House extensions in Cardiff

Cardiff received 182 householder applications in the last 12 months - about 4 a week. Rear extensions and dormers are the most common. Of the 119 decided so far, 115 were approved. If you're planning your own, the applications below show what people nearby applied for and how the council decided.

89 last 90 days
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23 last 30 days
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8 last 14 days

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Showing 50 of 89 applications
26/01392/HSE 6 Jul 2026 Registered

107 Brandreth Road Penylan Cardiff CF23 5LE

Single storey rear extension.

Cardiff 6 Jul 2026
26/01388/CLPUD 6 Jul 2026 Registered

20 Meadow Street Pontcanna Cardiff CF11 9PY

Construction of single storey rear extension.

Cardiff 6 Jul 2026
26/01393/FUL 6 Jul 2026 Registered

138 Rhymney Street Cathays Cardiff CF24 4DJ

Change of use from C3 Dwellinghouse to C4 House in Multiple Occupation (5 Bedrooms) and construction of rear dormer.

Cardiff 6 Jul 2026
26/01378/HSE 3 Jul 2026 Registered

65 Plantagenet Street Riverside Cardiff

GROUND AND FIRST FLOOR REAR EXTENSION

Cardiff 3 Jul 2026
26/01385/HSE 3 Jul 2026 Registered

6 Amherst Street Grangetown Cardiff CF11 7DR

Demolition of existing rear extension and construction of a single story wrap around extension.

Cardiff 3 Jul 2026
26/01369/HSE 2 Jul 2026 Registered

31 Pendragon Close Thornhill Cardiff CF14 9BD

Rear Dormer Extension

Cardiff 2 Jul 2026
26/01373/VAR 2 Jul 2026 Registered

243 - 245 Cathedral Road Pontcanna Cardiff CF11 9PP

Change of use to Class A3 Coffee Shop, external and internal alterations and other associated refurbishments. (Approved 05/12/2025 - 25/02566/FUL); Va...

Cardiff 2 Jul 2026
26/01351/LBC 29 Jun 2026 Registered

Queens Building HV Laboratory, Cardiff University Newport Road Roath Cardiff CF24 0TA

Replace existing single glazed windows with double glazed equivalents; replace the single glazed roof lantern with concrete tiles that match the exist...

Listed Building Consent Cardiff 29 Jun 2026
26/01336/FUL 26 Jun 2026 Registered

72 Albany Road Roath Cardiff CF24 3RS

GROUND FLOOR REAR EXTENSION AND SIDE EXTENSION TO SHOP WITH CHANGE OF USE TO ESTATE AGENCY PLUS SIDE DORMER LOFT CONVERSION TO FLAT 1

Full Planning Permission Cardiff 26 Jun 2026
26/01307/VAR 23 Jun 2026 Registered

2 Clyro Place Llandaff North Cardiff CF14 2LT

2 storey extension to side and single storey extension to rear (removal of existing). (Approved 1 May 2026- 26/00111/HSE):- Variation of Conditions 2 ...

Variation of conditions Cardiff 23 Jun 2026
26/01291/HSE 22 Jun 2026 Registered

42 Beatrice Road Whitchurch Cardiff CF14 1DT

Single Storey Rear Extension.

Householder Planning Permission Cardiff 22 Jun 2026
26/01285/FUL 22 Jun 2026 Registered

55 - 59 Despenser Street Riverside Cardiff CF11 6AG

Retrospective planning application of retractable canopy and acoustic fence

Full Planning Permission Cardiff 22 Jun 2026
26/01273/CLPUD 19 Jun 2026 Registered

19 Lon-y-parc Heath Cardiff CF14 6DF

Single storey rear extension.

Cert of Lawfulness Proposed (s192) Cardiff 19 Jun 2026
26/01281/FUL 19 Jun 2026 Registered

287 Cyncoed Road Cyncoed Cardiff CF23 6PA

Installation of a pergola with retractable roof to rear, use of rear external seating area.

Full Planning Permission Cardiff 19 Jun 2026
26/01263/FUL 18 Jun 2026 Registered

63 - 65 City Road Roath Cardiff CF24 3BL

Single storey rear extension.

Full Planning Permission Cardiff 18 Jun 2026
26/01250/HSE 17 Jun 2026 Registered

Rear Of 34 Hamilton Street Pontcanna Cardiff CF11 9BP

Proposed Double Garage to rear

Householder Planning Permission Cardiff 17 Jun 2026
26/01254/HSE 17 Jun 2026 Registered

9 Elaine Close Thornhill Cardiff CF14 9AT

Single storey front extension.

