Timber frame vs block vs ICF in Ireland: what to build with in 2026

If you are planning a self-build or a one-off house in Ireland, one of the first big decisions is the wall system. For decades the answer was simple: concrete block, usually cavity wall. Today you will hear just as much about timber frame and insulated concrete formwork (ICF).

There is no single right answer. Each system can deliver a warm, airtight, A-rated home if it is designed and built well. The differences are in cost, speed, the trades you need, and how much you can change your mind once work starts.

This guide sets out the practical trade-offs so you can have a better conversation with your architect, engineer and builder.

Why the wall system matters more than it used to

All new homes in Ireland must meet the Nearly Zero Energy Building (NZEB) standard under Part L of the Building Regulations, which in practice means an A2 BER or better. That pushes every system towards high insulation levels, very low air leakage and careful detailing at junctions.

So the question is less "which one is warmer?" and more "which one gets me to the standard most reliably, at a price and pace that suits my site and my budget?"

Concrete block (cavity wall or solid wall with external insulation)

Block is still what most Irish builders know best. Nearly every county has experienced blocklayers, and most engineers and planners are comfortable with it.

Strengths

• Familiar to builders, lenders, insurers and buyers

• Easy to make small changes on site, such as moving an opening

• Good thermal mass and a solid feel

• Materials widely available from local builders' providers

Weak points

• Slower: the shell is weather-dependent and needs drying time

• Wider cavities and careful detailing are needed to hit NZEB targets

• Airtightness relies heavily on the quality of plastering and sealing

• Labour availability can be a bottleneck in busy areas

If you go with block, ask how the builder handles cold bridging at window reveals, floor-wall junctions and lintels, and whether they have achieved good airtightness test results on recent jobs.

Timber frame

Timber frame has grown fast in Ireland. Government figures quoted in early 2026 put modern methods of construction, mostly timber frame, at around 70% of scheme houses built in 2025. It is also a common choice for one-off homes.

The frame is usually made off-site in a factory, delivered in panels and erected in days, with insulation and sometimes windows already fitted.

Strengths

• Fast: a weathertight shell in weeks rather than months

• Factory precision helps with airtightness and insulation

• Thinner walls for the same U-value, so more internal floor area

• Lower embodied carbon than concrete-heavy systems

Weak points

• Design must be fixed early, as late changes are expensive

• Lead times with manufacturers can be months in busy periods

• Needs careful protection from moisture during the build

• Some buyers and older tradespeople still prefer "solid" walls

When comparing timber frame suppliers, check what is included. One quote may cover the frame only; another may include insulation, membranes, windows and erection.

ICF (insulated concrete formwork)

ICF uses hollow blocks made from expanded polystyrene (EPS). They are stacked like large building blocks, reinforced with steel and filled with concrete. The insulation stays in place on both sides of the wall.

Strengths

• Very good U-values and airtightness built into the wall

• Strong, quiet and solid, with good fire and acoustic performance

• Concrete can be poured in conditions where blocklaying would stop

• Fewer separate layers, so fewer junctions to get wrong

Weak points

• Usually costs somewhat more for the wall itself; UK self-build guides suggest roughly 5–15% more than brick and block, though Irish quotes vary

• Mistakes during the pour are hard and costly to fix

• Needs an installer with ICF experience, which is harder to find outside larger towns

• Higher embodied carbon than timber because of concrete and EPS

Cost: what actually changes

People often expect a big price gap between systems. In practice the wall system is only one part of the total build cost. Foundations, roof, windows, heating, ventilation, electrics, kitchen and finishes all come on top and usually cost the same whichever wall you choose.

What tends to move the final cost is:

• Time on site. A faster shell can save on scaffolding, site costs and rent or mortgage overlap.

• Labour availability. Whichever trade is scarce in your county will cost more.

• Design complexity. Large glazed gables, steel and complex rooflines add cost in any system.

• Changes during the build. These are cheaper in block and dearer in timber frame or ICF.

Ask each builder or supplier to price the same drawings and the same specification, so you are comparing like with like.

Which one suits your project?

A rough guide, not a rule:

• Choose block if your local builder is strong in it, you want flexibility on site, and time is less pressing.

• Choose timber frame if speed matters, your design is settled, and you want maximum floor area within the walls.

• Choose ICF if you want a very solid, high-performance shell and can find an experienced installer near you.

Whatever you choose, the quality of design and workmanship matters more than the system. A badly built timber frame or ICF house will not perform better than a well-built block house.

Questions to ask before you commit

• How many homes in this system have you built in the last two years, and can I see one?

• What airtightness results did you get on recent jobs?

• What exactly is in your price: frame only, or insulation, windows and erection?

• What is the lead time from order to delivery?

• Who is responsible for the junction between your work and the next trade?

• Are you registered with the Construction Industry Register Ireland (CIRI)?

FAQ

Is timber frame as durable as block in the Irish climate?

Yes, when it is properly designed, protected from moisture during the build and finished with a suitable external cladding or render. Timber frame homes are common in wet climates such as Scotland and Scandinavia.

Can I get a mortgage on a timber frame or ICF house in Ireland?

Generally yes. Lenders are used to timber frame, and ICF is increasingly familiar. Your lender will want a certified design and sign-off from your assigned certifier under the Building Control Regulations. Check with your lender early.

Which system gives the best BER?

All three can reach an A2 BER or better. The result depends more on design, insulation levels, airtightness and the heating and ventilation system than on the wall type alone.

Get advice from people who have built

Still weighing it up? Post your plans in the Construction section of the Archizone forum and get practical answers from self-builders and trades who have done it. When you are ready to talk to suppliers, you can browse timber frame companies, builders and building suppliers on Archizone and contact them directly, free of charge.

Archizone Team