Blockwork for a Self-Build in Ireland — The Default Wall, with External Insulation

Blockwork is the default Irish wall, cheapest at €110–€160/m² of wall, slowest to build (6–9 weeks for a 150 m² house), and easiest to find trades for. The standard is a 100 mm concrete block inner leaf, a 50 mm cavity, and a 100 mm block outer leaf, with 50–100 mm of external insulation on the outside. U-value 0.15–0.22 W/m²K with external insulation. Airtightness depends on the render and the detailing; not proven at the panel level like timber frame or ICF. Airtightness 3–5 m³/m²·hr at 50 Pa is typical. Blockwork is a good choice on standard sites, tight budgets, and where local trades are block-trained. The cheapest path to a warm wall.

TL;DR

• Blockwork: €110–€160/m² of wall. 6–9 weeks to weathertight on a 150 m² house.

• U-value 0.15–0.22 W/m²K with external insulation. Airtightness depends on the render and detailing; not proven at the panel level.

• Easiest to find trades for. Materials stocked locally. Slower to build than other systems but cheaper per m² of wall.

When this matters most

You're considering blockwork and need to know the trade-offs.

When this doesn't apply

You've already chosen a wall system.

Frequently asked questions

How much does blockwork cost in Ireland?

€110–€160/m² of wall. For a 150 m² house: €22,000–€32,000 for the wall system, including blocks, insulation, and labour.

What is the U-value of a block wall?

0.15–0.22 W/m²K with external insulation. 100 mm block + 50 mm cavity + 100 mm block + 50–100 mm external insulation typically achieves 0.18. Add more insulation for 0.15.

Is blockwork good for BER A1?

Possible but harder than timber frame or ICF. Blockwork needs careful detailing for airtightness, and the render needs to be airtight (not all renders are). Most A1 builds use timber frame or ICF.

Sources

Building Regulations 2023, TGD-L. https://www.gov.ie/