ON THE BALL: PERFECT PRIMER
Stephen Boulton, Technical Service Manager for F. Ball and Co. Ltd., gives his advice on how to choose the best primer for any job.
Prior to the application of an adhesive or levelling compound, it is essential to prime a subfloor in almost all cases. There are different reasons for doing this, depending on the type of subfloor. Whether the subfloor is an absorbent or non-absorbent surface will also determine the best type of primer to choose.
The main reasons for priming are to promote adhesion when used over non-absorbent subfloors and reduce the absorbency of absorbent subfloors – essential for ensuring that levelling compounds and adhesives perform optimally. As well as general-purpose primers on the market, there are a range of formulations for specialist purposes, of which contractors should be aware.
WHY PRIMING WORKS When used over non-absorbent surfaces, such as waterproof surface membranes, terrazzo or ceramic tiles, primers serve the important role of promoting adhesion between subfloors and levelling compounds applied over them by creating a surface that is easier for the levelling compound to bond to.
Primers promote adhesion when applied over absorbent subfloors too, including porous concrete and sand/cement screeds. They also create a film to prevent the unacceptably rapid drying of a subsequently applied levelling compound or adhesive. If a levelling compound dries too quickly, this can lead to poor strength build-up in the levelling compound. Adhesives that dry too rapidly can lose their tackiness and ability to adhere floorcoverings properly.
The other main reason for priming before applying a levelling compound is to prevent pinholing, which is caused by the slow escape of air from absorbent surfaces, such as concrete or sand/cement screeds, which takes place while the floor levelling compound is curing. This creates tiny holes in the levelling compound at the surface, which have the appearance of pinholes or blisters once fully cured. The film created by applying a primer over the surface of the floor prevents this escape of air, reducing the risk of pinholing
12 | TIP OF THE MONTH
occurring. The use of an appropriate spiked roller will also help to remove any trapped air.
TYPES OF PRIMERS General-purpose primers can be used over both absorbent and non-absorbent surfaces. However, if preparing a particularly absorbent subfloor, it may be necessary to apply a second or third coat of the primer – the first coat applied dilute, and the second coat neat. This can be done using a roller, to ensure even coverage of the primer, which is often coloured to make this easier to gauge.
Primers are also available for a number of other specialist applications, including for use over calcium sulphate screeds – a popular choice in many new builds. A chemical reaction between calcium sulphate screeds and ordinary levelling compounds can cause the formation of ettringite; a crystalline material that can cause floor failure. To avoid any potential of this reaction occurring, F. Ball recommends that a calcium sulphate-based levelling compound is used over calcium sulphate screeds. For these situations, specialist acrylic primers are available, which promote the application characteristics of calcium sulphate-based levelling compounds.
PROPER PREPARATION A final word on subfloor preparation: before applying a primer, the contractor should make sure the subfloor is suitably prepared, dry and free from contaminants. This includes removing old adhesive residues when the job is a refurbishment or any laitance if it is a newly installed subfloor.
A moisture measurement test should also be conducted to determine levels of subfloor moisture. If relative humidity (RH) levels are above 75% (or 65% where wood floorcoverings will be installed), a damp proof membrane will be necessary to suppress excess moisture and provide a barrier to prevent moisture damage to the floorcoverings, which can result in floor failure.
www.f-ball.com www.tomorrowscontractfloors.com
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54
