Cracked, blown, hollow and stained render
Render usually fails in a few recognisable ways. Fine crazing over the surface is common on older render and may be mostly cosmetic. Wider cracks, particularly ones that run from the corners of windows and doors or follow a straight line across the wall, can let rain in and are worth dealing with sooner rather than later.
Blown render is render that has lost its bond with the wall behind. It often looks fine from a distance, but tapping it lightly with a knuckle or the handle of a screwdriver gives a dull, hollow sound instead of a solid one. Bulges, loose edges and sections that have already dropped away are the later stages. Staining, green growth and dark patches that stay damp after rain suggest water is sitting in or behind the render, sometimes from a failed gutter, a leaking downpipe or a cracked sill above.
Patch repair or re-render a whole elevation
When the problem is local, such as a cracked section below a window or a blown patch near a downpipe, the defective render can be cut back to sound material and the area re-rendered. A patch repair makes sense when most of the wall is firmly bonded and in reasonable condition.
Re-rendering a whole wall, or a whole side of the house, becomes the better option when hollow areas are scattered widely, when previous patches have failed or when the finish is so mixed that another patch would stand out. Taking off old render and starting again also gives the chance to deal with problems behind it. Stephen will tap-test and look over the wall, then explain whether patching or re-rendering is the more sensible choice. The rendering cost guide explains how these choices affect a quote.
Weather and drying: why timing matters
Render needs reasonable conditions to set and dry properly. Frost can damage fresh render before it has set, heavy rain can wash out the surface, and strong sun or drying winds can pull moisture out too quickly and lead to cracking. For that reason, external work is planned around the forecast.
Cold, wet spells can delay work, and in some months there may be fewer suitable days. It is better to wait for a settled window than to rush render on in poor conditions and see it fail. If your repair is urgent because water is getting in, it is worth asking about temporary measures while you wait for the right weather.
Matching texture and finish on a repair
One of the main worries with render repairs is whether the patch will show. Existing render may have a particular texture, colour or level of weathering that new material will not match straight away. Careful finishing helps the repair sit in with the surrounding wall, but on a painted wall the best result usually comes from redecorating the whole elevation once the new render has dried.
On unpainted or coloured render, an exact match is harder to promise, because the old surface has aged. Stephen will talk through how the repair is likely to look before work starts, so you can decide whether a patch, a larger section to a natural break such as a corner, or a full re-render best suits the house.
Preparing the wall and what happens on the day
Preparation is most of the job. Loose and hollow render is removed, the wall behind is checked and cleaned, and any problems such as damaged brickwork or blocked weep holes are flagged before new render goes on. Beads may be fitted to edges and corners to give clean lines, and the area around windows, doors and the ground is protected.
Before the work, clear plant pots, furniture and anything stored against the wall, and make sure there is safe access to the area. Ground-floor repairs can often be reached with steps or a platform, but higher work needs proper access such as scaffolding or a tower, which affects planning. Gutters and downpipes that caused the damage should be repaired so the new render is not soaked straight away.
Get your render looked at
If you have cracked or hollow render, a few photos of the wall, a close-up of the problem area and a note of when it first appeared will help Stephen understand the job.
Stephen O’Brien has 25 years’ experience and works on rendering as well as interior plastering. He is based in Headcorn and travels up to 25 miles, including Maidstone and Ashford. Call 07852 191811, Monday to Saturday between 7:30am and 6:30pm, or send a free quote request.
Questions homeowners ask
How do I know if render is blown?
Tap the wall gently. Firmly bonded render sounds solid, while blown render sounds dull or hollow. Bulges, cracks around a hollow area and loose edges are further signs that it has come away from the wall.
Can you patch render so it doesn't show?
A repair can be finished to sit in closely with the existing wall, but older render has weathered, so a perfect match is not always possible. Repainting the whole wall afterwards usually gives the most even result.
When is it better to re-render the whole wall?
When hollow patches are spread across the wall, earlier repairs keep failing, or the finish is already patchy, re-rendering the whole elevation usually gives a sounder, more even result than another repair.
Can render be applied in winter?
Only in suitable weather. Render should not go on when frost is expected, in heavy rain or on a frozen wall. Winter work depends on finding a mild, dry spell, so it may take longer to schedule.
Do I need scaffolding for render repairs?
Low-level repairs can often be done from steps or a platform. Work higher up the wall needs safe access such as scaffolding or a tower. Stephen will discuss what access the job needs when he looks at it.