External wall insulation (EWI) and render

This is general information, not a survey, design, legal or Building Control decision. The correct scope and standard depend on the property, work, date and regulatory route.

EWI adds insulation outside the existing wall and normally needs a compatible basecoat, reinforcement, render and detailing at openings, eaves, sills and services. The wall condition, exposure, moisture movement and substrate must be checked first.

A render finish is not automatically an EWI system. Product compatibility, fire performance, fixings and junctions should follow the selected system supplier's guidance and the design professional's specification.