Refurbishment and Laying of Original Parquet Blocks

Solid oak, beech or ash blocks can last for decades, and you can sand them several times. If they are firm and the tongues and grooves are intact, relaying them is a sensible choice. You keep the original look, the patina and a pattern that suits the original doors and frames, and you avoid unnecessary waste.

Refurbishment is especially worthwhile when:

• The blocks are solid wood and most of them have undamaged joints
• The floor has historic or aesthetic value
• You want the room to match the other rooms
• The subfloor needs repair, but the wood is in good condition

If the blocks are rotten, attacked by woodworm or have been wet for a long time, or if earlier sanding has left them too thin, it is usually better to replace at least part of the floor.

Preparation decides most of the quality. The gluing itself is only the second half of the job.

1. Careful lifting: the blocks come up by hand with gentle tools, so the tongues and grooves stay intact.
2. Cleaning the underside: old adhesive, bitumen or filler is removed from the underside and edges, so the new adhesive grips well and each block sits flat.
3. Sorting: each piece is checked for size, thickness and damage. Cracked or incomplete blocks are set aside or used along the walls, where the skirting will cover them.
4. Acclimatisation: the blocks should rest for several days, usually at least 48 hours, in the room where they will be laid, at normal room temperature and humidity.
5. Layout plan and dry lay: the floor fitter marks the axis of the pattern, decides how the rooms join and chooses the starting point. Some blocks are laid dry to confirm that they fit together.
6. Gluing: adhesive is spread on the subfloor with a notched trowel, and the blocks are laid to the pattern, pressed down and tapped home with a rubber mallet. The fitter keeps checking that the floor stays flat and the pattern stays straight.
7. Curing: the floor is left undisturbed until the adhesive has set. This usually takes roughly 12 to 24 hours, longer with some adhesives. The manufacturer states the exact time.

After curing comes sanding, filling and finishing. The same fitter often does these, but they are usually listed as separate jobs in the price list.

Why won't any wood glue do? Solid blocks move as humidity changes, and the adhesive has to cope with that movement. Today solid parquet is usually laid with water-free silane-based adhesives (MS or SMP polymers) or with polyurethane adhesives. Dispersion adhesives contain water, which can make the wood swell. Use them only where the manufacturer explicitly approves them for that block size and wood species.

The subfloor must be firm, flat, clean and dry:

• Concrete or cement screed is cleaned of dust before gluing, and its moisture content is measured. Whether it needs a primer depends on the adhesive system.
• Anhydrite (calcium sulphate) screed is usually sanded and vacuumed first. It is sensitive to moisture.
• OSB and gypsum fibreboard must be fixed firmly, with no bounce and with level joints.

If the existing base is badly uneven, it gets a levelling compound or a dry floor system made of gypsum fibreboards. In a block of flats, ask the building management or owners' association before you change the floor build-up, mainly because of impact noise for the neighbours. If the work goes further, for example into the floor or ceiling structure, check with your local building authority what the building regulations require.

The effort involved varies far more than with new parquet. The work goes faster when:

• The blocks were laid only on adhesive that separates easily
• Most pieces are whole and the same size
• The pattern is simple, such as straight rows
• The room is square with few cut-outs

It takes longer when there is a thick layer of bitumen on the underside, or when missing pieces have to be found in the same wood and profile. Herringbone, diagonal and bordered patterns also take longer. Awkward rooms with alcoves and door frames mean a lot of precise cutting.

With old floors, be careful with the adhesive. Old bitumen and tar adhesives can contain harmful substances, and in rare cases old floor layers also contain asbestos. If you have any doubt, have a sample tested. Only a licensed contractor may remove asbestos.

• Rough lifting. Prising blocks up with a chisel often snaps the tongue, and a good block becomes waste.
• Poorly cleaned undersides. Leftover bitumen creates bumps, so the block flexes or comes loose over time.
• Skipping acclimatisation. Blocks stored in a cellar or garage dry out after gluing, and gaps open up.
• Wrong adhesive or too little of it. Hollow spots form that knock or creak underfoot.
• No expansion gap at the walls. The wood has nowhere to expand, and the floor can lift.
• Shifted pattern axis. In herringbone, a small error at the start grows, and by the middle of the room it cannot be fixed without taking up a row.

Before sanding, or when you accept the work, walk across the floor slowly and look carefully. Check that:

• The blocks do not knock, flex or creak when you shift your weight
• The pattern runs straight and lines up with the door or main wall
• The transitions between rooms are smooth, with no steps in height
• An expansion gap is left at the walls, ready to be covered by the skirting
• No adhesive is squeezing out of the joints and the surface is free of smears
• Replacement blocks match the originals in size and profile
• The fitter has told you which adhesive was used and when sanding can start