BuildableFree beta

What are the largest development sites in Blanchardstown, Castleknock and Ongar?

484 development sites in Blanchardstown, Castleknock and Ongar are a hectare or larger, as of 25 Sep 2026. The largest is public land in Blanchardstown-Mulhuddart, at 38.9 ha (publicly owned land).

From public registers, checked 25 Sep 2026. Updated nightly.

Sites of a hectare or more in Blanchardstown, Castleknock and Ongar, largest first

  1. Public land in Blanchardstown-Mulhuddart

    Blanchardstown-Mulhuddart · Fingal · 38.9 ha · source

    Publicly owned land

    38.9 ha, Held by The Industrial Development Authority

  2. Public land in Castleknock

    Castleknock · Fingal · 32.41 ha · source

    Publicly owned land

    32.4 ha, Held by The Office of Public Works

  3. Public land in Blanchardstown-Mulhuddart

    Blanchardstown-Mulhuddart · Fingal · 31.27 ha · source

    Publicly owned land

    31.3 ha, Held by Fingal County Council

  4. Barberstown

    Ongar · Fingal · 29.59 ha · source

    Permitted, not started

    1243 homes granted 30 Mar 2023, expires 30 Mar 2033

  5. Hollywoodrath, Hollystown, Dublin 15

    Blanchardstown-Mulhuddart · Fingal · 28.54 ha · source

    Stalled build

    455 homes; commenced 24 Jul 2015, no completion certificate, planned end Jul 2016

  6. Public land in Blanchardstown-Mulhuddart

    Blanchardstown-Mulhuddart · Fingal · 27.33 ha · source

    Publicly owned land

    27.3 ha, Held by Dublin City Council

  7. Public land in Blanchardstown-Mulhuddart

    Blanchardstown-Mulhuddart · Fingal · 26.9 ha · source

    Publicly owned land

    26.9 ha, Held by Dublin City Council

  8. Public land in Blanchardstown-Mulhuddart

    Blanchardstown-Mulhuddart · Fingal · 25.15 ha · source

    Publicly owned land

    25.2 ha, Held by Electricity Supply Board

  9. Public land in Blanchardstown-Mulhuddart

    Blanchardstown-Mulhuddart · Fingal · 24.33 ha · source

    Publicly owned land

    24.3 ha, Held by Fingal County Council

  10. Land in Blanchardstown-Mulhuddart

    Blanchardstown-Mulhuddart · Fingal · 22.75 ha · source

    On the RZLT map, no permission

    22.8 ha, RZLT-liable and no live permission for 10+ homes on it

  11. Public land in Blanchardstown-Mulhuddart

    Blanchardstown-Mulhuddart · Fingal · 20.43 ha · source

    Publicly owned land

    20.4 ha, Held by Institute of Technology Blanchardstown

  12. ICU Department, Level 3, Connolly Hospital

    Blanchardstown-Mulhuddart · Fingal · 20.32 ha · source

    Stalled build

    commenced 15 Nov 2020, no completion certificate, planned end Nov 2020

  13. Public land in Blanchardstown-Mulhuddart

    Blanchardstown-Mulhuddart · Fingal · 19.47 ha · source

    Publicly owned land

    19.5 ha, Held by Health Service Executive

  14. Public land in Blanchardstown-Mulhuddart

    Blanchardstown-Mulhuddart · Fingal · 19.07 ha · source

    Publicly owned land

    19.1 ha, Held by Dublin City Council

  15. Public land in Blanchardstown-Mulhuddart

    Blanchardstown-Mulhuddart · Fingal · 14.96 ha · source

    Publicly owned land

    15.0 ha, Held by Minister for Agriculture, Food and the Marine

  16. Public land in Blanchardstown-Mulhuddart

    Blanchardstown-Mulhuddart · Fingal · 14.33 ha · source

    Publicly owned land

    14.3 ha, Held by Fingal County Council

  17. Land in Castleknock

    Castleknock · Fingal · 14.21 ha · source

    On the RZLT map (3% land tax)

