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Subfloor - Preperation & Solutions

The final appearance and durability of a decorative flooring largely
depend upon the subfloor it is stuck to. Forbo offers numerous subfloor system for your needs. Whether it be protecting heritage floors or for acoustic improvement.


Subfloor Preperation

Subfloor Preperation

Australian Standard AS1884-2012 outlines the requirements of a subfloor, the implications of which are set out.

Clean. If the subfloor is contaminated with any substance which will prevent the adhesive sticking to it, then that contaminant must be removed. This includes marker lines and paint. The surface should, of course, be thoroughly swept of all small loose debris and dust.

Smooth. Any nibs of concrete, lumps of mortar, nail or screw heads, peaks of floorboards and wood knots must be smoothed off. Failure to do this will result in the ‘telegraphing’ of these to the floorcovering surface with subsequent premature wear. Similarly, all cracks, holes, etc. should be filled and made good.

Even. Apart from being smooth, a subfloor must be even, otherwise, a wave appearance will result in the finished floor, and, in the case of tiling, difficulties will be experienced in keeping the tiles in bond (i.e. in line with each other).

Sound construction. A subfloor must be rigid and not subject to flexing, otherwise cracking of the floorcovering will ultimately result. With solid subfloors, the screed should be of good quality. Failure of adhesion will result if floorcoverings are laid over weak or powdery screeds. Permanently dry. Before any floorcovering is installed on a concrete floor the floor installer must be satisfied that the subfloor is dry and that there is no possibility of rising damp occurring. There are several danger areas, covered below.

Underfloor Heating

In floors incorporating underfloor heating systems, to eliminate the possibility of moisture being trapped beneath the warming system, the heating should be turned off for at least 48 hours before moisture testing is carried out.

Some floors may be heated by steam/hot water pipes. These should be treated with great caution. Difficulties with vinyl decorative floorcoverings can be experienced due to these systems which, if overheating, cause degradation of the covering. Similarly, steam pipes and/or hot water pipes laid too close to the surface and unlagged, may also cause damage to both adhesive and decorative finish. Clauses 3.1.3 of AS 1884-2012 refer further to the requirements and conditions for the installation of resilient floorcoverings on subfloors incorporating underfloor heating or hot water pipes. After the adhesive has dried gradually increase the heat.

Moisture Testing

Some moisture will always remain in the concrete and does no harm as it is static. If, however, the moisture level is still such that, in the right conditions, it will move rapidly upwards and break the adhesive bond with the floorcovering, causing bubbles and blisters or mould growth then a very expensive relaying of the floor will become necessary.

The problem may not show itself until the building is in commission with hot central heating pulling the moisture quickly up through the slab - perhaps a year or more after installation.

A correctly calibrated and installed hygrometer gives an accurate reading when the small volume of air trapped inside it is in equilibrium with the subfloor, i.e. when a series of readings show the same figure and it is not rising. If the readings show 70 percent relative humidity or less then they meet the acceptable dryness level suggested in AS 1884-2012.

This standard suggests that on normal concrete equilibrium will be reached in not less than 72 hrs. Experience shows that the vapour movement from power floated slabs is much slower, so that it can be even 2-3 weeks before equilibrium is reached and a true reading shown. When artificial drying aids have been used to accelerate drying out these should be turned off four days before taking final readings.

Calibration is done by placing the hygrometer over a saturated salt solution in a desiccator for four hours, after which the instrument should be adjusted to read 70°. In use the hygrometer should be sealed to the floor, either by using a ring of putty round the edges or by covering it with a 50-100cm square of transparent polythene, taped to the floor round the edges. Poor sealing will result in wrong readings.

The 70 percent figure set by Australian Standards realistically takes note of the margin of error still likely in a correctly used hygrometer. However, at above 70% RH fungus spores can grow. Note that the standard is the same for linoleum and vinyl.

Sarlibase T.E Underlay

Product description

Sarlibase TE underlay is an impervious lay underlay for use over damp or contaminated subfloors or in situations where conventional subfloor preparation cannot be carried out; for example, due to time constraints, or where the existing floor covering cannot be removed.

It is a stable underlay made up of a glass fibre scrim with a smooth vinyl top surface and a textured foam backing.

It can't be used with Forbo compact vinyl and linoleum floorcoverings, Tessera bitumen backed carpet tiles and Flotex sheet and PVC backed tiles.

Sarlibase is not recommended for use with foam backed or acoustic floor coverings, linoleum or PVC tiles.
It is also not recommended for use in hygiene sensitive areas such as clinical areas or clean rooms.


Technical specification

Reaction to FireISO 9239-1
Total ThicknessEN428 (ISO24346)1.5mm
Total weightEN430 (ISO23997)1300 g/m2
Roll LengthEN426 (ISO24341)35m
Roll Width EN426 (ISO24341)2m
Impact Sound ReductionEN ISO717-2∆Lw 7dB
Residual Indentation EN433 (ISO24343-1)≤ 0.1mm (1)
Dimensional StabilityEN434 (ISO23999)< 0.05%

Points to note

As a loose lay system the quality and surface appearance of the finished installation will be dependent on the quality of the subfloor.

Imperfections in the subfloor will grin through to the finished surface. The subfloor must be smooth, sound, and have no loose or poorly bonded patches on the surface. Any cracks, holes, uneven or ridged adhesives residues and other subfloor imperfections should be levelled with an appropriate smoothing compound.

