In short
- Most renders should not be applied below about 5°C, in rain, in frost or with frost forecast, or in strong direct sun and wind.
- In Surrey, late April to September is the most reliable window; lime work is best from spring to early autumn.
- Monocouche applied in cold, damp weather risks lime bloom; silicone can be slow to cure.
- Good contractors plan elevations around the forecast and protect fresh render with scaffold sheeting.
Weather limits
Each manufacturer publishes limits for its products. Typical conditions are:
- air and wall temperature above about 5°C during application and curing;
- no rain on fresh render until it has set;
- no frost for at least 24 hours after application, longer for lime;
- no application on walls in strong direct sun or drying winds, which cause fast drying and cracking.
Month by month in Surrey
| Period | Suitability |
|---|---|
| November to February | Risky: cold, damp, short days; frost common |
| March and October | Possible with care and sheeting; watch overnight frost |
| April to June | Good; watch for heavy showers |
| July and August | Good; avoid working in direct midday sun |
| September | Very good: warm, often settled |
Lime is more sensitive
Lime render cures slowly and is vulnerable to frost for weeks. It is generally planned between spring and early autumn, with protection from sun, wind and rain.
Booking ahead
Good rendering contractors are busiest in spring and summer. Enquiring in late winter gives time for surveys, planning checks and colour samples before the season starts.
Protecting fresh render
Good crews use scaffold sheeting or hessian to shield fresh render from rain, wind and direct sun, mist-spray lime renders to control drying, and avoid starting an elevation late in the day if rain or frost is forecast overnight. Ask how they will protect the work in the weather expected during your programme.
Sun and heat
Summer brings its own risk. Render applied to a wall in strong sun dries too quickly at the surface, which can cause cracking and colour variation. Crews often follow the shade around the house, working each elevation when it is out of direct sun.
Questions people ask
Can you render in winter?
Sometimes, on mild dry days with protection and heating, but risk rises. Many contractors avoid rendering from December to February.
What happens if it rains on fresh render?
It can wash out the surface, cause patchiness and, on monocouche, lime bloom. Scaffold sheeting helps.