Listed Buildings: What Is Allowed

The general principle

Listing protects the special architectural or historic interest of a building, inside and out. Works that affect that interest need listed building consent. Secondary glazing is treated favourably because it adds an independent element rather than altering the historic window, and because it can be removed later without loss of fabric. The assessment is about harm and reversibility, not about the product itself.

When consent is usually needed

The more the installation touches historic fabric, the more likely consent is required. Fixing into modern plaster or later linings in a Grade II house is often considered outside the scope. Fixing onto original joinery, working on a decorative or stained glass window, altering a shutter box, or any work in a Grade I or II* building will usually need an application. When in doubt, ask, because retrospective applications are far harder.

• Ask the conservation officer before ordering
• Grade I and II* usually need an application
• Decorative and stained glass raise the bar
• Retrospective applications are much harder

What is generally accepted

Slim aluminium frames set back into the reveal, sight lines aligned with existing glazing bars or the primary meeting rail, recessive colours rather than bright white, mechanical fixings into later material, openable units so the original window can still be used and maintained, and a specification that can be unscrewed and taken away. On decorative windows, a fixed or lift out panel with the slimmest possible frame is often preferred.

Where to get the final answer

Your local planning authority's conservation officer makes the decision, and Historic England publishes the national guidance behind it, including advice on energy efficiency and windows in historic buildings. Read the guidance, then email the officer with photographs of the windows and a description of what you propose. We prepare drawings, sections and specifications for any window we have surveyed at no cost.