Below the surface are hidden benefits that contribute to a successful flooring installation.
There are several ‘behind the scene’ considerations that need to be taken before a final floorcovering is installed. Everything below the surface of the final floor, from the condition of the subfloor, screeds; underlays; access flooring and cable management; underfloor air conditioning and floor heating; need to be considered as part of the overall planning process after selecting a specific floor type. These materials and items are the very foundation upon which everything else related to flooring is built.
Subfloor and Screeds: Condition & Preparation
The condition of the subfloor is a defining factor in the success of any flooring installation. The ideal subfloor is one that is dry, clean, even and free of cracks, and if not provided with the solution, the subfloor has to be prepared with a suitable moisture barrier by grinding or sanding, priming, levelling compounds or de-coupling systems and cast resins. The primary goal therefore is to attain a levelled subfloor and a good quality screed.
Screeding a floor is the simple act of applying a well-blended mixture of cement with graded aggregates and water to a floor base in order to form a sturdy subfloor that is capable of taking on the final floor finish or act as a wearing surface. It is one of the most vital steps in flooring that plays a major role in ensuring the quality, finish and durability of the entire floor.
Careful and correct preparation of the subfloor is a major part of any satisfactory floorcovering installation. The finished floor is only as good as the subfloor, which is why its condition and quality directly affects the performance of the finished floor.
Before any installation, a contractor should evaluate the subfloor to determine its condition, paying attention to the following:
• Cracking and/or structural movement
• Scaling concrete and/or loose, poorly bonded materials
• Degree of tolerance to varying flat surfaces and levels
• Surface contaminations that may interfere with the proper bonding of adhesives
• Compressive strength
• Structural integrity
• Moisture intrusion and/or future exposure to moisture
• pH/alkalinity – adhesives compatibility
Some form of preparation will always be required, with the following options available:
• Skim coat or patch minor imperfections
• Sanding of rough spots/areas
• Grinding of “high spots”
• Manual or mechanical removal of contaminants such as old mastics, adhesives, glues, etc.
• Levelling or flattening of the surface using special polymer-modified cements
• Moisture evaluation and various remediation methods
• Sealing and removal of above-floor protrusions
• Sweeping, cleaning and vacuuming
One of the major challenges that will affect the condition of the screed and substrate, as well as the preparation techniques carried out thereafter, is undoubtedly moisture levels.
If a floorcovering is laid with excessive moisture present, the adhesive can degrade and malfunction, which in turn could cause the floorcovering to come away from the slab. Many types of floorcoverings will suffer from product failure, condensation, blistering, movement and other forms of deterioration if moisture is present.
Whatever the reason might be for moisture in screeds or in old slabs, it is very important to obtain moisture readings prior to all installations. Unfortunately, no surface test or meter is sufficiently accurate. The reason for this is because too often, moisture vapour slowly permeates upward through the dense top finish and, because moisture is released in small qualities, it evaporates more quickly and does not show significantly with surface testing methods.
The only way to obtain an accurate reading, and to tell what is happening below the surface, is by drilling at least 40% into the depth of the screed or slab. Drilling into the screed, in conjunction with the use of a moisture meter designed to test below-surface moisture, is therefore critical. Once the hole is drilled into the screed or slab, an electronic sensor can be inserted that will accurately read the % RH moisture in the screed, as well as measure the screed temperature, which has an effect on the speed at which moisture evaporates.
Temperature is also important when applying adhesives and self-levelling screeds. Alternatively, one can choose from a variety of meters equipped with probes which are inserted into the hole, which give a comparable numeric reading that translates into an RH reading.
An underlay is defined as the smooth surface used as the substrate for the floorcovering. They are very important aspects of any flooring project in both residential and commercial applications, which is why their appropriate selection and installation is crucial to the proper wear and stability of any floorcovering. As the quality of the finished floor will only be as good as the subfloor over which is has to be laid, the importance of using an underlay can’t be stressed enough, regardless of the type of floor being used.
The underlay sits between the substrate and the flooring material, and is meant to absorb the roughness or imperfections of subfloors, so that the floorcovering can be installed on top of a smooth, hard surface that will give the material extra support.
Underlays for soft flooring like carpet are very different from those for hard surfaces, and others may be required to perform certain functions, such as providing a moisture barrier, acoustic insulation, cushioning and increased stability. Most underlays are comprised of recycled material, for example, rubber, and are fully recyclable, thereby enhancing their environmental performance. Many also offer anti-microbial and non-allergenic properties, are durable and suitable for use with underfloor heating.
Whatever floorcovering is anticipated, the underlay requirement should be discussed with the manufacturer or supplier before materials are ordered or installed.
