House extensions in Three Rivers

Three Rivers received 580 householder applications in the last 12 months - about 11 a week. Rear extensions and dormers are the most common. Of the 424 decided so far, 384 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 172 applications
2 days ago Pending 26/1371/FUL

Tinkers Halt Sandy Lane Northwood HA6 3ES

Conversion of garage into habitable accommodation, alterations to the fenestration including installation of a juliette balcony and removal of bay win...

Full Application Three Rivers
2 days ago Pending 26/1436/CLPD

76 Hill Rise Rickmansworth Hertfordshire WD3 7NX

Certificate of Lawfulness Proposed Development: Installation of an outbuilding

Certificate of Lawfulness - Proposed Use Three Rivers
7 Sept 2026 Pending 26/1382/CLPD

1 Wyatts Lodge Solesbridge Lane Chorleywood Rickmansworth Hertfordshire WD3 5SW

Certificate of Lawfulness Proposed Development: Installation of external heating and cooling pump

Certificate of Lawfulness - Proposed Use Three Rivers
7 Sept 2026 Pending 26/1416/PDE

263 Uxbridge Road Rickmansworth Hertfordshire WD3 8DP

Prior Approval: Construction of a single-storey rear extension (depth 6m, maximum height 3.9m, maximum eaves height 3m)

PD - Extensions Three Rivers
4 Sept 2026 Pending 26/1380/FUL

Crossley Wylde Loudwater Lane Loudwater Rickmansworth Hertfordshire WD3 3JD

Installation of rooflights

Full Application Three Rivers
4 Sept 2026 Pending 26/1381/LBC

Crossley Wylde Loudwater Lane Loudwater Rickmansworth Hertfordshire WD3 3JD

Listed Building Consent: Installation of rooflights

Listed Building Consent Three Rivers
3 Sept 2026 Pending 26/1198/FUL

The Court Rickmansworth Road Chorleywood Rickmansworth Hertfordshire WD3 5SG

Removal of existing fencing boundary treatments to north east and north west boundaries and construction of new wall and railing boundary treatments

Full Application Three Rivers
3 Sept 2026 Pending 26/1200/LBC

The Court Rickmansworth Road Chorleywood Rickmansworth Hertfordshire WD3 5SG

Listed Building Consent: Removal of existing fencing boundary treatments to north east and north west boundaries and construction of new wall and rail...

Listed Building Consent Three Rivers
3 Sept 2026 Pending Consideration 26/1263/RSP

17 Edson Close Leavesden Watford Hertfordshire WD25 7BX

Retrospective: Conversion of garage into habitable accomodation; alterations to the fenestation and alterations to driveway.

Retrospective application Three Rivers
3 Sept 2026 Pending 26/1402/RSP

111 Hayling Road South Oxhey Watford Hertfordshire WD19 7DD

Retrospective:Construction of a single storey outbuilding.

Retrospective application Three Rivers
3 Sept 2026 Pending Consideration 26/1055/FUL

19 Harvey Road Croxley Green Rickmansworth Hertfordshire WD3 3BN

Construction of a single storey rear extension and raised patio to rear with ramp

Full Application Three Rivers
2 Sept 2026 Pending 26/1328/FUL

109 Greenfield Avenue Carpenders Park Watford Hertfordshire WD19 5DG

Construction of single storey rear extension including an extension to the existing roof and the insertion of dormers to the front, sides and rear, si...

Full Application Three Rivers
2 Sept 2026 Pending Consideration 26/1398/PDE

99 St Georges Drive Carpenders Park Watford Hertfordshire WD19 5HE

Prior Approval: Construction of a single-storey rear extension (depth 6m, maximum height 3.5m, maximum eaves height 3m)

PD - Extensions Three Rivers
2 Sept 2026 Pending 26/1384/FUL

Swandrift Trout Rise Loudwater Rickmansworth Hertfordshire WD3 4JZ

Demolition of existing conservatory and construction of part single, part two storey rear extension, single storey side extension, extension to double...

Full Application Three Rivers
1 Sept 2026 Pending Consideration 26/1390/NAC

Warner Bros. Studios Leavesden Warner Drive Watford Hertfordshire WD25 7LP

Neighbouring Authority Consultation: Part retrospective application for existing and extension of the acoustic timber fence on Backlot 2.

