Introduction: Underlight a Wooden Step the Easy Way

About: I'm a chartered mechanical engineer and life-long maker. I especially like making useful things from cheap materials, including waste, and fixing things that would otherwise be scrap. I'll have a go at anythin…

Light washing down the riser of a feature step not only adds the wow factor, but also draws attention to the change in level and makes it less likely anyone will trip over it. If you use 5V LED strip instead of the more usual 12V type, then it can be powered discreetly from a nearby USB socket. No need to call an electrician or tie up a power socket, and no power supply to hide away. I did this project for a total cost of about £17, and that included buying a good quality USB socket plate. It will cost a little more if you need to fit a whole new socket outlet because there isn’t already one close to the step.


A 5V LED strip fitted with a USB plug

A combined power and USB charger socket

A router and suitable bit, vibrating multi-tool or chisel

A drill and 10mm bit

A small mirror

White spirit / mineral spirits and a rag

A hot melt glue gun and glue sticks

Sticky tape

A few clothes pegs

Small scissors

Several small cable clips

Optional - a tiny neodymium magnet and superglue

Step 1: Choosing an LED Strip

Go online and search for 5V USB LED strip/tape. You’ll be offered various lengths from a metre or less up to perhaps 5m. These strips with a cable and USB plug on one end are mainly sold for sticking around TVs and computer screens to bling them up a bit and are very inexpensive.

The LED strip needs to be at least as long as the width of the step it is going to illuminate. Pay attention to the distance between cutting points when you are looking at the options – you can only shorten the strip at these points. Ideally you want to be able to cut it to the exact length required, certainly no more than an inch or so short, or there’ll be a gap in the light at one or both sides of the step. The cutting distance is sometimes expressed as every so many LEDs, you’ll need to check how many LEDs per metre/foot there are. For example, the strip I bought could be cut every 3 LEDs and there were a total of 120 LEDs in the 2m length, so it could be cut every 100x2x3/120 = 5cm.

I recommend going for the silicone-encased, waterproof strip rather than bare strip. The silicone keeps the dust and insects out and should make it last longer. It costs little extra and adds almost nothing to the overall dimensions.

Various types of surface-mounted LEDs (SMDs) are available. In decreasing order of brightness three commonly found chips are 2835, 5050 and 3528 with the numbers indicating the dimensions – 2835 modules measure 2.8mm x 3.5mm, for example.

Each 5050 chip is 3 times as bright as a 3528 chip. The newer 2835 chips are brighter still. I was worried that they may be too bright for this application, especially when I checked the specification of the 2m strip I was considering and found that its light output was 960 lumens, more than a standard 60W light bulb. But I bought that strip with 2835s and I haven’t regretted it. Go for as bright as you can unless you have a very wide step and you’re concerned to keep the power consumption low because you want to have the light on all the time.

You should consider the power consumption because it will affect the current drawn and therefore the output required from the USB socket that is going to drive the strip. The 5V strip I bought was rated at 0.12W per LED and 60 LEDs per metre, and I knew I was going to have to shorten it to about 1.85m or 111 LEDs pulling 13.3W. That meant it could happily draw a current of 2.66A (Volts x Amps = Watts, 5V x 2.66A = 13.3W). Most double USB charger sockets in the UK seem to come with a 1.2A socket and a 2.4A socket, so I knew that even if I used the higher amperage socket I wouldn’t risk frying my LEDs. Unless you can find a higher current USB charger socket, this imposes a practical upper limit of 12W–rated strip (5V x 2.4A = 12W) if you want it to produce its full rated light output. Which is another reason to choose the brightest SMDs you can find.

Look at the width of the strip too - try to find one that’s as narrow as possible so that the light output will be close to the riser. The practical minimum is about 8mm wide. The depth is also important because a deep slot could weaken the step, but fortunately most LED tape is only about 2mm thick.

Light colour is another factor. White LED strip is usually the cheapest, but there are other single colour LED strips available too. White strip can be bought in cool white or warm white shades - I would always choose warm white for living rooms and bedrooms, cool white for kitchens, bathrooms and offices. There isn’t much point in going for red, blue or whatever unless your step is painted white, and if it is then buying an RGB (multicolour) strip probably makes more sense. RGB strips allow changes of colour and you can even turn on fancy dynamic lighting effects when you have a party, but you will need to find somewhere to hide the in-line control unit.

