Our Heat Resistant Render and Plaster System
When you see a 'hole in the wall' or cassette stove, it looks clean and uncluttered. There is no distinct tile or brick surround like you would see in a fireplace. It is just there, in the wall. But looks can be deceptive. Like an iceberg, there is a lot going on below the surface; the interior of the cavity has to be properly lined, a chimney and flue system has to carry away exhaust gases and the wall around the stove needs a bit of special treatment to stay in good condition.
It won't come as a surprise to know that a stove gets very hot and that some of the heat is transferred to the surrounding wall. Ordinarily, living room walls are covered with a layer of plaster and then painted or papered. This plaster contains a high level of gypsum. If it is subjected to high temperatures, it starts to dry out and crack and will eventually fall off.
So the wall around a cassette stove needs a heat resistant plaster to stay looking good. This is a specialised formulation designed to withstand high temperatures up to 650°C. When finished it looks much like ordinary plaster and it is applied in much the same way to a layer either of fireplace render or to fireplace construction board. If you are setting a stove into an existing chimney breast, the simplest solution is to use the render and plaster system over the front surface.
The first step to ensure the best results is to remove all traces of old plaster from the chimney breast and from all your tools and equipment as any traces of gypsum can make the heat resistant plaster form into clumps and set too quickly. Once the masonry has been exposed and cleaned, apply a layer of fireplace render. Leave it for three days to dry out thoroughly, then you can apply the plaster.
It is important to leave a smooth finish with the trowel as heat resistant plaster is very dense and cannot be sanded down later. Another three days drying time is needed before you can go on to paint the wall. Follow the manufacturer's instructions for lighting the stove for the first time. It is generally advised to run it at a moderate heat for short periods and build up gradually.