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What type of foundations do I need for a house in Ireland?

The foundation type is determined by the ground beneath your site, the loads from the building and the water table, not by preference. Strip, trench fill, raft and piled foundations are all used in Ireland, and the choice should follow a site investigation and be designed by a competent engineer to satisfy Part A of the building regulations.

Foundations transfer the weight of the building into ground that can carry it without excessive settlement. Where firm natural ground is close to the surface, shallow strip or trench fill foundations are usually the most economical solution. Where the ground is soft, variable, made up of fill, or where loads are high, a raft or piled solution may be needed instead.

Part A of the building regulations requires the structure, including the foundations, to be designed and constructed so that loads are safely transmitted to the ground. In practice this means a structural or geotechnical engineer sizes the foundation using information from a site investigation, and the design is inspected during construction.

Foundation types commonly used in Ireland

  • Strip foundation — a concrete strip under load-bearing walls in firm ground
  • Trench fill — a deep, narrow trench filled with concrete, common where trenches are deep
  • Raft — a reinforced slab spreading load over the whole footprint on weaker or variable ground
  • Piled — piles carrying load to deeper competent strata or rock
  • Pad foundations — isolated bases under columns, often combined with ground beams

How the decision is made

The sequence is investigate, design, then build. Trial holes or boreholes establish soil type, strength, groundwater level and depth to rock. The engineer uses that data to select the foundation type and depth, allowing for trees, slopes, existing structures and any history of filling on the site.

Sources

Last reviewed 25 August 2026. General information only — not legal or planning advice.

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