Clean, repaint or re-render? Choosing the right fix for tired render

Updated 6 November 2026 · By the Render Cleaning team

Short answer: If render is sound and simply stained by algae or dirt, cleaning is by far the cheapest fix and usually restores most of its appearance. Repainting suits painted render that is flaking or faded, a coloured coating suits sound render whose colour has faded unevenly, and re-rendering is only needed where render is cracked, hollow or failing.

Clean, repaint or re-render? Choosing the right fix for tired render

Start with the condition, not the colour

Green, grey and black discolouration is almost always surface growth and dirt, which cleaning removes. The real question is whether the render underneath is sound. Tap the wall with a knuckle or the handle of a screwdriver: a dull, hollow sound means the render has come away from the wall. Look for cracks wider than a hairline, bulges and areas where render has fallen away. Those need repair whatever you decide about the surface.

Small amounts of hollow render, such as a patch around a window or at the base of a wall, can usually be cut out and patched. The challenge is matching colour and texture, especially on through-coloured and textured finishes, so patches often show. If a wall has many small repairs to do, it can be more sensible to clean, repair and then apply a coloured coating across the whole elevation so everything matches.

Comparing the options

Option	Best when	Typical UK guide cost (semi-detached)	Typical disruption
Clean	Render sound, stained by algae or dirt	£300 to £600	One day
Clean and protective treatment	Shaded walls that green up quickly	£400 to £900	One day
Clean and repaint	Painted render that is flaking or faded	£1,500 to £3,500	Several days, often with scaffold
Render coating or recolouring	Sound render with uneven fading	£2,000 to £5,000	Several days with scaffold
Re-render	Cracked, hollow or failing render	£5,000 to £12,000 or more	One to three weeks with scaffold

These are rough guide ranges and vary widely with house size, access and region. Scaffolding is often a large part of the cost of painting and re-rendering.

When cleaning is enough

The render is firmly bonded with no hollow areas
Cracks are no more than fine hairlines
The colour beneath the growth is still acceptable
Painted render has sound paint with no flaking
You want the most cost-effective option

Fine hairline cracks are common in cement-based render and are usually cosmetic. They are worth watching rather than worrying about, but any crack that lets water in, gets wider over time or follows a step pattern through the wall should be looked at, as it may point to movement in the structure rather than a render problem.

When to repaint or recoat

Painted render needs repainting when the paint is flaking, chalking heavily or badly faded. Cleaning comes first in every case, because paint will not bond to growth or dirt. Through-coloured renders such as monocouche do not normally need painting, but where the colour has faded unevenly, specialist breathable render coatings can restore an even colour. Choose a product compatible with the render, as ordinary masonry paint can reduce the breathability of some systems.

When re-rendering is the right call

Large hollow or blown areas across the wall
Cracks that are wide, growing or letting water in
Render that is crumbling or falling away
Damp problems traced to failed render
You want to add external wall insulation at the same time

Re-rendering can count as a renovation of a thermal element under building regulations when a large enough share of a wall is renewed, which can trigger requirements to improve insulation. Check with your local building control body before major re-rendering work.

A sensible order of work

Have the render cleaned first. With the growth gone, cracks, hollow areas and paint failure are much easier to see, and you will know whether a few small repairs are enough or a bigger job is needed. Fix the causes of staining at the same time, such as leaking gutters, overflowing downpipes and sills without drips, so whichever option you choose lasts longer.

Clean the render and treat any stains
Inspect for hollow areas, cracks and paint failure once dry
Fix gutters, downpipes, sills and other water sources
Repair small defects, or plan larger repairs or re-rendering
Repaint or recoat only if the surface still needs it
Apply a protective treatment and plan a maintenance cycle

If you live in a conservation area or a listed building, check with your local planning authority before changing the colour or finish of the render, or re-rendering in a different material. Older solid-walled buildings in particular may need breathable lime-based renders and paints rather than modern cement or acrylic products.

What happens if you leave it

Algae on its own rarely damages sound render, but leaving heavy growth for years has knock-on effects. Walls that stay green also stay damp for longer, which can encourage moss and lichen, speed up the breakdown of masonry paint and, on porous renders, increase the risk of frost damage where water sits in fine cracks. Heavy growth also takes longer and more product to clean, so the eventual job costs more.

Growth spreads from the worst walls to neighbouring areas
Paint on painted render fails sooner
Moss and lichen take hold in textured finishes
Staining becomes harder to remove fully
The property looks neglected to buyers and tenants

Cleaning at the first signs of growth is the cheapest way to look after render over its life.