The Statutory Framework: Class 1 Exemptions Explained
In Dublin City, Dún Laoghaire-Rathdown, South Dublin, and Fingal, the 40-square-metre rear extension exemption is the most powerful tool available to homeowners looking to modernise 1930s to 1980s properties without waiting 4 to 6 months for local council approval.
Governed by Schedule 2, Part 1, Class 1 of the Planning and Development Regulations 2001, this exemption allows single-storey extensions to the rear of a dwelling house, provided four fundamental statutory conditions are strictly maintained.
The Four Non-Negotiable Conditions
1. 25m² Minimum Private Garden SpaceAt least 25 square metres of private open amenity space must remain in the rear garden after the extension is complete. Driveways and side passages do not qualify.
2. Height Restrictions & Eaves AlignmentThe height of the extension walls cannot exceed the existing eaves height of the main dwelling. If constructing a flat roof with parapet, the top of the parapet must not breach this statutory datum.
3. Cumulative Historic CalculationsAny previous extension built by prior owners since the house was constructed must be deducted from your 40m² allowance.
4. No Side or Front VisibilityExempt extensions must be located strictly to the rear of the property. Side extensions require standard planning permission.
Architectural Tips from Sérgio Gratival
'Homeowners often think 40 square metres is small, but in Dublin suburban semi-detached homes, a 40m² open-plan extension combined with knocking down the existing rear kitchen wall creates a dramatic 75m² to 90m² living, dining, and kitchen pavilion flooded with natural light.'
— Sérgio Gratival, Managing Director & Master Builder, JSG Construction Limited