On this page:

  1. Introduction
  2. What are renders and plasters made from?
  3. How can I tell which material my render or plaster is?
  4. Do I need Listed Building Consent for works to my render or plaster?
  5. Contact us

An introduction to renders and plasters

Render and plaster is a coating material applied over the top of a building's structural fabric. The term 'render' is commonly used for external finishes, with 'plaster' used for internal ones. However, other differences between the two terms also exist.

External render protects the fabric from rain, wind and frost damage. Both render and plaster draught-proof a building, and provide a clean and smooth finish that's easy to decorate.

Render and plaster - especially if it is historic, or characteristic to an area of building type - forms part of the character of a listed building, or non-designated heritage asset.

Historic render and plaster will often be attractive in appearance, will show the building's traditional form, and will reflect local building materials and crafts. Its detail can also tell us a lot about a building - for example, decorative plasterwork probably reflects high status or a wealthy owner, whereas a smooth, plain plaster might suggest a simpler and more functional character.

What are renders and plasters made from?

The two most common historic types are lime render/plaster and clay daub.

Lime render/plaster is made from:

  • lime (a calcium-based mineral)
  • sand or chalk
  • hair or other fibres
  • sometimes additional minerals are added, which alter its relative performance. These are called 'pozzolans'

Clay daub is made from clay minerals, which have often been combined with straw and other minerals again.

These materials are absorbent and porous, and allow a building to 'breathe'. They also flex with the building.

In the twentieth century, cement and gypsum became more prevalent for renders and plasters, and many buildings were re-rendered/plastered with these materials. However, these materials are impermeable and rigid.

As most buildings built before 1919 were constructed to allow moisture to enter the fabric and evaporate, and the materials used mean that - to some extent - they move. Therefore the materials used in the re-rendering/plastering were unsuitable.

A timber framed wall is likely to be badly affected by damp, if an impervious hard cement render is applied to either the interior or exterior.

Once a timber framed, clay lump or soft brick building has been encased in a hard cement render, the best course of action is often to remove it all and then re-render it with a soft lime or clay plaster.

How can I tell which material my render or plaster is?

The following list details some typical identifying features (but may not be conclusive on their own):

  • Lime or clay renders and plasters typically have a more irregular/uneven profile than cement or gypsum
  • Visible signs of damp and cracking are often indicative of a cement render that has trapped moisture, or failed to flex with the building
  • Detach a small bit of the render/plaster and look for distinct lumps of chalk or hair (which suggests lime) or straw (which suggests clay)
  • It's normally much easier to crumble a small bit of a lime or clay render/plaster in your hand, than it is with cement
  • If the backing is visible, then the type of backing will usually indicate the render/plaster type. Lime render/plaster is often applied to timber laths, whereas cement render/plaster is often applied to a metal mesh or expanded metal laths
  • If you apply a small amount of vinegar to a sample and it fizzes, it is likely lime-based
  • Previous Listed Building Consent applications may detail recent render/plaster replacements
  • Plastering companies can often undertake chemical analysis of a sample to decide its exact mix

To some extent, the answer will depend upon the relative historic interest of the current render/plaster.

However - as a general guide:

  • Small patch repairs with matching materials and methods do not normally need Listed Building Consent. If the existing material is of no historic interest, then we normally allow replacement of up to 50% of an elevation without the need for Consent. However, this percentage will likely be lower if the render/plaster is of historic interest
  • You will normally need Consent for patch repairs that use different materials, which would include - for example - changing the type of aggregate, or the ratios within the mix
  • You will normally need Consent to replace entire walls or elevations with render/plaster (whether with a matching or non-matching material or mix). You may not need it if the wall or elevation in question is part of a modern extension of no historic interest
  • You will normally need Consent to change the finish of render/plaster (for example, changing from a pebbledashed to smooth finish (or vice versa), or adding or removing pargetting). This includes the external walls of a modern extension
  • You will normally need Consent to add a render/plaster finish where it does not currently exist, or to permanently remove a render/plaster finish and leave the underlying fabric exposed

Have another question? Contact us

If you haven't found the information you were looking for on this webpage, please read our Renders and plasters on historic and listed buildings guidance (which covers this topic much more extensively).

If you still need further advice, please contact our Heritage team.

Email heritage@baberghmidsuffolk.gov.uk

Phone 0300 123 4000 (Option 5, then Option 3)

Write to us:

Heritage Team

Babergh and Mid Suffolk District Councils

8 Russell Road

Ipswich

IP1 2BX