How to sand floorboards

If you’ve pulled back your carpets to reveal wooden floorboards then no doubt you’ll want to restore them to their former glory. Beautifully varnished floorboards are a timeless classic that suit a myriad of decorating styles, from Victorian and Edwardian to mid-century modern, Scandi and the 21st century.

Sanding and sealing them is a straightforward job, but like most DIY tasks, the quality of finish is all about the prep.

How to prepare your floor for sanding

Before you start sanding, ensure the boards are in good condition, with no wide gaps which could result in draughts or protruding nails which could tear your abrasive sheets.

Step 1

Begin by driving in any nails below the surface of the boards with a hammer and punch. Any nails which stick up will tear your sanding sheet. Nail down any loose boards and replace any damaged ones, ideally using boards of a similar age if you can. Consider swapping the damaged boards with ones from other rooms in your home where the floorboards aren't exposed.

Step 2

Fill any gaps between the boards. If they're very wide, consider lifting and re-laying the floorboards more tightly, filling the final remaining gap with an extra board. Otherwise, if the gaps aren’t too wide, you can simply glue in narrow strips of wood between each gap.

Step 3

Leave the filler strips slightly raised and allow the glue to dry thoroughly. Then plane or sand the filler strips down until they're level with the adjacent boards. Finish by sweeping your floor clean.

How to sand floorboards

You'll need to hire a heavy-duty industrial sander and an edge sander to sand your floorboards efficiently. Most hire companies offer drum or belt sanders for sanding large areas of domestic floor, although some companies offer disc sanders which are more suitable for medium-sized areas. An edge sander is a powerful handheld tool for getting into corners and up close to skirting boards.

Make sure someone at the hire shop shows you how to change the abrasive sheets and fit them tightly. Sanding creates a lot of dust, so seal doors to other parts of your home with masking tape and plastic dust sheets to contain the mess. Wear a dust mask and close-fitting eye protection when sanding and cover up in an overall. Keep the flexes of sanders out of the way by draping them over your shoulder, and plug them into a residual current device (RCD) to protect you from shocks if the flexes become damaged.

Step 1

Start at one end of the room, leaving about two-thirds of the floor exposed in front. Start the sander with the drum off the floor, then walk forward and gently ease the drum to the floor. Always sand in the direction of the grain. As you reach the end of the strip, carefully begin to raise the drum off the floor.

Step 2

With hand-held edge sanders, load the sandpaper so it's tight, start with the sander off the floor and lower it gently.

Step 3

Again, sanding with the grain, move the machine back and forth in a narrow zigzag pattern. Once you have done this for a foot or two, do one long swipe along the edge next to the wall to ensure that area is completely clean, then move on.

SAFETY TIP: Always unplug the sander when you need to change the sandpaper!

How to seal floorboards

Once your floorboards are stripped bare it’s time to seal and protect them to keep them looking their best for longer.

Step 1

Sweep and thoroughly vacuum the sanded floor. Then, go over it with a lint-free cloth dampened with white spirit. Allow to dry. You can use a clear or tinted varnish to seal and protect the boards. If your boards are in good condition with an even colour then a clear varnish is ideal. If your boards are irregular colours or you want to alter the colour to suit your décor, then a tinted varnish or floor paint is the best option. Choose between a matt or gloss finish depending on the look you desire. Apply the varnish using a brush or floor pad, to get a really durable, even finish.

Step 2

Thin the varnish for the first coat by adding 10% of white spirit to make it easier to work with. The first coat will seal the wood. Then, starting in the corner of the room furthest from the door, brush the varnish in the direction of the wood grain, checking that no pools form. For consistency, as you get to the other side of the room, turn the brush or pad around and apply the varnish from the other end.

Step 3

When the first coat has dried, remove any lumps or specks with fine abrasive paper and wipe clean with a lint-free cloth dampened with white spirit. Apply two more unthinned coats, leaving around two hours drying time between coats.

How to avoid common mistakes when sanding and varnishing floorboards

• Always fill gaps between boards and hammer flush any protruding nails to prevent draughts and torn abrasive sheets
• Start the sander with the drum off the floor and lower it slowly to prevent the abrasive sheet catching and tearing or sanding one are too roughly
• Always sand with the grain of the wood to ensure a smooth, even result with out unsightly streaks or gouges
• Thoroughly vacuum any dust from the surface of the floor before varnishing to ensure a smooth, lump-free finish
• Start varnishing in the corner of the room that’s furthest from the door and work backwards towards the door so you can get out of the room without treading on the wet varnish
• Always apply a thinned first coat of varnish to seal the wood before applying subsequent layers of un-thinned varnish

Top photo by DIY Photolibrary/Construction Photography/Avalon/Getty Images