GF Glue Down LVT installation guide

1. Tools and materials

• Tape measure, straight edge, combination square, pencil and chalk line
• Sharp utility knife with spare blades
• Moisture-testing equipment suited to your subfloor (a hygrometer for concrete and screed)
• Primer and smoothing compound suited to your subfloor
• A recommended LVT flooring adhesive and the notched trowel its manufacturer specifies
• A 68kg articulated floor roller
• Knee pads, safety glasses and a dust mask

2. Delivery, storage and acclimatisation

• Check that the design, quantity and batch number are what you ordered, and that nothing is damaged. Do not fit planks with visible faults: set them aside and contact your retailer.
• Store the boxes flat, indoors and no more than four high.
• Acclimatise the flooring, together with the adhesive and any new plywood, in the room where it will be fitted for at least 48 hours. Keep the room at a steady 20–21°C, and never outside 18–27°C.
• Take planks out of the boxes about 30 minutes before you use them, and mix planks from several boxes as you go to spread natural shade variation.
• Where there is full-height glazing, bi-fold doors or a conservatory, shade the windows during acclimatisation, fitting and for 24 hours afterwards.

3. Subfloor preparation

Fit kitchen units, islands and other fixed furniture before the floor, never on top of it.

Almost every glue-down failure starts with the subfloor. It must be clean, dry, sound, smooth and flat, and free from anything that could stop the adhesive bonding, such as oil, paint, old adhesive, sealers or marker pen.

Flatness	No more than 3mm deviation under a 2m straight edge (SR1 to BS 8204). Grind off nibs and ridges.
Moisture	Test concrete and screed with a hygrometer over 72 hours. Only fit if the reading is 75% RH or lower and the moisture content is no more than 2%. Above that, apply a surface damp-proof membrane first.
Damp-proof membrane	Concrete and screed must have an effective damp-proof membrane. If there isn’t one, or it is damaged, apply a surface damp-proof membrane before smoothing.
New concrete and screed	Allow roughly one month per 25mm of thickness for the first 50mm to dry, and longer for thicker slabs, then test before fitting.
Smoothing compound	Apply a smoothing compound at least 3mm thick, with the primer its manufacturer recommends, over all concrete, screed, asphalt, tiled, metal and ground-down painted floors.

Particular subfloors

• Power-floated concrete: shot blast to open the surface, then prime and smooth. Do not use curing agents or surface hardeners.
• Calcium sulphate (anhydrite or gypsum) screeds: remove any laitance mechanically, use the special primer these screeds need and check moisture carefully. Take advice from the adhesive manufacturer first.
• Mastic asphalt: never glue LVT directly to asphalt. Apply a smoothing compound approved for asphalt at least 3mm thick.
• Magnesite and woodblock floors: remove them and bring the base up to standard. Do not fit over them.
• Ceramic, quarry and terrazzo tiles: make sure they are firmly fixed, degrease, fill joints and cracks, key the surface and apply at least 3mm of smoothing compound.
• Painted or epoxy-coated floors: remove paint by grinding or blasting. Well-bonded epoxy can stay once ground, then smooth over it.
• Existing floor coverings: lift them and remove as much old adhesive as possible, then smooth. Never lay GF glue-down LVT over another floor covering. Take care with very old floors, which can contain asbestos.
• Expansion joints in the building: carry them through the new floor using a proprietary expansion joint cover. Never fill them with smoothing compound.

Timber subfloors

• Joists: fix tongue and groove structural plywood or OSB over the joists to create a stable base: 19mm for joist spacings of 406–486mm, 19–22mm for 487–608mm and 22–28mm for 609mm and over.
• Existing floorboards and chipboard: secure loose boards, replace damaged ones and sand off high spots. Then overlay with flooring-grade plywood at least 5.5mm thick (EN 636-3, EN 314-2 Class 3), with staggered joints. Fix with 20mm+ ring-shank nails or countersunk screws at 100mm centres around the edges (12mm in from the edge) and 150mm centres across the sheet.
• Condition new plywood in the room for at least 3 days before fixing. Do not overlay boards with a moisture content above 7%.
• Boards treated with a wood preservative can stop the adhesive bonding. Never glue directly onto them: overlay them with plywood first.
• Suspended timber floors at ground level must be well ventilated underneath, through clear air bricks.

4. Underfloor heating

GF glue-down LVT is suitable for both warm-water and electric underfloor heating. It is not suitable for heating systems installed before 1990.

• The system must be fully tested and commissioned before the floor is fitted.
• Turn the heating down to a low, steady setting at least 48 hours before fitting, keep it there during fitting and for 48 hours afterwards, then raise the temperature slowly over several days. Avoid sudden changes while the adhesive cures.
• The temperature at the adhesive line must never exceed 27°C.
• Use a specialist high-temperature or epoxy adhesive over underfloor heating.
• If the system also cools, fit condensation protection so the pipe temperature stays within 3°C of the room’s air temperature.

5. Setting out

Planks

• Plan the layout so no cut piece is shorter than 150mm, and so the last row is not a thin sliver.
• Stagger the rows at random, keeping end joints at least 300mm from the end joints in the neighbouring rows.
• Run planks along the longest wall or towards the main source of light, unless the room suggests otherwise.
• Some designs are directional and have arrows on the back. Follow the instructions in the box.

Herringbone, chevron and basketweave

• Find the centre of the room and snap a chalk centre line, with a second line at 90° to it.
• Dry lay two or three rows of the pattern along the centre line and check that every corner is exactly 90°. A small error repeats and grows across the room.
• Check the distance to the starting wall is even across the room before you spread any adhesive.

Stone-effect tiles

• Start from the centre of the room, squaring the layout off the longest wall or a main feature.
• Unbox and shuffle tiles to spread the pattern. Where the design calls for it, turn alternate tiles to avoid repeats.
• Stagger tile joints by at least 200mm where the design is laid in offset rows.

6. Adhesive

• Use a recommended LVT flooring adhesive and follow its manufacturer’s instructions exactly: trowel notch, open time and coverage.
• Spread only as much adhesive as you can cover within its open time. Replace the trowel as soon as the notches wear.
• With a pressure-sensitive adhesive, flatten the trowel ridges with a lambswool roller so they do not show through the finished floor.
• Over underfloor heating, use a specialist high-temperature or epoxy adhesive. In conservatories, rooms with large areas of glass and anywhere the temperature swings, use a high-temperature, polyurethane or epoxy adhesive.
• Wipe fresh adhesive off the surface straight away with a damp cloth. If it has dried, soften it with warm water and lift it with a soft brush. Never use solvents.

7. Laying and rolling

• Work in sections, laying each plank or tile firmly into the wet adhesive. Keep joints tight with no gaps or overlaps.
• For herringbone and chevron, lay the pattern in strips from the centre line outwards and check alignment and 90° corners every few rows.
• As each section is laid, roll it in both directions with the heavy floor roller, then roll the whole floor again when you have finished.
• Leave a 2.5mm gap around the perimeter, pillars and fixed features, increasing to 5mm in rooms over 100m² or longer than 10m.
• Cut and fit the perimeter pieces last.

8. After fitting

• Keep foot traffic off the floor for 24 hours while the adhesive sets.
• Wait 72 hours before moving heavy furniture back, rolling heavy loads over the floor or wet-mopping it.
• Fit protective felt pads to furniture and use non-rubber-backed mats at entrances from day one.
• Look after the floor as described in the GF LVT and SPC care guide.