Neighbouring Authority Consultation Three Rivers
1 Sept 2026 Pending 26/1372/FUL

108 Winton Drive Croxley Green Rickmansworth Hertfordshire WD3 3QT

Demolition of existing conservatory and side extension; construction of a single storey front, side and rear extension with rooflights

Full Application Three Rivers
1 Sept 2026 Pending 26/1325/FUL

The Annexe 70 The Mead Carpenders Park Watford Hertfordshire WD19 5BU

Alterations to fenestration

Full Application Three Rivers
28 Aug 2026 Pending 26/1351/FUL

32 Leigh Rodd Carpenders Park Watford Hertfordshire WD19 5BJ

Construction of a single storey side and rear extension; conversion of garage into habitable accommodation; alterations to the fenestration

Full Application Three Rivers
27 Aug 2026 Pending Consideration 26/1365/FUL

Morningside Bridle Lane Loudwater Rickmansworth Hertfordshire WD3 4JB

Construction of a single storey rear extension; conversion of garage into habitable accommodation; alterations to the fenestration

Full Application Three Rivers
27 Aug 2026 Pending Consideration 26/1375/PDE

8 Gonville Avenue Croxley Green Rickmansworth Hertfordshire WD3 3BY

Prior Approval: Constructon of a single storey rear extension (depth 6m, maximum height 2.95m, maximum eaves height 2.95m)

PD - Extensions Three Rivers
26 Aug 2026 Pending Consideration 26/1354/FUL

1 Halifax Close Leavesden Watford Hertfordshire WD25 7GG

Construction of front porch; alterations to boundary treatments including replacement of fence with brick wall

Full Application Three Rivers
26 Aug 2026 Pending 26/1359/FUL

36 Girton Way Croxley Green Rickmansworth Hertfordshire WD3 3QN

Construction of single storey rear extension; alterations to landscaping including demolition of outbuilding and construction of outdoor kitchen; inte...

Full Application Three Rivers
26 Aug 2026 Pending Consideration 26/1361/FUL

90 Sherborne Way Croxley Green Rickmansworth Hertfordshire WD3 3PG

Construction of a single storey rear extension

Full Application Three Rivers
25 Aug 2026 Pending Consideration 26/1350/FUL

26 Ebury Road Rickmansworth Hertfordshire WD3 1BN

Conversion of ground floor storage space to habitable accommodation; alterations to the fenestration

Full Application Three Rivers
25 Aug 2026 Pending Consideration 26/1321/RSP

10 Hyde Lane Nash Mills Hemel Hempstead Hertfordshire HP3 8RY

Part retrospective: Construction of a part single, part two storey side extension; loft conversion including with a rear dormer and front roof light; ...

Retrospective application Three Rivers
24 Aug 2026 Pending Consideration 26/1341/FUL

75 Gallows Hill Lane Abbots Langley Hertfordshire WD5 0DD

Construction of a two storey rear extension; alterations to the fenestration

Full Application Three Rivers
24 Aug 2026 Pending Consideration 26/1265/FUL

6 Chiltern Drive Mill End Rickmansworth Hertfordshire WD3 8JS

Demolition of existing side projection and construction of a new two storey attached dwelling; associated subdivision of site and new access.

Full Application Three Rivers
24 Aug 2026 Pending Consideration 26/1296/FUL

Elm Lodge Old Uxbridge Road West Hyde Rickmansworth Hertfordshire WD3 9XY

Construction of single storey rear extension and first floor side extension; conversion of garage into habitable accommodation; alterations to the roo...

Full Application Three Rivers
24 Aug 2026 Pending Consideration 26/1339/FUL

1 Plaitford Close Rickmansworth Hertfordshire WD3 1NJ

Construction of part-single, part two storey side front and rear extensions; conversion of garage into habitable accommodation; alterations to the fro...

Full Application Three Rivers
21 Aug 2026 Pending Consideration 26/1275/FUL

100 Penrose Avenue Carpenders Park Watford Hertfordshire WD19 5AA

Construction of single storey rear extension; construction of new front porch; hip to gable roof extension with increase in ridge height and removal o...

Full Application Three Rivers
21 Aug 2026 Pending Consideration 26/1326/FUL

6 Mutchetts Close Garston Watford Hertfordshire WD25 9TS

Construction of part single part two storey side and rear extension; partial conversion of garage into habitable accommodation; construction of front ...

