Suspended vs Solid Floor in Ireland — Timber Suspended, Solid Slab, or Beam-and-Block
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Three floor types for an Irish self-build. Solid slab (raft): a reinforced concrete slab on the ground, with insulation and a radon barrier beneath. Standard for most sites because it's cheap, integrates underfloor heating, and provides a continuous insulation layer. Suspended timber: a timber floor over a subfloor void, supported on the perimeter foundation. Used on sites with high water tables or difficult ground. Beam-and-block: precast concrete beams with infill blocks, grouted together. Used on sites with high water tables or where a solid slab isn't suitable. Most Irish self-builds use a solid slab (raft). Building Regulations 2023 TGD-A (Structure) governs.
TL;DR
Three floor types: solid slab (raft, standard on most sites), suspended timber (over a subfloor void, for difficult sites), and beam-and-block (precast concrete beams with infill blocks, for sites with high water tables).
Solid slab is cheapest and integrates subfloor insulation. Suspended timber is faster on high water tables. Beam-and-block is the middle option.
Most Irish self-builds use a solid slab (raft) for the cost, the integration with underfloor heating, and the continuous insulation layer.
When this matters most
You're at foundation design stage and need to choose the floor build-up.
When this doesn't apply
The floor is poured.
Frequently asked questions
What is the cheapest floor for a self-build in Ireland?
Solid slab (raft): €180–€260/m², including subfloor insulation and radon barrier. Cheapest and most common for Irish self-builds.
When is a suspended floor used?
High water table, contaminated ground, or sites where a solid slab is unsuitable. Suspended timber is faster on these sites; beam-and-block is the concrete alternative.
Can I put underfloor heating on a suspended floor?
Yes, but it's more expensive than on a solid slab. Suspended timber requires a low-profile heating system; beam-and-block needs a screed on top to embed the pipes.
Sources
Building Regulations 2023, TGD-A (Structure). https://www.gov.ie/
Frequently asked questions
What is the cheapest floor for a self-build in Ireland?
Solid slab (raft): €180–€260/m², including subfloor insulation and radon barrier. Cheapest and most common for Irish self-builds.
When is a suspended floor used?
High water table, contaminated ground, or sites where a solid slab is unsuitable. Suspended timber is faster on these sites; beam-and-block is the concrete alternative.
Can I put underfloor heating on a suspended floor?
Yes, but it's more expensive than on a solid slab. Suspended timber requires a low-profile heating system; beam-and-block needs a screed on top to embed the pipes.