A new or enlarged door or window opening normally needs building regulations approval for the structural work. The window installer's scheme certificate does not, by itself, cover a new opening and lintel. Planning permission is a separate question, depending on the property and the changes to its exterior. [1] [2]
Check the planning position first
For a house with the relevant permitted development rights, new or replacement windows and doors can often be installed without a planning application where the applicable conditions are met. Appearance matters, and a bay window can fall under extension rules rather than ordinary window replacement. Flats do not benefit from the same householder rights. [2]
For an upper-floor window in a side elevation under the relevant householder rules, the glazing must be obscure and the window non-opening unless the opening part is more than 1.7 metres above the floor. Also check Article 4 directions and planning conditions before relying on permitted development. [3]
Listed building consent is a separate check where new openings affect a listed building's special character. Approval of the window's technical specification does not answer that heritage question. [4]
Design the opening, not just the window
The engineer needs to establish the loads above the opening, the support required and whether the masonry at each end can carry the resulting load. Wider openings may need a different beam or additional support. Where a replacement stays the same width and the loading is unchanged, an existing lintel may be suitable, but that needs confirmation rather than assumption. [5]
Include the bearings, any padstones and fire protection in the design. Ask for the drawing to distinguish retained structure from new work so the builder is not left to infer the support arrangement from the window supplier's dimensions. [5]
Temporary support also needs planning. The safe construction sequence is not established merely by showing the finished lintel on a drawing; the wall and any supported construction must remain stable while the opening is formed. [6]
Coordinate the performance requirements
The window or door specification must address energy performance, ventilation, relevant escape requirements and safety glazing. A new opening close to a boundary can also need assessment for external fire spread. These checks may limit a proposed opening even where the structure can support it. [7]
Do not assume a large opening window is enough to meet every ventilation requirement. Background ventilation and rapid airing have different functions, and the replacement or new window must fit the ventilation arrangement for the room. [8]
Separate the approval responsibilities
Agree in advance who is dealing with the structural application and who will certify the glazing installation. A competent person scheme route is available only for work within that installer's registration; it does not turn the installer into the approver for all associated building work. [1] [9]
Ask the designer, engineer and installer to use the same opening dimensions and finished floor levels. This is a practical coordination check: structural clearances, threshold details, glazing and ventilation must work together rather than being specified as unrelated items. [5] [7]
Work planned for 2027
The 2026 editions of Approved Documents F and L include existing-dwelling provisions. For non-higher-risk work they take effect on 24 March 2027, subject to transitional arrangements. Recheck the applicable ventilation and energy specification rather than assuming that a window ordered now fixes the rules for later work. [10] [11]