Two-storey extension drawings for Three Rivers homes — bedroom above, living space below, drawn against the 3-metre projection and 7-metre boundary rules and to Three Rivers District Council's design guidance, delivered in days and revised free until your decision.
Three Rivers District Council granted 93% of the householder planning decisions it made in its latest published year — 6 points above the 87% England-wide householder average. Metropolitan Green Belt covers roughly three-quarters of the district, so the plan pushes growth onto brownfield and town-centre sites rather than releasing countryside, which is where a policy-literate drawing pack earns its keep. Its dominant Victorian (1837–1901), Edwardian (1901–1910), interwar (1918–1939) and postwar (1945–1970) housing stock sets the design brief on most streets.
Class A and Class B set the thresholds — a rear dormer to 40m³ on a terrace or 50m³ on a semi or detached, and a single-storey rear extension to 3m on a terrace or 4m on a detached house — beyond which Three Rivers District Council needs a full application. Three Rivers carries at least one Article 4 direction, and conservation areas including Rickmansworth, Chorleywood Common and Moor Park remove those rights outright, so we confirm your exact address before a line is drawn. A validated householder application in Three Rivers is determined against an 8-week statutory target.
Rickmansworth (the historic market-town core with a Victorian and Edwardian centre and its own conservation area), Chorleywood (a Metro-land commuter village of Arts and Crafts and interwar houses around Chorleywood Common), Moor Park (a private gated estate of large interwar detached houses under an Article 4 direction), Croxley Green (mixed Victorian and interwar suburban housing gathered around the green), Abbots Langley (a village with a historic core and postwar suburban growth) and Sarratt (a rural green-belt village of historic vernacular cottages) — these are the Three Rivers pockets our drawings cover most. Heritage designations here include Rickmansworth, Chorleywood Common, Moor Park, Croxley Green, Sarratt and Abbots Langley. Three Rivers District Council weighs each proposal against the Three Rivers Core Strategy (adopted October 2011) and Development Management Policies LDD, where part of the district around Chorleywood and Rickmansworth falls within the Chilterns National Landscape (AONB), where landscape protection is at its highest. Converted flats are common through Rickmansworth and around the stations, and none of them hold householder permitted-development rights.. On roofs the borough is hipped roofs on the 1930s Metro-land semis and gabled and dual-pitch roofs on the older village cottages, over interwar and Edwardian Metro-land semi-detached and detached houses across Chorleywood, Croxley Green and Moor Park, Victorian and Edwardian terraces around Rickmansworth, postwar estate housing at Abbots Langley and South Oxhey and period vernacular cottages in the green-belt villages of Sarratt and Heronsgate.
Adding at first floor changes the question the case officer asks. A single-storey extension is judged mostly on daylight and garden loss; a two-storey extension is judged on overlooking, bulk against the neighbouring roofline, and whether it reads as part of the house or bolted onto it. Three Rivers is largely interwar and Edwardian Metro-land semi-detached and detached houses across Chorleywood, Croxley Green and Moor Park, Victorian and Edwardian terraces around Rickmansworth, postwar estate housing at Abbots Langley and South Oxhey and period vernacular cottages in the green-belt villages of Sarratt and Heronsgate, and hipped roofs on the 1930s Metro-land semis and gabled and dual-pitch roofs on the older village cottages set what a matching roof actually means here.
The permitted-development route exists but is narrow: 3 metres of rear projection, a 7-metre stand-off from the rear boundary, eaves and ridge no higher than the original, and side-facing upper windows obscure-glazed and non-opening below 1.7 metres above floor level. Most two-storey schemes fail one of those, usually the 7-metre boundary rule on a shorter garden, and go in as a full application instead. We establish which route applies before designing, because it changes the drawing set.
Metropolitan Green Belt covers roughly three-quarters of the district, so the plan pushes growth onto brownfield and town-centre sites rather than releasing countryside. The Moor Park Article 4 direction covers the private Moor Park estate and conservation area, removing permitted-development rights so external alterations to these large interwar houses need consent, and further conservation areas such as Rickmansworth and Chorleywood Common layer additional controls.
Some two-storey rear extensions are permitted development. You will need a full application to Three Rivers District Council if any of these apply:
We set the projection and boundary distance on the site plan, prove the roof-pitch match on the elevations, and specify obscure glazing on the side windows — the three things Three Rivers District Council checks first — then submit a validation-complete pack.
Below is Three Rivers District Council's real householder decision record, drawn from official planning statistics and refreshed as new data lands. Three Rivers grants a high share of decisions overall, with green-belt containment across most of the district and Chilterns AONB protection the recurring constraints on larger schemes. Two-storey schemes attract more neighbour comment than any other householder work, so the overlooking and daylight case has to be made on the drawings.
Source: MHCLG planning application statistics (householder decisions, England, 1 April 2025 - 31 March 2026). Compare every borough on our London approval-rate league table.
Tell us about your project and get a fixed, no-obligation quote back within one working day. If you don't need planning permission at all, we'll tell you that too — for free.
Across Rickmansworth, Chorleywood and Moor Park, the schemes that succeed set the first floor back from the ground floor, keep the ridge below the original, and treat the flank wall as blank or obscure-glazed. On interwar and edwardian metro-land semi-detached and detached houses across chorleywood, croxley green and moor park, matching the eaves line matters more than matching the brick: an extension that carries the existing eaves through reads as original even in a different material.
