Special Subfloors : part I

SUBFLOORS FOR FLOOR COVERINGS

A RAPID TOUR OF THE ENTIRE SPECTRUM

Photo – Bona

Photo – Bona

A subfloor along with substrate preparation, is one element in wooden floor fitting which disappears from sight once a floor is complete. Whether we talk about moisture resistance, levelling, acoustic refinement, or a combination of all those goals, a subfloor still directly affects the quality of the final floor. In other words, it is absolutely vital. Two developments stand out. Firstly, there is the emergence of universal subfloors and, secondly, subfloors designed for a specific case. This time we give a rapid summary snapshot, but in future editions we’ll zoom in.

Clients deserve an explanation! There are certainly more jobs in the construction industry where the final assignment is preceded by a lot of preparation. Take painting, for instance. Painters are often occupied for several days with all sorts of repair jobs before they can put a stroke of paint on the wall. It’s exactly the same with fitting parquet. Preparing a substrate and fitting a mezzanine floor sometimes take up as much time as the final floor fitting itself. Both work and materials show up on the bill. Clients deserve an explanation for those extra costs. Floor fitters should explain why those preliminary operations are so necessary. The substrate Before we present the various sorts of subfloors, it would seem helpful to outline the elementary conditions which the substrate has to meet. Lots of parquet producers put these conditions forward as a guarantee condition.

Dry The fact that the screed and the floorboards have to be checked for their moisture content in advance is absolutely basic. You could call it a basic condition. Floor fitters have at their disposal various measuring instruments for this purpose.

Flat The subfloor onto which a wooden floor is fitted has to be flat. There is sometimes a certain lack of clarity about the term ‘flatness’. It is certainly important to realise that not even a new screed necessarily meets the flatness requirements for fitting parquet.

Solid It might seem obvious that the substrate has to be solid, but this is often taken with a pinch of salt. A grain illustrates perfectly what

‘solidarity’ means. With a glued fitting, the glue is applied with a jagged spatula. If the screed isn’t solid enough, there is a risk of grit or grains coming loose from the screed and getting mixed into the glue. Obviously, that is disastrous for a qualitative fitting.

Clean When we use the word clean, this means that all possible residue of adhesive, paint, plaster, grease, oil, and dust should be removed completely. The substrate has to be completely free of all those elements. The slightest infringement can impede the glueing.

What does the subfloor do? Now that we have outlined the requirements for the substrate, we can immediately answer the question about all the things which a subfloor can do.

Damp screen A floor needs protection against possible rising damp. This protection can consist of a fluid damp screen (epoxy primers) or damp foils. Apart from these chemical damp screens, there are various sorts of waterproof foils. They can be applied in combination with subfloors which, in turn, serve a different purpose. More and more subfloors are already fitted with damp screen (waterproof) foil so that the fitting can go ahead in one motion.

Levelling Levelling can be done perfectly well with a levelling agent or levelling compound. A levelling agent is generally fluid and self-levelling. The fact that most levelling compounds set very quickly means that very little time is lost. Levelling compounds are suitable for floating and glued fitting. However, for a floating fitting it is also possible to fit a levelling subfloor. The market offers several wood products (plates) for this purpose. Apart from wooden subfloors, we also find soft subfloors (in panel form or in rolls) with a very high levelling capacity.

Sound refinement As we have said, the subfloor has to be dry, flat, solid, and clean. Those are basic requirements. In addition, it might also be necessary to improve the acoustics. Subfloors which refine the sound can exert an influence on airborne sounds or impact sounds or both. Airborne sounds are vibrations reproduced by the source of a sound in the air e.g. the human voice, the radio, music, a running engine, and such like. On the other hand, impact sounds are created between materials. Typical impact sounds in buildings, for instance, are footsteps, a sliding chair, or the hanging of a frame.

Multifunctional or specialist For both floating and glued fittings we are seeing the emergence of more and more subfloors which combine as many functions as possible. Various subfloors in rolls (for floating fitting) combine certain (foam) synthetics and a damp screen so that various goals can be achieved in one sweep e.g. levelling, moisture resistance (via an integrated damp screen), or sound insulation. Furthermore, there are subfloors which are designed specifically for a specific application. That can relate to extra sound refinement, fire resistance, floor heating, etc. Food for thought for the next few editions!

One specialist

STEICO New product STEICOunderfloor LVT Ecological underlay for vinyl and design floors Sound proof insulation made out of natural wood fibre Ecological underlay panels STEICOunderfloor LVT are made from resource-saving natural wood fibre without any harmful additives – contributing to a healthy indoor climate. The insulation boards are designed for single-layer floating installation in dry areas of LVT and vinyl coverings of the MMFA sub group 2. Its special underside surface improves punctual uneven floor levels. With an impact sound reduction of 19 dB, the boards provide excellent acoustic insulation. Different to STEICOunderfloor underlay for laminate floorings, STEICOunderfloor LVT is only 2.3 mm thick (compared 3-7 mm) - perfectly suited for new buildings as well as renovations, where floor constructions can often only have a limited thickness. The high compressive strength (>600 kPa) and density of approx. 600 kg/cbm ensures maximum security and protects the flooring at its best. www.steico.com

Photo – STEICO