Varnishing a wooden floor

(Although this article refers to varnishing a wooden floor, the same basic principles apply where the floor is to be painted)

It is possible to re-varnish a previously varnished floor which is in good condition (see here), however if the previous varnish has started to wear in some areas, is cracking or flaking the only real option is to remove the original varnish and start again.

Any other previous finish (varnish, wax, oil, polish) needs to be completely removed before varnishing so that the timber is free of dirt, wax, polish and grease etc. Once the old finish has been removed, the floorboards will need to be sanded and, if required, stained.

Modern varnishes vary quite a lot between, and within, different brands; always use varnish specified for floor, it will have been formulated specifically with the wear and tear associated with a floor finish. See this page for the various types of varnish available.

Basic tips:

  • Only varnish on a dry, clear floor, ensure that any staining is completely dry and brush/vacuum the floor to remove all trace of dust.
  • Never try to paint a floor around furniture in the room, always remove everything so that you have a clear areas to work in.
  • Always follow the manufacturer's instructions regarding application and safety - with the various modern varnishes available, this article can only give a general overview, the manufacturers instruction must be paramount.
  • Always allow plenty of ventilation to prevent build up of fumes.
  • Remember that although you will need to ventilate the room, you don't want dust all over your varnish - so pick a time when there is little or no wind.
  • Always start at the far side from the door and work back to the door - then you can exit the room without walking on your work.
  • Always make sure that the floor is clean and dry before starting to varnish.
  • Always wear soft clean shoes, you don't want to mark the timber before you varnish it.
  • Concentrate on varnishing one or two floorboards at a time working along their length, avoid overlapping onto adjacent floorboard. If you have to stop and leave the job for any reason, finish to the end of a floorboard.
  • Remember that varnishing a floor is not the same as varnishing a piece of classic furniture; most people are at about 2 metres away from the floor and so a bit of unevenness or dust in it will not be seen.
  • Remember that varnish usually needs to be applied in temperatures at least 20°C (70°F), so with the window open for ventilation, pick a warm spell.
  • Remember that varnish tends to dry slow in high humidity, so allow less or more time between coats depending on the conditions.

First coat of varnish

The first coat of varnish needs to be thinned using the appropriate thinner (typically by 25 to 50%, but check the manufacturer's instructions) - this coat will act as a sealer on the timber, providing a bond between the timber and the subsequent coats of varnish. Typically 'thinned' varnish is 'almost like water', so it is easy to work with but also easy to splash about.

Use a 10cm (4 inch) brush and apply the thinned varnish along the length of the floorboards, there should be no need to spread the varnish across the grain. Complete the length of a couple of floorboards before moving onto the next ones. Try to avoid spreading onto the edge of the adjacent floorboard as any overlapping may be visible in the final job.

Allow to dry in accordance with the manufacturer's 'overcoating' guidelines.

Remaining coats of varnish

Check with the manufacturers instructions but typically at least three further coatings of un-thinned varnish should be applied.

For these coats, use a 10cm (4 inch) brush and apply the varnish first across the grain and then brush the varnish along the grain; once the varnish has started to set, don't go back over it with the brush as it will retain the brush marks.

Complete the length of a couple of floorboards before moving onto the next ones. Again try to avoid spreading onto the edge of the adjacent floorboard as any overlapping may be visible in the final job. To reduce the risk of a visible overlap, vary the floorboards being varnished with each coat, i.e. on the thinned coat start with floorboards 1 and 2, then do 3 and 4 and so on; for the next coat start by doing floorboards 1, 2 and 3, then do 4 and 5; and then with the next coat revert to starting with floorboards 1 and 2, then do 3 and 4; and the next coat do 1, 2 and 3, then do 4 and 5 - this might sound complicated but will reduce the risk of edge marks appearing.

Allow adequate time between coats, even after the recommended drying time, take care when walking on it - use soft clean shoes and use a kneeler to spread your weight when applying the next coat.

Before applying the final coat, use a DRY fine (at least 120) wet-and-dry abrasive to lightly rub down the surface and then clean the dust.

Waiting for the varnish to cure

Don't be in a hurry to start using the floor, the varnish manufacturer may give a recommended time for leaving it before moving in the furniture (it could be 72 hours (3 days) plus). This is quite different from the 'dry for overcoat' time as this only means that the coat is cured enough to take the next coat but it will still be soft and easily marked by furniture and stick to rugs etc. The longer you can leave the floor before moving furniture in, the better.

Re-varnish

Where a varnished floor is in reasonable condition, it can be freshened up without fully stripping the original finish. The final appearance may not be as good as if the whole floor were stripped, sanded and completely re-varnished, any damage to the original surface may remain visible.

The hints above also apply here.

Preparation

Wash the floor using a mild detergent in warm water to remove any grease etc.

When the floor has dried, go over the whole floor with a fine (at least 120) abrasive paper to provide a key for the new varnish and remove any stubborn marks.

Identify any areas where the varnish has broken down so that the timber underneath is exposed. Rub down these areas to remove any loose or lifting varnish. On these areas apply a coat of thinned varnish as described above - brush the thinned varnish over the area and onto about 25mm (1 inch) of the surrounding sound original varnish.

Once this has dried, apply at least 2 coats of UN-thinned varnish as described above over the whole floor area.

The note above concerning leaving the varnish to cure also applies.