How much does a house extension cost in Ireland?
There's no reliable published price range for an extension in our source price book — it explicitly flags its only general-building day-rate figure as an unverified 2023 estimate with 'no current published norm', so we don't show a number we don't trust. Extensions and structural projects vary too widely by scope, site conditions and materials for a single range to be honest — get two or three on-site quotes instead.
Ground conditions, foundation type, and whether planning permission or an exemption applies all affect cost before a single block is laid, which is why a generic 'per m²' figure is misleading for this kind of project.
The fairest way to compare builders is against identical drawings and a shared specification, so every quote is pricing the same thing rather than each builder's own assumptions.
Ask each quote to separate labour from materials clearly, and to show VAT treatment — the two-thirds rule can tip a materials-heavy extension from 13.5% to 23% VAT on the whole job (see our VAT guide).
What to check
- Are quotes based on the same drawings and specification
- Does the quote separate labour from materials clearly
- Is VAT treatment shown (13.5% vs the 23% two-thirds-rule trigger)
- Planning status, if the project needs permission
When to call a pro
Get drawings or at least a clear written brief ready before asking builders to quote.
Sources
- Irish Trade Price Book v1, 17 August 2026, §2 note and §6 verification list item 3
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