The required detail follows the work and the relevant Approved Documents. [1] [2]
Begin with the actual building
Identify what is existing, what will be removed and what will be new. Show levels and sections where they affect foundations, floor build-ups, roof construction or headroom. Existing conditions that remain uncertain should be identified for investigation rather than disguised by drawing an assumed standard arrangement. [3] [4]
For a loft conversion, for example, the new floor and roof structure, stairs and escape arrangements need to work together. A staircase outline that fits a planning plan does not by itself demonstrate the required headroom or fire protection. [4] [5] [6]
Coordinate the technical disciplines
The package should address the requirements relevant to the project. These can include:
- foundations, structural support and connections, coordinated with calculations;
- fire separation, escape routes and necessary protection to structure;
- insulation, glazing and continuity at junctions;
- ventilation systems and air paths;
- foul and rainwater drainage, including inspection access;
- stairs, guarding, access and relevant services. [3] [6] [7] [8] [9] [5]
This is a scope checklist, not a statement that every small alteration requires a separate specialist report for every item. Ask the designer to identify what is relevant and how it is evidenced.
Include information outside the drawing sheets
Structural calculations, energy calculations, product evidence and drainage information may accompany the drawings. Keep document references and revisions aligned so that a changed beam, opening or insulation specification is not contradicted elsewhere in the package. The dutyholder guidance requires designers to coordinate relevant design work and information. [10]
Where Thames Water requires a build-over application, its checklist asks for specific drainage and foundation information. That agreement is a separate approval process, but the construction drawings need to reflect the agreed arrangement. [11]
Resolve matters before they become site problems
Record any plan-check requirements and identify which details must be settled before that part of the work starts. If a supplier proposes a different product or the builder finds a different existing condition, have the design implications assessed rather than treating the change as an informal substitution. [12] [10]
State the regulatory edition
The published 2026 energy and ventilation documents include changes taking effect from 24 March 2027, with transitional arrangements. A drawing note should identify the applicable standard for the project; publication of a new document is not, by itself, its commencement date. [13] [14] [15]
At completion, retain the final design information alongside test results, installation certificates and the completion declarations. [16]