So you’re planning to paint or stain your stairs. But how do you get them ready for a new coating? To remove the old finish and make the surface nice and smooth, you will have to sand down the staircase.
First of all, if the stairs were previously carpeted, remove all tack strips, staples and nails left behind. Hammer them below the surface if they are too hard to extract. Use wood putty to fill in any cracks and nail holes, and leave to dry. Now for the sanding part. The quickest way to tackle the large stair parts such as treads and risers is to use a sanding machine.
Types of sander
Belt sander – best for large flat surfaces such as stair treads
Random orbital sander – suitable for a wide range of flat and gently curved surfaces
Sheet orbital sander – good for light-duty sanding, including into corners
Detail sander – ideal for light-duty sanding into corners and small spaces
Chunky and powerful, a belt sander is something of a blunt instrument. It is designed for heavy-duty tasks on large flat surfaces where speed, not finesse, is the main aim, so is ideal for use on staircase treads and risers. It works using a belt of sandpaper that revolves around rollers set at either end of the tool.
Random orbital sander
This is the most versatile type of sanding machine, widely used by carpenters, cabinet makers and DIY fans. If you are only going to buy one sander, this would probably be your best bet.
The tool works using a circular sanding disc which vibrates and rotates at high speed while at the same time moving in an elliptical (irregular) orbit. This ensures that no part of the disc will travel along the same path twice, almost eliminating the risk of leaving swirl marks on the wood. By attaching different discs, you can use it for both coarse and fine finishing work.
As a random orbital sander has a round base plate you won’t be able to get into the corners of the staircase. These fiddly areas are best tackled using a detail sander. Alternatively, to save extra expense, you could do the job manually with a sanding block, which is simply a rectangular bar of wood or cork wrapped in sandpaper.
Sheet orbital sander
An alternative to a random orbital sander is the sheet orbital sander, also known as a finishing or block sander. It is used with square or rectangular sheets of sandpaper attached to a vibrating pad which moves in tiny circles. Designed for rounding off sharp edges and smoothing down wooden surfaces before applying paint or varnish, this type of sander is lightweight and easy to operate.
It is ideal for fine wood sanding, removing paint and varnish, rounding off sharp edges and smoothing over hardened wood filler. The square shape of its base plate lets you get into corners, too. However, it is not as powerful as a random orbital sander and is more likely to leave marks.
Small and light, a detail sander features a small triangular base plate. This lets you reach into awkward spaces that wouldn’t be possible with a belt or random orbital sander. It is designed for small fiddly tasks needing a high degree of accuracy – perfect for sanding into the corners of treads and risers, and along the base rail, handrail and any other narrow parts of the staircase.
If you haven’t used a mechanical sander before, I strongly recommend practising beforehand on some scrap wood. It’s surprisingly easy to make swirls! Don’t start on anything important until you have got a feel for the machine. Always attach a dust bag or extractor hose, if possible, and wear a dust mask and safety goggles.
When removing the old finish from your stairs you should begin with a coarse sandpaper grain of 40 or 60 grits, then swap to increasingly finer paper of up to 120 or 180 grits until the surface is smooth enough.
For the best results, sand in the direction of the wood grain and keep the tool moving all the time. Don’t press down hard – this will produce an uneven finish. Leave the weight of the machine to provide the correct amount of pressure. Try not to tilt the tool, otherwise you could create unwanted marks.
When you have finished, switch the sander off and wait for the disc or belt to stop turning before you remove it from the work surface. Afterwards, vacuum the whole staircase and sponge down all the surfaces with warm water and mild detergent. Rinse thoroughly, and allow to dry.
Sanding the spindles
Don’t try to use a sanding machine on the spindles, or balusters. Instead, wrap strips of sandpaper around the posts and rub them back and forth to remove the old finish. Do the same with any other curved stair parts that are difficult to work on with a mechanical sander. You may have to use chemical paint stripper on intricately carved components.
If it’s essential to remove every last bit of paint or varnish from your spindles – before replacing with wood stain, for example – you might want to consider saving time and effort by simply buying new spindles in your preferred finish.