Householder Planning Permission Cardiff 17 Jun 2026
26/01255/HSE 17 Jun 2026 Registered

15 Hawker Close Splott Cardiff CF24 2PN

Single story porch extension, double storey side extension, single storey rear extension.

Householder Planning Permission Cardiff 17 Jun 2026
26/01252/FUL 17 Jun 2026 Registered

276 North Road Gabalfa Cardiff CF14 3BL

CONVERSION FROM TWO TO THREE FLATS OVER THE EXISTING OFFICE WITH REAR DORMER LOFT CONVERSION

Full Planning Permission Cardiff 17 Jun 2026
26/01241/CLPUD 16 Jun 2026 Decided

134 Taff Embankment Grangetown Cardiff CF11 7BJ

Rear dormer roof extension.

Cert of Lawfulness Proposed (s192) Cardiff 16 Jun 2026
26/01242/FUL 16 Jun 2026 Registered

33 Dalton Street Cathays Cardiff CF24 4HB

Change of use from a single dwelling house to 2 no. two-bedroom flats, including a two-storey rear extension and associated external alterations

Full Planning Permission Cardiff 16 Jun 2026
26/01239/HSE 16 Jun 2026 Registered

104 Heol Hir Llanishen Cardiff CF14 5AD

Single storey rear extension, small double height extension and attic conversion including roof extensions and alterations.

Householder Planning Permission Cardiff 16 Jun 2026
26/01229/NMA 15 Jun 2026 Decided

57 Celyn Avenue Cyncoed Cardiff CF23 6EJ

Proposed Non-Material Amendment to Planning Permission 25/02767/HSE- minor alterations including a rooflight to the front roof slope and addition of a...

Non Material Amendment Cardiff 15 Jun 2026
26/01195/HSE 10 Jun 2026 Registered

3 Gelligaer Gardens Cathays Cardiff CF24 4LT

Single-storey rear extension.

Householder Planning Permission Cardiff 10 Jun 2026
26/01202/HSE 10 Jun 2026 Decided

72 Timothy Rees Close Llandaff Cardiff CF5 2AU

Two storey side & single storey rear extension with other external alterations.

Householder Planning Permission Cardiff 10 Jun 2026
26/01201/FUL 10 Jun 2026 Registered

100 Brunswick Street Canton Cardiff CF5 1LL

Change of use from dwelling to 6 bedroom (7 occupant) HMO. Including rear dormer loft conversion

Full Planning Permission Cardiff 10 Jun 2026
26/01192/HSE 9 Jun 2026 Registered

15 Celyn Grove Cyncoed Cardiff CF23 6SH

Single storey side extension.

Householder Planning Permission Cardiff 9 Jun 2026
26/01179/CLPUD 8 Jun 2026 Awaiting decision

Y Gocyd Heol-y-parc Pentyrch Cardiff CF15 9NB

Single storey side extension.

Cert of Lawfulness Proposed (s192) Cardiff 8 Jun 2026
26/01182/CLPUD 8 Jun 2026 Decided

20 Heol-yr-efail Rhiwbina Cardiff CF14 4SR

Ground floor side extension, replacing existing.

Cert of Lawfulness Proposed (s192) Cardiff 8 Jun 2026
26/01183/CLPUD 8 Jun 2026 Decided

27 Clos Ton Mawr Rhiwbina Cardiff CF14 6RH

Single storey rear extension, hip to gable roof and rear dormer loft conversion.

Cert of Lawfulness Proposed (s192) Cardiff 8 Jun 2026
26/01177/HSE 8 Jun 2026 Registered

28 Llandaff Road Riverside Cardiff CF11 9NJ

Single-storey rear extension, and raising the roof of rear lean-to building.

Householder Planning Permission Cardiff 8 Jun 2026
26/01174/HSE 5 Jun 2026 Registered

40 Downton Road Rumney Cardiff CF3 3BJ

Single-storey side extension and demolition of existing detached garage.

Householder Planning Permission Cardiff 5 Jun 2026
26/01163/HSE 4 Jun 2026 Registered

30 Hazelhurst Road Llandaff North Cardiff CF14 2FX

New garden room to replace the existing garden shed.

