Foundation Cost by Soil Class in Ireland — The €/m² by Class 1 to Class 5+

Foundation cost in Ireland by soil class: Class 1–2 (rock, gravel, dense sand) — strip foundation, €120–€180/m². Class 3–4 (firm clay, silt, sand with clay) — raft, €180–€260/m². Class 5+ (peat, made ground, fill) — piled raft, €280–€450/m². Add €40–€80/m² for a sloped site, €30–€60/m² for a high water table, €8–€15/m² for a radon barrier in high-radon areas. A 150 m² house foundation: €18,000–€27,000 (Class 1–2) up to €42,000–€67,500 (Class 5+). A soil test (€1,500–€3,000) tells you which. Most sites are Class 3–4 and use a raft.

TL;DR

• Foundation cost by Irish soil class: Class 1–2 (rock, gravel, dense sand): €120–€180/m². Class 3–4 (firm clay, silt, sand with clay): €180–€260/m². Class 5+ (peat, made ground, fill): €280–€450/m².

• Add €40–€80/m² for a sloped site. Add €30–€60/m² for a high water table. Add €8–€15/m² for a radon barrier in high-radon areas.

• A 150 m² house: €18,000–€27,000 (Class 1–2) up to €42,000–€67,500 (Class 5+). A soil test (€1,500–€3,000) tells you which.

When this matters most

You're pricing foundations or choosing a site.

When this doesn't apply

Foundation is poured.

Frequently asked questions

How much does a foundation cost in Ireland?

By soil class: Class 1–2: €120–€180/m². Class 3–4: €180–€260/m². Class 5+: €280–€450/m². Add for slope, water table, radon. A 150 m² house: €18,000–€67,500.

How do I find out my soil class?

Commission a site investigation (€1,500–€3,000). Includes boreholes, soil samples, and a geotechnical report. Engineer uses the report to specify the foundation.

Can I build on Class 5+ ground in Ireland?

Yes, with a piled raft foundation (€280–€450/m²). Piles transfer the building load to a firm bearing stratum below the poor soil. Common on former bogs and made ground.

Sources

Geological Survey Ireland, Irish Soil Classification System. https://www.gsi.ie/

Building Regulations 2023, TGD-A (Structure). https://www.gov.ie/