Certificate of compliance with planning permission — what the architect's opinion covers and what it does not

Retention applications were 17% of everything lodged with the seven Greater Dublin councils in the 12 months to 12 September 2026 — 1,996 of 11,409 — and the register shows 215 of the 1,138 decided were refused. Most of those retention cases exist because a sale stalled: the buyer's solicitor asked for a certificate of compliance with planning permission, and nobody could give one. The certificate is the document that turns "there is an extension" into "the extension is lawful", and a house without it sells late or sells cheap.

What the certificate actually says

Strictly it is an opinion, not a certificate. Since the 1990s the Law Society of Ireland and the RIAI have published agreed forms on which an architect, chartered engineer or building surveyor states that, in their opinion, the building was constructed in substantial compliance with a named planning permission and with the Building Regulations. "Substantial" is doing work in that sentence. The form lets the professional list deviations that they judge immaterial — a window 200 mm from where it was drawn, a boundary wall a course higher — and a buyer's solicitor will usually accept them.

The opinion covers a named permission and its conditions. It does not say the house has no other planning history, that a neighbour has not appealed the latest grant, or that the extension built in 2004 was exempt when it went up. Those are the register's questions, and the planning search guide sets out what the €85 law-searcher's report returns and misses.

If the works were exempted development rather than permitted, the form changes: the professional certifies that the works were exempt under the class they name in Schedule 2 of the Planning and Development Regulations 2001, and gives the measurements that make it so. For a rear extension that is the floor area, the height, and the private open space left behind. Our reading: ask for the measured survey behind the exemption opinion, because the 40 m² and 45 m² thresholds are where sales fall over.

Who can sign, and what they check

The signatory needs professional indemnity insurance, because the buyer's lender relies on the opinion. An architect who supervised the build signs from their own inspections. One who did not — the usual case when a 20-year-old house is sold — signs from a site visit, the permission and its drawings on the council's file, and the register. The council's register under section 7 of the Planning and Development Act 2000 is a public document; the file itself is inspected at the counter or, for most Dublin councils, online.

Expect the visit to take an hour and the opinion to cost a few hundred euro for a straightforward house. Expect a refusal to sign where the extension on the ground is not the extension on the drawings, and a suggestion that you apply for retention before you list. Retention takes a minimum of eight weeks and the register shows one in five refused, so do it before the sale rather than during it.

Building Regulations since 2014

The compliance opinion has two halves, and the second changed on 1 March 2014. The Building Control (Amendment) Regulations 2014 (SI 9/2014) require a commencement notice, an assigned certifier and a Certificate of Compliance on Completion lodged on the Building Control Management System for new dwellings and for extensions over 40 m². A house built after that date should have the completion certificate on the BCMS register, and a buyer's solicitor asks for it by name. A house built before it relies on the professional's opinion alone.

The 2014 rules brought an opt-out for one-off houses and domestic extensions (SI 365/2015), so a self-built extension since September 2015 may lawfully have no assigned certifier. It still needs the commencement notice, and the register of those notices is what our commencements layer is built from.

What the opinion will not tell a buyer

Three gaps come up in the sales we see on the register. The first is an open observation window or appeal on a neighbouring application that will change the house's outlook; the opinion is silent on it, and the deadlines page lists what is open. The second is an unexpired permission on the site itself — a grant for a second house in the garden, say, that the vendor never mentioned. The third is the 14-day notification to the council that the July 2026 garden-dwelling exemption requires: a Class 3A garden dwelling with no notification on file is not exempt, whatever the measurements say.

Frequently asked questions

Is a certificate of compliance with planning permission a legal requirement?

No statute requires one. It is a conveyancing convention: the Law Society's standard requisitions on title ask the vendor to produce it, and a lender will not release funds without it for any house with a permission on its record.

Who can give a certificate of compliance in Ireland?

An architect, a chartered engineer or a chartered building surveyor with professional indemnity insurance. The Law Society and RIAI publish the agreed forms; the signatory need not have supervised the works.

What if the extension has no planning permission?

The professional will not certify it. The routes are an opinion that the works were exempted development, if the measurements support it, or a retention application to the council — 17% of applications in the Greater Dublin Area are retention, and about one in five is refused.

Does a certificate of compliance cover the Building Regulations?

The standard form has a Building Regulations section. For works commenced since 1 March 2014 the buyer will also ask for the Certificate of Compliance on Completion from the BCMS, unless the opt-out for a single house or domestic extension applied.

How long is a certificate of compliance valid?

It has no expiry. It speaks to the building as it stood on the date of inspection, so a buyer years later will usually want a fresh opinion covering any later works.

The planning search guide sets out what the law searcher's report returns; the retention guide covers the application that fixes most compliance gaps. See the register for any address in the Explorer, or open the Dún Laoghaire-Rathdown place page for that council's live retention share.

Figures from the register on 12 September 2026 (live callouts refresh hourly); law checked 12 September 2026. Check with the council or a planning consultant before relying on this.