Technical Manager Joe Ragdale offers valuable advice on the storage and application of Wetherby’s products & systems.
The wet and cold weather conditions we’re likely to sustain throughout the winter months can create many problems for rendering. Products and systems must be applied in the correct conditions and protected adequately to prevent system failures during this difficult period. I would like to make you aware of the best working practices during these months to reduce the risk of wash offs and product failures.
Firstly it is imperative that all WBS products are carefully stored and protected from frost. Should any of these products become partially frozen, the product will be ruined and will have to be discarded appropriately. In pre-mixed silicone products, even when the ice melts and the product returns to a liquid it cannot and must not be used as it will not be fit for purpose and the binders that hold the render together will no longer work. All bags and tubs of Wetherby product must be carefully stored off the ground and kept completely dry; using an insulation board to store the products on will help to reduce the chances of the product freezing in storage containers.
Application of all polymer modified renders, adhesives, primers and silicone products can only occur when the temperature is 3°C and rising or 5°C and falling with no frost forecasted. These products will only cure in temperatures above 4ºC and applying in lower temperatures will result in the render remaining wet on the wall, increasing the chances of damage due to frost or wash offs in heavy rain.
Wetherby products are water based and therefore dry through physical evaporation; cold temperatures significantly slow this process down and in turn dramatically extend drying times. Weather forecasts must be consulted before application to ensure the render has a reasonable period of time in adequate temperatures to allow the product to cure.
Humidity levels are another factor that should be taken into consideration when applying WBS products.
Wetherby renders will only cure in relative humidity levels of less than 90%. Higher humidity levels of over 90% will prevent the products from curing as the amount of relative humidity in the air will be higher than the moisture content of the material itself and therefore the product will be unable to cure. Again applying products in high humidity will lead to the render remaining wet on the wall for extended periods making it susceptible to frost damage and wash offs.
Wetherby’s new Mineral Render PLUS system is designed to combat winter conditions since it dries independently of humidity, providing an improved product for the damper times of the year.
I trust this is useful information and will help to ensure damage to the WBS render systems in winter conditions is kept to a minimum.