Full Application Three Rivers
21 Aug 2026 Withdrawn 26/1343/CLPD

10 Hyde Lane Nash Mills Hemel Hempstead Hertfordshire HP3 8RY

Certificate of Lawfulness Proposed Development: Conversion of garage into habitable accommodation

Certificate of Lawfulness - Proposed Use Three Rivers
19 Aug 2026 Pending Consideration 26/1330/PDE

2 Ashburnham Close South Oxhey Watford Hertfordshire WD19 7PY

Prior Approval: Construction of single storey rear extension (depth 4.5m, maximum height 3.3m, maximum eaves height 2.8m)

PD - Extensions Three Rivers
19 Aug 2026 Pending Consideration 26/1338/FUL

Talland Chorleywood Road Rickmansworth Hertfordshire WD3 4ER

Erection of new vehicular access onto Chorleywood Road including alterations to the front boundary wall

Full Application Three Rivers
19 Aug 2026 Pending Consideration 26/1219/FUL

40 The Clump Rickmansworth Hertfordshire WD3 4BQ

Alterations to driveway to include blocking up of existing access and construction of front boundary wall and electronic gate

Full Application Three Rivers
19 Aug 2026 Pending Consideration 26/1277/FUL

17 Lysander Way Abbots Langley Hertfordshire WD5 0TN

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

Full Application Three Rivers
18 Aug 2026 Pending Consideration 26/1209/FUL

Langsett 22 Chorleywood Bottom Chorleywood Rickmansworth Hertfordshire WD3 5JR

Creation of new vehicular access; alterations to driveway

Full Application Three Rivers
18 Aug 2026 Pending Consideration 26/1220/FUL

28A Sandy Lodge Way Northwood HA6 2AS

Substantial demolition; part single part two storey front and rear extensions; conversion of loft into habitable accommodation; replacement of roof; i...

Full Application Three Rivers
18 Aug 2026 Pending Consideration 26/1282/FUL

Rose Cottage 87 Quickley Lane Chorleywood Rickmansworth Hertfordshire WD3 5PG

Construction of single storey side extension; alterations to the fenestration; alterations to the patio

Full Application Three Rivers
18 Aug 2026 Pending Consideration 26/1311/CLPD

34 Canterbury Way Croxley Green Rickmansworth Hertfordshire WD3 3SS

Certificate of Lawfulness Proposed Development: Loft conversion including hip-to-gable roof extension; construction of a rear dormer; installation of ...

Certificate of Lawfulness - Proposed Use Three Rivers
17 Aug 2026 Pending Consideration 26/1270/CLPD

139 Tudor Way Mill End Rickmansworth Hertfordshire WD3 7HN

Certificate of Lawfulness Proposed Development: Loft conversion including hip to gable roof extension, construction of a rear dormer; installation of ...

Certificate of Lawfulness - Proposed Use Three Rivers
17 Aug 2026 Pending Consideration 26/1295/FUL

252 Baldwins Lane Croxley Green Rickmansworth Hertfordshire WD3 3LQ

Extension to existing dormer and installation of rooflights.

Full Application Three Rivers
17 Aug 2026 Approved 26/1313/EEC

St Pauls Church Langleybury Lane Huton Bridge Sarratt Langleybury Hertfordshire WD4 8QQ

Remove four rows of pews (8 in total) from the rear of the church.

Ecclesiastical Exemption Consultation Three Rivers
14 Aug 2026 Pending Consideration 26/1017/FUL

Land South Of Old House Lane Kings Langley Hertfordshire WD4 8RR

Part retrospective: Change of use of land for use as a residential caravan site, providing a total of 6 pitches, alterations to hardstanding and erect...

Full Application Three Rivers
14 Aug 2026 Pending Consideration 26/1302/FUL

65 Harvey Road Croxley Green Rickmansworth Hertfordshire WD3 3BS

Conversion of garage into habitable accommodation; demolition of existing rear existing extension; construction of part single, part two storey rear e...

Full Application Three Rivers
14 Aug 2026 Pending Consideration 26/1259/RSP

The Halfway House Public House 91 Uxbridge Road Rickmansworth Hertfordshire WD3 7DQ

Retrospective application: Installation of fire escape ladder and supporting tower

Retrospective application Three Rivers
14 Aug 2026 Pending Consideration 26/1246/FUL

Rosebay 20 South Road Chorleywood Rickmansworth Hertfordshire WD3 5AR

Construction of single storey rear extension, detached garage to side and rear of dwelling and outbuilding to rear

Full Application Three Rivers
13 Aug 2026 Pending Consideration 26/1276/FUL

11 Hazelwood Road Croxley Green Rickmansworth Hertfordshire WD3 3EA

Construction of detached annexe

Full Application Three Rivers
13 Aug 2026 Pending Consideration 26/1284/FUL

4 Westland Close Leavesden Watford Hertfordshire WD25 7GH

Demolition of existing conservatory and construction of single storey rear extension

Full Application Three Rivers
13 Aug 2026 Pending Consideration 26/1298/FUL

Warner Bros. Studios Leavesden Warner Drive Watford Hertfordshire WD25 7LP

Retention and extension of the existing acoustic timber fence on Backlot 2.

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.