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The importance of a solid substrate

When planning flooring projects, the substrate must be one of the first considerations. It’s vital to the success of any project because if the substrate isn’t properly prepared, the installation will probably fail.

CONTRACTORS often turn to our technical experts for advice on how to approach the issue of the substrate not being properly prepared, recognising that this early-stage involvement is crucial to the flooring system’s performance overall. Manufacturing companies’ technical representatives can play an invaluable role with the contractor by working together in an initial inspection.

Structural strength
Out onsite, an early inspection can determine the extent and nature of any cracking. In certain cases, it can also unearth more serious technical structural problems.

As part of the visit, issues with cracking and damage can be dealt with by a remedial specification specific to the issues that exist – no one solution works for all crack repairs so it’s always better to get a visit arranged by technical service who can best advise on a remedial package. The strength of the surface can also be established of the floor in question.

Special considerations
Pay careful attention to areas such as upstands, as well as details such as gullies, drainage outlets, and pipe penetrations during the inspection. All these are potential problem areas and need to be carefully considered in the process too.

On refurbishment jobs, an inspection can also help pinpoint what the building was used for previously, and what likely contaminates from past use are embedded into the substrate. Oils, chemicals, and other products used over the years could provide a hidden problem, which can be identified in an inspection of the substate. Where an issue is identified, the contractor has several recourses including the use of mechanical means to remove solid material such as mortar spots or old adhesive.

Where liquid contamination is an issue, it’s better to get a technical service visit arranged to get the best advise as the type of contamination can have different remedial specifications and is often specific to the contamination – whether it be old paint, solvent, or oil. Please ensure you contact our technical services division.

Moisture matters
When it comes to installing floor finishes, excess moisture can be a real issue – seriously threatening the success of the project overall, with costly consequences. Moisture in floors generally comes from one of two sources when the building is watertight.

The first is related to newbuild projects, where there can be constructional moisture contained within the newly installed subfloor.

The second scenario is where there’s no DPM in the subfloor construction or it’s deemed ineffective. This may be owing to it having degraded or expired over time. This situation is usually encountered in older buildings.

In existing buildings, it’ll be the ground floor which will be affected by excess moisture.

In the case of moisture on a newbuild project, there’s a chance excess moisture can also affect the building’s upper floors as well as the ground floor.

Some research work can help build a better picture of the situation. This can be done by taking moisture readings as a starting point. There are various methods of testing and it’s best to seek advice on the best way to achieve an accurate result.

Once readings have been taken, next steps can be decided. If it’s found readings are over 75% relative humidity, then the question can be asked – does the subfloor need an epoxy surface DPM or moisture vapour suppressant?

Traditionally, an epoxy surface DPM, has been used where readings are up to 97.9% relative humidity (theoretically 99.9%).

Before this can be applied it’s vital the subfloor is surface dry, even, and contaminant-free. If the surface isn’t even, pre-smoothing of the subfloor is recommended to ensure the effectiveness and maximum coverage of the surface dampproof membrane.

Once this is achieved, the epoxy DPM is then applied directly to the subfloor followed by a primer and then a smoothing compound. The selected floorcovering is then adhered with a suitable flooring adhesive.

It’s worth noting some TREMCO smoothing compounds can be applied directly to the TREMCO DPM without the requirement of a primer, but we’d strongly advise contractors to always contact the manufacturer for further guidance on this.

When readings are up to 95% relative humidity in a newbuild project, and there’s an effective DPM installed under the subfloor, a moisture vapour suppressant can be used.

Levelling up – and think about the future
Consider uneven substrate surfaces. In some circumstances, where the substrate is roughly surfaced, it may be necessary to utilise a moisture tolerant smoothing compound prior to installing the DPM. To achieve a uniform finish, a further coat of the compound can be laid to ensure the adhesive and floor covering deliver the desired even finish.

And finally, when conducting all stages of the inspection, specification, and installation, it’s essential for the flooring specialist to remain mindful of the building’s eventual function, to ensure it’s fit for purpose for the future.

Occupancy also needs to be considered in relation to the products and methodology chosen. It may, for instance, be appropriate to choose products offering very low odour or that are EC1 compliant to respect locations like hospitals or food production facilities.

Some detective work is often required to ensure a flooring installation gets off to the best possible start. In all situations, correct preparation remains essential to success and, in this important area.
Tarjinder Singh is technical services manager at Construction Products Group (UK) – manufacturers of Flowcrete and Tremco flooring

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