The main purpose of under-floor waterproofing membrane is to prevent rising damp from entering concrete or other floor surfaces. In addition it prevents contamination of concrete during the pouring process. Users have the option of choosing black or green sheets or co-extruded membranes with one side in black and the other side in green. Although green is the most popular colour in the building industry, the black membranes with the same thickness are equally up to the task and will last just as long. In 2011 a new product has been introduced that is green on one side and black on the other. This is a co-extruded membrane that is thinner (and therefore cheaper) but yet it will also be SABS certified. All under-floor waterproofing membranes are made of low-density recycled polyethylene (plastic).
PXD Plastics therefore play a vital role in the recycling and reuse of waste plastic because we use between 2500 and 5000 tons of recycled plastic per year for making these products and channeling them to the building and construction industry. It is estimated that the combined volume of recycled plastics that is used for making this specific product is between 10000 and 30000 tons per year in South Africa. Actual volumes used per year mainly depend on the healthiness of the building/construction sector which may vary in line with cyclical up or downturns in the economy.
Two types of SABS certified membranes are available, namely:
- A co-extruded (multilayer) membrane that is black on the one side and green on the other side. This membrane has a minimum thickness of 170 micron and is recommended for housing or light industrial projects. This product has been approved for SABS certification in 2011.
- A monolayer green membrane with a minimum thickness of 250 micron (this product is also available in black colour). This is the conventional product that has been available in South Africa for many years. It is suitable for housing, industrial or any project where under-surface waterproofing is required.
These membranes are normally 30 meters long and are provided in widths of 1, 2, 3, 4 or 6 meters. Longer lengths or other widths can also be manufactured provided that the quantities required are sufficient to warrant a special production run. Specific mechanical properties and strengths of the membranes are described in the SANS 952 specification. Apart from having a very low water vapour transmission rate (to prevent rising damp) the following properties are considered to be of vital importance for an under-floor waterproofing membrane (especially when concrete is poured onto it):
- It should have a high puncture resistance;
- It should have a high tear resistance;
- It should have very good tensile properties (breaking strength and a high percentage elongination before it breaks);
- It should have a high resistance against accelerated aging.
These membranes will last a lifetime provided that is installed correctly and not damaged prior to and/or during the concrete pouring process.