Domestic projects in Wales: dutyholder responsibilities

[edit] Introduction

On 27 August 2026, CIAT published guidance reminding members and affiliates providing services on domestic projects in Wales of the dutyholder requirements introduced by the Building etc. (Amendment) (No.2) (Wales) Regulations 2025, which came into force on 1 July 2026, subject to the applicable transitional provisions.

[edit] Assignment of duties by domestic clients

Regulation 11T(1) enables a domestic client to assign the specified duties in regulations 11R(1)–(3), 11V(2)–(5), 11Z4 and 11Z5:

• to themselves; or
• to another person.

The assignment must be recorded in a written statement meeting the requirements of regulation 11T(1).The statement must confirm that the person undertaking the duties understands them and is able to carry them out. It must also contain the required project and contact information and applicable signatures.

The statement must be completed:

• before the building control approval application is submitted where the project includes higher-risk building work requiring such an application; or
• before the construction phase begins for any other project.

[edit] Where no assignment is made

Where the domestic client does not make an assignment under regulation 11T(1), regulation 11T(3) provides for the duties in regulations 11R(1)–(3) and 11V(2)–(5) to be carried out by:

• the contractor, where there is only one contractor; or
• the Principal Contractor, where there is more than one contractor; or
• the Principal Designer, where there is more than one contractor and the domestic client and Principal Designer have agreed in writing that the Principal Designer will fulfil those duties.

This default allocation under regulation 11T(3) does not include the duties in regulations 11Z4 and 11Z5. These are, however, expressly included among the duties that a domestic client may assign under regulation 11T(1).

Members and affiliates should therefore establish precisely which duties have been assigned, which duties apply by default and to whom they apply.

[edit] Appointment of the Principal Designer and Principal Contractor

Where there is more than one contractor, or it is reasonably foreseeable that more than one contractor will work on the project, regulation 11U requires the client to appoint in writing a Principal Designer and Principal Contractor in accordance with that regulation.

Separately, where the domestic client does not make the appointments required by regulation 11U, regulation 11T(4) provides that:

• the designer in control of the design phase of the project is the Principal Designer; and
• the contractor in control of the construction phase of the project is the Principal Contractor.

Members and affiliates should therefore distinguish between duties assigned under regulation 11T(1), the default allocation of specified duties under regulation 11T(3), and the default Principal Designer and Principal Contractor provisions under regulation 11T(4).

[edit] Minor work

Regulation 11Z7 provides that a client is not required to comply with Part 2B where the building work or design work consists only of work described in Schedule 4.

Members and affiliates should therefore establish whether the work falls within this provision before advising a domestic client on the duties that apply. This should not be treated as a general exemption from the dutyholder regime simply because a project is small or minor.

[edit] Responsibilities of designers

Under regulation 11Z2(1), a designer must not start design work unless satisfied that the client is aware of the duties owed by the client for the building work to which the design relates under all relevant requirements.

The legislation does not prescribe a particular process by which the designer must notify the client or require the designer to retain written evidence of that notification. Nevertheless, CIAT recommends that members and affiliates explain the relevant duties clearly and, where appropriate, in writing, and retain an appropriate record. This can provide useful evidence of the basis on which the designer was satisfied, before starting design work, that the client was aware of their duties.

Members and affiliates should therefore establish and record:

• which duties are legally applicable to the domestic client;
• whether the client exemption under regulation 11Z7 applies;
• whether an assignment has been made under regulation 11T(1);
• whether the assignment is to the domestic client or another person;
• precisely which duties have been assigned and to whom;
• whether any duties under regulations 11Z4 or 11Z5 have been assigned;
• whether the written statement contains the required confirmations, information and signatures;
• whether the statement was completed by the applicable statutory deadline;
• whether the project involves one contractor or more than one contractor, or whether more than one contractor is reasonably foreseeable;
• who has been formally appointed as Principal Designer and Principal Contractor; and
• whether either role has arisen by default under regulation 11T(4).

The Welsh regime therefore gives domestic clients specific flexibility over who undertakes certain duties, but this is accompanied by detailed requirements around assignment, written statements and dutyholder arrangements. Members and affiliates should ensure that the position is established clearly at the outset, properly documented and reviewed if the project arrangements change.

Clear written advice, properly completed statements, defined appointments and appropriate project records can help domestic clients understand their responsibilities and reduce uncertainty for members, affiliates and the wider project team.

This article originally appeared on the AT website on 27 August 2026.

--CIAT

[edit] Related articles on Designing Buildings

• Building regulations.
• CDM.
• CIAT.
• CIAT articles.
• Domestic client.
• Dutyholder.
• Principal Contractor.
• Assignment.
• Principal Designer.
• What the Building Safety Act 2022 means for construction clients.