Here, grinding is understood to mean that the floor surface is sanded to clean wood, and thus free from old surface treatments.
After finishing, the floor must appear flat, even and uniform, without jumping, sanding or striping.
The abrasive result always depends on the condition of the wood floor. If the floor has large joints between the boards, cracks and crevices, deep holes, seam holes or other deep damage, they cannot be removed with abrasion. But with a reasonable normal abrasion that does not reduce the floor thickness abnormally, even an old floor will appear renewed, but with its original patina and structure.
Sanding of new floors in connection with laying is described in TRÆ 64 Wood Floors - Laying.
Drained floors should be vacuumed carefully and surface treated immediately after abrasion for best results.
Surface treatment with lacquer, lye, soap and oil is described in TRÆfakta guidelines 07, 08 and 09, as well as in supplier instructions.
If the surface treatment is to be carried out later, the floor must be completely uncovered, see further in TRÆ 63 Wood floors - Selection and maintenance.
The floor for the floor must be stable and without failure, because local deflections on the floor will cause uneven and therefore unsatisfactory grinding results. It is therefore important to:
- Stroke floors must be stable
- The floor of a swimming floor must not have any significant whims
- Beam layers must not be resilient.
The attachment of the floor in the form of nails, screws or glue must be in order.
Floors suitable for abrasion
Most wood floors can be abraded. How many times it is possible depends on the thickness of the floor wear layer or the wood floor thickness.
Floors that have previously been sanded or which have a special structure or surface treatment can limit the possibilities. Therefore, all wood floors should be inspected before being abraded.
Grinding should only be done on wood with 6-10% wood moisture and in rooms with a humidity of 30-60%. The shrinkage or expansions in the floor and joints that may occur when the moisture is outside the stated intervals may cause damage to the subsequent surface treatment and possibly. fugespartling.
Floors unsuitable for abrasion
- Floors with a residual wear layer less than 2 mm
- Laminate floors and veneer floors.
Floors that are lacquered with a so-called anti-scratch surface can be difficult to abrade. It is a factory treatment, so seek advice from the floor supplier.
Checking the floor before grinding
If there is uncertainty as to whether a floor is suitable for abrasion, information on invoice, in laying instructions, brochures or similar can help. When the product name is known, the floor supplier will be able to state whether the floor is suitable and how thick the wear layer was originally.
The thickness of the wear layer should always be checked prior to abrasion, especially when the floor has previously been ground:
- On solid floors, the distance from surface to fer / notch assembly is important. It is measured with a thin metal sheet
- On lamella floors, a drill sample with at least ø12 mm drill can be made, or measured in a joint where the wear layer is visible
- Slat floors should also be checked for loose wear.
Repair and repair
To achieve a satisfactory grinding result, the floor must be reviewed and defects must be remedied:
- Visible stitch heads in floor slabs must be dipped before abrasion so as not to destroy abrasive paper or cause sparking in the abrasive dust
- If parts of the wear layer have come loose, it must be glued before grinding
- Larger injuries and cams should be released or spared before grinding
- The floor must be cleaned of any residues of oil, grease, mortar, filler, silicone, etc.
- Sand strips and edge strips at doors must be removed.
Failure to grind lamella floors
When grinding lamella floors, there will always be a risk that parts of the wear layer will come loose, because the wear layer is glued to the underlying part of the floorboard. Is there any suspicion of possible glue slip, eg. because the floor has been water damaged, the floor should not be abraded.
Sanding older wood floors is usually done in 3 steps:
Aim to remove all previous surface treatments and marks on the surface and smooth the floor. The condition of the floor determines the roughness of the abrasive paper to be used. Usually paper with grain 36 or coarser is used for very uneven floors and floors with many lacquer layers. The grinding is done with a high roller pressure on the grinding machine. For smooth floors, coarse sanding can be carried out with grain size corresponding to intermediate grinding, grain 60 or 80.
Intermediate grinding is intended to remove grinding tracks after rough grinding. The grinding is done in two steps, the first step with grinding paper grain 80 or coarser, and ending with abrasive paper grain 100 on coniferous wood (pine, douglas, spruce, etc.) and with grain 120 on hardwood (oak, ash and all tropical tree species). The grinding is done with a low roller pressure on the grinding machine.
Edges are usually sanded with slightly coarser grain size than the rest of the floor to achieve as smooth a grinding result as possible, and with the same structure along the edges as the rest of the floor.
The final finishing of the surface is partly intended to smooth out the areas with different abrasive structure which result from grinding with edge grinder and belt grinder, and partly to obtain a smooth surface for the subsequent surface treatment. After grinding, the floor surface must be free of structural differences between edges and the floor surface in general.
The fine grinding is carried out with a grinding machine provided with the grinding wheel, which corresponds to grain 100 on softwood and grain 120 on hardwood. Alternatively, the belt grinder can be used for fine grinding when working with the lowest possible roller pressure.
Floor slabs roughly sanded diagonally, see figure 1, Plane grinding of floor slabs. Intermediate grinding and fine grinding are carried out in the longitudinal direction of the boards, see figure 1, Fine grinding of floorboards.
Floors with pane pattern, herringbone pattern and similar patterns, where the tree is in different directions, are first sanded diagonally, see figure 1, planar grinding of the pattern parquet, and finally in the longitudinal direction of the room, alternatively in the same direction as the incident daylight, see figure 1, Finishing the pattern parquet.
In small rooms, the abrasion can be carried out with belt sander in the longitudinal direction of the wood. Where this is not possible, the grinding can be carried out with a round grinder. In very small spaces, the grinding can exceptionally be carried out across the longitudinal direction of the wood, but the result is usually inferior.
Corner, stairs, etc.
Hard-to-reach floor areas, e.g. corners and connection to pipes, columns, etc. normally sanded with edge or bib. For small, difficult-to-reach corners, scrapers can be used. Stairs are usually sanded with edge or eccentric grinder.
Abrasive dust affects the mucous membranes and lungs, and can be carcinogenic to prolonged exposure. Therefore, the following protective measures should always be followed:
- Use respiratory filter for abrasive dust
- Use sanding machines with a vacuum cleaner equipped with HEPA filter
- Wear hearing protection. Abrasive dust in all forms is flammable and can ignite. Therefore, the following safety precautions should always be followed:
- Vacuum cleaners must always be emptied of sanding dust after sanding
- Abrasive dust is burned or stored fireproof outdoors
- Connect machines to power supply with fault circuit breaker.