What Conservation Officers Look For

Sight lines and alignment

The first thing assessed is how the new frame reads against the old window. A horizontal that lands halfway across a pane looks wrong from inside and from the pavement. Aligning the meeting stile or rail with an existing glazing bar, transom or the primary meeting rail makes the addition almost disappear. On multi pane and margin light windows, slim profiles and fixed or lift out panels are usually preferred over chunky running gear.

Set back within the reveal

A unit set well back into the reveal sits in shadow and is far less visible externally. It also gives the cavity depth that acoustics need, so the conservation answer and the performance answer point the same way. Where the reveal is shallow and the frame has to be face fixed, officers will want to see it landing on later linings or the architrave rather than on original joinery.

• Deeper set back, less visible outside
• Deeper cavity, better acoustic result
• Face fixing acceptable onto later linings
• Shadow gaps preferred to flush finishes

Fixings and what they land in

This is the point most often queried. Mechanical fixings into modern plaster, later linings or the architrave are usually accepted. Fixings into historic glazing bars, sash boxes, shutter panelling or original mouldings usually are not. Bonded and magnetic systems raise questions because removal can pull finishes off with them. Recording fixing positions on the drawing answers the question before it is asked.

Finish and colour

Bright white against dark stained joinery draws the eye straight to the new frame. A recessive finish matched to the primary window, or a heritage grey or off white, is the safer specification, and polyester powder coating to any RAL colour costs no more than stock white. On dark stained or painted period joinery we default to matching rather than contrasting.

• Match the primary joinery where possible
• Full RAL and heritage colour range available
• Powder coated finish, not applied paint
• Avoid bright white on dark original frames

Reversibility and the original window still working

Officers want confidence that the building can be returned to its earlier state and that the historic window can still be opened, maintained and repainted. That means an openable secondary system on any window in use, tool free access to the cavity, and a clear statement that nothing is fixed to or planted onto original fabric. Where the window is decorative and never opens, a fixed panel is usually fine and often preferred.

The drawings and paperwork that get approvals

A complete submission usually includes internal and external photographs of every affected window, a plan showing the position of each one, a section through the reveal showing frame position, set back and fixings, the manufacturer specification for profile, finish and glass, and a short heritage statement covering harm and reversibility. We prepare drawings and specifications free for any window we have surveyed, and we will amend them if the officer asks for a change.