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Selecting the right smoothing compound for the job

Selecting the right smoothing compound for the job
Adam Jones

Published by Adam Jones - Technical Consultant

Adam has been part of the Bostik team for more than a decade. Starting as an apprentice laboratory technician, he spent a number of years supporting performance testing and new product developments within the flooring range.

As part of my role in the Technical Services department here at Bostik, one of my duties is to assist our Training Manager – Paul Sycamore – with delivering subfloor preparation training to floor layers nationwide. Typically, when asking what smoothing compounds they are currently using, we get one, maybe two, product names in response. Whilst I can completely understand the appeal of having a go-to product, I find it interesting that I never get the answer that I’m waiting for… it varies depending on what the installation needs.

In this article, I will talk about the different types of smoothing compounds that manufacturers such as Bostik have available, and why selecting the right product for the demands of the job will benefit your installations.

Firstly, it may be useful to explain a little about the two distinct differences you will find in smoothing compounds. Some are mixed with water (one-part, bag only) and some come with a pre-measured bottle of liquid (two-part, bag and bottle). Both types come with some advantages and disadvantages.

Standard latex smoothing compounds – These are products that are sold as a bag and a bottle. Generally, these are mid-strength products, ideal for projects where the subfloors won’t have had any previous applications or residues stuck to the floor. Usually, they will be applied to a freshly laid substrate which has received some mechanical preparation. Whilst they are not quite as “sticky” as the high-end bag and bottle products, they are typically stronger and more resistant to impact and indentation by chair legs, caster wheels, etc. Standard latex products are also typically moisture tolerant, making them the ideal choice for DPM sandwich systems, where a pre-smoothing layer of smoothing compound is needed.

Standard water-mix smoothing compounds – Available only as a bagged product, no liquid is supplied. These are generally mid-high strength products. Again, these are ideal for projects where the subfloors are in good condition.

Provided there is a reliable source of water on site, these can provide cost and application benefits over bag and bottle smoothing compounds, as well as being more environmentally sustainable. Water-mix products typically handle and apply easier than bag and bottle ones. They are also the ideal choice for contractors who apply it to large areas as they are pumpable and typically have a longer working time. One of the disadvantages of bag only products is that they do not usually offer moisture tolerance, so there may be some limitations on the areas of usage.

Fast-track smoothing compounds – These products can be available as bag and bottle, or water-mix. They typically utilise different types of cement to standard smoothing compounds to ensure the excess moisture is lost rapidly, as well as the setting and formation of the strength. These are the ideal choice for projects with a fast turnaround as they allow floor coverings to be installed in as little as 45 minutes (typically 3 hours for most common resilient floor coverings). Fast-track products can also be beneficial in the colder months, where standard products will struggle to dry for several days.

Fibre-reinforced smoothing compounds – Typically water-mix products, these are the ideal choice for subfloors that might experience some slight movement or deflection. The main areas of usage for these types of products would be timber substrates or to encapsulate or cover underfloor heating systems. The fibres assist in preventing crack formation as the floor goes through temperature fluctuations or slight dimensional changes.

Heavy-duty smoothing compounds – Standard smoothing compounds are designed to be covered over with floor coverings as soon as they are dry. Because of this, they can be quite poor at resisting heavy traffic/abrasion, as these forces are absorbed by the floor covering.

In situations where the compound itself is just going to be painted/sealed and then left to be the finished floor (warehouse areas, garages, etc.), or if floor coverings are to be installed but the expected dynamic loads are extreme, a high-strength compound with good resistance to abrasion is required. These compounds will come with a much higher compressive strength and a much higher resistance to abrasion and rolling loads. That makes these products the ideal choice for heavy usage areas.

Low-tension/high-adhesion smoothing compounds – A premium bag and bottle smoothing compound. These types of smoothing compounds are the go-to choice for most installers here in the UK. These products are ideal for refurbishment work where residues of previous preparation materials are present as they don’t require the intensive subfloor preparation that other standard smoothing compounds do, which can save the installer time and money.

Hopefully, this makes it easier to understand why we manufacturers have such an extensive range of smoothing compound options. When it comes to subfloor preparation, it is important to know that there is no one product that does everything on every job! Selecting the correct product to meet the needs of the installation environment can save costs, help avoid potential failures, and ultimately benefit you as an installer.

Should you ever be unsure about which product would be best suited for your installation, don’t hesitate to contact the technical department of your chosen supplier, who will be more than happy to guide you in the right direction.