Budgeting a Self-Build in Ireland 2026 — The 5 Numbers Every Self-Builder Must Know
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Five numbers every self-builder must know: build €/m² (€2,500–€3,800 SCSI Q1 2026), site works (15–25% of build), fees (8–12% of build), VAT (€30k–€90k on a €500k build), contingency (10% minimum). Set them in the first month. Re-check at each design stage. The five numbers catch 80% of cost overruns. Example: a 180 m² house at €3,000/m² = €540k build. Plus site €80k, fees €50k, VAT €60k, contingency €54k. Total: €784k. Most first-time self-builders who run over budget did so because they didn't set the five numbers early, didn't re-check at design stages, or didn't have a 15% contingency. The five numbers are the foundation of the budget; the cost plan is the detail.
TL;DR
Five numbers every self-builder must know: build €/m² (€2,500–€3,800), site works (15–25% of build), fees (8–12% of build), VAT (€30k–€90k on a €500k build), contingency (10% minimum).
Set them in the first month. Re-check at each design stage. The five numbers catch 80% of cost overruns.
A 180 m² house at €3,000/m² = €540k build. Plus site €80k, fees €50k, VAT €60k, contingency €54k. Total: €784k.
When this matters most
You're at the start of the journey and need to set the budget.
When this doesn't apply
You've already signed a building contract with a fixed price.
Frequently asked questions
What are the 5 numbers for a self-build budget?
Build €/m² (€2,500–€3,800), site works (15–25% of build), fees (8–12% of build), VAT (€30k–€90k on a €500k build), contingency (10% minimum). Set them in the first month.
How much should I budget for a 180 m² self-build in Ireland?
€540k build (at €3,000/m²) + site €80k + fees €50k + VAT €60k + contingency €54k = €784k total. 15% contingency is safer.
When should I set the self-build budget?
In the first month, before you brief the architect. The five numbers (build €/m², site works, fees, VAT, contingency) catch 80% of cost overruns. Re-check at each design stage.
Sources
SCSI, Tender Price Index Q1 2026. https://www.scsi.ie/
Frequently asked questions
What are the 5 numbers for a self-build budget?
Build €/m² (€2,500–€3,800), site works (15–25% of build), fees (8–12% of build), VAT (€30k–€90k on a €500k build), contingency (10% minimum). Set them in the first month.
How much should I budget for a 180 m² self-build in Ireland?
€540k build (at €3,000/m²) + site €80k + fees €50k + VAT €60k + contingency €54k = €784k total. 15% contingency is safer.
When should I set the self-build budget?
In the first month, before you brief the architect. The five numbers (build €/m², site works, fees, VAT, contingency) catch 80% of cost overruns. Re-check at each design stage.