Render serves two basic functions. One is it’s protective qualities as render acts as waterproof for the wall which enables them breathe by allowing water vapour move from the inside to the outside of the structure while also working to prevent water or rain from finding its way inside the structure. While the second function is the decorative qualities as render is able to provide the structure with a fine finish and colour to make the building a lot more appealing and correcting faults in line and level in the masonry.
If you wish to apply render on your external wall, you’d probably be wondering just how thick the render should be to perfectly serve both of functions. In this article, we’re going to take a look at just that!
For a render thickness, the British Standard Wind Driven Rain Index has come up with 4 ratings which include Sheltered, Moderate, Severe as well as Very Severe. An area with Very Severe rating include South West England. This rating implies that the thickness of the render in this area should be increased to at least 20mm for a direct one coat render applications as well as 5 to 6 external wall insulation base coat applications. And if you happen to reside within one mile of the coast, it’s strongly recommended you incorporate an extra repellent protection like Paraguard AG from Parex.
In general, render that’s prepared on site with cement and sand should be have a minimum of 20mm to 25mm thickness. Although, it should be noted that the quality of the render is based on quality of the sand incorporated, the design mix as well as being largely dependent on how good the mixing technique from the applicator is. The most common reasons why traditional renders fails is due to both poor mixing ratios and low quality materials used.
