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Sanding wooden floors

Often a real wood floor can be hidden under carpets, and by sanding and staining it can transform it into an attractive and expensive-looking feature which you won't want to cover up again.


Preparation

Start by clearing the room of all furniture and remove curtains etc as they will otherwise become covered in dust.

Remove all floor coverings.

Now you have the chance to look at the whole floor and decide if it is going to be worth sanding.

If there are:

  • Wide gaps between the floorboards or between the floorboards and the skirting board;
  • A lot of split boards - this often happens where fixing nails are near the edge or ends of floorboards;
  • A variety of fixings, i.e. some floorboards nailed down while others are screwed;

you may decide that the final sanded look won't be very pleasing without a lot of remedial work.

If the floor is in reasonable condition, sweep up any loose debris and go over the complete floor using a nail punch to drive the nail heads down at least 3mm (1/8th inch) below the surface. Be very particular that all nails are dealt with as any protruding nail heads may damage the sanding machine.

Check for any loose floorboards, use new nails to secure these, and drive the nail heads into the floorboard.

If necessary, cut out and replace any sections of floorboard which needs replacing - try to replace using the same type of timber as the original;any finish applied may look different when applied to different types of timber.

Check for any old carpet tacks etc on the surface - these should ideally be removed without damaging the wood around them or, if they are impossible to remove, shear off the heads with pliers and drive the shaft into the floorboard.

If there is any serious paint on the floor, remove as much as possible either using a chemical paint stripper (preferred) or heat gun (this runs the risk of allowing the paint to soak further into the timber).

If necessary the old floor finish needs to be removed before sanding as otherwise, the original finish may clog the abrasive.

Sanding in general

Belt floor sanderSmall floor areas can be sanded with just a handheld rotary sander and a handheld sanding block for finishing the corners where sander won't reach.

For larger floors, it is easier to use a belt (or drum) floor sander (shown right) for the main area of the floor while the handheld rotary sander will still be needed for the edges and other areas that the belt sander cannot cover. Again you will need a handheld sanding block for finishing the corners where neither sander will reach.

As sanding floor will produce a lot of dust, you will need goggles and a face mask to protect you from inhaling the dust. A pair of ear defenders are also a good idea.

The amount of sanding required will depend upon the state of the floorboards.

  • If they are extremely rough, warped or marked, you will need to start by sanding the floor diagonally before sanding along the lengths of the floorboards.
  • If the floorboards are fairly clean and level, only sanding along the lengths of the floorboards will be necessary.

Always finish sanding using a fine grade abrasive (120 grit size) and go from coarse to fine in 40 sizes (i.e. if the first abrasive is 40 or 60, then use 80 or 100 and finish with 120).

Before any power sanding, open the windows and seal the door; wear old clothes, a face mask, goggles, ear defenders and clean soft shoes.

Always tilt the belt sander so that the abrasive is off the floor before starting it and tilt the sander again at the end of each run and when you switch it off. Never let the sander run without it moving, this will gouge the floorboards.

Sanding diagonally

First run diagonallyFit the belt floor sander with a coarse abrasive (40 or 60 grit size) and starting in one corner of the room run the sander diagonally across the floor and tilt it just before hitting the far skirting board. Then run the sander back parallel with the first run overlapping it by a small amount. Continue with parallel, overlapping runs until as much of the floor as possible has been sanded.


Second diagonal sanding Starting in an adjacent corner to the first sanding, go over the whole floor area again such that the sander now crosses the first sanding runs at rightangles.


Sanding the areas the belt sander won't reach.

Sanding edges and cornersUse the smaller, handheld rotary sander to sand the edges of the floor where the belt sander could not touch using the same grade of abrasive as used on the belt sander. Do this after each time you have finished using the grade of abrasive on the sander, this will get all parts of the floor to the same smoothness before moving onto a finer abrasive.

The rotary sander won't get into the corners, and these areas need to be sanded using a hand held sanding block with the appropriate grade abrasive.

Sanding along the lengths of the floorboard.

If the floor has been sanded diagonally (as above) or the floorboards are in very good condition, start with a medium abrasive (80 or 100 grit size).

If the floor has not been sanded diagonally (as above) and the floorboards are marked, start with a coarse abrasive (40 or 60 grit size).

Lengthwise sandingStarting from one end of the room adjacent to the long wall, run the belt sander along the length of the room. At the end, turn the machine and run it back parallel with and slightly overlapping the first run.

NOTE: Some guidelines say "always work with the grain of the timber, not against it" which is very good advice except that individual floorboards don't necessarily have the grain running in the same direction and it is sometimes hard to work out the direction of the grain anyway!

Having done two lengths in opposite directions, compare the finish across the two runs to see if the direction of grain can be established - if one direction has given an obvious smoother finish, that was done in the direction of the grain.

Either repeat this going up and down the room (if the grain of the floorboards cannot be be established), or do the rest of the floor in overlapping strips 'with the grain'. Also sand into any recesses as necessary until the whole floor has been covered.

Sand the edges and corners again using the appropriate grade of abrasive.

Change the abrasive on the belt sander to a finer grit and repeat; if the floor was sanded 'up and down' follow the same procedure but start against the opposite wall so that each strip is sanded in the reverse direction - if the floor was sanded 'with the grain', repeat again 'with the grain'.

If appropriate, change the abrasive to a finer grit and repeat.

Final touches

Look over the floor for any blemishes, these can be 'touched up' by either using the hand held rotary sander or the handheld sanding block using fine abrasive (120 grit).

Tidying up

When all the sanding has been completed, use a soft broom to sweep up the saw dust; when there's a pile, it can be scooped up and put into bags.

Use a hose vacuum cleaner (with a soft bristle attachment) to collect the remaining dust - as you've just sanded the floor, keep the vacuum cleaner on a rug or piece of cardboard so that it does not mark the floor.

Your clothes and hair will be dusty, so the sooner you change and have a tidy up, the less saw dust you will drop on the floor.

With a soft brush, sweep the walls, wall fitting, mantelpiece, skirting boards, window and door frames etc to dislodge any saw dust which has collected there. Leave the room for an hour or two for the saw dust to settle and brush and/or vacuum the floor again.