Poor surface preparation can lead to costly floor failures. With this in mind, the UltraFloor Technical Team has produced a simple guide which explains the correct process to follow.

SUBSTRATE PREPARATION The suitability of a subfloor/substrate should always be fully assessed before carrying out any preparation or installing a floorcovering. British Standard 8204 should be referred to for full guidance and clarification.

The main criteria to be assessed is whether the subfloor is sound and solid. Is it dry, free from contamination and laitance free? If the answer to any of these conditions is ‘no’, then the subfloor is not suitable to be laid onto and further preparation is required.

TESTING FOR MOISTURE If a subfloor has not reached the required level of dryness before a floorcovering is laid then residual moisture held between the aggregate and cement (or other binder) will slowly be released. This will then reach the subfloor preparation and the floorcovering causing damage from beneath.

85% of complaints are as a result of moisture, Source: FITA

Testing the moisture of a subfloor can be relatively straightforward, providing you know what you are assessing and have the appropriate equipment. British Standards are in place and subfloors/substrates should be tested in accordance with the British Codes of Practice BS 8203, BS 5325 and BS 8201. A BS hygrometer box should be used. This will provide a Relative Humidity (RH) reading. A reading above 75%RH is higher than is recommended to lay floors without a surface DPM.

If a moisture reading taken is greater than 75%RH then the subfloor is considered wet (when laying textile/resilient floorcoverings, 65%RH for wood). Provided the subfloor is suitable to receive moisture protection products, either a DPM or an MVS can be used.

Usually a two-coat application of an epoxy damp proof membrane may be used where there is an absence of a constructional base DPM, provided there is no hydrostatic pressure. Epoxy damp-proof membranes should not be used in projects where hydrostatic pressure is a concern. In such cases the use of pressure relief drainage and/or external tanking systems must be the primary method of protection against moisture.


CONTAMINATION AND LAITANCE Following British Standard 8204, all subfloors/substrates must be free from contaminants that may prevent adhesion such as dust, oils, grease, surface laitance, water-soluble adhesive residues, weak smoothing underlayments and so on.

Various methods and machines exist which are designed for the preparation, removal and finishing of substrates prior to the application of any flooring product. They include STGs,

shotblasters, planers, grinders, multi-strippers and dust extractors. It is recommended that you seek advice on the appropriate method and equipment for your job.

Smooth, dense surfaces can be roughened by mechanical scabbling to enhance the key.

WHY SHOULD YOU PRIME? Once the substrate has been fully assessed and the necessary preparation completed, priming of the subfloor should be considered. Priming of subfloors/substrates is key to ensuring the selected smoothing underlayment can perform to its optimum as it improves the flow and workability of the smoothing underlayment.

There are three basic reasons why priming is important. Firstly, priming reduces the absorbency of the floor; secondly it increases adhesion and finally, correct priming acts as an interface between materials preventing failure by reaction. The simple process of using the appropriate primer will minimise issues and result in a smoother and stronger underlayment, a reduction in labour time and ultimately create a surface fit to lay the thinnest of decorative coverings onto.

This guide has been extracted from the new UltraFloor brochure which is now available. The brochure has been written by the UltraFloor Technical Team and details further preparation guidance on topics including underfloor heating and specific subfloor/substrate types. SUBFLOOR PREPARATION | 39

Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52  |  Page 53  |  Page 54  |  Page 55  |  Page 56  |  Page 57  |  Page 58  |  Page 59  |  Page 60  |  Page 61  |  Page 62  |  Page 63  |  Page 64  |  Page 65  |  Page 66  |  Page 67  |  Page 68