Householder Planning Permission Cardiff 4 Jun 2026
26/01153/CLPUD 4 Jun 2026 Decided

Great Ormes House Ferry Court Grangetown Cardiff

Remediation works comprising of replacement rendering, cladding and balcony decking. Installation of cavity barriers within brickwork and inspection o...

Cert of Lawfulness Proposed (s192) Cardiff 4 Jun 2026
26/01156/CLPUD 4 Jun 2026 Decided

Kilcredaun House Ferry Court Grangetown Cardiff CF11 0JG

Remediation works comprising of replacement rendering, cladding and balcony decking. Installation of cavity barriers within brickwork and inspection o...

Cert of Lawfulness Proposed (s192) Cardiff 4 Jun 2026
26/01144/HSE 3 Jun 2026 Registered

53 Braunton Avenue Llanrumney Cardiff CF3 5HW

Ground floor rear and side extension with raised ground levels.

Householder Planning Permission Cardiff 3 Jun 2026
26/01143/LBC 3 Jun 2026 Registered

41 Lon Isa Rhiwbina Cardiff CF14 6EE

Single and double storey rear extension.

Listed Building Consent Cardiff 3 Jun 2026
26/01148/FUL 3 Jun 2026 Registered

Clive Lodge 51 Clive Road Canton Cardiff CF5 1HG

Two storey side extension, infill side extension, rear dormer roof extension, hip to gable and ridge raise of the rear ground floor annex and installa...

Full Planning Permission Cardiff 3 Jun 2026
26/01142/HSE 3 Jun 2026 Registered

41 Lon Isa Rhiwbina Cardiff CF14 6EE

Single and double storey rear extension

Householder Planning Permission Cardiff 3 Jun 2026
26/01149/FUL 3 Jun 2026 Decided

1 - 3 Stadium Close Leckwith Cardiff CF11 8TS

Canopy over store room car park to front elevation.

Full Planning Permission Cardiff 3 Jun 2026
26/01131/HSE 2 Jun 2026 Registered

67 Windermere Avenue Cyncoed Cardiff CF23 5PS

Rear dormer and hip to gable roof.

Householder Planning Permission Cardiff 2 Jun 2026
26/01134/HSE 2 Jun 2026 Decided

20 Queensberry Road Penylan Cardiff CF23 9JJ

Two storey side extension.

Householder Planning Permission Cardiff 2 Jun 2026
26/01124/HSE 2 Jun 2026 Decided

24 Victoria Park Road East Canton Cardiff CF5 1EG

Single storey rear extension, demolishing existing, and rear dormer loft conversion.

Householder Planning Permission Cardiff 2 Jun 2026
26/01137/HSE 2 Jun 2026 Registered

Brynawel Cardiff Road Creigiau Cardiff CF15 9NL

Single Storey Garage / Store building including minor associated external works

Householder Planning Permission Cardiff 2 Jun 2026
26/01133/HSE 2 Jun 2026 Registered

6 Lon Penllyn Rhiwbina Cardiff CF14 6BZ

Hip to gable roof with rear flat roof dormer and single storey extension

Householder Planning Permission Cardiff 2 Jun 2026
26/01141/HSE 2 Jun 2026 Decided

39 Llanrumney Avenue Llanrumney Cardiff CF3 4BQ

Converting conservatory to a solid-wall extension, rear dormer roof extension.

Householder Planning Permission Cardiff 2 Jun 2026
26/01118/FUL 1 Jun 2026 Registered

Cardiff University 6 Museum Place Cathays Cardiff CF10 3BG

Retrospective Planning Application for Single-Storey Storage Unit, AC Units, and First-Floor Pergola.

Full Planning Permission Cardiff 1 Jun 2026
26/01114/CLPUD 1 Jun 2026 Decided

80 Heol Uchaf Rhiwbina Cardiff CF14 6SR

Hip to gable and rear dormer roof extension.

Cert of Lawfulness Proposed (s192) Cardiff 1 Jun 2026
26/01107/HSE 29 May 2026 Decided

92 Colchester Avenue Penylan Cardiff CF23 9AZ

Ground floor rear extension with pergola.

Householder Planning Permission Cardiff 29 May 2026
26/01128/HSE 29 May 2026 Awaiting decision

7 Chester Close Trowbridge Cardiff CF3 0EP

Single storey rear extension.

Householder Planning Permission Cardiff 29 May 2026
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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 Cardiff?
Yes. Click "Set up alerts" on this page and you'll get a daily or weekly email listing every new extensions application published by Cardiff. You can also narrow the alert to a postcode, street, or drawn area.

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