Rob Speke, technical academy manager at Saint-Gobain Weber, shares expert advice on the dos and don’ts of preparing substrates. The preparation of your work surface
before any final floorcovering is critical to ensure optimal bond, durability and to correct uneven floors. Here are some of
the technical aspects that you as flooring installers need to consider when starting any flooring project.
MOISTURE CONTROL Many final floor finishes can be considered as moisture sensitive, meaning moisture from the substrate can lead to failure of the final flooring. When considering a project and the subfloor preparation required, often the best place to start can be the moisture levels.
While the requirement for a substrate to have a relative humidity (RH) of 75% is probably the most well-known floor finish requirement, it is important to check the exact requirement for the finish required, as sometimes this can be different. Once this has been ascertained, the moisture content of the substrate can be measured using an appropriate method, such as a hood hygrometer.
If the substrate moisture level is found to be above the level required by the final floor finish, then the substrate must either be left to dry for longer or can be treated with a moisture control system, such as weberfloor DPM, which will act as a barrier to moisture from the subfloor causing issues with the final finish.
Use of a moisture control system allows project timelines to be accelerated by facilitating swift overlay.
CLEANING AND PRIMING THE AREA The best way to prepare a substrate is to always remove dust first. You might need to grind or shotblast it depending on how poor the substrate is, so you’ll need a good brush and vacuum to remove dust.
Priming sufficiently is crucial. We would recommend that surfaces are primed at least twice, using a soft bristled brush. Some people might use atomisers instead of a brush, but the problem with that is it doesn’t get into the pores of the substrate, which can create a lot of air bubbling and pin holing. It can also reduce the flowability of any good flooring compound.
For best results, you should prime the project the night before you plan on applying the flooring compound, come in the next morning and give it another quick coat with the primer – I’d advise using an acrylic floor primer for use with all cementitious and hemi-hydrate floor screeds. Then, by the time you’ve set up your machine and prepped everything, the primer will have soaked in sufficiently. You shouldn’t really be leaving it longer than 36 hours because then you’re going to have problems with dust particles and people walking over the primed floor.
BENEFITS OF ACRYLIC PRIMERS
FOR FLOORING It’s very common to find people using epoxy primers for flooring jobs, but acrylic primers get the job done with huge
46 | SUBFLOOR PREPARATION
reductions in time (drying in just 3-5 hours as opposed to 24 hours for a standard epoxy floor primer) and cost, not to mention the added health benefits and the fact they don’t need specialist transport and storage.
We know that the main concern contractors will have about switching from an epoxy resin primer to an acrylic floor primer is bond strength. A strength rating of 1.5MPa is required for industrial projects which is easily achievable with certain acrylic primers.
Couriers will often charge more for the transportation of epoxy primers as they can be viewed as hazardous materials and storage considerations need to made for, whereas Weber’s own acrylic primer, weberfloor 4716, has no hazard warning CLP label and therefore no specialist transportation requirements.
PREPARING THE WORKSPACE Regardless of whether it’s a thin smoothing compound or a thicker screed, there should be a 10mm soft foam barrier placed around all walls, pillars and columns, because anywhere where the flooring compound meets another rigid
IT’S ALL IN THE PREP
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