How to Lay Engineered Wood Flooring: Fitting Guide

How Is Engineered Wood Flooring Laid?

There are three methods, and the subfloor decides which one you use. Over concrete the floor is normally glued down or laid floating on an underlay with a damp-proof membrane beneath it. Over joists or an existing timber floor it is secret-nailed or floated. Whichever method you use, the subfloor has to be dry, flat to within about 2 mm over 2 m, and the boards need a 10 mm expansion gap at every wall.

The rest of this page is the full specification we fit to — acclimatisation, moisture readings, expansion, underlay, and the step-by-step method. It is written for whoever is laying the floor, whether that is us or you.

Responsibility and Standards

Engineered flooring is a natural product. Allow for a grading tolerance of 5%.
Acclimatise the flooring for at least two days in the installation environment before fitting.
Keep packs sealed until immediately before fitting. If you inspect boards early, reseal the packaging straight away.
Some boards may bow slightly due to the lamination process. This corrects itself during installation.
Do not install any board with an obvious defect. Contact us before fitting — we can exchange it. Use stain putty or filler stick for minor corrections; this is standard practice.
Install to British Standard BS 8201:1987, which covers recommendations for laying hardwood flooring.
Once you install the floor, you and the owner accept the product.
Do not install engineered flooring in bathrooms. High humidity in those areas will damage it.

Expansion Gaps

Leave a minimum gap of 10mm between the boards and all walls. Allow the same gap around fixed objects such as pipes.
This gap lets the floor expand and contract with changes in humidity.
For rooms longer or wider than 6m, increase the gap by 1.5mm for each extra metre.
For rooms longer or wider than 12m, incorporate a movement joint.

Storage and Handling

Store packages in a dry place. Open them only immediately before fitting.
This protects boards from short-term humidity changes before installation.
Never store boards on their side or end.
When you remove boards from the packing, do not bend them — this can crack the varnish.

Subfloor Preparation

Level a concrete subfloor with a self-levelling compound or screed. Level a wooden subfloor with a sander.
If the subfloor is an existing wood floor, check it has adequate support before you start.
If the subfloor lacks rigidity, fit 12–18mm plywood — preferably tongue and groove — between the existing floor and the new engineered boards.

Humidity and Moisture

Keep the ambient humidity at 40–60% RH and the temperature at 18–24°C during installation and afterwards.
Measure the moisture content of the subfloor before laying the boards.
For a concrete subfloor, the relative humidity must not exceed 35–40% RH (approximately 2% moisture content). Note: BS 8201 specifies 75% RH, but at that level adhesives will not bond reliably — target 35–40%.
For a wooden subfloor, the moisture content must be 8 ± 1%.
To test concrete without specialist equipment: tape a 1m² piece of polythene to the floor for four to five days. If condensation appears under the membrane or the concrete darkens, moisture is too high.
Always use a moisture barrier on concrete. Over a recently cast slab, lay a 0.2mm plastic membrane with joints overlapping 200mm or taped.

Underlay and Underfloor Heating

Always use an underlay designed for floating engineered flooring. We recommend Timbermate Excel or Woodtex with the appropriate joint tape — both incorporate a moisture barrier.
If you bond the flooring permanently to the subfloor, use a professional installer.
For underfloor heating, use only a flooring product the manufacturer specifies as compatible.
You can add a sound insulation layer below the boards. Timbermate Excel or Woodtex work well for this purpose.

Layout and Fitting Details

Measure the room width before you start. Calculate the width of the last row. If it would be too narrow, make the first row narrower to achieve a balanced finish.
Stagger end joints between adjoining rows by at least 500mm.
Apply glue to the top edge of the female groove only — not the bottom. Check the manufacturer’s instructions, as some products vary.
Always use a professional tapping block such as a Unika Professional Push Block. Use a pull bar at walls. Never use a board as a tapping block — it damages the top lamina or lacquer.
Use professional compression straps to draw boards tightly together for the final fit.
Wipe away any glue that squeezes from joints immediately with a damp cloth.
If you fit thresholds by screwing through the boards, keep screws at least 10mm from all board edges.
Nail skirting boards to the wall only — never to the floor.
Lay the flooring last. If other trades continue after fitting, protect the boards with fibreboard or corrugated cardboard.

