When refurbishing a fireplace wall, it is worth first distinguishing between the base layer and the smooth finish. Fire-resistant FR plaster and HRP putty serve different functions. Applying a new layer over a cracked or overheating casing does not eliminate the cause of the problem.
FR plaster and HRP putty: what differentiates them?
Vitcas FR fireproof plaster is a material for appropriate masonry surfaces and can serve as a base for finishing. Vitcas HRP putty, or Heat Resistant Plaster, is used to achieve a smooth surface on a compatible, prepared substrate. The English word plaster does not mean here that both products perform the same function.
In the system description, the manufacturer distinguishes FR resistance up to 1400°C and HRP up to 650°C. A higher base parameter does not increase the final layer's resistance. Also, the paint on the putty must correspond to the temperature at the place of application.
First, assess the old surface
Remove weak and detached layers, but before covering cracks, check where they come from. Does only the coating crack, or do the panels move as well? Are the ventilation grilles clear? Does the crack return after each repair? Such information will help distinguish between finishing renewal and full casing repair.
A stable old layer is not automatically a compatible substrate for a new product. Check the documentation to see if it can be left in place and what preparation is required.
Work sequence
- Determine a compatible substrate and the required primer layer.
- Prepare the surface and the primer, if indicated for the selected system.
- Measure the water and mix the material according to the product sheet.
- Maintain the required thickness, application temperature, and working time of the mixture.
- Wait for the required drying before painting and starting up the fireplace.
In a cold seasonal house, first ensure proper room conditions. Intensive heating immediately after applying the material is not a method for evenly drying the wall. If the finish cracks or peels again, check the ventilation, support, and arrangement of materials before the next layer.