Finally, think about the length of cable that is required to reach the socket. It’s not easy to find USB tape fitted with a lead longer than 1 metre, so if you have a mains socket that’s further than that away from the step, say up to 5m, your best bet is probably to make up your own power lead and solder it to a length of LED tape. This is only really an option if you can hide the lead behind the skirting board (baseboard) or tuck it under the edge of the carpet, otherwise there’ll be a lot of cable on view. There will be some voltage drop with a longer lead, and consequently reduced light output, so that should influence your choice of SMD.

Step 2: Fitting a USB Charger Socket

Before doing this, you should check that swapping a socket outlet without being a qualified electrician, or giving notice to the local authority first, is legal where you are. You also need to be confident that you understand how to work on a mains voltage circuit safely. Otherwise, call in an electrician, this is a 10 minute job (if that) for someone who knows what they're doing and it shouldn’t cost much. Maybe save this up until the next time you have an electrician in the house for some other, more vital job.

Single and 2-gang charger socket plates are made by lots of different manufacturers nowadays, and it’s really not a difficult job to swap one in as a replacement for a standard power socket. I would suggest taking advice at the trade counter of your local electrical supply merchant as to which brands are most reliable, because the USB chargers have been known to fail, or to buzz annoyingly, after just a few months. Aldi sometimes sell them for as little as £6.99 in the UK.

Before you go to buy the replacement socket plate, undo the screws that are holding the existing one to the wall – PULL THE APPROPRIATE FUSE OR MCB FIRST IN THE CONSUMER UNIT, OR TURN OFF THE SUPPLY TO THE WHOLE HOUSE IF IN ANY DOUBT – and pull it away from its back box a little. Shine a torch in to see from which direction the cables feed into it. In the UK there will normally be 2 cables into a socket because we use 30A ring mains for power, but if this is a spur off the ring then there will only be one, and if this is a ring socket from which a spur has been taken then there will be three – which could make fitting a charger socket challenging, because the USB power supply takes up additional space compared with an ordinary power socket. Make sure you understand how power sockets are wired in your own country and can identify what is going on behind there.

If you have solid floors then the cables probably come from above, and if you’re upstairs with a suspended floor then they probably come from below, but they may enter the back box from left or right instead. The reason it’s a good idea to check before buying a new socket plate is that the USB-charger variety of socket tends to be more cramped at the back – there’s more going on there – and some brands are better suited than others to cables coming in from a particular direction. Again, ask advice at the shop – when you’ve screwed the socket back onto the wall and restored the power.

I’m not going to give any detailed instructions on how to swap in the new charger socket, because you shouldn’t be doing it unless you already know how or have someone who does to advise you. But all you are doing is removing the wires going into each of the live, neutral and earth terminals on the back of the old socket plate and inserting them into the equivalent terminals on the new socket plate. Don’t forget to earth (ground) the plate itself if it’s metal.

Step 3: Cutting the Channel

First of all, these are the parts of a step or staircase I'll be referring to:

  • the tread is what you stand on
  • the riser is the vertical board at the back of each tread
  • the nosing is the front edge of the tread that protrudes beyond the riser below

The LED strip needs to be recessed so that it cannot be seen, and so that the light has already spread by the time it escapes from the recess and the individual point sources (the SMDs) are not obvious. A recess just 1-2mm deeper than the maximum depth of the strip is enough. For a straight step the recess can be 1mm wider than the strip, but it’s better to go up to 2mm clearance for a curved step, to allow room for the tape to be persuaded into a curve.

This task is SO much easier if you can do it on a new step before it is installed, or if you can remove the tread in question from an existing step. You need to cut a slot along the underside of the nosing (the protruding edge of the tread) to accommodate the LED strip, as close as possible to the riser down to the step below so that the light washes down the face of the riser. Examine the underside of the nosing to see if the riser butts up to it, or if the top of the riser fits into a recess cut into the nosing. In the latter case you will have to be careful not to cut the new slot so close to the existing one that the edge breaks away – 5mm (approx. ¼”) should be safe in a hardwood, as long as your tools are sharp so the wood doesn’t splinter.

