F. Ball technical service manager Stephen Boulton takes us through the steps to achieving a high-quality flooring finish when working over raised access flooring.

Raised access flooring is popular for a wide variety of settings, in particular commercial environments. However, installing floorcoverings over this kind of subfloor requires a few special considerations to ensure the long-term performance of the installation.

Consisting of horizontal panels, typically made of metal or concrete, supported by adjustable ‘legs’, raised access flooring provides an elevated structural floor above a solid substrate, such as concrete, allowing space beneath for electrical wiring and other services found in modern commercial environments.

Installing floorcoverings over raised access panels presents a few specific considerations. Before beginning, contractors should check the height of the elevated floor is consistent, ensuring no safety hazards and a level base for the application of subfloor preparation products. Gaps between the panels must be filled and, as usual, it’s important to apply a primer as part of the subfloor preparation process. The flexible nature of the substrate also means that a flexible levelling compound should be selected to accommodate movement in the subfloor.

MIND THE GAP When installed, raised access panels have small joints between them, which allow for movement as a result of normal foot traffic and temperature changes. If a levelling compound is applied directly over the top of raised access panels, these gaps may result in weak points, which can cause the levelling compound to crack and lose its integrity. Therefore, the gaps must be filled before a levelling compound is applied and floorcoverings are installed to ensure the performance of the installation throughout its lifetime.


Priming is also important when working over raised access panels. When used over non-absorbent subfloors, such as metal panels, priming serves to promote the application characteristics of subsequently applied levelling compounds. When used over absorbent subfloors, such as panels made of cementitious materials, priming also serves to promote adhesion, as well as stopping the unacceptably rapid drying of levelling compounds.

TWO IN ONE Nowadays, cement-based primers, such as F. Ball’s Stopgap Fill and Prime, are available that are designed specifically for use over raised access panels, which fill the gaps at the joints between the panels whilst priming the subfloor at the same time. These cement-based primers have a thixotropic consistency, meaning that they flow freely when stirred but set to a gel-like consistency on standing. This enables the joints to be filled to minimise movement of the substrate. These primers are also suitable for use over raised access panels and substrates with well-bonded, waterproof adhesive residues prior to the application of a levelling compound.

Once the primer has cured, a levelling compound should then be applied to create a smooth base for the receipt of new floorcoverings. In these situations, contractors should select a flexible levelling compound, such as F. Ball’s Stopgap 700 Superflex. These flexible levelling compounds contain tiny fibres that help the product deal with subfloor movement, preventing cracks and maintaining the levelling compound’s integrity, rendering small movements in flexible subfloors harmless.

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