Removing old linseed-oil finishes from wooden floors

Øens HåndværkerCentralPublished August 14, 2026 · 9 min. read

This guide covers fernis, the traditional Danish floor finish made from long-boiled linseed oil and a drying agent. According to Center for Bygningsbevaring, it became widespread in Denmark from the mid-1800s. Repeated coats can leave a dark, oily-looking surface. Removal methods include sanding, washing soda and buttermilk, chemical stripping and heat. The right approach depends on the floor and whether historic material needs to be preserved.

• 175 kr/m2Including VAT and a standard finish, from 36 m2
• 24 hoursResponse with fixed price
• Workmanship guaranteeOn all work performed

What is varnish on a floor?

Traditional linseed oil varnish contains a drying agent and cures into a tough, yellowish-brown coating in and on the wood. Center for Bygningsbevaring explains in its guide on floor surface treatment that varnishing became widespread from the mid-1800s because the treatment made the boards more durable and easier to keep clean.

The difference between varnish and modern floor lacquer is crucial when the floor needs renovation. Lacquer forms a film on top of the wood and can be sanded off in one layer. Varnish has penetrated the pores and grain of the pine wood over decades, and it therefore sits deep within the wood - not just on the surface.

Varnish was the dominant floor treatment until lacquer came onto the market in the 1950s, making it possible to have light-colored floors instead of the characteristic dark ones. Therefore, you will almost exclusively find varnished floors in buildings from before 1960: townhouses and older apartments in Frederiksbjerg, Trøjborg, and Vesterbro in Aarhus, not in new constructions on Aarhus Ø, where floors are typically engineered wood flooring or lacquered oak from the factory. If you are unsure what you have, you can get an assessment of its condition along with a quote for sanding and treatment of wooden floors.

Why do varnished floors get so dark?

Varnish darkens because linseed oil oxidizes and yellows, and because each new layer applies on top of the previous one. The Center for Bygningsbevaring states directly in its guide on surface treatment of floors that the many layers of varnish eventually create a very dark floor, and both the colour and material effect change significantly.

Boiled linseed oil itself is darker and thicker than raw linseed oil. If you apply it on pine wood, which is rich in resin and yellows naturally, you will end up after 60-100 years with the characteristic dark reddish-brown tone familiar from older ground-floor apartments. Beneath the varnish, the wood is almost always several shades lighter - which is why a sanded pine floor often pleasantly surprises the owner.

How do you remove varnish from the floor?

Varnish is removed by breaking down or dissolving the hardened linseed oil film and extracting it from the top millimetres of the wood. Machine sanding down to the bare wood is the fastest method and the only one that also levels an unevenly worn floor. Washing soda and buttermilk is the gentle but slow method recommended by the Center for Bygningsbevaring for floors worth preserving.

The restriction on dichloromethane in paint removers is found in Commission Regulation (EU) No 276/2010, which amends REACH. Products with 0.1% by weight or more of dichloromethane were not allowed to be marketed for the first time to private and professional users after December 6, 2010, and sales to this group ceased entirely after December 6, 2011. If you buy a varnish remover today, it is therefore based on other solvents or alkaline systems, which in practice means a longer working time and more applications.

Can you sand off varnish yourself?

Yes, it is possible, but varnish is the most difficult surface for a private individual to sand off. The varnish is soft and heat-sensitive, and the friction heat from the belt sander melts it, clogging the sandpaper after just a few square metres. The work requires coarse grit (around 24-40) and frequent paper changes.

The other pitfall is machine operation. A belt sander that stands still for two seconds leaves a depression that will be visible forever in backlighting. On a fully varnished plank floor, the machine must also be guided diagonally across the boards in the first pass to remove the varnish from the grain, which requires experience. The difference between the three interventions on a worn floor is detailed in the guide on light sanding, full sanding, or planing, and the trade-off between DIY and professional work is discussed in the article on floor sanding: DIY or professional.

If you choose a professional, the result is covered by a workmanship guarantee, and the price is fixed before the machines enter the door.

How much does it cost to have varnish sanded off?

The standard rate for floor sanding with a standard finish is 175 kr per m2 including VAT from 36 m2. Old varnish may affect the preparation required, so we inspect its condition before confirming the quotation. Any additional work is agreed explicitly rather than described as a higher standard finish rate.

At the current standard rate of 175 kr per m2 including VAT, sanding and applying a standard finish to a 65 m2 pine floor gives an illustrative total of 11.375 kr including VAT. The condition of any old varnish must be assessed before the quotation is confirmed. Read our floor sanding price guide.

How many times can a varnished floor be sanded?

A solid wooden floor typically tolerates 4-6 full sandings in its lifetime, while engineered wood flooring can handle fewer because the wear layer above the glue joint is limited. A varnished floor is almost always solid pine or spruce, so there is usually enough material - but varnish requires a deeper initial cut than lacquer.

Check the planking in a door frame or near a hatch before starting work. If the boards are worn down so far that nail heads are protruding, they must be countersunk first, otherwise they will tear up the sandpaper. We delve deeper into this in the guide on how many times a wooden floor can be sanded and in the one about sanding plank floors.

What should the floor be treated with once the varnish is gone?

After sanding, pine needs a suitable protective finish. Standard options include lacquer, oil, or lye followed by soap or oil; lye alone is a pre-treatment. A lacquered floor may last around 10 years before resanding, depending on use, while an oiled floor typically needs re-oiling every 1 to 2 years and can often be repaired locally.

If you want to maintain the light tone that emerges once the varnish is sanded off, lye treatment is the obvious choice - lye counteracts the natural yellowing of pine and spruce. Read more in the guide on lye treatment of floors, and compare the two most common choices in the comparison of lacquering vs. oiling of wooden floors.

You must factor in drying times when planning: oil requires approx. 1 day before light use, lacquer 1-3 days depending on the number of coats. Furniture should only be brought in when the surface is fully cured. The first few months of care are described in the guide on maintenance of newly sanded wooden floors.

How dangerous is the dust from sanding?

Wood dust from sanding is considered carcinogenic in Denmark when exposed in larger quantities over a longer period. Therefore, the Danish Working Environment Authority requires effective dust extraction at source. The cited guidance gives a limit of 1 mg of inhalable wood dust per m3 of air, averaged over an 8-hour working day. See Træ.dk.

Varnish dust is also greasy and settles in textiles. Professionals sand with machines directly connected to a vacuum cleaner with a fine filter, and the room is sealed off. Rags with linseed oil residues must be placed in water or air-dried spread out, as linseed oil can spontaneously combust. Read more about how much actually gets into the air in the guide on dust from floor sanding.

Get the price for your floor

Send a couple of pictures of the floor and the square metres, and you will receive a fixed price for sanding and treatment - with a response within 24 hours. Call 20 98 88 11 or write to us here. The price is fixed before the work begins.

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Øens HåndværkerCentral

We sand and surface-treat floors, stairs, balconies, wooden terraces and worktops - based in Aarhus Ø and with tasks nationwide. You get a fixed price before work begins and a workmanship guarantee on the work performed.

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