House extensions in Three Rivers

Three Rivers received 659 householder applications in the last 12 months - about 13 a week. Rear extensions and dormers are the most common. Of the 511 decided so far, 463 were approved. If you're planning your own, the applications below show what people nearby applied for and how the council decided.

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Showing 50 of 161 applications
22 Oct 2026 Pending Consideration 26/1663/FUL

161 New Road Croxley Green Rickmansworth Hertfordshire WD3 3HB

Construction of first floor rear extension and front porch; internal alterations and alterations to fenestration including new windows to side elevati...

Full Application Three Rivers
22 Oct 2026 Pending Consideration 26/1620/FUL

17 Rendlesham Way Chorleywood Rickmansworth Hertfordshire WD3 5HS

Demolition of existing rear conservatory and construction of single storey rear extension

Full Application Three Rivers
21 Oct 2026 Pending Consideration 26/1667/CLPD

36 Parkfield Chorleywood Rickmansworth Hertfordshire WD3 5AZ

Certificate of Lawfulness Proposed Development: Erection of a front brick boundary wall with piers and metal gates

Certificate of Lawfulness - Proposed Use Three Rivers
21 Oct 2026 Pending Consideration 26/1653/FUL

11 Hillcroft Crescent Oxhey Hall Watford Hertfordshire WD19 4PB

Demolition of existing shed and construction of new outbuilding

Full Application Three Rivers
21 Oct 2026 Pending Consideration 26/1608/FUL

94 Wolsey Road Moor Park Northwood Hertfordshire HA6 2EH

Construction of part single, part two storey rear extension; loft conversion including increase in ridge height with front and rear dormer windows, in...

Full Application Three Rivers
20 Oct 2026 Pending Consideration 26/1578/FUL

137 High Street Rickmansworth Hertfordshire WD3 1AR

Part change of use of the ground floor and first floor commercial premises to residential use (Use Class C3)and creation of two residential flats incl...

Full Application Three Rivers
19 Oct 2026 Pending Consideration 26/1658/PDE

99 St Georges Drive Carpenders Park Watford Hertfordshire WD19 5HE

Prior Approval: Construction of a single-storey rear extension (depth 6m, maximum height 3.7m, maximum eaves height 2.82m)

PD - Extensions Three Rivers
16 Oct 2026 Pending Consideration 26/1654/FUL

47 Carpenders Avenue Carpenders Park Watford Hertfordshire WD19 5BS

Re-location of entrance and construction of front porch

Full Application Three Rivers
16 Oct 2026 Pending Consideration 26/1616/FUL

8 Rosemarie Close Leavesden Watford Hertfordshire WD25 7NP

Construction of a single storey front extension to the garage

Full Application Three Rivers
15 Oct 2026 Pending Consideration 26/1568/FUL

The Mulberry Bush Moor Lane Sarratt Hertfordshire

Reduction of ground levels; alterations to boundary treatment; alterations to hard and soft landscaping including car parking; installation of sewage ...

Full Application Three Rivers
14 Oct 2026 Pending Consideration 26/1645/PDE

13 Curtis Close Mill End Rickmansworth Hertfordshire WD3 8QA

Prior Approval: Construction of a single storey rear extension (depth 3.2m, maximum height 2.95m, maximum eaves height 2.87m)

PD - Extensions Three Rivers
13 Oct 2026 Pending Consideration 26/1615/FUL

6 Winton Crescent Croxley Green Rickmansworth Hertfordshire WD3 3QX

Construction of a single storey rear extension

Full Application Three Rivers
12 Oct 2026 Pending Consideration 26/1627/FUL

Marthas Vineyard Violet Way Loudwater Rickmansworth Hertfordshire WD3 4JP

Demolition of rear porch; construction of two storey side extensions; construction of front entry porch; conversion of garage into habitable accommoda...

Full Application Three Rivers
9 Oct 2026 Pending Consideration 26/1619/FUL

12 Margeholes Carpenders Park Watford Hertfordshire WD19 5AP

Construction of a single storey side and rear extension; conversion of garage into habitable accommodation

Full Application Three Rivers
9 Oct 2026 Pending Consideration 26/1576/FUL

16 Shepherds Way Rickmansworth Hertfordshire WD3 7NJ

Construction of single storey rear and side extension and loft conversion including hip to gable extension and insertion of rear dormer

Full Application Three Rivers
8 Oct 2026 Pending Consideration 26/1564/FUL

55 Silk Mill Road Oxhey Hall Watford Hertfordshire WD19 4TW

Construction of single storey front and rear extensions

Full Application Three Rivers
8 Oct 2026 Pending Consideration 26/1536/FUL

3 Cherry Croft Croxley Green Rickmansworth Hertfordshire WD3 3AL

Replacement of existing timber windows with UPVc windows

Full Application Three Rivers
8 Oct 2026 Pending Consideration 26/1468/CLPD

80 Hayling Road South Oxhey Watford Hertfordshire WD19 7BP

Certificate of Lawfulness of Proposed Development: Addition of one bedroom to a six bedroom House of Multiple Occupancy

Certificate of Lawfulness - Proposed Use Three Rivers
7 Oct 2026 Pending Consideration 26/1609/FUL

Maintenance Compund The Aquadrome Frogmoor Lane Rickmansworth Hertfordshire

Demolition of existing office building; construction of replacement office building with solar panels; alterations to the shed including alterations t...

