Double Storey Extension Drawings in Isleworth TW7
Fixed-fee, MCIAT-chartered double storey extension drawings for Isleworth (TW7) homeowners — London Borough of Hounslow validation and local constraints handled from the start.
TW7 covers Isleworth, from the Georgian riverside huddle of Old Isleworth around the church to the leafier Victorian villa streets of Spring Grove, and most homeowners here are weighing a rear or side-return kitchen extension or a loft conversion to add space without leaving a settled address.
Because the Isleworth Riverside and Spring Grove conservation areas both sit inside the outcode, the first step is a boundary check: a scheme that is permitted development on an unprotected street can need a full householder application once you are inside the conservation area, especially for anything affecting a front or riverside elevation.
Planning in Isleworth (TW7): what to know before you apply
Most rear extensions and loft conversions outside the conservation areas proceed under permitted development, subject to size and eaves limits. Inside Isleworth Riverside or Spring Grove, or on any listed building, expect a full householder application and, for listed properties, separate listed building consent.
Typical Isleworth housing stock
The Old Isleworth riverside keeps Georgian and early-Victorian terraces and cottages around the church and Church Street, while Spring Grove and the wider TW7 streets run to substantial Victorian and Edwardian semi-detached and detached villas.
Streets we regularly draw for in Isleworth
Church Street · Lower Square · Mill Plat · North Street
Double Storey Extension Drawings for Isleworth (TW7) homes: the package and the process
Every double storey extension drawings we prepare for an Isleworth property is drawn to London Borough of Hounslow’s validation standards and tuned to the TW7 constraints above. Here is what the drawing package covers and how the process runs from first survey to approval.
A double storey extension builds a second floor above a single-storey side or rear addition, typically adding a bedroom and bathroom upstairs over a widened kitchen or reception room below. Because the foundations and roof of a single-storey extension already carry most of the fixed cost of building, adding a floor on top is often the most cost-effective way to gain two rooms rather than two separate projects. The trade-off is scrutiny: a two-storey addition sits closer to eye level with neighbouring windows and gardens, so councils examine massing, roofline and boundary distance more closely than they would a single-storey extension.
DrawingsDirect draws double storey side and rear extensions for full planning and building regulations, with structural calculations for the additional floor load and foundations produced in-house by our MCIAT-chartered team, on a fixed fee. If a single storey is enough, see our Rear Extension and Side Return Extension pages, or combine both with a Wraparound if you are extending sideways as well as up.
Do I need planning permission for a double storey extension in London?
Almost always. Permitted development rights for two-storey extensions are far more restrictive than for single-storey work, particularly on how close the new structure can come to a boundary and how closely its roof pitch and eaves height must match the existing house, so most double storey projects are drawn and submitted as full householder planning applications rather than relying on permitted development.
Where the property sits in a conservation area or is subject to an Article 4 direction, any remaining permitted development allowance for a second storey is typically removed entirely, reinforcing the need for a full application. We check your property's status and your borough's design guidance before drawing.
How do councils control the impact of a double storey extension on neighbours?
Because a second storey introduces new windows and massing at first-floor level, London boroughs apply design guidance aimed specifically at protecting neighbouring light, privacy and outlook.
- The 45-degree rule, tested at neighbouring windows, to check the extension does not block an unreasonable amount of daylight
- A common design expectation that a two-storey side extension is set in roughly 1 metre from the shared boundary, rather than built hard against it
- A first floor commonly set back from the ground floor front elevation, so the upper storey reads as subordinate to the main house from the street
- Obscure or high-level glazing on flank walls facing directly into a neighbour's garden or windows, to limit overlooking
| Option | What it adds | Typical fee |
|---|---|---|
| Single-storey rear extension | A ground-floor kitchen-diner only, may qualify for permitted development | see Rear Extension Drawings, from £1,100 |
| Double storey side or rear extension | Two rooms across two floors, usually needs full planning | Full Planning pack ~£1,600–£2,400 |
| Double storey + Building Regulations (structural) | Combined pack including structural calculations for two-floor loads and foundations | Planning + Building Regs pack ~£2,200–£3,850 |
| Wraparound (rear + side return) | Combines two single-storey extensions into one L-shaped ground floor | see Wraparound Extension Drawings, from £2,200 |
Double Storey Extension Drawings in Isleworth TW7 — FAQs
How much does a double storey extension cost to design in London?+
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What extra control applies in Bedford Park?+
Does Heathrow or the river affect my Hounslow project?+
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