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Planning permission for a basement

Converting an existing basement inside the house usually needs no planning permission: works that only affect the interior are exempted development. A new basement, a new light well at the front or a protected structure is a question for the council.

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  • Section 4(1)(h)interior works: exempt
  • Section 5a declaration settles it
  • Protected structuresinterior works can need permission
  • 50%of the garden: Dublin City's basement limit

When you need permission

Converting an existing basement. Works that affect only the interior of a building, or don't materially change how it looks, are exempted development under section 4(1)(h) of the Planning and Development Act 2000. Waterproofing, insulating and fitting out an existing basement inside the house usually falls under that.

Digging a new basement, or extending one. Treat it as needing permission. It adds floor area below ground, affects the structure and can affect the neighbours. Councils look at flood risk, drainage, light and the effect on the houses beside you.

New light wells and windows. A new opening at the front changes how the house looks, so it can take away the exemption. At the back it's less likely to.

Protected structures. On a protected structure even interior works can need permission. Ask the council for a section 57 declaration on what you can do.

Not sure? Ask the council for a section 5 declaration: it decides whether a piece of work is development and whether it's exempt.

Dublin City Council's basement rules

Dublin City Council's development plan has its own basement policy:

  • No basements used as homes below the flood level in Flood Zones A and B.
  • A basement shouldn't generally take up more than 50% of the garden.
  • In conservation areas and beside protected structures, deep basements are discouraged.
  • The water table, underground streams and sewers have to be considered, and sustainable drainage is recommended.
  • A means of escape to ground level, enough daylight (the council can ask for a daylight analysis) and natural ventilation where possible.

Other councils have their own development plans. The company you're matched with knows the local ones.

After planning: building control

Planning and the Building Regulations are separate. Every basement conversion has to meet the Building Regulations, permission or not. Where the work needs planning permission, a Commencement Notice goes to the council's building control section before work starts. See the Building Regulations.

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Questions we get asked

Do I need planning permission to convert my basement?

Usually not, if it's an existing basement and the work is inside the house. A new front opening or a protected structure changes that.

Do I need planning permission to dig a basement?

Usually yes, for a new basement. Ask the council, or apply for a section 5 declaration.

What is a section 5 declaration?

A written decision from the council on whether a piece of work needs planning permission.

Can a basement be a separate flat?

Not without planning permission. Turning part of a house into a separate home is a change of use.

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