House extensions in Three Rivers

Three Rivers received 302 householder applications in the last 12 months - about 6 a week. Rear extensions and dormers are the most common. Of the 180 decided so far, 167 were approved. If you're planning your own, the applications below show what people nearby applied for and how the council decided.

198 last 90 days
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53 last 30 days
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20 last 14 days

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Showing 50 of 198 applications
26/1084/FUL 6 Jul 2026 Pending Consideration

Invergarry 33 Astons Road Moor Park Northwood Hertfordshire HA6 2LB

Demolition of existing conservatory; construction of part single, part two storey rear extension; conversion of garage into habitable accommodation; l...

Three Rivers 6 Jul 2026
26/1083/FUL 6 Jul 2026 Pending Consideration

15 Highfield Way Rickmansworth Hertfordshire WD3 7PP

Single storey rear extension; insertion of rear dormers, front porch, alterations to fenestration and alterations to rear patio

Three Rivers 6 Jul 2026
26/1077/PDE 3 Jul 2026 Pending Consideration

36 Girton Way Croxley Green Rickmansworth Hertfordshire WD3 3QN

Prior Approval: Single storey rear extension (depth 5.75 metres, maximum height 3.45 metres, maximum eaves height 3.45 metres)

Three Rivers 3 Jul 2026
26/1061/CLPD 1 Jul 2026 Pending Consideration

74 Hill Rise Rickmansworth Hertfordshire WD3 7NX

Certificate of Lawfulness Proposed Development: Single storey side extension

Certificate of Lawfulness - Proposed Use Three Rivers 1 Jul 2026
26/1059/PDE 30 Jun 2026 Pending Consideration

50 Claremont Crescent Croxley Green Rickmansworth Hertfordshire WD3 3QR

Prior Approval: Single storey rear extension (depth 6.00 metres, maximum height 3.15 metres, maximum eaves height 3.00metres)

PD - Extensions Three Rivers 30 Jun 2026
26/1057/FUL 30 Jun 2026 Pending Consideration

Ingle Lodge Bridle Lane Loudwater Rickmansworth Hertfordshire WD3 4JB

Construction of two storey rear extension, first floor side extension and insertion of front and flank dormer windows

Three Rivers 30 Jun 2026
26/1049/FUL 29 Jun 2026 Pending Consideration

42 Margeholes Carpenders Park Watford Hertfordshire WD19 5AR

Single storey front extension.

Full Application Three Rivers 29 Jun 2026
26/1046/FUL 29 Jun 2026 Pending Consideration

91 Muirfield Road South Oxhey Watford Hertfordshire WD19 6LU

Erection of dropped kerb for vehicular access and installation of block paving

Full Application Three Rivers 29 Jun 2026
26/1050/FUL 29 Jun 2026 Pending Consideration

24A Berry Way Rickmansworth Hertfordshire WD3 7EY

Alterations to the rear fenestration.

Three Rivers 29 Jun 2026
26/1052/FUL 29 Jun 2026 Pending Consideration

35 Lower Road Chorleywood Hertfordshire

Installation of rooflights to front and rear roofslopes

Three Rivers 29 Jun 2026
26/1040/PDE 26 Jun 2026 Pending Consideration

90 Sherborne Way Croxley Green Rickmansworth Hertfordshire WD3 3PG

Prior Approval: Single storey rear extension (depth 5.00 metres, maximum height 2.90 metres, maximum eaves height 2.90 metres)

PD - Extensions Three Rivers 26 Jun 2026
26/1042/FUL 26 Jun 2026 Pending Consideration

36 Girton Way Croxley Green Rickmansworth Hertfordshire WD3 3QN

Loft conversion including hip to gable roof extension; construction of a rear dormer; installation of rooflights and removal of chimney stack, single ...

Full Application Three Rivers 26 Jun 2026
26/1044/PDA 26 Jun 2026 Pending Consideration

Glenwood Harthall Lane Kings Langley Hertfordshire WD4 8JN

Prior Approval: Change of use of existing agricultural building to dwellinghouse (Class C3) with operational works including an extension to the build...

Three Rivers 26 Jun 2026
26/1037/FUL 25 Jun 2026 Pending Consideration

Edgehill Sandy Lane Northwood HA6 3ES

Conversion of garage into habitable accommodation including alterations to fenestration and rooflights.

Full Application Three Rivers 25 Jun 2026
26/1035/CLPD 25 Jun 2026 Pending Consideration

90 Sherborne Way Croxley Green Rickmansworth Hertfordshire WD3 3PG

Certificate of Lawfulness Proposed Development: Single storey rear extension; loft conversion including hip to gable extension, rear dormer and front ...