With the tread removed from the staircase, turn it upside down and rout out a slot. Make it a little shallower than you think to start with and try the LED tape in it, then just go as deep as you need to hide the tape when viewing level with the underside of the nosing.

If you have to cut the slot in situ, it’s unlikely you’ll be able to get a router into the space, or be able to cut close enough to the riser even if you do. Draw pencil lines then follow them using an oscillating multi-tool fitted with a segmented or E-cut blade to cut the edges of the slot, followed by a chisel to remove the material between. If you don’t have a multi-tool or there’s insufficient space to use it, then you’ll have to cut the slot by hand with a chisel while lying on the floor.

Lightly sand the slot to remove splinters and clean up the edges, but you can leave the base fairly rough so the glue has something to key into.

Now drill any holes needed to get the power lead to the start of the slot. You’ll probably need to drill from the end of the slot through the nosing, emerging right beside the skirting board, or better still, behind it – remove the skirting first. The hole needs to be big enough to feed the LED strip through, not the USB plug, so 10mm diameter should be sufficient.

Use a vacuum cleaner to get rid of the sawdust and then wipe out the slot with a rag dipped in white spirit. It needs to be dust-free or the glue won't stick.

Step 4: Installing the LED Strip

Without peeling off the tape covering the glue, try the LED strip in the slot, starting from the end nearest the socket and positioning it so that the LED strip starts right at the end of the slot, next to the hole for the power lead. Be careful not to put any strain on the soldered joint – anchor the power lead close to the joint temporarily with sticky tape if you don’t have someone to hold it for you while you work your way along to the far end of the step, checking as you go that the strip fits neatly in. If the LED strip is much too long, cut it roughly to length at the cutting point beyond the one you think you will eventually use.

That done, feed the strip down through the hole you drilled and reposition it where it was, this time with the power lead in the hole. Hold it in place every few inches – unless the nosing has an unusually large overhang, it should be possible to do that with clothes pegs, but take care to avoid the LED modules and resistors. Lay a small mirror on the step to help you do this. When you get to the far end, cut the strip at the appropriate place – make it a little too short rather than too long, and then move the whole strip along if necessary so that there is an even gap at each side of the step.

Now you can start peeling off the backing protecting the sticky underside of the LED strip, a few inches at a time, pressing the strip gently into the slot. When you reach the cut end there’s no real need to seal it, but it wouldn’t do any harm to stick a small piece of clear adhesive tape over the gap in the silicone coating to stop spiders crawling in. Replace each clothes peg as you reach it and leave them in place for a few hours. Test the strip still works at this point, using a laptop or some other portable USB power supply if you don’t yet have your charger socket wired in.

It’s unwise to rely on the holding power of the sticky backing, especially where the LED strip is facing downwards. Apply hot melt glue with a cocktail stick to secure alternate edges of the strip every few inches. Use a mirror again to do this, and keep the hot glue away from the SMDs and other vulnerable components. Once the glue is hard, remove any wispy strands with a small pair of scissors.

Use a nail-in cable clip to anchor the power lead to the underside of the tread just before it disappears into the hole. If that’s not possible, then clip it instead on the top, where it emerges, but close to the wall so that the clip won't be seen.

Step 5: Powering Up

Plug the USB into the charger port on your new socket and check the LED strip lights up. Now work out how you are going to run the power lead from where it emerges on the top of the step to the socket, and where you can hide a coil or loop of excess length. The obvious places are under the edge of the carpet (between the gripper and the skirting board) or behind the skirting board itself. If the latter, you’ll need to cut a slot in the back of the board near the socket for the lead to emerge, or else create a channel in the plaster / plasterboard. Secure the lead to the floor or wall with cable clips, remembering to leave enough slack to allow it to be inserted and removed from the charger port with ease. Don't forget to tuck the end of the lead into the slot or channel before refitting the skirting board, it helps to stick it in place with tape.

As a final touch, you can store the USB lead off the floor when it’s not in use by sticking a tiny neodymium magnet to the socket plate. First you’ll need to test that the magnet you are planning to use has enough strength to hold the plug, and experiment a bit to find the best position for it. Paint the magnet to match the socket before gluing it on (I just used cyanoacrylate superglue) and you’ll hardly notice it.

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