Rendering and the winter challenge

Rendering and the winter challenge

Whilst the Covid pandemic has impacted the way many of us do our day-to-day work, in the construction sector the ongoing and unpredictable British winter brings a new set of challenges.  From rainstorms to gale force winds, deep frosts and even the occasional snow event, working outside during the winter months can derail a project timeline causing costly delays. But what impact do severe weather events have on the application and type of materials we specify? Matt Allen of the Sika Building Finishing Team looks at rendering in the winter months.

Our weather has become increasingly erratic in recent years which means that contractors need to be flexible in terms of their workforce to ensure projects remain on track. For the renderer, one of the biggest issues in winter is cold and wet weather. If the temperature is below 5°C or falling then water in the render begins to crystalize, which begins to affect the curing of the product and can result in the product failing to reach its optimum strength or performance. This generally results in a dusty surface to the render when cured which can then cause surface staining from water run-off.

If the water freezes within the wet render, this stops the curing process and will affect the renders strength. An uncured render that has suffered the effects of freezing can lead to the surface of the render being very crumbly and friable. This damage would need to be rectified and in the worst case fully removed and replaced.

Another issue is the substrate in cold weather as its crucial to avoid applying renders to an unprotected frozen or frosted surface. Keeping the substrate dry will also prevent water getting behind the render which can potentially freeze.

Newly applied finishes also need to be protected from frost in cold weather and rapid drying until the render has cured. Polythene sheeting is recommended for curing and can also be part of the scaffolding system. This should be arranged to hang clear of the wall in such a way that it does not form a tunnel through which the wind could increase the evaporation of water from the render. The polythene sheeting must not be in contact with the render products as this could produce a patchy appearance.

Whilst for some, the biggest challenge in winter may be simply a case of workers suffering from cold hands and feet on site, all parties need to be prepared for whatever mother nature throws at them in the winter months.  It’s also important to stick with the professionals, as a skilled and experienced applicator will be aware of the risks and challenges of applying renders in adverse weather conditions.

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