Recently I got a new set of sofas and armchairs to go in my living room. They were perfect apart from one small problem – the legs were too short. By that I mean that the underside of the sofas were too close to the ground to allow my Roomba vacuum cleaner to fit underneath. As you can see from this picture, a Roomba will happily clean underneath furniture, but only if there’s enough room – in the case of my model, about three and a half inches (90mm).
I definitely wanted to make sure that my Roomba could fit underneath the new sofas – I have three dogs and hardwood floors, so hair will inevitably gather if it’s not being picked up. I started looking at chair raisers – there are some very nice hardwood ones available – but quickly realised that there were two problems. Firstly, I would need three sets, which would set me back the best part of $100. Secondly, there’s no way to adjust the height – I wanted to raise my sofas and chairs up by only the minimum amount necessary. So I decided to make my own.
Design
The basic plan is to use a hole saw to cut a bunch of circular wooden disks out of cheap timber planks, and then stack the disks together until they’re the right height. Then, to securely hold the legs of the sofa, you’ll cut a final disk with a cut-out section in the middle where the sofa leg will go. A photo of the rough finished product should make things clearer:
This one was made from 3/4 inch (18mm) planed timber, and I used three layers to give a total height of 2¼ inches (54mm). The top layer was made from the same piece of wood, but doesn’t contribute to the height of the sofa – the sofa leg just sits in the round depression so that it’s held securely. This is the rough version – if you’re going to be able to see the leg raisers, you could sand the outside and stain or paint for a nicer finish.
Construction
The trick to cutting out these perfectly circular disks of wood is to use a hole saw - a circular blade that fits into a normal drill and cuts round holes.
For this project we need to cut two sizes of hole – a big one for the main layers, and a smaller one for the sofa/chair leg to fit into. Rather than buying two individual saws, it’s cheaper to buy a set that contains a range of sizes. You’ll also need an electric drill and some smooth planed timber – try to get a plank that’s 3/4 inches thick and about 5 inches wide.
Now, on to the cutting. Disclaimer: power tools are dangerous – take care!
If you look at your hole saw, you’ll see that the central drill bit protrudes a bit beyond the cutting saw part. The trick to cutting nice neat holes is to drill through your wood until the central bit emerges on the other side, but before the saw part has cut all the way through. Then, turn the wood over and finish off the cut from the other side, using the central hole to make sure that you’re cutting in exactly the same place. If you just cut all the way through from one side, then you’ll get a load of splinters where the saw breaks through the wood. Most hole saws have a small hole in the back that you can use to poke out the circular disk if it is stuck – do this gently, as you don’t want to dent the wood.
While you’re cutting, watch out for any sign of overheating, like smoke. The friction between the saw and the wood can cause it to get very hot. Also, be careful not to touch the blade immediately after you’ve finished a cut as it will probably be hot. A hole saw generates a large amount of sawdust – much more than normal drilling – so make sure you do it somewhere that will be easy to clean up. Also, when you're using the larger size hole saws, the torque on the drill is going to be much greater than when drilling a normal-sized hole, so don't break your wrist. If you have a drill press, use it.
The easiest way to figure how how many layers you need is by trial and error. Cut out four disks using the largest hole saw in your set, and put them underneath the four legs of your sofa. If it’s still not high enough, cut another four and repeat. Be careful, because at this stage there is nothing holding the disks together, so they could easily slip.
Once you’ve got enough layers to raise your sofa to the right height, cut one more set of disks for the top layer that will hold the legs. Now comes the clever bit – we will use a hole saw to cut another disk from inside the first one, leaving us with a ring-shaped bit of wood that will hold the leg securely. The trick to this is to cut the inner hole just big enough to hold the existing sofa leg, so measure it and pick the hole saw from your set that is just big enough to fit. If your existing sofa leg is round, then just measure across it; if it is square then measure on the diagonal. If the size is in between two of your hole saws, then pick the smaller one and enlarge the inner hole after glueing. Use the drill bit hole in the centre of your wooden disk to make sure that you drill the inner hole in the exact middle. You’ll probably want to clamp the wooden disk when drilling it, as there might not be much clearance between the edges of the disk and the hole that you’re drilling.
When all the drilling is done, you’ll be left with a stack of wooden disks (3 in my case) and a wooden ring for each leg. Assemble each raiser by glueing the bottom of each disk to the top of the one below it, and glueing the bottom of the ring to the top of the uppermost disk (take a look back at the photo above to see what I mean). Because you’ve made the disks from planed wood, the tops and bottoms should be perfectly flat and easy to glue. And because you’ve used a hole saw to make the disks they should all be exactly the same diameter, so it should be easy to get them to line up.
Once the glue has dried, it’s time to check that the sofa legs fit into the depressions on the top of each raiser. If you’ve cut the holes slightly too small, then the best way to enlarge them slightly is with a rotary tool like a Dremel with a drum sander.You could also use a round file or a piece of sandpaper, but it will take quite a lot longer!
If necessary, you can tap the bottom of the raisers with a mallet to get them seated securely on the sofa legs – the slight friction between the leg and the wood will help to hold them on securely.
Finally, finish the raisers however you like. I simply sanded the outside to a nice smooth finish, but if the raisers are going to be on display, then you could stain or paint them to match the rest of your furniture.
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