14–15mm Engineered Floating Floor

You can lay 14mm engineered flooring as a floating floor or bond it permanently to the subfloor. For full bonding, use a high-solids adhesive such as Rewmar MS Polymer flexible wood flooring adhesive. We recommend a professional installer for glued installations.

Suitable subfloors include concrete, plywood, existing wooden floors and vinyl floor coverings.
Clean the surface thoroughly before installation.
The subfloor must be dry and level.
Keep humidity at 40–60% RH and temperature at 18–24°C during and after installation.

Step-by-Step: Floating Floor Method

Clean the subfloor and check it is level. Use a straight length of board as a guide — allow ±2mm within 2 metres.
Level any uneven areas with self-levelling compound (concrete) or a sander (wood).
Undercut door linings so the board and underlay slide underneath.
On concrete, lay a polythene membrane first, then the underlay. We recommend Timbermate Excel or Woodtex with joint tape.
Orient boards to face the main daylight source. Lay them at right angles to any existing floorboards below.
Place the first row with the female groove toward the wall. Use 10mm spacers along the wall edge.
Fit the last board of the first row with a laying jemmy. Close the header joint, then insert spacers at the narrow end.
Apply glue along the end joints and the full length of each lengthwise joint.
Apply glue to the top edge of the female groove. Tap boards together with a hammer and professional tapping block. Use compression straps to complete the joint.
Start the next row with the offcut from the previous row. Keep end joints at least 500mm from row to row.
Fit each board from the open side: close the header joint first, then tap down the length. Use PVA glue on all joints and compression straps to finish.
For pipes: drill the hole, cut out the waste with a saw, position the board, glue the offcut back, then cover with a pipe ferrule.
Mark and cut the last row using a piece of board as a guide.
When the glue has set, remove the spacers. Fix skirting boards or scotia to the wall — do not press them tight against the floor.
Leave the glue to cure overnight before use.
Re-coat high-traffic or kitchen floors with a fresh coat of lacquer or oil before general use.

Floating, Glued or Secret-Nailed: Which to Use

The three methods are not interchangeable. This is how they compare on the things that actually decide the choice.

	Floating	Glued down	Secret-nailed
Suits	Concrete, plywood, existing timber or vinyl	Concrete and screed, plywood	Joists or a sound existing timber floor
Needs underlay	Yes — plus a membrane over concrete	No, but the base must be clean and sound	No
Underfloor heating	Works, slightly slower to heat the room	Best option — heat transfers directly	Not usually
Underfoot	Slight give and a hollower sound unless a good underlay is used	Solid and quiet, closest to a traditional floor	Solid, with the usual timber-floor sound
Can it be lifted later	Yes, board by board	No — removal destroys the boards	Partly
Cost to fit	Lowest	Higher: adhesive plus the labour to spread it	Middle

Herringbone and chevron are the exception: those are glued down, always. A floating herringbone floor moves as one loose sheet and the pattern opens up.

The Two Things That Go Wrong Most Often

Skipping the moisture reading. A concrete slab can look and feel dry and still be pushing moisture upwards for months. The polythene test described above costs nothing and takes four days; a floor that cups because nobody did it costs the whole floor. Over a recently poured slab, allow roughly one week of drying per millimetre of thickness before you even measure.

Closing the expansion gap. The 10 mm gap is not a suggestion, and it is undone more often after fitting than during it — by a skirting board nailed through into the floor, a threshold strip screwed down too close to a board edge, or a heavy unit sitting hard against the wall on top of the boards. The floor then has nowhere to go and lifts in the middle of the room.

Having the Floor Fitted

If you would rather not do it yourself, this specification is what our fitters work to. We measure on site, check what is under the existing floor and take moisture readings before anything is ordered — see wood floor installation for how we work, or look at recent jobs on the our work page, including a whole ground floor of herringbone in Norwood and wide oak through an extended house in Dulwich.

Materials for the Job

We supply the floor and everything that goes under it: underlays from £1.40 per m² excluding VAT, including acoustic underlay at £8.29 and an underlay made for underfloor heating at £4.71; flexible adhesive for bonded floors; and thresholds, edge bars and scotia from £4.05.

The floors themselves: 130 engineered wood floors, of which 82 are priced online between £25.99 and £83.99 per m² excluding VAT, median £47.99. Herringbone starts at £25.99, and there are 11 floors on clearance from £36.49. You can order three samples free, see full boards at the Forest Hill showroom, or send your measurements for a quote.