Full Application Three Rivers
6 Oct 2026 Pending Consideration 26/1448/FUL

42 Winton Drive Croxley Green Rickmansworth Hertfordshire WD3 3RD

Demolition of existing conservatory and construction of a single storey side and rear extension; alterations to the patio

Full Application Three Rivers
5 Oct 2026 Pending Consideration 26/1581/CLPD

Millstream 101 Uxbridge Road Rickmansworth Hertfordshire WD3 7DJ

Certificate of Lawfulness Proposed Development: Demolition of the existing rear dormer and first floor roof extension and construction of loft convers...

Certificate of Lawfulness - Proposed Use Three Rivers
5 Oct 2026 Pending Consideration 26/1579/CLPD

23 Shire Lane Chorleywood Rickmansworth Hertfordshire WD3 5NQ

Certificate of Lawfulness Proposed Development: Construction of a two storey rear extension; loft conversion including part hip-to-gable roof extensio...

Certificate of Lawfulness - Proposed Use Three Rivers
5 Oct 2026 Pending Consideration 26/1569/CLPD

1 - 3 Old Mill Road Hunton Bridge Kings Langley Hertfordshire WD4 8RD

Certificate of Lawfulness Proposed Development: Alterations to fenestration.

Certificate of Lawfulness - Proposed Use Three Rivers
5 Oct 2026 Pending Consideration 26/1554/FUL

66 Westbury Road Northwood HA6 3BY

Construction of part single, part two storey side and rear extension; removal of chimney stack; alterations to the fenestration; internal alterations

Full Application Three Rivers
5 Oct 2026 Pending Consideration 26/1542/FUL

70 Chiltern Drive Mill End Rickmansworth Hertfordshire WD3 8JZ

Construction of two storey side extension and single storey rear extension

Full Application Three Rivers
5 Oct 2026 Pending Consideration 26/1454/FUL

18 Batchworth Lane Northwood HA6 3AT

Part Retrospective: Construction of a part single, part two storey front side and rear extension; conversion of the garage into habitable accommodatio...

Full Application Three Rivers
5 Oct 2026 Pending Consideration 26/1193/PDA

Great Sarratt Hall Farm The Green Sarratt Hertfordshire

Prior Approval: Change of use of existing agricultural building to two residential dwellings with operational works and extension to building and asso...

PD - COU of Agricultural Three Rivers
5 Oct 2026 Pending Consideration 26/1470/PDE

6 Sycamore Approach Croxley Green Rickmansworth Hertfordshire WD3 3TN

Prior Approval: Single storey rear extension (depth 4.5m, maximum height 3m, maximum eaves height 3m)

PD - Extensions Three Rivers
2 Oct 2026 Pending Consideration 26/1495/FUL

Woodoaks Farm Denham Way Maple Cross Rickmansworth Hertfordshire WD3 9XQ

Installation of glazed doors within the existing north and south threshing openings of the Black Barn and retention of existing external timber doors

Full Application Three Rivers
2 Oct 2026 Pending Consideration 26/1511/LBC

Woodoaks Farm Denham Way Maple Cross Rickmansworth Hertfordshire WD3 9XQ

Listed Building Consent: Installation of glazed doors within the existing north and south threshing openings of the Black Barn and retention of existi...

Listed Building Consent Three Rivers
2 Oct 2026 Pending Consideration 26/1526/FUL

6 High Elms Cottages Woodside Road Abbots Langley Watford Hertfordshire WD25 0LA

Construction of a single storey rear extension

Full Application Three Rivers
2 Oct 2026 Pending Consideration 26/1501/FUL

St Josephs Catholic Primary School Ainsdale Road South Oxhey Watford Hertfordshire WD19 7DW

Alterations to boundary treatments

Full Application Three Rivers
1 Oct 2026 Pending Consideration 26/1566/LBC

The Court Rickmansworth Road Chorleywood Rickmansworth Hertfordshire WD3 5SG

Listed Building Consent: Removal of existing fencing boundary treatments to western boundaries, construction of new wall and railing boundary treatmen...

Listed Building Consent Three Rivers
1 Oct 2026 Pending Consideration 26/1300/FUL

19 Chestnut Avenue Rickmansworth Hertfordshire WD3 4HA

Construction of a two storey front and rear extension; conversion of loft into habitable accommodation; installation of front rooflights; alterations ...

Full Application Three Rivers
1 Oct 2026 Pending Consideration 26/1550/RSP

26 Grove Farm Park Northwood HA6 2BQ

Retrospective Application: Construction of an outbuilding.

