How to install solid oak floorboards

A helpful guide

We recommend that the installation of solid oak flooring is carried out by a professionally trained wood floor fitter, or a competent person with suitable experience. Each professional or experienced fitter will have their own installation techniques, and each property and installation will require a different approach to the next.

Depending on the local environment and the property, each floor will enjoy its own characteristics once fitted. Whilst we can’t cover every aspect, here are some useful general guidelines:

Suitability of solid oak floorboards

Suitable for:

  • Most domestic applications such as living rooms, dining rooms, hallways, bedrooms, landings, conservatories, children’s play areas and home offices.
  • Most commercial applications such as offices, reception areas, meeting rooms and board rooms.

Unsuitable for:

  • Rooms that have excessive fluctuations in moisture, humidity or temperature such as bathrooms, utility rooms, cellars, basements, wet rooms or saunas.
  • Underfloor heating (please see our underfloor heating guidelines)

Site Conditions

The building must be weather-tight, the heating system working, and all ‘wet’ trades (plastering, painting etc.) must be completed and fully dry. All guttering and rainwater goods must be properly fitted and fully functional. All windows and doors must be glazed, sealed and fully functional.

At the time of delivery, installation, and thereafter, room temperature would ideally be between 18oC to 20oC, and relative humidity between 45% to 55%.

The delivery of your floorboards to site should ideally be within a week of the floor being installed.

Storage on site of pre-packed standard profile flooring

Once you have received delivery of pre-packed solid oak floorboards, the packs should be taken indoors immediately and stacked in the room where they are to be installed to acclimatise. Packs should be stacked flat horizontally (not on edge) in the centre of the room. The boards should not be removed from their packs, however the ends of the packs can be opened to assist air flow.  To assist air flow further, spacers can be placed between the packs. Use wooden spacers which are long enough to span the full width of a pack. Use at least three spacers per running metre so that the weight is evenly distributed. Ensure the spacers are identical thickness, and that packs are not in direct contact with the sub-floor. Leave to acclimatise in the room for at least 3-4 days prior to installation.

Sub-floors (i.e. the existing floor over which the flooring is being fitted)

Sub floors must be flat, dry and clean.  If you have an uneven subfloor, your wooden flooring will not sit on top correctly.  You will need to check that the entire subfloor is flat.  Any unevenness of more than 3mm needs to be addressed.  On a concrete subfloor, ridges and dips can be smoothed out using a self-levelling compound.  On a wooden subfloor, you can line the surface with 18mm plywood board or thicker.

Wooden sub-floors such as timber joists, battens, ply or floorboards should have a moisture content of no more than 14%. This can be measured with a moisture meter.

Concrete sub-floors should have a moisture content no higher than 3%. This can be measured with a hygrometer.

Expansion provision

Hardwood flooring is kiln dried to a moisture content of 9% to 11% prior to despatch. As local conditions vary in each property, the moisture content of wooden flooring will fluctuate depending on the heat and humidity. Floorboards, therefore, contract and expand during their life (however we are generally unaware of this happening).

It is essential that an expansion gap of at least 15mm is left around the perimeter of the room, and around any obstructions such as columns, radiator pipes, door casings, hearths etc. and in doorways between rooms. In rooms larger than 10m x 8m, and in rooms which are subject to regular fluctuations, it may be necessary to provide larger expansion gaps. Your fitter will be able to advise further. Expansion gaps can be covered with a variety of solid skirting or trims. It is essential that the natural movement of the boards isn’t impeded.

Installation of pre-packed flooring

Take the boards out of the packs immediately before installation; draw from at least 3 packs to ensure a good colour/grade mix which is to your liking and repeat this process as the floor is laid. Decide on which direction to run the planks (usually with the light-fall from windows or along the length of the longest wall.) Use wedges to maintain expansion gaps during installation and remove them after completing the floor installation. Try to stagger joints in adjoining rows. The first and last rows may require cutting down.

Fitting methods

Solid oak flooring should be mechanically fixed to the sub-floor with nails or glue. It should not be floated.

Secret Nailing

It is good practice to apply a polythene damp proof membrane (DPM) over concrete sub-floors which are to have battens or joists fitted for secret nailing. Any joints in polythene DPM must be overlapped by 200 mm and be taped with polythene adhesive tape. The DPM should be taken up the walls by 25mm or more (this will be hidden behind skirting). Insulation can be placed between joists or battens. For old concrete sub-floors, we recommend that a liquid DPM is applied prior to the polythene DPM.

For existing wooden sub-floors make sure that any existing nail or screw heads are flush with the surface of the joists or battens. For uneven wooden sub-floors fit 18mm plywood or thicker over the joists or battens to provide a level surface.

Voids below wooden sub-floors must be adequately ventilated and a DPM should be fitted to prevent moisture intake by joists, battens, ply or floorboards.

Secret nail to wooden sub-floors (joists, battens, ply or floorboards) at an angle of 45o through the shoulder of the tongue using lost-head nails. Be sure to punch the nail head below the surface of the tongue. Nail length should be twice the thickness of the floorboard or a little longer. Professional fitters will use specialist nailing devices. The first and last rows should also be face nailed near to the edges (face nails will be covered by skirting boards). Joists or battens should be fixed at no more than 400mm centres. If nailing to existing floorboards, fit the new boards at 90′ or 45 to them, nailing every 300mm. If nailing to ply, nail every 200mm.

Stick Down

It is good practice to apply a liquid damp proof membrane (DPM) over concrete sub-floors which are to have floorboards stuck down to them.

Use a permanently elastic Polymer glue system. The glue should be spread out using a notched trowel to the glue manufacturer’s specification. Only spread as much glue as you can cover within the curing time of the glue, and always follow the glue manufacturer’s instructions.

A few more thoughts

Oak flooring is a natural product. Each board is unique, and, depending on grade, may have knots, sapwood and colour variation which are not preferred by customers. Unwanted natural defects can be cut out during installation and the resultant cut boards can be used at the end of rows.

We would recommend that an additional 10% of the floor area is purchased to allow for boards which are rejected due to their appearance, and wastage resulting from the removal of unwanted natural defects.

The dimensions of solid oak planks can vary slightly – this is a typical characteristic and is part of the unique character of your floor!