In the area where the wood flooring is to be stored and laid, site conditions must be the same as expected when the area will be in use. The room must be weather tight, heating system installed and operating at normal output, all wet trades must be finished and dry. Hardwood flooring is a hygroscopic material and is affected by changes in moisture content. Temperature and relative humidity of the air should remain constant to avoid excessive expansion and contraction of the flooring after installation. All solid wood flooring should be acclimatised to its environment for a period of at least 7-14 days prior to installing with moisture content of 8-10%.
Subfloors
Subfloors are generally seen as hidden areas and occasionally not prepared with the attention they require. The foundation should be prepared in the correct manner so as to support the covering structure. All subfloors should be level to within +/- 3mm over a 2-metre straight edge. Ensure that existing concrete beneath sheet material or battens contains an adequate damp proof membrane and is dry to within moisture content of 2.5/3%. As a precaution against potential moisture a layer of thousand-gauge polythene can be laid over the concrete prior to installation of the sheet material or padded battens. Sheet material and padded battens should be laid free floating not fixed directly to the concrete (never penetrate the DPM). As a rule, batten centres should be approx. 350-400mm depending on the grade of flooring.
Wooden Subfloors should be plywood (WBP) or moisture resistant particleboard of flooring grade quality V313 P5 chipboard with both needing expansion gaps when fitted. When installing over existing softwood flooring it is best to lay in the opposite direction, or when laying in the same direction, first install 6mm plywood (WBP). Ensure all existing boards are securely fixed and do not creek when walked upon.
Ground floor joists are often suspended over a void vented by airbricks to the external environment. Precautions should be made to separate the hardwood flooring from the moist air beneath, as failure to do so could result in irreversible cupping of the new floor.
Concrete Subfloors must be inspected by a wood floor professional to gauge suitability for a wood floor. All porous or dusty concrete subfloors must be primed and without fail moisture checks must be taken, ideally moisture content in a concrete slab should be 2-3%, if required a moisture barrier can be applied for example using Wakol Express Primer PU280 which is a one component polyurethane resin primer (1 coat) or DPM (2 coats). One coat will suppress 3% moisture, 2 coats will suppress 6%. Measuring the relative humidity of the sub floor prior to laying the boards is of great importance. When laying wood flooring, the maximum allowable relative humidity for a concrete sub floor must be ascertained, a reading of <65% relative humidity is required by BS8201.
If self-levelling compound is required it is imperative that the manufactures guidelines are checked for compatibility with timber floors and compliant with BS8204 Screeds, Bases and in Situ Floorings.
Site Conditions
The site must be sealed from the external environment, and the heating and air conditioning systems are working at a normal output to maintain a stable atmospheric environment with the room temperature 16 – 26 ° C, both during installation and thereafter. Wet trades such as plastering and painting, must be completed and dry at the time of installation. Humidity levels in the air should be between 45-65%.
Recommended Installation and Fixing
All wood flooring products should be installed to the British Standard BS 8201 1987. The code includes recommendations relating to the work in laying hardwood flooring. It is important to allow a minimum 10mm (recommended 15mm) expansion gap against all perimeter and fixed objects such as pillars etc
Nailing
Planking can be nailed (Porta nailer machine) directly to any clean, sound, dry softwood subfloor i.e. 18mm flooring grade sheet material (WBP plywood), softwood battens/joists (not suitable for 14mm thick flooring) or existing softwood floorboards.
Glue Down
Engineered wood flooring can be installed by fully bonding the wood floor to the subfloor with flexible wood floor adhesive using for example - Pallmann P4 600cc sausage, which is a high viscosity adhesive made for gun application, also known as a ‘sausage systemʼ. Rapid setting, the hardened adhesive has a firm texture and can be used on nearly all sub floors (recommended for subfloors with slight unevenness).
Pallmann P5 Solvent free and water free, high-elastic strength adhesive for wood flooring which is applied using a notched trowel it retains the trowel pattern and can be used on nearly all sub floors.
Floating
Engineered wood flooring (15mm/20mm thickness) may be installed as a floating floor on most subfloors as long as they meet the details described above. This is achieved firstly by laying a 3mm or thicker purpose made underlay at 90° to the planned direction of the flooring, then laying the flooring and bonding the interlocking boards at the tongue and groove joints with a D3 grade moisture resistance PVA adhesive. The adhesive is applied to the upper or upper and lower horizontal portion of the groove. Do not inject adhesive into the base of the groove (e.g. as the groove edge of the boards face upward vertically) as this may prevent the tongue and groove joints from closing. Its strongly recommended that both header and length joints be bonded with PVA to avoid potential gapping as wood expands and contracts.
Maintenance
WATER AND WOOD DO NOT MIX. Never wet mop as this could cause permanent damage to your hardwood flooring. Wipe spills as soon as possible, vacuum or dust mop regularly to remove dust and debris. Incorporate entrance mats at all entrances to reduce water and grit from footwear etc. Apply maintenance products in line with the manufacturer’s instructions.
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