Just when Bono may have thought his planning application to expand his house - Temple Hill, Vico Road, Killiney - further skyward had no opposition, An Taisce submitted its objection to Dún Laoghaire-Rathdown County Council at the 11th hour.

The U2 frontman applied last month for a 130sq m (1,400sq ft) roof extension and a conservatory saying his current 595sq m (6,400sq ft) of living space no longer meets the family's needs. The extension would house a main bedroom (bringing the number of bedrooms to five), a study, two en suites, two dressingrooms and storage. Apparently it would be a lightweight prefab structure placed over the pitched roof which, says Bono'sarchitect Colin Jennings, could be removed at short notice. A ground floor conservatory with a terrace above is also part of the plan.

But An Taiscesays the house is within a conservation area and it doesn't approve of the lead roof finish, the metal frame windows of the extension and decorative panels which it says are out of keeping with the architectural integrity of the building. It also says the extension would "distract" from two protected structures, singer Enya'sAyesha Castle and Killiney Hill Obelisk.

Saying that it is "disappointed" that the council hasn't listed Temple Hill, An Taiscepoints to the substantial size of the home which is made up of the main house, mews, coach-house, folly, gardener's shelter, changing facilities, and recreation building.

It suggests "a more sympathetic extension with a similar design and finish to the original house should be considered".