Retrospective application Three Rivers
30 Sept 2026 Pending Consideration 26/1555/CLPD

50 Harthall Lane Kings Langley Hertfordshire WD4 8JH

Certificate of Lawfulness Proposed Development: Stationing of a mobile home to be used as an annexe

Certificate of Lawfulness - Proposed Use Three Rivers
30 Sept 2026 Pending Consideration 26/1532/FUL

73 Wolsey Road Moor Park Northwood Hertfordshire HA6 2ER

Construction of two storey side and rear extensions including accommodation in the roof space; alterations to fenestration.

Full Application Three Rivers
30 Sept 2026 Pending Consideration 26/1525/FUL

22 Meadow Way Rickmansworth Hertfordshire WD3 7NQ

Construction of a single storey side and rear extension; installation of roof lights; internal alterations; alterations to fenestration; alterations t...

Full Application Three Rivers
30 Sept 2026 Pending Consideration 26/1531/FUL

119 Oaklands Avenue Oxhey Hall Watford Hertfordshire WD19 4TN

Demolition of existing garage; construction of a single-storey side and rear extension.

Full Application Three Rivers
30 Sept 2026 Awaiting decision 26/1530/PDE

66 Westbury Road Northwood HA6 3BY

Prior Approval: Single storey rear extension (depth 6m, maximum height 3m, maximum eaves height 3m)

PD - Extensions Three Rivers
29 Sept 2026 Pending Consideration 26/1551/FUL

Eastcott East Lane Bedmond Abbots Langley Hertfordshire WD5 0QG

Construction of a detached garage

Full Application Three Rivers
29 Sept 2026 Pending Consideration 26/1491/FUL

Popes Croft Chandlers Lane Chandlers Cross Rickmansworth Hertfordshire WD3 4NE

First-floor extension, including demolition of existing roof and construction of new roof, to create two-storey dwelling; and two-storey front extensi...

Full Application Three Rivers
28 Sept 2026 Pending Consideration 26/1529/FUL

41 Main Avenue Moor Park Northwood Hertfordshire HA6 2LH

Change of existing side extension as outdoor area covered by pergola, demolition of conservatory and porch and construction of single storey front, si...

Full Application Three Rivers
23 Sept 2026 Pending Consideration 26/1457/FUL

5 Portland Heights Batchworth Lane Northwood HA6 3HE

Demolition of existing conservatory; construction of single storey side and rear extensions; alterations to the fenestration

Full Application Three Rivers
23 Sept 2026 Pending Consideration 26/1435/FUL

Halfacre Parrotts Close Croxley Green Rickmansworth Hertfordshire WD3 3JZ

Construction of ground floor rear infill extension; increase in ridge height to roof; insertion of front, side, and rear dormer windows; insertion of ...

Full Application Three Rivers
23 Sept 2026 Pending Consideration 26/1488/FUL

Lantern House Dog Kennel Lane Chorleywood Rickmansworth Hertfordshire WD3 5EE

Construction of a single storey front and rear extension; relocation of existing pergola, conversion of garage into habitable accommodation; alteratio...

Full Application Three Rivers
22 Sept 2026 Pending Consideration 26/1410/FUL

The Court Rickmansworth Road Chorleywood Rickmansworth Hertfordshire WD3 5SG

Removal of existing fencing boundary treatments to western boundaries, construction of new wall and railing boundary treatments

Full Application Three Rivers
22 Sept 2026 Pending Consideration 26/0975/FUL

43 Russell Road Moor Park Northwood Hertfordshire HA6 2LP

Two storey front, side and rear extension; basement and loft conversion including increase in ridge height; construction of 3no. dormers; installation...

Full Application Three Rivers
22 Sept 2026 Pending Consideration 26/1484/FUL

16 Valley Walk Croxley Green Rickmansworth Hertfordshire WD3 3SY

Construction of a detached outbuilding

Full Application Three Rivers
22 Sept 2026 Pending Consideration 26/1262/FUL

4A Parkside Road Northwood HA6 3HL

Construction of first floor front extension; alterations to the fenestration; alterations to the roof form, including installation of rooflights; inte...

Full Application Three Rivers
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Frequently asked questions

When do you need planning permission for a house extension?
Single-storey rear extensions up to 4m (detached) or 3m (semi-detached / terraced) are usually permitted development. Two-storey extensions, anything in a conservation area, or larger projects almost always need a planning application.
What's the difference between planning permission and permitted development?
Permitted development rights let you build certain things without applying for planning permission, subject to specified limits. Anything outside those limits, whether taller, larger or in a protected area, needs full planning permission.
How long does a householder application take?
The statutory target is 8 weeks from validation. Most simple householder extensions are decided within that window; complex or contested cases, especially those drawing a lot of comments, can take longer.
Can I get email alerts for new extensions applications in Three Rivers?
Yes. Click "Set up alerts" on this page and you'll get a daily or weekly email listing every new extensions application published by Three Rivers. You can also narrow the alert to a postcode, street, or drawn area.

We check Three Rivers's planning portal daily. New extensions applications appear here within a day of being published.