Certificate of Lawfulness - Proposed Use Three Rivers 25 Jun 2026
26/1028/PDE 24 Jun 2026 Pending Consideration

52 Barton Way Croxley Green Rickmansworth Hertfordshire WD3 3QA

Prior Approval: Single storey rear extension (depth 6.00m, maximum height: 2.95m, maximum eaves height: 2.95m)

PD - Extensions Three Rivers 24 Jun 2026
26/1029/FUL 24 Jun 2026 Pending Consideration

73 Ebury Road Rickmansworth Hertfordshire WD3 1BL

Single storey side and rear extension with rooflights

Full Application Three Rivers 24 Jun 2026
26/1031/FUL 24 Jun 2026 Pending Consideration

Willow House Wagon Way Loudwater Rickmansworth Hertfordshire WD3 4JE

Alterations to the rear fenestration.

Full Application Three Rivers 24 Jun 2026
26/1024/FUL 23 Jun 2026 Pending Consideration

The Briars House 13 The Briars Sarratt Rickmansworth Hertfordshire WD3 6AU

Conversion of existing garage and construction of a single storey link extension to form residential annexe

Full Application Three Rivers 23 Jun 2026
26/1019/FUL 22 Jun 2026 Pending Consideration

Holly Trees Trout Rise Loudwater Rickmansworth Hertfordshire WD3 4JR

Installation of electric timber front gate with pedestrian gate access.

Full Application Three Rivers 22 Jun 2026
26/1012/CLPD 19 Jun 2026 Pending Consideration

68 Watford Road Croxley Green Rickmansworth Hertfordshire WD3 3BP

Certificate of Lawfulness Proposed Development: Loft conversion including hip-to-gable roof extension, rear dormer and front roof lights

Certificate of Lawfulness - Proposed Use Three Rivers 19 Jun 2026
26/1004/CLPD 19 Jun 2026 Pending Consideration

39 Bishops Avenue Northwood HA6 3DD

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

Certificate of Lawfulness - Proposed Use Three Rivers 19 Jun 2026
26/1005/RSP 19 Jun 2026 Pending Consideration

Conifers 11 Grovewood Close Chorleywood Rickmansworth Hertfordshire WD3 5PU

Retrospective: Replacement of pre-existing glazed pitched conservatory roof with flat roof.

Retrospective application Three Rivers 19 Jun 2026
26/1001/FUL 18 Jun 2026 Pending Consideration

17 Killingdown Farm Way Croxley Green Rickmansworth Hertfordshire WD3 3GB

Construction of a single storey side and rear extension

Full Application Three Rivers 18 Jun 2026
26/0991/FUL 18 Jun 2026 Pending Consideration

90 Baldwins Lane Croxley Green Rickmansworth Hertfordshire WD3 3LP

Part-Retrospective: Construction of front porch, conversion of garage into habitable accommodation and internal alterations.

Full Application Three Rivers 18 Jun 2026
26/0998/FUL 18 Jun 2026 Pending Consideration

16 Ridgehurst Avenue Leavesden Watford Hertfordshire WD25 7AY

Construction of single storey side and rear extensions.

Full Application Three Rivers 18 Jun 2026
26/0982/PDE 17 Jun 2026 Pending Consideration

2 On The Hill Carpenders Park Watford Hertfordshire WD19 5DR

Prior Approval: Demolition of existing extension, Construction of single storey rear extensions. (Maximum depth: 6.00m, Maximum height: 3.45m, Maximum...

PD - Extensions Three Rivers 17 Jun 2026
26/0983/FUL 17 Jun 2026 Pending Consideration

49 Sherborne Way Croxley Green Rickmansworth Hertfordshire WD3 3PE

Demolition of existing conservatory and construction of single storey rear extension

Full Application Three Rivers 17 Jun 2026
26/0986/FUL 17 Jun 2026 Pending Consideration

76 Eastwick Crescent Mill End Rickmansworth Hertfordshire WD3 8YJ

Demolition of existing storage building conservatory; construction of rear and side extension; alterations to fenestration, including construction of ...

Full Application Three Rivers 17 Jun 2026
26/0966/FUL 15 Jun 2026 Pending Consideration

53 Oakhill Road Maple Cross Rickmansworth Hertfordshire WD3 9RE

Demolition of existing garage, construction of part two storey, part first floor side and rear extensions

Full Application Three Rivers 15 Jun 2026
26/0973/CLPD 15 Jun 2026 Pending Consideration

125 Windmill Drive Croxley Green Rickmansworth Hertfordshire WD3 3FB

Certificate of Lawfulness Proposed Development: Loft conversion including rear dormer and front rooflights.

Certificate of Lawfulness - Proposed Use Three Rivers 15 Jun 2026
26/0968/FUL 15 Jun 2026 Pending Consideration

Pennhurst 1 Berks Hill Chorleywood Rickmansworth Hertfordshire WD3 5AG

Alteration and extension of driveway.

Three Rivers 15 Jun 2026
26/0964/CLPD 12 Jun 2026 Pending Consideration

130 Abbots Road Abbots Langley Hertfordshire WD5 0BL

Certificate of Lawfulness Proposed Development: Construction of detached single storey garage/outbuilding

Certificate of Lawfulness - Proposed Use Three Rivers 12 Jun 2026
26/0963/FUL 12 Jun 2026 Pending Consideration

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

Extensions to temporary school building in association with on-site filming activities.

