FEATURE
ON THE BALL Tip of the Month:
Preparing a subfloor effectively is essential to maximise the aesthetic appearance and long term performance of a new floorcovering. Over the next few months, Stephen Boulton, Technical Service Manager at F. Ball and Co. Ltd., will guide us through the key stages of the subfloor preparation process, starting with testing for moisture.
Prior to installing any decorative floorcovering, it is essential to test the subfloor for moisture. Moisture testing must be performed in accordance with British Standards 5325, 8203 and 8201 by measuring the Relative Humidity (RH) level within a subfloor. Where the RH is above 75%, the installation should not proceed until an appropriate and effective damp proof membrane - such as Stopgap F75 or F76 epoxy resin system or a Stopgap Isolator loose lay membrane - has been applied, as excess moisture can result in blistering of the floorcovering or even complete failure of the flooring installation.
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Which types of subfloor pose most risk of moisture? All floors need to be carefully examined for moisture. Although it became mandatory in 1965 for all new buildings to incorporate a damp proof membrane at ground floor level, there are instances where buildings constructed after this date will still be susceptible to moisture. For example, the existing damp proof membrane may be damaged or not performing efficiently, or the area may have been compromised by a water leak. In both cases, a new waterproof surface membrane should be installed.
A particular risk for new buildings is the presence of residual construction moisture in the floor slab, which takes a considerable amount of time to dry out naturally. In this situation, the application of a waterproof surface membrane will enable a floorcovering to be installed straight away.
What is the most accurate method of testing for moisture within a subfloor? In the first instance, an indicative test using a radio frequency moisture meter, such as the Protimeter AquantTM, offers a quick and easy method of testing moisture levels. If only low levels of moisture are present, the flooring installation can proceed as planned. However, if the meter indicates that a subfloor contains excessive moisture, further investigation is required so that the appropriate treatment can be identified.
To accurately measure the level of moisture in the subfloor, the recommended methods of moisture testing are either a calibrated digital hygrometer or the Protimeter MMS with moisture probes that are inserted into pre-drilled holes in the slab. The digital hygrometer is temporarily sealed to the floor to isolate the device from the surrounding air, providing a direct reading of the RH.
Measurements should be made at a number of points across a floor once the air inside the meter is in equilibrium with the surrounding air. Equilibrium can be assumed when two matching consecutive readings are taken over 24 hours.
Where RH levels are measured at below 75%, the surface is considered sufficiently dry to receive the floorcovering and the installation can proceed without further treatment. As wood floors are particularly sensitive to moisture, F. Ball recommends a maximum RH level of 65% without applying a waterproof surface treatment. Contractors should also consult the wood flooring manufacturer for advice.
www.f-ball.co.uk
www.tomorrowsflooring.com
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