What Is Render?
Written by James Walker · Last reviewed 16 August 2026
James Walker has 2 degrees in construction (BSc (Hons) Building Surveying · MSc Environmental Design of Buildings) and an extensive background in issue resolution, resolving over £4 billion of consumer issues.
On this page
Render is a coating applied to external walls to protect them from weather and to give a finished appearance. It is usually cement-based, lime-based, or a modern polymer system.
Why it fails
Render cracks as buildings move, and once cracked it lets water in behind, where it then cannot easily dry out. Blown render, which has lost its bond and sounds hollow when tapped, does the same.
This is one of the most common causes of penetrating damp, and it is frequently misdiagnosed as rising damp because the symptom appears at low level.
Cement and lime
On older solid-wall properties, cement render can cause problems. Traditional buildings were designed to let moisture move through the wall and evaporate. A cement coating traps it.
Lime render breathes, which is why it is specified on period properties. Using the wrong one is not a preference, it can actively damage the wall.
What to check
Where render is being repaired or replaced, ask what type is going on and why, particularly on anything built before about 1919. Ask also whether render is being carried down over the damp proof course, doing so bridges it, and causes damp.
How it works
Help your project succeed with Trusted Payments
