Planning: compare the old and new appearance
“Same opening” does not necessarily mean “same appearance”. Show the proposed frame material, proportions, opening pattern and glazing beside the existing window. Planning Portal advises checking with the council where the work changes appearance or dimensions. [1]
Secondary glazing inside the existing window will normally avoid an external planning change. A listed building is different: work affecting its special character can require listed building consent, including alterations that do not need a planning application. [1]
Householder permitted development rules should not be used as the permission route for a flat. Also check whether any planning condition or relevant Article 4 direction affects the property. [3]
Lease: who controls the replacement?
Establish whether the windows or door are part of your demise or the landlord's responsibility. The lease may require consent and may set requirements intended to maintain the building's appearance. Ask whether a building-wide replacement programme is already planned before ordering your own units. [4] [5]
Where a landlord is commissioning major communal work, the service-charge and consultation process is separate from an individual leaseholder's licence to alter. Do not assume that the same procedure applies to both situations. [5]
Building regulations: specify performance
Replacement glazing is controlled work. Planning Portal identifies thermal performance, safety glazing, ventilation and escape among the relevant checks. Choose the replacement as a complete design, not just a frame with an attractive energy label. [1]
Ask the installer to identify the approval or competent-person certification route and the evidence you will receive. For a higher-risk building, the Building Safety Regulator's guidance explains the particular exceptions for competent-person work and the need to include such work in an application when it is part of a wider project. [6] [7]
Entrance doors are not ordinary internal doors
The door between a flat and the common corridor or stair can form part of the building's fire precautions. LEASE recommends checking the existing fire-risk assessment and using a competent installer. The leaf, frame, seals, glazing, ironmongery and installation need to work as a suitable doorset. [2]
Keep its product evidence and installation records. Replacing the leaf alone without checking the frame and surrounding construction is not a reliable specification. [2]
Changes to allow for
The 2026 building regulations package introduces revised energy and ventilation provisions from 24 March 2027 for relevant non-higher-risk work, subject to transition. It does not mean every replacement in an existing flat must meet the whole new-build Future Homes Standard. [8]
Further Approved Document B changes to fire-resistance classifications take effect on 2 September 2029, again with transition. Check the applicable edition when specifying a future replacement. [9]