Flooring sealants need to be aesthetically pleasing as well as functional. The role of a sealant is to absorb the movement in buildings, provide a waterproof seal, absorb vibrations, minimise sound transmissions, seal the flooring against drafts as well as seal it against pests and dirt.
The term “sealant” is very broad, and in the construction and flooring industry can have very different meanings and applications. This can range from something that is applied to seal a substrate against rising damp – such as a vapour or moisture barrier, against ingress of water into underlying layers – such as a waterproofing compound, to absorb and allow for movement in structures and buildings – such as a joint sealant, or as a protective layer over a surface – such as a surface sealant.
For a better understanding the various “sealants” and their purposes, we will deal with them individually:
Polyurethane technology has been around for many years as a suitable sealant for interior and exterior sealing of expansion joints between concrete slabs, tile panel movement joints and for sealing between concrete or brick wall joints. While there are a number of sealant manufacturers offering solutions with polyurethane components, this technology has its limitations due to standard polyurethane formulations containing isocyanates making them susceptible to bubbling, says Lance Anderson, Product Manager at Den Braven.
“This type of bubbling can occur when the sealant is exposed to direct heat during application, or the substrates still containing moisture, and the overuse of water when tooling can also contribute,” says Lance.
Polyurethane sealants generally allow for a 10-minute open time before skinning takes place, which means that the applicator needs to work fast to extrude in small areas and then quickly tool off, which could lead to the possibility of skinning already taking place. This can then entrap the gases which need to escape when curing. To overcome this issue, new technologies that offer high performance characteristics for sealants have been developed. Some of the characteristics of these next generation sealants include increased weathering and chemical resistance, increased adhesion strength and better abrasion resistance, as well as low temperature extrusion ability.
Matte vs high gloss systems
“Most flooring types that require sealants come with a factory finish which varies in intensity from a simple protective acrylic zinc cross linked dressing designed to protect the flooring from scratches etc. during the installation process, to reinforced poly-urethane finishes which are designed to last for several years,” says Mac Dougall of iTe Products.
With resilient flooring types such as vinyl flooring, the simple sealer used as installation protection is stripped 72 hours after installation and then a new sealer is applied in two or more coats, followed by a regular maintenance regime, depending upon the product or system chosen. The frequency or intensity of the programme implemented is dependent on the specific application and the traffic intensity, as well as other factors such as dustiness of the environment, tracking of soiling and hygiene factors.
The zinc cross linked sealers are usually acrylic emulsion and are blended with waxes and chemicals to create a sealed surface to protect the vinyl from wear and tear and soiling. These sealers were traditionally very hard when buffed, giving a high gloss finish. This surface was then “spray buffed” daily to replenish the surface and keep the sealer from becoming scuffed or soiled.
“The problem with high gloss sealers is that every imperfection in the floor or sub-floor shows up glaringly, spoiling the overall appearance of the floor. Sealers that have a low gloss finish, often called matt sealers, have become increasingly popular in order to maintain a better-looking finish. The old school view point of ‘if it’s shiny, it’s clean’ tends to avoid these finishes and rely on the high gloss systems,” says Alistair.
The modern approach of flooring manufacturers is to develop coatings which can be applied to the surface of the flooring during the manufacturing process, says Alistair.
“Poly-urethane coatings evolved into reinforced poly-urethane coatings, and today some manufacturers market their products with their specific branded systems. Because the maintenance of these floor coverings is a significant cost factor in the long term, these no/low maintenance systems are very popular. In fact, over seven to eight years, the maintenance cost can exceed the original installation cost,” adds Alistair.
When asked what sealant to use before tiling, Sharon Margon, Technical Advice Supervisor at Tal says that in most instances a waterproofing system is actually needed.
“For tiling a shower enclosure, a balcony, parapet walls etc., the installation of a suitable waterproofing system prior to tiling will ensure that there is no ingress of water through the tiling installation to the wall behind, or through the ceiling of the room below the tiled surface,” says Sharon.
With tiled floors, it is very important to note that the waterproofing system must be compatible with cementitious tile adhesives. Using compatible products ensures that the end result is a well “sealed” and sound installation.
MOISTURE AND VAPOUR BARRIERS
“Similarly, prior to the installation of underlayments and resilient floor coverings such as vinyl, where prevailing moisture levels within the substrate do not attain 5% (75% RH) or less, it is not a sealant that is required, but rather a moisture barrier,” says Sharon.
Alistair agrees that substrate moisture is a potential cause of failure in resilient flooring applications.
“Vinyl flooring generally has a low tolerance for screed or substrate moisture, and when exposed to levels exceeding 3%, moisture related problems become the single largest source of failure. Over the years, manufacturers of substrate or screed preparation products have spent fortunes developing moisture barrier systems to provide a solution to this problem. The most commonly used systems today come from epoxy-based products,” says Alistair.
“For a moisture barrier to function effectively, it must form a barrier which either prevents moisture from rising through it, or preferably, reduces the vapour transmission rate to levels which are tolerable for the flooring or adhesive used to bond the flooring, or to any components that may be affected by rising moisture,” says Alistair.
A high-density barrier coat prevents the debonding of coatings and floor toppings due to high moisture vapour emission rates (MVER). This type of ‘sealant’ is also used to eliminate out-gassing of concrete.
“When selecting a vapour barrier, it is important that it is compatible with the underlayment compound or floor coating intended for the final floor finish, and that the application thickness is sufficient to halt moisture and vapour emissions,” advises Sharon.
In some cases, although a floor may test dry, moisture within the substrate can fluctuate over prolonged periods, depending on high ground water tables and substrate porosity after surface preparation, thus it is prudent to install a vapour barrier before installing vinyl floor coverings.
This barrier is in fact a film which penetrates the substrate and binds into it preventing lifting under vapour pressure. In other words, the substrate must be such that this is possible, therefore screed moisture levels must not prevent penetration and no contaminants that may prevent bonding may be present. Substrates with a very high moisture content may also require the application of a moisture tolerant primer prior to the vapour barrier.
These moisture barriers effectively trap the moisture below them permanently, thus not removing the source of the problem, but preventing it from damaging the system.
“These products are sophisticated and each manufacturer has their specific set of guidelines for application which must be adhered to,” concludes Alistair.
Specialised tip: The role of a sealant is to absorb the movement in buildings, provide a waterproof seal, absorb vibrations, minimise sound transmissions, seal the flooring against drafts as well as seal it against pests and dirt.
Photo credits: TAL
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