Access Flooring & Cable Management
Installed above the concrete subfloor, a raised access floor can be as low as 90mm, but at 37 – 65mm it is preferable to use a cable management system as opposed to a raised access floor. This is because at 37-65mm high the access floor panel is 32mm thick creating a distance between the concrete floors and the underfloor panel of only 33mm maximum, which can’t accommodate anything.
This is where a cable management system is used. Cable management systems are available at heights of 37mm, 60mm, 90mm and 120mm. The panel is only 2mm thick so the installation of underfloor services can work in a cable management environment. A raised access floor is designed to go into buildings specifically designed for access flooring. A cable management system is not an adjustable raised floor; it is designed to manage cables. Some buildings are not designed for an access floor and therefore a cable management system would be more suitable.
When it comes to subfloor preparation for access flooring, it is absolutely critical that you have a good quality, levelled screed floor that enables smooth and rapid installation. Too often the quality of a screed is sacrificed due to a low MPa concrete mix ratio being used to top the casted slabs, resulting in inferior screed strength. Cost saving and a lack of understanding of the subfloor/screed purpose are the main two culprits for these ongoing problems access flooring companies experience when installing a screed. By fully understanding the purpose of the subfloor on screed several of these challenges will be eliminated.
Underfloor air conditioning
Although underfloor air conditioning is not the only answer for the provision of comfortable offices and commercial buildings, it does provide a considerable number of benefits, and it is logical to run this information in line with access flooring.
A raised access floor is a load bearing, raised or elevated floor installed above the concrete subfloor in a building, supported by vertical, adjustable pedestals. The void below the floor or plenum thus created provides an environment that can safely accommodate mechanical and electrical services, smoke detection, data and voice services and, in many instances, underfloor air conditioning.
Air plenums are designed for an air conditioning system. The air conditioners are switched off at night and the air trapped in the designed space is cooled by the concrete. During the day the air is recycled into the building via diffusers. In this manner you have created an air conditioned plenum.
The underfloor plenum can deliver conditioned air directly into the occupied zone of the building, referred to as underfloor air distribution (UFAD). Air can be delivered through a variety of supply outlets located at floor level (most common), or as part of the furniture and partitions. UFAD systems have several potential advantages over traditional overhead systems, including improved thermal comfort, improved indoor air quality, and reduced energy use.
The floor plenum can also be used as a large duct for HVAC systems resulting in higher operating efficiencies as conditioned air can be supplied closer to occupants via floor grilles. Access floor perforated air panels or grilles can furthermore be fitted with an adjustable opposite blade damper that is used to balance the airflow and thus control the localised temperature of equipment in Data Centres.
By combining a building’s heating, ventilating, and air-conditioning (HVAC) system with all major power, voice, and data cabling into one easily accessible service plenum under the raised floor, significant improvements can be realised in terms of increased flexibility and reduced costs associated with reconfiguring building services.
With modern floor heating the accent is on installing the heating system immediately under the floorcovering regardless of what type of floor is being used, and every floor type can be accommodated. There has been a great demand for quick-response heating in South Africa, which is better achieved with electric floor heating that has been installed just beneath the floor finish.
Response time varies depending on the thickness of the floorcovering. It takes approximately 15-30 minutes to heat, and the heat will be evenly distributed throughout the room within an hour, while the cooling down process takes 30 minutes to an hour. Furthermore, electric floor heating can be installed in both large and small areas, and for a number of commercial applications such as hotel lobbies, bathrooms, offices, boardrooms, cafeterias, hospitals etc.
Although tiles, especially marble, slate and natural stone, are considered ideal when attempting to heat a room because of their thermal conducting properties, wood, laminate and vinyl floors can also be heated in a safe and comfortable manner.
An underfloor heating consultant should advise on the correct flooring insulation and controller to be used with the chosen heating system in order to maximise comfort levels, increase response times and reduce energy consumption. Floor insulation also prevents downward heat loss into the concrete slab, increasing the efficiency of one’s heating system while saving on energy consumption. Heat loss areas should also be taken into consideration as it affects the performance of a heating system, ensuring the selected heating system meets desired expectations.
Modern technology has consequently resulted in systems that are fully programmable, totally safe in operation, energy efficient, unobtrusive and will add comfort and value to any building.
When turning to any of these materials or items mentioned above, it pays to consult an expert and to ensure that the installations are carried out by a competent, reliable company.
Acknowledgement and thanks go to http://www.cbe.berkeley.edu/underfloorair/techoverview.htm; http://www.flooring-professionals.com/the-importance-of-subfloor-prep/ and www.polyflor.co.za for the information contained in this article.