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What is a render mix and how is it chosen?

A render mix is a blend of sand with a binder, usually cement, lime or both, plus water and sometimes additives. The right mix depends on what the wall is built from, how exposed it is and which coat is being applied, so a renderer should set it for your wall.

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What goes into a render mix?

Render is a mortar spread over the outside of a wall to protect it from rain and give it a finish. Most renders have three or four parts:

  • Sand. The bulk of the mix. Its grading, from fine to coarse, changes how the render handles and how much binder it needs.
  • Binder. Cement, lime, or both. The binder sets and holds the sand together.
  • Water. Enough to make the mix workable, but not so much that it weakens it.
  • Additives. Plasticisers, waterproofers or fibres in some mixes, and pigments in coloured renders.

Many renderers now use bagged or factory-made renders, which arrive with the binder and additives already blended and only need water. Others mix on site from separate materials.

QuoteZila is starting in Cheshire, with Crewe, Nantwich and Sandbach among the first towns, and anyone in the UK can post a job. This page explains how a render mix is chosen so you can talk to a renderer about it.

Why is there no single render ratio?

Because the right mix depends on the wall. The Mineral Products Association's guidance on rendering mortar says its recommendations follow the national annex to BS EN 13914-1, which covers external rendering and lists mixes suitable for rendering [S1]. Those mixes are given by designation, with proportions of cement, lime and sand [S1].

A renderer chooses from that range based on:

  • The background. Dense brick, soft brick, block and old stone all take render differently. A strong mix on a weak wall can crack or come away.
  • Exposure. A wall facing driving rain needs a different approach to a sheltered one.
  • The coat. Undercoats and finishing coats can use different mixes, so ask what goes into each one.
  • The finish. Smooth, textured, scraped, pebble dash or a coloured through-body render each have their own needs.

A ratio copied from somewhere else may suit a different wall entirely. Ask your renderer what they will use and why.

How does lime render differ from cement render?

Lime and cement set in different ways and behave differently once they have set. Historic England says traditional construction is mostly semi-permeable, letting moisture move through the wall, and that lime mortars, renders and plasters keep beneficial permeable properties [S2].

In practice, that means:

  • Older solid walls, built before cavity walls became normal, often need a breathable render so moisture can dry out. Lime is the usual choice.
  • Modern brick or block walls with a cavity often take cement-based or polymer renders, or a system render from one manufacturer.
  • Patching old render usually calls for a mix that matches what is already on the wall.

If your house is old, listed or timber framed, ask for a renderer who works with lime, and ask what they would use on your wall.

Is mixing render dangerous?

Wet cement needs care. HSE says wet cement is highly alkaline and can cause serious burns, particularly if it gets trapped against the skin, for example inside a glove or a boot [S3]. It advises waterproof gloves that fit snugly at the wrist and washing cement off the skin as soon as possible [S3].

Other things to bear in mind:

  • Dry cement and lime powder irritate eyes and lungs, so mix outside and wear eye protection.
  • Rendering a house wall usually means working from a scaffold, and that is a job for a renderer with the right access equipment.
  • Rain or frost can damage fresh render, so a renderer will watch the forecast before starting.

What should you ask a renderer?

Ask each renderer the same questions:

  • Which render system or mix will you use, and why for this wall?
  • How many coats, and how thick?
  • Will you remove old render, or render over it?
  • What beads and stop ends will you fit at corners, windows and the base of the wall?
  • Is scaffolding in the price?
  • What happens if the wall behind is worse than expected?

Check whether you need permission too. The Planning Portal says replacing existing render with render of a similar appearance does not need planning permission, but rendering a house for the first time, or changing the type or colour of render, is likely to change its appearance [S4]. It also says that in a conservation area you need planning permission before cladding the house in materials including render [S4].

Jobs you might post

These are examples, not taken from real job posts.

  • "Old render on the gable end is cracked and hollow in places. Please quote to hack off and re-render."
  • "Patch repair to render around a new window opening. Please match the existing finish."
  • "Older solid-walled cottage. Looking for a renderer who works with lime to quote for the front elevation."

Get quotes from renderers

Describe the wall, how big it is, what is on it now and the finish you want, with photos if you can. Up to five matched local businesses can send you a quote [QZ2]. QuoteZila is free for customers and local businesses [QZ1].

Honest status: QuoteZila is new. We're starting in Cheshire, beginning with Crewe, Nantwich and Sandbach, and growing area by area. Anyone in the UK can still post a job or register a business. How fast you get quotes depends on how many local businesses have joined near you. Businesses can register and receive jobs straight away. We don't check insurance, qualifications or registrations, so please check these yourself before you hire.

Posting a job is not open yet

See our plasterers page and builders page. For a traditional finish, see what changes the cost of lime render.

Questions about render mixes

What is the ratio for a render mix?

There is no single ratio. UK guidance from the Mineral Products Association points to mixes listed by designation in the national annex to BS EN 13914-1, with cement, lime and sand proportions. The choice depends on the wall and the coat, so ask your renderer which mix they will use.

Is lime render better than cement render?

It depends on the building. Historic England says traditional solid walls are mostly semi-permeable and that lime renders keep useful permeable properties. Many modern walls of brick or block take cement-based or ready-mixed renders. On an older house, ask a renderer who works with lime.

Can I mix render myself?

You can buy sand, cement and lime, or bagged render that only needs water. Wet cement is highly alkaline, and HSE warns it can cause serious burns, so wear waterproof gloves and wash it off skin quickly. Large walls and anything off a ladder are jobs for a renderer.

Do I need planning permission to render my house?

Often not, if the new render looks like the old. The Planning Portal says replacing render with render of a similar appearance does not need planning permission, but rendering a house for the first time or changing the type or colour can. In a conservation area, check first.

Does QuoteZila check the renderers who quote?

No. We don't check insurance, qualifications or registrations, so please check these yourself before you hire. You can report a quote or a business from your job page.

This page is general information, not professional or legal advice. QuoteZila does not check Gas Safe, WaterSafe, NFRC, NICEIC or other registrations against the register on your behalf: look them up yourself.

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Sources

  1. QZ1: QuoteZila product fact. QuoteZila home and FAQ copy.
  2. QZ2: QuoteZila product fact. QuoteZila FAQ "How does getting quotes work?".
  3. S1: Learning text 12: Properties of rendering mortar, Mineral Products Association (Mortar Industry Association). Accessed 2026-10-28. https://www.mortar.org.uk/MPAMortar/media/Mortar/Publications/Learning-Texts/LT12-RenderingMortar.pdf
  4. S2: Properties of Traditional Building Construction, Historic England. Accessed 2026-10-28. https://historicengland.org.uk/advice/technical-advice/retrofit-and-energy-efficiency-in-historic-buildings/traditional-buildings-and-energy-efficiency/properties-of-traditional-building-construction/
  5. S3: Construction hazardous substances: Cement, HSE. Accessed 2026-10-28. https://www.hse.gov.uk/construction/healthrisks/hazardous-substances/cement.htm
  6. S4: Interactive House FAQ: Do I need planning permission to render the outside of my house?, Planning Portal. Accessed 2026-10-28. https://interactive.planningportal.co.uk/faqs/do-i-need-planning-permission-to-render-the-outside-of-my-house