How do I fix loose or lifting parquet blocks?
Why parquet blocks lift, how to lift and re-bed them cleanly, and the moisture problem that has to be dealt with first or the repair simply repeats.
- Difficulty
- intermediate
- Time
- 2 hr
- Read
- 3 min
- Safety
- warning
Short answer
A loose block has lost its bond to the substrate, and the cause is nearly always moisture from below or a failed old bitumen bed. Lift the loose blocks, clean both faces without creating dust, deal with the moisture, and re-bed with a flexible flooring adhesive. Never glue a block back onto a damp or dusty base.
Parquet is small blocks of solid wood bedded onto a substrate, usually with bitumen in older floors. Two things break that bond: moisture coming up through a slab and expanding the blocks, and the bitumen itself losing its grip after many decades. A lifting block is therefore a message about what is underneath it, and re-gluing without reading the message wastes the work.
Safety
The black adhesive under old parquet is usually bitumen, and bitumen-based flooring adhesives from roughly the 1950s to the 1980s can contain asbestos. Do not sand, grind, chip or dry-scrape unknown black adhesive. If the blocks are old and the bedding is black and brittle, treat it as potentially asbestos-containing and get it identified before disturbing it.
What you'll need
- a wide bolster or a stiff scraper
- a flexible flooring adhesive suitable for solid wood
- weights or a means of holding blocks down while curing
- a moisture meter or polythene for a damp test
- a vacuum
Step by step
- Map the loose area by tapping.Tap across the floor with a knuckle or a small mallet. Bonded blocks sound solid; loose ones sound hollow. The hollow area is nearly always larger than the visibly lifted one, and you need to know its extent before you start.
- Lift the loose blocks carefully and keep them in order.Ease a wide bolster under an edge and lift straight up. Number the backs with a pencil and lay them out in the pattern they came from — parquet blocks wear individually and putting them back in a different order shows.
- Look at what is on the back and on the substrate.Old black brittle bitumen, or modern adhesive? If it is old black material, stop and get it identified before doing anything abrasive to it. This is the point at which the asbestos question is answered.
- Test the substrate for damp.Tape polythene down over the exposed base for several days. If moisture appears on the underside, the slab is wet and re-bedding will fail. That has to be resolved with a surface damp proof membrane before any block goes back.
- Clean both surfaces without creating dust.Scrape the block backs and the substrate mechanically, keeping the material damp or contained. Vacuum thoroughly. Adhesive will not bond to a dusty or greasy face.
- Check the block fit before gluing.Swollen blocks may no longer fit back in. A block that has grown will have to be eased on the edges, and if a whole area has expanded, blocks have to be removed to create room — jamming them back in causes the next lift.
- Bed them in a flexible adhesive.A flooring adhesive suitable for solid wood, which stays slightly flexible rather than setting rock hard. Notch the adhesive out with the trowel the manufacturer specifies, so coverage is full — voids under a block are what makes it hollow and loose again.
- Weight them down while the adhesive cures.Boards and weights, sandbags, or anything flat and heavy. Blocks lifted at the edges will curl back up while the adhesive is still green.
- Leave the floor alone for the full cure, then clean up.Once cured, any squeeze-out is trimmed, and the repaired area is sanded and finished with the rest of the floor if a full restoration is planned.
Common mistakes
- Gluing blocks back over damp — The moisture is what pushed them off. A new adhesive on a damp slab fails the same way, usually faster.
- Using a rigid adhesive — Solid wood blocks move seasonally. A rigid bond either breaks or takes the surface of the substrate with it.
- Sanding old black adhesive to clean the base — This is the specific action that turns a possible asbestos-containing material into airborne fibres. Identify first.
- Putting blocks back in the wrong order — Decades of different wear, light and finish on each block means a reordered patch is visible even after refinishing.