slate with traditional dormer windows, and the whole storey reading as though the terrace was always that height. On the borough's victorian and edwardian terraces across chiswick, this is the single biggest volume the roof can give — close to a full floor.
The borough's western edge sits under Heathrow flight paths, so glazing, ventilation and noise mitigation surface on larger schemes. We follow any established mansard line on the terrace, keep the slope and materials traditional, and where a row has none yet, draw a design that could set the pattern rather than break it — the argument Hounslow Council needs to grant on a roof this visible.
We draw mansard roofs on the period-terrace streets across the borough. A few of the neighbourhoods where Hounslow mansards come up most often:
Mansard loft drawings for Chiswick's Victorian and Edwardian terraces wrapped around the Bedford Park garden suburb — roofline-matched, slate-detailed and drawn to Hounslow Council's guidance.
Mansard loft drawings for Brentford's older riverside terraces alongside recent waterfront redevelopment — roofline-matched, slate-detailed and drawn to Hounslow Council's guidance.
Mansard loft drawings for Isleworth's the Old Isleworth riverside conservation area and Georgian frontages — roofline-matched, slate-detailed and drawn to Hounslow Council's guidance.
Mansard loft drawings for Osterley's interwar semis on the fringe of Osterley Park — roofline-matched, slate-detailed and drawn to Hounslow Council's guidance.
Mansard loft drawings for Feltham's postwar and interwar suburban estates to the south-west — roofline-matched, slate-detailed and drawn to Hounslow Council's guidance.
Mansard loft drawings for Hounslow's the town centre with mixed terraces and converted flats — roofline-matched, slate-detailed and drawn to Hounslow Council's guidance.
A mansard wins the most space of any loft but asks the most of the planning case. This is how it compares in Hounslow.
| Loft type | Planning route | Space gained | What Hounslow Council checks |
|---|---|---|---|
| Mansard | Always a full application | Close to a full extra storey | Roofline, streetscape, terrace match |
| Rear dormer | Often permitted development | A room across the back slope | Volume and eaves set-back |
| Hip-to-gable | Full application | Full width where the roof is hipped | Balance with the paired neighbour |
| Rooflights only | Usually permitted development | Light and headroom, no new shape | Rooflights within the existing slope |
In conservation areas such as Bedford Park and Old Chiswick, a mansard is judged on how it sits within the protected roofline of the terrace.
A fixed process built around how Hounslow Council validates and decides mansard applications — most drawings are submission-ready within seven days of survey.
Send us your Hounslow postcode and terrace type. We confirm your conservation and Article 4 status, check whether the row already has a mansard line to follow, and score your odds against live Hounslow Council decisions.
We measure the parapet, ridge and party walls, and the roofline of the neighbouring houses — the numbers the new slope, its height and the terrace match depend on.
Chartered designers develop the rebuilt roof to your brief, drawn to Hounslow Council's roof-alteration and conservation guidance with the slope, slate face, dormers and party walls detailed on the page.
We submit the householder application, manage validation and case-officer queries, and revise the drawings free until Hounslow Council issues its decision.
Always. A mansard rebuilds the roof into a steep rear slope with a flat top, and that wholesale change of roof shape is well outside permitted development — so it needs a full householder application to Hounslow Council on every street, designated or not. On a terrace in a conservation area such as Bedford Park and Old Chiswick the roofline is protected, so the design is scrutinised more closely still.
It is a rebuilt roof with a steep, near-vertical rear slope and a small flat top, which creates almost a full extra storey inside — far more than a dormer returns. Hounslow's period terraces are the classic mansard candidates, and where a row already carries mansards a new one that matches the line is the most likely of all lofts to be approved despite being the largest. Hounslow Council is the decision-maker.
Because it reshapes the whole roof rather than adding a box to it. The steep slope pushes the walls out almost to vertical and the flat top lifts the ceiling, so the usable floor runs nearly the full footprint of the house at head height — close to a complete storey. That is why, in Hounslow, a mansard is chosen when a dormer or hip-to-gable will not give enough room. Hounslow Council is the decision-maker.
It can, but the case is harder. Where a terrace already has a consistent mansard line, matching it is straightforward; on an unbroken row, Hounslow Council weighs whether your mansard would break the skyline or could set an acceptable pattern for the street. We draw the design to sit within the terrace and make that argument on the elevations rather than leave it to chance.
Almost certainly, on both sides. A mansard rebuilds the roof up to and across the party walls with the neighbours either side, so the Party Wall etc. Act applies to each and notice must be served before work starts — separately from Hounslow Council's planning decision. We detail both party walls on the drawings and flag the notices early so surveyors can be appointed without holding up the build.
We price each Hounslow mansard individually, because the terrace, the roofline match and the party-wall detailing vary street to street, and send a fixed, no-obligation quote within one working day. It covers the full drawing pack with free revisions until Hounslow Council approves, and we confirm the roofline case at the outset. Call 020 7864 7245 to start.
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