Lay a Stone-Effect Floor With Karndean Korlok Planks in 9 Steps for 40% Faster Fitting

Korlok Select RKP planks come in 12 mm thick stone-effect formats with a pre-attached K-Core backing. Their loose-lay locking edge is the main difference from Karndean’s older fully bonded Knight Tile range, where the whole floor is glued down.

That K-Core backing gives each plank enough rigidity to ride over small subfloor imperfections. The working tolerance opens to roughly 3 mm of deviation across a 2 m straightedge, while a glued LVT calls for sub-1 mm flatness. On a typical 20 square metre kitchen-diner, that difference is where the headline 40 percent time saving comes from.

Moisture readings before layout

Start with moisture, because the click system will not rescue a wet base. A sand-cement screed needs to read at or below 75 percent relative humidity on a Tramex CMEXpert II or a comparable hygrometer probe. A calcium sulphate screed sits lower, around 0.5 percent CM by weight.

High readings are the common route to a stone-effect floor that cups or shows a grout-line shadow six months later. Even a screed passing at 74 percent relative humidity can drift if the damp-proof membrane below it has been compromised. In that situation, a click field may give no early sign, while a bonded floor would often reveal trouble through adhesive failure.

For a screed test, drill two or three insulated sleeves into the slab, cap them, and leave them sealed for 72 hours before taking the relative humidity reading. Timber needs a different check. Use a pin-type meter in the joists and the deck boards; both should land between 8 and 12 percent moisture content, with no more than 5 percentage points between joist and deck readings.

A wide gap between those timber readings points to a damp path from below. Underlay will not mask that path.

Flatness follows the moisture checks. Lay a 2 m aluminium straightedge across the room in a grid pattern and mark every hollow deeper than 3 mm. Fill those hollows with a fibre-reinforced smoothing compound such as Mapei Ultraplan or Ardex K15, feathering the edges to nothing.

High spots on a concrete screed need grinding back with a diamond cup wheel on an angle grinder, with dust extraction running. Korlok tolerates more movement than glued LVT, yet a 6 mm ridge under a click joint can pop the locking edge apart within weeks.

Acclimatisation in the room

Leave the planks flat in the room where they will be fitted for 24 to 48 hours, with the boxes opened and the temperature stable at 18 to 27 degrees Celsius. Upright storage bends the acclimatisation step out of shape. Boxes left in a cold van overnight can reintroduce dimensional variation after the subfloor has already been brought into tolerance.

Nine fitting steps

Once prep is signed off, the working order is fixed. The dry-lay in step three is the point that prevents repeated stone prints from lining up across the field.

1. Snap a chalk line down the long centre of the room, then add a perpendicular line checked square with a 3-4-5 triangle, so the field starts from the middle and cut planks land evenly at both walls.
2. Spread Karndean’s recommended pressure-sensitive adhesive in the perimeter band, typically a high-tack acrylic such as Karndean Floor Adhesive, about 200 mm wide against every wall, using a fine-notch trowel. Let the adhesive flash off to tacky.
3. Dry-lay three or four rows across the centre, mixing planks from at least three different boxes so no two identical grout patterns sit side by side.
4. Begin click-fitting the field from the centre line outward, angling the long edge in first at roughly 20 degrees and dropping the short end home until the click is felt.
5. Stagger end joints by a minimum of 150 mm between adjacent rows; a shorter offset reads as a repeating seam under raking light.
6. Tap each joint closed with a white rubber mallet and a Karndean tapping block. A steel hammer used directly on the joint crushes the locking lip.
7. Cut perimeter planks by scoring the wear layer with a hooked vinyl knife and snapping the K-Core over a straightedge. Intricate cuts around pipes go on a jigsaw with a fine downcut blade.
8. Press the perimeter planks into the tacky adhesive band and roll the whole floor with a 45 kg articulated floor roller within the adhesive’s open time, working bubbles outward.
9. Leave a consistent 5 mm expansion gap at every wall and fixed object, to be covered later by the skirting or a Karndean trim profile.

The centre-out method pushes cumulative width error to the walls, where the cut plank can absorb it. If the layout is allowed to creep from one wall across the room, the final wall can be left with a sliver-width plank.

Expansion gap

Korlok’s K-Core expands and contracts with temperature across a day. The 5 mm perimeter gap at walls, doorways, and kitchen island bases gives that movement somewhere to go.

Close the gap to nothing and the growing floor has no escape route. The usual result is a lift in the centre of the room.

Cutting the stone-effect print

Stone-effect Korlok carries a printed grout-line registration, echoing the joints that real travertine or limestone would have between tiles. Tile-format planks such as the Frosted Birch or the stone ranges need the printed bevel edges to align across each joint. A broken grout line is visible immediately, especially close to skirting.

Before cutting a perimeter piece, dry-set it over the laid plank it will meet. Transfer the grout-line position with a pencil as well as the wall distance. That extra mark controls how the printed joint lands when the cut piece is turned into place.

A hooked vinyl knife handles straight cuts through the wear layer. Once scored, the plank snaps cleanly over a metal straightedge because the K-Core fractures along the cut line. For an L-shaped cut around a door architrave, score both legs of the L, snap one leg, then finish the second with a sharp utility knife.

Curved cuts around a WC soil pipe or a radiator pipe need a jigsaw fitted with a downcut blade running at low speed. That setup keeps the visible wear layer from chipping on the face.

Doorway thresholds work best when the plank runs through under the door line where possible, with the expansion gap maintained beneath the closed door. A Karndean stair nosing or a Z-bar threshold trim covers the transition to carpet or to a different floor height. Mitre the trim ends at 45 degrees on a mitre saw so the corner reads clean.

Worked example: a 20 square metre kitchen-diner

Take a room 5 m by 4 m, using planks at 1480 mm by 235 mm. Each plank covers 0.3478 square metres. The raw count is 20 divided by 0.3478, which gives around 58 planks before waste.

Stone-effect layouts with grout-line matching usually run 10 to 12 percent waste because perimeter cuts cannot always be reused. Order 65 planks for that room. With Karndean’s typical box yield of 3.34 square metres, the order comes to seven boxes.

Adhesive use falls sharply because the glue goes into the perimeter band. A room with an 18 linear metre perimeter and a 200 mm adhesive band uses 3.6 square metres of glue area. A 5 kg tub of Karndean adhesive, covering roughly 5 square metres per kilogram on a fine notch, covers that with margin from a single tub.

A fully bonded 20 square metre LVT job needs four kilograms of adhesive minimum. The material and labour saving on the glue step alone is where the 40 percent figure earns its place.

Fitting time for a competent installer runs around 4 to 5 hours for this room with Korlok’s click field. A comparable fully glued floor takes around 7 to 8 hours because it needs full trowel coverage, roller passes across the entire area, and longer open-time management. The 48 hour acclimatisation period and the subfloor prep day sit outside that fitting-time figure and remain identical for both methods.

Cleaning and finish

Travertine needs an impregnating sealer worked in before grouting and a topical seal after. Korlok’s stone-effect wear layer is factory-sealed and needs no site sealant.

The finishing pass is a pH-neutral clean with Karndean Remove to lift adhesive haze, followed 24 hours later by Karndean Refresh if a satin sheen is wanted. Keep furniture and heavy kitchen appliances off the floor for the first 24 hours while the perimeter adhesive cures to full grab. A floor that needs no site sealant can still show adhesive haze after the roller leaves, so the last visible decision is whether the factory-sealed surface is left matte-clean or given a satin sheen.