Do not use on weak or friable surfaces. The subfloor can have some contaminants adhered to it, such as paint, old oil stains, dirt, etc. – if in doubt contact Forbo Flooring Technical Services Department.

It is not necessary to attend to day joints or construction joints provided they do not cause a difference in level. Uneven joints should be repaired and/or levelled before laying the underlay.

  • Sarlibase T.E Fire report

    Sarlibase T.E fire report

  • Sarlibase T.E Underlay Installation Guide

    Sarlibase T.E insallation guide

Quick Fit Subfloor System

Forbo QuickFit Subfloor System

Rapid QuickFit subfloor system
Forbo Quickfit is an instant, loose lay, subfloor system with a self-adhering Forbo foam underlay – it is ideal for linoleum and vinyl floorcoverings in both commercial and residential projects. The system has a 23dB impact sound reduction result and perfectly suited for multilevel projects.

Wood or cementitious subfloors can be levelled quickly and easily without any “grin through” from the subfloor panels. An ideal solution, as a smooth subfloor is essential for a perfectly installed floor.

The upper and lower panels are pre coated on one side with adhesive and are ready for installation.


After installation, the floorcovering can be fully adhered to the Forbo Quickfit panels. Forbo Quickfit panels should always be installed on Forbo foam or a similar product. The 4mm PE foam underlay
performs as an excellent moisture barrier and provides additional impact sound reduction (23dB with 2mm Marmoleum).

No specialist tools are required for the installation of Quickfit. It is a floating construction, which can be easily removed at the end of its life.


QuickFit Installation video

  • Forbo Quickfit technical datasheet

    QuickFit - product information

  • Quickfit Installation guide

    Quckfit installation

Acoustic Underlay Solution

Acoustic underlay solution

Forbo's sarlibase acoustic underlay
Forbo Vinylbase is a resilient PVC acoustic underlay incorporating a glass fleece reinforcement and foam backing that provides additional acoustic performance for compact vinyl and linoleum products.

Impact sound reduction values of 18dB can be achieved with Forbo project vinyl and linoleum collections installed on Vinylbase acoustic. As with any soft underlay indentation resistance will be reduced compared to the floor covering directly adhered to the subfloor. An indication of both the impact sound reduction and indentation resistance values is given in the table below.

Vinylbase/floor covering CombinationImpact sound reduction in dB (ISO717-2) Residual Indentation * (EN-ISO 24343-1)
surestep,safestep≥ 18dB< 0.3mm
eternal≥ 18dB< 0.2mm
allura 0.7≥ 18dB< 0.2mm
marmoleum≥ 18dB< 0.15mm

*residual indentation values are indicative and may vary depending on the type and quantity of adhesive used.

Underlay Acoustic

Technical specification

Weight:1.2 kg per sqm
Thickness: 2 mm
Roll length: 35 lm
Width:2 m
Impact sound reduction: ∆Lw 18 dB
Thermal Resistance:0.008 m².K / W
Fire behaviour:8.2kW/m2 / smk dvlp 146.40%.min

Points to note

Can be combined with ETERNAL, ALLURA 0.55 and 0.7, SURESTEP, SAFESTEP, MARMOLEUM* and any compact** vinyl flooring.

• For Marmoleum products Forbo Corkment is also available.

• Forbo Sarlibase acoustic is not suitable for use with acoustic vinyl or linoleum floor coverings

Points to note

When trimming seams in the floor covering take care not to cut into the surface of the underlay. Avoid double cutting seams on the underlay if possible use a suitable protection between the underlay and the floor covering Sarlibasae acoustic is not designed for use under acoustic linoleum or vinyl floor coverings.

Leave the completed installation for 72 hours before putting into service. The finished floor may be subject to foot traffic during this period providing suitable protection is in place.

In the event of any queries, or if further assistance is required please contact Forbo Flooring Technical Services before proceeding with the installation. The installed floor covering should be left for 24 hours before seam welding.
For any further quesstions, please email us

  • Sarlibase Acoustic - Technical data sheet

    Sarlibase Acoustic Technical datasheet

  • Sarlibase Acoustic Material safety datasheet

    Sarlibase acoustic MSDS

  • Sarlibase Acoustic Fire Report

    Sarlibase acoustic fire report

Moisture and pH subfloor guide

Forbo Flooring Systems Evidence Guide for those subfloors that exceed the acceptable requirements of subfloor moisture & subfloor pH (Alkaline) levels as pertaining to AS 1884 - 2012

Moisture in concrete floors can adversely affect flooring materials and the adhesion of floor coverings. Australian Standard AS 1884 - 2012 states that concrete subfloors shall be considered sufficiently dry for the installation of resilient floor coverings if the moisture content of the subfloor does not exceed 75% as tested using the in situ probe test in accordance with ASTM F2170 or 70% as tested using the surface mounted insulated hood test in accordance with ASTM F2420. Three tests shall be performed for the first 100 m2 and at least one additional test for each additional 100 m2 and other recommended positions in accordance with ASTM F2420. A written test record of moisture results should be completed recording:

(a) Physical address of subfloor tested.
(b) Type of subfloor tested.
(c) Testing regime.
(d) Date and time of measurements taken.
(e) Location of testing equipment.
(f) Results of readings taken.
(g) Subfloor temperature and relative humidity at time of test results.
(h) Ambient temperature and relative humidity at time of test results.
(i) Type, make, model and serial number of the test equipment and its calibration status.