How Do I Prepare Old Wooden Floorboards For Varnish Or Oil?

If your house was built before 1980/90 you will already have floorboards in your house, the floorboards can be prepped and varnished with some DIY tips.

Varnishing Floorboards Guide
Varnishing Floorboards Guide

Like all DIY improvement around the house, preparation is always key to success. The more prep work you do before varnishing the better your boards will look.

Preparing Your Floorboards

Make sure your room has been removed of all furniture and give it a good sweep.

Depending on the condition of your floorboards you might need to repair or replace any boards that are warped, rotten or split.

If you purchase some reclaimed floorboards then they will fit in better because the size and condition will vary.

If you are going to buy new timber floorboards from the DIY shop then these boards will be a few millimetres thicker/wider than the original floorboards.

Repairing Your Floorboards

Also, new floorboards will not look the same once varnished! So, it is best to use reclaimed floorboards so they match exactly.

Repairing Your Floorboards
Repairing Your Floorboards

Once you have repaired your floorboards you must now make sure they are fixed to the joists correctly.

Nails are best for this because you can use a hole punch to make sure they are below the level of sanding.

  1. Remove any boards that are split, rotten or warped
  2. Use reclaimed floorboards so they match
  3. Nail any loose boards to the joists below
  4. Be sure to use a hole punch so your nails are about 1/3 in
  5. Prominent nails will rip the belt on your sander

Belt Sanding Your Floorboards

Once you have check all nail heads are below the level of sanding you can start using the belt sander on your wooden floors.

Going with the grain or direction of the floorboards will create a better surface for varnishing.

You should start with a rough grade, then gradually reduce this until you get to a fine grade for extra smoothness.

  • Make sure nail heads are below the sanding line
  • Use a hole punch to push them about 2/3 through the floorboards
  • Be sure you are nailing them to the joists underneath
  • Joists will run parallel with the floorboards
  • Start sanding with a rough belt sand
  • Then you must finish with a low-grade belt
  • Go with the direction of the boards/grain
  • Keep moving in the direction of the boards
  • Do not keep the belt sander in one position
  • Use a smaller handheld sander for the edges
  • In general, you will want to take about 2/3 mm off

Varnishing Your Floorboards

Once your floorboards have been prepared for varnishing you must clean any debris, hoovering the area and edges so nothing dries into the varnish.

Use a cloth with white spirit to clean any oils or grease in the wood.

Before varnishing be sure you are wearing glasses, gloves and a mask, also open a window because floor varnish can be harmful.

  • Hoover the whole area
  • Clean the boards with white spirit
  • Wear gloves, mask and goggles

So once you come to varnishing you will want to start in the corner the furthest away from the floor, so when you finish varnishing your floorboards you are leaving the room through that door until the varnish dries.

Use a soft brush do not use a nylon brush because it will leave brush marks. Make sure your brush is natural because you have thinner bristles.

Using your brush each floorboard evenly so you get good distribution, always paint with the natural grain of the wood.

So painting length ways slowly making your way across the room to the door, never walk over your varnished floor because you will leave footprints.

Once your floor is dry, you can add another coat to make the varnish darker, or leave it lighter. This is up to the one undertaking this DIY task.


Revealing the old floorboards can be a hit or a miss, some floors are prestine but others not so much.

It depends on the work carried out on the house over the years. Some homeowners have replaced theirs with chipboard because they have loose over time.

If your boards are in good condition then there is no reason why you can not enjoy a wooden/varnished floor for many years to come.

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