What happens below the floor is not always well understood, even though there is a lot of information available.
Floors in Africa spoke to experts within the industry, and asked what their top insights are for contractors and specifiers about substrate preparation.
It is critical to assess the condition of a substrate before starting the preparation process.
The most commonly used assessment tools or techniques include:
- A visual assessment of the floor space to determine what needs to be done, and what the state of the floor is, i.e., contaminated with old underlayments, mortars, grease, oils and skim plasters.
- Tile reverberating rods, steel bars or hammers can be used to test for loose, hollow sounding or friable areas. Cracks and visual degradation could allude to a potential problem.
- Evaluation of the quality of the floor through tensile pull-off testing, using a pull-off tester and 50mm dolleys.
- A concrete rebound (Schmidt) hammer is used to test the compressive strength of the substrate.
- Moisture meters take moisture readings in terms of the percentage moisture or relative humidity in a substrate.
- Evaluate the ambient and floor temperatures to ensure that both are within the floor coverings capability or recommended application guidelines.
- Evaluate the humidity levels before application of the floor covering to ensure that they are within the recommended parameters stipulated by the supplier.
The substrate is the core and backbone of any flooring installation, providing both aesthetics and functionality. The consequence of neglecting substrate preparation is, in short, a likely failure of the installation, where the floor cannot perform as intended. Substrate preparations include:
- Allowing the stipulated curing/drying times of the substrate, whether it is a new concrete floor or a cementitious screed.
- Remedial work on weak and friable substrates.
- Removal of contaminants and debonding layers, through mechanical abrasive blast cleaning or grinding.
- Removal of dust, loose and friable material, preferably by vacuum.
- Correct substrate priming.
These are all vital attributes to sustainable flooring installations.
The cost of failure
Generally, floor preparation can be very accurately costed, unless there are elements which are not visible or known at the time – i.e., when the floor is hidden by an existing covering, making an accurate assessment of what needs to happen more difficult.
But can a failed floor installation be quantified in terms of costs?
Yes, say the experts. The cost of repairing a failed floor will far outweigh the costs of undertaking the installation correctly the first time round. Added to this will be time delays before the project handover, or unnecessary inconvenience and disruption to the end customer.
Common mistakes on site
Common mistakes seen on site that contractors may typically make with substrate preparation include the following:
- Not paying enough attention to the high moisture content on a substrate, or not testing for moisture at all.
- Disregarding curing times of new concrete, screed or repair, or levelling compounds.
- Inadequate cleaning of contaminated floors and no dust removal.
- The lack of, or incorrect, priming agents.
Climate and environment
There are specific climate-related challenges that impact substrate preparation that need to be addressed.
Whilst a substrate may test “dry” when conducting moisture testing on the floor, it should be noted that surface beds may be subjected to high and/or fluctuating moisture levels due to high water tables, seasonal changes etc. Rising water tables can induce rising damp in substrates, which can cause issues in some floor finishing layers.
In projects where an existing breathable floor covering, such as a carpet, is removed, the moisture test may indicate low levels of moisture vapour emission rates (MVER). However, as the floor was able to “breathe” before being covered with a vinyl floor covering, for example, moisture may be drawn to the surface again.
Moisture barriers are there to protect self-levelling systems, the floor finish itself and the adhesive keeping the floor finish down.
Diamond grinders generate a lot of dust, but units are now available with attached vacuum cleaners. This will drastically reduce the amount of dust generated and/or distributed during the grinding process, and are especially suited for “live” or operational sites where normal grinding procedures are not viable.
In South Africa, SANS 10070:2013 stipulates the requirements for resilient floor coverings, but it doesn’t cover methodology. The adoption of European standards largely drives the local industry.
Flooring professionals should therefore follow industry best practice when it comes to substrate preparation. Ideally all substrates should have a low moisture content, must be clean and uncontaminated, and should be diamond grinded to leave a concrete surface profile (CSP) of a value of 3-4 (light).
Several products are low-VOC (volatile organic compounds) or VOC-free, but progress is slow in the industry to produce substrate preparation materials that are sustainable, partly due to the lack of regulations or standards where green products are concerned. There are, however, councils and organisations such as the Green Building Council of South Africa (GBCSA), who are doing excellent work in stipulating emission rates and guidelines for achieving green building status.
Issue: What are the biggest issues around substrate preparation locally?
Solution: Industry experts share insights into the biggest concerns for the flooring professional and specifier, to prevent failed flooring installations.