    14.2 ha, On the 2027 draft RZLT map

  18. Public land in Blanchardstown-Mulhuddart

    Blanchardstown-Mulhuddart · Fingal · 13.77 ha · source

    Publicly owned land

    13.8 ha, Held by The Industrial Development Authority

  19. Public land in Blanchardstown-Mulhuddart

    Blanchardstown-Mulhuddart · Fingal · 13.25 ha · source

    Publicly owned land

    13.2 ha, Held by The Industrial Development Authority

  20. Public land in Blanchardstown-Mulhuddart

    Blanchardstown-Mulhuddart · Fingal · 13.12 ha · source

    Publicly owned land

    13.1 ha, Held by The Industrial Development Authority

  21. Land in Castleknock

    Castleknock · Fingal · 12.79 ha · source

    On the RZLT map (3% land tax)

    12.8 ha, On the 2027 draft RZLT map

  22. Public land in Blanchardstown-Mulhuddart

    Blanchardstown-Mulhuddart · Fingal · 12.2 ha · source

    Publicly owned land

    12.2 ha, Held by Dublin City Council

  23. Public land in Blanchardstown-Mulhuddart

    Blanchardstown-Mulhuddart · Fingal · 11.87 ha · source

    Publicly owned land

    11.9 ha, Held by The Industrial Development Authority

  24. Public land in Blanchardstown-Mulhuddart

    Blanchardstown-Mulhuddart · Fingal · 11.2 ha · source

    Publicly owned land

    11.2 ha, Held by The Industrial Development Authority

  25. Public land in Blanchardstown-Mulhuddart

    Blanchardstown-Mulhuddart · Fingal · 11.18 ha · source

    Publicly owned land

    11.2 ha, Held by Dublin City Council

Showing 25 of 484. See them all →

Go further

New development sites in Fingal, every Monday

The week's new sites: permission running out, council selling land, derelict or stalled. Each with its source. Free while in beta.

More about Blanchardstown, Castleknock and Ongar

Is there development land for sale in Blanchardstown, Castleknock and Ongar?
Buildable found 62 sites in Blanchardstown, Castleknock and Ongar with a public sign they could come to market, as of 25 Sep 2026: 26 council sites proposed for sale, 2 sites with planning permission running out or recently expired, 2 derelict sites on the register and 41 stalled builds. These come from public registers, not agents' listings, so many are not advertised yet.
How many development sites are there in Blanchardstown, Castleknock and Ongar?
Buildable tracks 1,663 development sites in Blanchardstown, Castleknock and Ongar, as of 25 Sep 2026: every site with a public reason it could be built on or sold, from the councils' and national registers. They include 9 permitted schemes not started, 13 derelict sites, 32 council land sales and 41 stalled builds.
How much land in Blanchardstown, Castleknock and Ongar is on the RZLT map?
1,104 ha of land in Blanchardstown, Castleknock and Ongar is on the Residential Zoned Land Tax map, across 1,093 parcels (2027 draft RZLT map), as of 25 Sep 2026. 991 ha of it has no live permission for 10 or more homes. The tax is 3% of market value a year, collected by Revenue on maps the councils make.
How much zoned land in Blanchardstown, Castleknock and Ongar has no planning permission?
991 ha in Blanchardstown, Castleknock and Ongar is zoned for housing, on the RZLT map and has no live permission for 10 or more homes: 1,038 parcels, as of 25 Sep 2026. Land on the map is liable for the Residential Zoned Land Tax of 3% of market value a year.

Data as of 25 Sep 2026. Sources: Council Residential Zoned Land Tax maps; Land Development Agency, Register of Relevant Lands; Planning applications (Department of Housing national planning data).

Cite this: What are the largest development sites in Blanchardstown, Castleknock and Ongar? Buildable, data as of 25 Sep 2026. https://buildable.ie/q/largest-development-sites-dublin-15

Facts from public registers, not advice. Every question · How it works