Modular Buildings guides, calculator & reference
Every modular buildings cost guide, specification comparison, interactive calculator, FAQ and technical glossary on modularbuildings.ie in one place.
Browse the guides below or jump straight to the interactive calculator on the homepage.
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Core modular buildings guides
Detailed guides covering prices, specifications and what to check before you book.
45 m² Class 3A garden dwellingsSince 27 July 2026 (S.I. No. 340 of 2026), a 32 to 45 m² habitable dwelling in your rear garden is planning-exempt with 14-day council notice.Class 3A rules in full →
Modular home pricesShell €1,200 to €1,800 a m², fitted garden rooms €1,600 to €2,400 a m², and turnkey habitable units €2,400 to €3,200 a m² incl. 13.5% VAT.Full price guide →
Garden offices & rooms (Class 3)Non-habitable offices, gyms and studios up to the 30 m² Class 3 limit: €18,000 to €32,000 for 12 to 16 m², up to €55,000 for 30 m².Garden offices & rooms →
Turnkey modular homesStandalone 1, 2 and 3 bed modular houses (€175,000 to €255,000 for 75 to 85 m²): planning, BCAR and 60-year structural warranties.Turnkey modular homes →
Foundations & service hook-upsGround screws (€90 to €120 a m²) vs concrete slab (€140 to €220 a m²), plus water, foul waste and ESB cable trenches (€3,500 to €9,500).Foundations & services →
Classrooms & commercial unitsModular classrooms, sports clubhouses, clinics and site offices built to commercial Building Regulations, DAC and fire safety standards.Commercial modular →Calculators, FAQ and glossary
| Resource | What's inside | How it helps |
|---|---|---|
| Interactive Cost Calculator | Live price range | Select your specification options to get an instant Irish guide price. |
| Master FAQ Hub | 12 questions answered | Straight answers on pricing, preparation, timelines, rules and aftercare. |
| Technical & Trade Glossary | 15 terms defined | Plain-English definitions of every modular buildings specification and standard. |
| All 26 Counties Index | 26 county pages | Local housing data and one vetted modular building supplier that covers your county. |
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Tap what you want to build, the size and your county. Your request goes to one vetted modular building supplier that covers your county, and they ring you with a written specification and price.
Questions people ask
Can I build a 45 m² modular home or granny flat in my back garden without planning permission?
Yes, since 27 July 2026, if you meet the Class 3A conditions in S.I. No. 340 of 2026. A detached habitable garden dwelling between 32 m² and 45 m² in the rear garden of a house is exempt from planning permission provided total garden structures do not exceed 45 m², the owner lives in the main house, it connects to the main house's services, it is not sold separately or used for short-term letting, you give the local council 14 days prior written notification with your Eircode, it meets Building Regulations, and work finishes by 31 December 2030.
What is the difference between Class 3 (30 m²) and Class 3A (32 to 45 m²)?
Class 3 (updated by S.I. No. 338 of 2026) covers non-habitable garden rooms, home offices, gyms and sheds up to 30 m² — you cannot sleep or live in a Class 3 room. Class 3A (S.I. No. 340 of 2026) covers a detached habitable garden dwelling (granny flat) of 32 m² to 45 m² with a kitchen, bathroom and bedroom.
How much does a modular building or garden dwelling cost in Ireland?
An insulated, fitted garden office or room (12 to 30 m²) costs €18,000 to €55,000 including 13.5% VAT. A turnkey habitable 32 to 45 m² Class 3A modular dwelling with kitchen, shower room, foundations and service connections costs €65,000 to €135,000 (€2,400 to €3,200 a m²).
Is VAT on a modular building 13.5% or 23%?
When a modular builder supplies and installs the building on your site (under Revenue's two-thirds rule for construction services), the reduced 13.5% VAT rate applies. If you buy a supply-only flat-pack kit with no installation, it is taxed as goods at 23% VAT.
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