Part of the district around Chorleywood and Rickmansworth falls within the Chilterns National Landscape (AONB), where landscape protection is at its highest. We draw the 45-degree daylight test from the neighbour's nearest habitable window, show the window positions in section, and set out the steel and foundation implications early — a two-storey extension changes the load path, so the structural design and the planning design have to be developed together rather than in sequence.
We draw two-storey extensions across Three Rivers. A few of the areas where they come up most often:
Two storey extension drawings for Rickmansworth — the historic market-town core with a Victorian and Edwardian centre and its own conservation area — dimensioned against the 3m and 7m limits and drawn to Three Rivers District Council's guidance.
Two storey extension drawings for Chorleywood — a Metro-land commuter village of Arts and Crafts and interwar houses around Chorleywood Common — dimensioned against the 3m and 7m limits and drawn to Three Rivers District Council's guidance.
Two storey extension drawings for Moor Park — a private gated estate of large interwar detached houses under an Article 4 direction — dimensioned against the 3m and 7m limits and drawn to Three Rivers District Council's guidance.
Two storey extension drawings for Croxley Green — mixed Victorian and interwar suburban housing gathered around the green — dimensioned against the 3m and 7m limits and drawn to Three Rivers District Council's guidance.
Two storey extension drawings for Abbots Langley — a village with a historic core and postwar suburban growth — dimensioned against the 3m and 7m limits and drawn to Three Rivers District Council's guidance.
Two storey extension drawings for Sarratt — a rural green-belt village of historic vernacular cottages — dimensioned against the 3m and 7m limits and drawn to Three Rivers District Council's guidance.
The first-floor limits are tighter than the ground-floor ones. This is how the common cases compare.
| Scheme | Permitted development? | Deciding limit | What Three Rivers District Council checks |
|---|---|---|---|
| Two-storey rear, 3m projection, 7m+ to boundary | Often yes | 3m projection / 7m boundary | Roof match, side-window glazing |
| Two-storey rear, under 7m to boundary | No — full application | Rear-boundary distance | Overlooking, daylight, garden loss |
| Two-storey side extension | No — full application | Side elevation | Gap to boundary, street rhythm |
| Two-storey wraparound | No — full application | Combined footprint | Bulk, massing, neighbour amenity |
| Any two-storey on designated land | No — full application | Designation | Character and appearance |
Limits from the GPDO 2015, Schedule 2, Part 1, Class A — two-storey rear extension conditions.
A fixed process built around how Three Rivers District Council validates and decides two-storey applications.
Send us your Three Rivers postcode and garden depth. We measure the 7-metre boundary rule against your plot, confirm designation status, and score your odds against live Three Rivers District Council decisions.
We measure the original rear wall, eaves and ridge heights, garden depth and every neighbouring window that faces the site — the inputs the daylight and overlooking case is built from.
Chartered designers develop the two-storey addition to your brief with the roof and eaves resolved, and we coordinate the load path so the structural scheme and the planning scheme are the same building.
We submit the application, manage validation and case-officer queries, and revise the drawings free until Three Rivers District Council issues its decision.
Often, but not always. A two-storey rear extension can be permitted development if it projects no more than 3 metres, sits at least 7 metres from the rear boundary, does not exceed the existing eaves and ridge, and has obscure-glazed non-opening side windows below 1.7 metres. In Three Rivers, the 7-metre rule is what most commonly forces a full application to Three Rivers District Council.
No part of a permitted-development two-storey rear extension may come within 7 metres of the boundary opposite the rear wall of the house. It exists to protect the neighbour behind you from being overlooked at first floor. On shorter Three Rivers gardens this is decisive, and we measure it on survey before any design work rather than discovering it at validation. Three Rivers District Council is the decision-maker.
Not under permitted development — two-storey side extensions always need a full application to Three Rivers District Council. They are assessed on the gap to the boundary, whether the street's rhythm of spaces between houses survives, and whether the extension is subordinate to the original. Setting the first floor back from the front building line and down from the ridge is what usually makes the difference.
Overlooking is the most common objection, and it is answerable on the drawings. We position habitable-room windows away from neighbouring gardens, obscure-glaze and fix shut anything on the flank below 1.7 metres, and show the sight lines in section. Where the geometry is tight, a rooflight or a high-level window gives the same daylight without the mutual overlooking that draws objections. This applies to your Three Rivers address specifically. Three Rivers District Council is the decision-maker.
Almost certainly. Excavating within 3 metres of a neighbouring structure and building on or up to the boundary both trigger the Party Wall etc. Act 1996, and a two-storey extension usually does both. It is entirely separate from Three Rivers District Council's planning decision, so we flag the notice period early and detail the junction on the drawings.
Yes. Adding a floor changes the load path from roof to foundation, so beams, padstones and foundation depths all need designing and calculating for building control. Planning and building regulations are separate consents, and the structural set is what building control assesses — we prepare both so the approved scheme is the buildable one. This applies to your Three Rivers address specifically. Three Rivers District Council is the decision-maker.
We quote each Three Rivers two-storey extension individually, because plot depth, roof form and structural complexity vary house to house, and send a fixed, no-obligation quote within one working day. It covers the drawing pack with free revisions until Three Rivers District Council approves. Call 020 7864 7245 to start.
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