Question 1

How much does a house extension cost in Ireland?

Accepted Answer

A single-storey rear extension typically costs €1,500–€2,500 per m². A standard 25m² extension costs €40,000–€60,000 fully finished including VAT. Two-storey extensions cost more due to structural complexity.

Question 2

Do I need planning permission for a house extension in Ireland?

Accepted Answer

Extensions under 40m² to the rear of a house may qualify as exempted development, provided they meet certain conditions. Side extensions and any extension that brings the total over 40m² require full planning permission.

Question 3

How long does a house extension take in Ireland?

Accepted Answer

A typical single-storey extension takes 10–16 weeks from start to finish. Planning permission (if required) adds 8–12 weeks. Two-storey extensions take 16–24 weeks.

Question 4

Do I need an engineer for a house extension in Ireland?

Accepted Answer

Yes. A chartered engineer or architect is required to sign off on the structural design and issue a Certificate of Compliance. This is needed for your solicitor and mortgage lender if you sell the property.

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