Keen-M strongly recommended that installation is carried out by a professional wood flooring fitter with a proven track record in installation procedures. Furthermore the following information should not be regarded as strict instructions but as guidelines for installation only.
There are three main installation methods for wooden floors:
Nailing, Floating, and Gluing.
- Ensure site conditions are dry
- Ensure sub-floor is sufficiently level and dry.
- Always use a moisture barrier over cement ground floors.
- Use adhesive only for floors which are intended to be glued down.
- For floor batten construction, ensure the battens are packed where necessary. Always fix the packing to the battens. Do not place batten ends in a line, they must be staggered throughout the floor area and laid end to end.
- Always leave the correct expansion allowances at walls and all fixed points. Gaps may also be necessary between boards, depending on the type of system used.
- If any floor boards/planks appear faulty, do not install them, set them aside or cut to waste.
- Make sure that the client has the floor maintenance instructions.
Common Flooring Procedures – Setting Out
Check the customers preference. The position of the doors and windows may be a consideration here, as well as the direction of existing floor boards or joists.
Solid hardwood floors mainly expand width ways. It is often advantageous to lay the boards so that the number of board widths is kept to a minimum. Expansion gaps at doorways are often necessary where hardwood is laid through rooms. It is usual to lay the boards parallel to the longest wall.
For most rooms, set out from one wall, using temporary spacers or wedges to form the expansion gap. Don’t forget that the wall may not be straight and it may be necessary to scribe the board to the line of the wall. Check that the gap can be concealed with the relevant moulding.
Lay the boards so that the tongue edge points into the room. It is important to lay the boards so that the strip pattern is as random as possible. This not only has a better appearance but also avoids weak points in the floor where gapping may occur. Boards must be laid so that the header joints and stave the next row. However, the off-cut can be trimmed if necessary to produce a ‘random stagger’, the pattern should then be maintained for the rest of the row.
Expansion Allowances: Perimeter
Clear gaps are necessary around the perimeter of the floor and at all fixed points. The size of expansion gaps may vary and will depend upon:
1. The width and length of floor
2. The type of floor
Wooden blocks, wedges or similar can be used to form the gaps between the edges and the walls. These are left in place until the floor has been completed. The expansion gaps will usually be covered and hidden from view by skirting boards, quadrant, or scotia moulding. Expansion spacers should be removed before skirting etc is installed.
Intermediate Expansion Gaps
When nailing solid floors, 2mm expansion gaps will be necessary between boards. The size and frequency of these will depend on:
1. The type and width of the board.
2. The anticipated site conditions such as heating, ventilation and humidity levels of the building when in use.
3. Knocking boards together.
Ensure that a wooden block is used when knocking boards together as this will protect the tongue from being damaged by hammer blows.
Adhesive: Any excess glue may squeeze up between the joints. Wipe off immediately with a damp cloth.
Fitting the last row of boards: Cut the last row of boards to fit, not forgetting to make the appropriate allowance for a clear expansion gap.
Radiator Pipes: Ensure the cut out for the pipe is large enough to allow for the same expansion as along the wall. The tapered wedge cut out behind the hold is glued back into place with adhesive.
Door frames: Use an off-cut of flooring and underlay as a guide when sawing the bottom of the doorframe.
Doorway: The ramp is joined by a ‘loose tongue’ joint to join the boards together and is not fixed down to the sub floor.
Thresholds: The threshold cover strip is fixed to one side only. It is good practice to substitute a more solid piece in doorways to accommodate the extra amount of traffic.
Timber Sub Floors: An intermediate layer or underlay is usually necessary. Sometimes, this may also incorporate a moisture barrier. Use only a thin underlay as grey felt paper or a proprietary type available from the board manufacturer.
Battens & Joists: These are installed to a timber sub-floor. When nailing, ensure the correct nail size and type is selected to suit the floor type.
Use spacers to form expansion allowances between the wall and the first row of boards, a clear gap is necessary.
The first and last row of boards must be ‘face nailed’ through the surface. The nail head must be punched below the surface and filled.
All other rows must be ‘secret nailed’. Using a nail gun these nails are driven at a 45 degree angle.
Make sure the gaps, which are left between the boards, are appropriate to the floor system and site conditions of the building when in use.
Installation by gluing
While nailing may be the most common method of laying wooden flooring, there will be instances where it is necessary to lay underlay directly onto an existing floor (usually concrete).
For a floating floor all boards must be glued together along the sides and at the ends. Apply adhesive uniformly to the bottom edge of the groove. Knock the boards together using a wooden block to protect the board ends. Work along the board, closing the joints as evenly as possible. Draw the board together and wipe away any excess adhesive with a damp cloth.
Blocks or wedges used to form expansion gaps are usually placed at the sides and at the end of the floor area, and should be left in place until the adhesive is dry. They are then removed prior to the edge detail (such as skirting) being fixed.
Choice of Underlay
Choose a type to suit the floor and its intended use. Underlays are generally used to provide sound reduction and shock absorption to varying degrees. Some products also include a moisture barrier. Underlay’s intended for carpets and other floors are generally not suitable for use with wooden flooring.
Unfinished floorboards must be sanded at least three times. The higher the sandpaper grit is, the rougher the sandpaper is. When sanding it is best to work down through the grades to get a smooth finish (e.g. 40-60-120). All dust, dirt, and wood particles must be removed. Some filler may be required at joints, cracks or holes; these should also be sanded.
The floor is then finished using special floor finishes. Always follow manufacturer’s instructions. The number of coats that are placed on the floor will depend on the traffic / amount of use expected e.g. a floor in a bar would require more coats of varnish than a sitting room of a home.
- Flooring must be brought into its new environment for a period of approx. 10-14 days prior to fitting and allowed to acclimatise until moisture content of 7% – 10% is achieved. Generally this applies to all species of solid wooden flooring. In the case of UFH it is recommended that the flooring is placed in the fitting environment for 3-4 weeks prior to fitting.
- On areas where concrete or cement sub-floors exist it is recommended that a layer of 10,000 gauge polythene is placed beneath flooring battens.
- Where battens are being use it is recommended that they are spaced at approx. 300mm centres. It is also suitable to nail to existing joists with 400mm centres.
- Expansion gaps of at least 18mm should be left around all sides of the floor and expansion of 2mm in every 10 boards i.e. washer space.
- The use of insulation between joists and battens is advantageous in a number of areas such as, sound absorption, and added R-value.
- All solid wood flooring should be nailed using either 38mm or 50mm flooring cleats, sanded and finished with a minimum of three coats of floor sealer.
- When measuring a floor area allow a 5% waste for grading and cutting.
Engineered/ Semi Solid Flooring
- The sub-floor or base should be dry, level and permanent, concrete floors should also be levelled.
- Boards should preferably be laid in the direction of incoming light, and wastage of approx 3% – 5% should be allowed for when measuring up.
- Flooring must be brought into its new environment for a period of approx 2 days prior to fitting and allowed to acclimatise.
- A layer of foam underlay 2mm – 3mm in depth is placed on top of the subfloor and the tongue and groove planks are glued together and placed directly on top of the foam underlay.
- It is recommended that an expansion gap of 13mm is left between walls around the perimeter of the floor.
- Installation by floating is suitable for all semi-solid / Engineered floors, and some brands of solid flooring, usually of an area no greater than 25 square meters.