Build an American-style kotatsu

According to wikipedia, "A kotatsu, used almost exclusively in Japan, is a low, wooden table frame covered by a futon, or heavy blanket, upon which a table top sits. Underneath is a heat source, often built into the table itself." - source

This instructable will teach you how you can build one for yourself for those cold winter months.

Step 1: Materials check

Required:
- Ikea LACK coffee table (Ikea )

• The legs on traditional kotatsu are 36cm (about 14.5") tall. When I was in Japan, I found this to be way too short for me to sit comfortably which is why the Ikea LACK works so well. The LACK also has a lower shelf portion which can be used as the final tabletop.
• This can also be already assembled or unassembled. It can also be whichever size and color you feel fits your home. I used the bigger size.

- Kotatsu heater

• The hardest piece of equipment to obtain. Try BeNippon or Ebay.
• IMPORTANT: Kotatsu heaters are designed to be mounted upside down and have no required clearance. Do not use any heating element but a kotatsu heater otherwise you run the risk of starting a fire!

- A 120 V to 100 V step-down voltage transformer

• The second hardest piece of equipment to obtain. American outlets put out 120 V but Japanese appliances run on 100 V. Try searching Google, Ebay, and Amazon. This is the one I purchased from Amazon but is no longer in stock. Look at your heater and see how much wattage is required to run it. You'll want your transformer to be able match that.

- 4 angle/L brackets

• Get these at any hardware store.
• IMPORTANT: Make sure that the screws that came with your kotatsu heater fit the bracket AND that the sides of the brackets are long enough to accommodate the thickness of the heater unit.

- Screws or nails that fit your angle brackets

• These will be used to attach the brackets to the bottom of the LACK.
• Just take a look at your brackets and get the right number and size of screws or nails to properly secure the bracket to the table. I used screws.

- Comforter/blanket thing

• Based on the size of LACK that you have, you will need an appropriate sized comforter/quilt/blanket. It needs to be large enough to fit over the top of the table and have some slack to cover the people sitting under it.
• Thickness depends on how warm you want it to be.
• As far as design goes, feel free to go wild. It can be in any print you can find that will match your home or you can even make it yourself!

Optional:
- Electric drill and proper drill bits/screwdriver tips

• If you end up using screws, this will make drilling pilot holes and screwing in the screws much easier.

- 4 Washers

• For securing the kotatsu heater to the brackets.

- Tabletop

• If you don't like the LACK shelf as a tabletop, you want a different color, or perhaps you want one that fits EXACTLY, getting a custom tabletop may interest you.

Comments

[Silver Skeeter]

It's pretty sturdy without the bottom piece. At least, it's as sturdy as a coffee table made by Ikea can be ;).

[am4d]

How sturdy is this particular table without the bottom shelf in place?
I assumed the bottom shelf might have been designed to also give the legs support.

[sushiwasabi]

where can i buy a custom tabletop in canada, calgary? And is there any online store?

[Silver Skeeter]

Sorry, I don't live in Canada so I'm unable to help you. Good luck!

[lindseygloria]

You can buy a kotatsu from the online japanese grocery store marukai. or just the heater. if they are out, which they usually are, call them. they have great customer service and are willing to do phone orders. another place online that sells the tables and heaters is Jlist.

[kderusha]

Just so you know, BeNippon is shut down, sadly. It seems eBay and local Asian furniture stores are the only way to obtain a kotatsu heater anymore.

[Silver Skeeter]

I didn't know that! Thanks for the info.

[Frederbee]

I built my own kotatsu in Canada, and I ordered a heater from the US called a cozy legs heater. It was designed to mount to the back of a desk, to save money heating office buildings (since the heat rises up and only heats the employee, not the room). It's electric, solid panel, doesn't get too hot to touch with your bare knees, and heats up the under the table area in about 10-15 minutes. It does not require air flow, as it functions much like a heating pad/blanket. It's expensive, but SO worth it n.n My winter here was -40C most of the time, and it costs me a lot to heat my house so I stick to this and keep the thermostat down low

[maxim775]

A 10 V heater in series would be a cheaper way to account for the voltage difference. I suspect a 12 VDC heater (something automotive is what I'm thinking) would be close enough. Be aware that while a heating element won't care, not all DC heaters will work on AC, depending on the control circuitry.

[maxim775]

Better yet, why not just use an electric blanket under the comforter (for more insulation)?

[Jaie]

I've wanted to build one for years and have researched them pretty throughly.

I think it is great if more Americans start using them, lots of other countries (including in the middle east) use some method using a table, and blanket and heater. I'm in Upstate NY where in February, you can have the heat on 80 and still feel cold.

And I've even debated using an Ikea table. (nearest Ikea is 5 hours) my biggest concern with your design is that in most traditional designs even for the Iranian tables, these are called korsi, btw, you have ventilation. In the Japanese tables I've seen, the main table is open at the top and the top sits on just as you have it in your picture, on top of the blanket in winter, exposed in less cold seasons. Now, obviously back in the old days when the heaters used coal and kerosene you wanted air flow, but with electric heaters you also need some air flow. Not just to prevent a fire but because you could burn out the motor in the fan from overheating. Easily done if you don't have any additional air circulating.


Have you used it a full winter yet? I'm curious if someone using this table doesn't feel the need to get up and turn the heat up "just a little more" if they are warm enough under the table.

And you need your bowl of oranges ;)

[Silver Skeeter]

Do you have any links to photos of kotatsu with this ventilation? When I was in Japan, I don't remember seeing any ventilation.

That said, I primarily use it in the winter when I have friends over. I start it on high but eventually end up having to turn it to the lowest setting because it gets incredibly warm underneath the blanket. That takes about 10 minutes.

If Ikea is not an option, you can take any table and convert it to a kotatsu using the same steps -- you'll just need to obtain an additional piece for the countertop.

Good luck and let me know if you have any more questions!

[frodo69]

I live in Australia, what kind of step-down voltage transformer would I need?

[Silver Skeeter]

From this site (http://www.adaptelec.com/index.php?main_page=document_general_info&products_id=237), it says that Australia uses 240V. You would need a 240V to 100V step-down transformer.

[Giesterfarher]

I love Instructibles! I was watching an Anime and saw the characters referring to the Kotatsu. When I realized what it was, I had to have one. After trying too find one to buy, I found they were WAY over priced and available only from Japan.

I'm now building one for myself. Thanks for the tips on sourcing the Heater unit!

[Silver Skeeter]

Good luck! It's really quite easy. Let me know if you have any questions.