Full Application Three Rivers 12 Jun 2026
26/0955/CLPD 11 Jun 2026 Pending Consideration

31 Carpenders Avenue Carpenders Park Watford Hertfordshire WD19 5BS

Certificate of Lawfulness Proposed Development: Proposed loft conversion including hip to gable extension, rear dormer and front rooflights

Certificate of Lawfulness - Proposed Use Three Rivers 11 Jun 2026
26/0956/FUL 11 Jun 2026 Pending Consideration

37 Blacketts Wood Drive Chorleywood Rickmansworth Hertfordshire WD3 5PY

Construction of single storey front extension, single storey rear extension; garage conversion including alterations to existing garage roof and raise...

Full Application Three Rivers 11 Jun 2026
26/0954/FUL 11 Jun 2026 Pending Consideration

11 Nightingale Road Rickmansworth Hertfordshire WD3 7DE

Demolition of existing rear projection and construction of new single-storey side and rear extensions, pitched roof over existing side extension and a...

Full Application Three Rivers 11 Jun 2026
26/0942/FUL 10 Jun 2026 Pending Consideration

Woodfield House Chalfont Lane Chorleywood Rickmansworth Hertfordshire WD3 5PP

Construction of a detached garage building within the front curtilage and alterations to front driveway

Full Application Three Rivers 10 Jun 2026
26/0951/FUL 10 Jun 2026 Pending Consideration

31 Carpenders Avenue Carpenders Park Watford Hertfordshire WD19 5BS

Construction of first floor front extension; loft conversion with hip to gable roof extension and rear dormer, front rooflights

Full Application Three Rivers 10 Jun 2026
26/0948/FUL 10 Jun 2026 Pending Consideration

The Willows Shire Lane Chorleywood Rickmansworth Hertfordshire WD3 5NT

Substantial demolition of existing dwelling; re-construction of dwelling to include part single-storey, part two-storey front, side and rear extension...

Full Application Three Rivers 10 Jun 2026
26/0939/FUL 9 Jun 2026 Pending Consideration

2 Ralston Way South Oxhey Watford Hertfordshire WD19 7BH

Loft conversion including increase in ridge height, with hip to gable roof extension, rear dormer and front rooflights; alterations to ground floor do...

Full Application Three Rivers 9 Jun 2026
26/0936/FUL 9 Jun 2026 Pending Consideration

8 Abbey Drive Abbots Langley Hertfordshire WD5 0TL

Demolition of existing conservatory and construction of single story rear extension; conversion of garage into habitable accommodation

Full Application Three Rivers 9 Jun 2026
26/0935/FUL 8 Jun 2026 Pending Consideration

53 St Marys Avenue Northwood HA6 3AY

Construction of single storey rear extension with roof lantern, installation of window to side elevation

Full Application Three Rivers 8 Jun 2026
26/0928/CLPD 8 Jun 2026 Pending Consideration

50 Harthall Lane Kings Langley Hertfordshire WD4 8JH

Certificate of Lawfulness Proposed Development: Stationing of mobile home for ancillary residential use as annexe

Certificate of Lawfulness - Proposed Use Three Rivers 8 Jun 2026
26/0930/PDE 8 Jun 2026 Pending Consideration

116 Penrose Avenue Carpenders Park Watford Hertfordshire WD19 5AA

Prior Approval: Single storey rear extension (depth 6.00 metres, maximum height 2.81 metres, maximum eaves height 2.81 metres)

PD - Extensions Three Rivers 8 Jun 2026
26/0923/CLPD 5 Jun 2026 Pending Consideration

115 Frankland Road Croxley Green Rickmansworth Hertfordshire WD3 3AS

Certificate of Lawfulness Proposed Development: Loft conversion including hip to gable roof extension, with rear juliet dormer and front rooflights

Certificate of Lawfulness - Proposed Use Three Rivers 5 Jun 2026
26/0924/FUL 5 Jun 2026 Pending Consideration

6 Mallard Road Abbots Langley Hertfordshire WD5 0GA

Demolition of existing conservatory and construction of single storey rear extension with roof lantern

Full Application Three Rivers 5 Jun 2026
26/0920/PDE 4 Jun 2026 Decided

87 Durrants Drive Croxley Green Rickmansworth Hertfordshire WD3 3NY

Prior Approval: Single storey rear extension (depth 6.00 metres, maximum height 3.00 metres, maximum eaves height 3.00 metres)

PD - Extensions Three Rivers 4 Jun 2026
26/0904/FUL 3 Jun 2026 Pending Consideration

36 Shepherds Way Rickmansworth Hertfordshire WD3 7NL

Demolition of existing single storey side extension, construction of part-single, part-two storey side extension, single storey rear extension and sid...

Full Application Three Rivers 3 Jun 2026
26/0905/FUL 3 Jun 2026 Pending Consideration

36 Shepherds Way Rickmansworth Hertfordshire WD3 7NL

Construction of single storey rear extension and first floor side extension, loft conversion including increase in ridge height with rear dormers and ...

Full Application Three Rivers 3 Jun 2026
Recency
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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 — taller, larger, 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 with objections) 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.