Build an American-style Kotatsu

Published

Introduction: 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.

Step 2: Attach Brackets to Kotatsu Heater

Doing this step first will eliminate most of the time you would have wasted by measuring the size of your heater, placement of your brackets, location of holes, etc. etc.

1. Figure out the orientation you want for your brackets.
2. Line each bracket up against the screw holes of the heater and screw them in.
  • If you had opted for washers, be sure to place them appropriately.

Easy!

Step 3: Determine Placement of Heater

1. If your LACK is already assembled, remove the bottom shelf and flip your Ikea LACK over. Otherwise, just flip the table top over.
2. Place your heater + brackets on the underside of the tabletop.
3. Perform a dry test to make sure that bracket properly connects to the underside of the tabletop.
4. The location of your home's wall sockets will determine the heater's orientation. Play around too see which configuration works best for you.

Step 4: Attach Heater to Underside of Tabletop

Now that you've determined where you want your heater and which direction it will face, it is time to make it permanent. How you do that will depend on whether you chose to go with screws or nails.
  • Note: The number of screws/nails you will need will be dependent on the brackets you are able to find .The ones I chose have two openings on each side so I needed 8 screws total..

Screws
1. Grab your electric drill and drill a pilot hole through an opening on the first bracket.
2. On your drill, switch out the drill bit and insert the appropriate screwdriver tip.
3. Drive the screw in.
4. Repeat steps 1-3 for each bracket. I recommend doing it this way (instead of drilling all the pilot holes first and then driving all the screws in) because it gives you a slightly larger margin of error in case you are imprecise with your pilot holes or driving.

Step 5: The Fun Part - Decorating and Final Assembly

Now that your heater unit is properly attached, you may now flip your LACK right side-up again. Or, if your LACK is not yet assembled, now is a good time to assemble it. Make sure you don't put in the little pegs for the shelf since the shelf will be acting as our NEW tabletop.

1. Throw your comforter/blanket over the top of the LACK and then place the tabletop over the comforter.
2. Plug your transformer into the wall (making sure that the input voltage is correct)
3. Plug the kotatsu heater power cord into the transformer
4. Plug the other end of the power cord into the heater itself.
5. Turn on the heater!

Step 6: Enjoy Your Creation!

Take a seat underneath your new kotatsu and enjoy the warmth!

Activity suggestions:
- Watch a movie with your boyfriend/girlfriend.
- Have friends over for shabu shabu
- Light up a hookah

3 People Made This Project!

Recommendations

  • Woodworking Contest

    Woodworking Contest
  • Make it Move Contest

    Make it Move Contest
  • Casting Contest

    Casting Contest
user

We have a be nice policy.
Please be positive and constructive.

Tips

Questions

30 Comments

user

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 ;)

2 replies

I'd assume a kotatsu heater has a thermostat and can operate at its maximum setting.

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!

Where can I get some cheap kotatsu chairs?? I made a kotatsu following these instructions and its awesome so far. The only thing that sucks is sitting on the floor for long periods of time without any back support and every floor chair i see is at least 45 dollars :(

1 reply

you might want to consider this zaisu chair (http://www.ebay.com/itm/282293041650?_trksid=p2057872.m2749.l2649&var=581413901798&ssPageName=STRK%3AMEBIDX%3AIT). I bought it the cushion is pretty soft and looks good, besides it is folderable. Please look at the size because it is a bit small though.

zaisu.jpg

Eat your hamburgers, Apollo.

B195IHhIUAAqoso.png

"Do not use any heating element but a kotatsu heater otherwise you run the risk of starting a fire" - Thanks for the tip! I was worried about that.

I followed your instructions and your product recommendations and I finally built my kotatsu this year! It turned out fantastic. Thank you so much for writing this article.

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.

2 replies

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

For Maxim775 NOW YOU ARE TALKING!

A step down transformer for this application is unnecessary, expensive, and a bad idea all round. Also, it may or may not drive you crazy with its trademark 60Hz hum (in the case of a direct transformer).
Realistically, 120VAC should cause no problem whatsoever. In fact, many sources on the web say that people have been using Japanese kotatsu in the US without any modifications, and haven't experienced any problems whatsoever.
Mains voltages are highly variable even within a country, often easily with 10-15% differences, so appliances are always designed to allow some leeway.

Does the top of the kotatsu slip around much? The bottom shelf of the ikea table doesn't seem to heavy and I fear it might slip around to much and I would have to constantly readjust it. Thank you in advance.

user

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.

1 reply

The table is just as stable without the bottom shelf. The shelf doesn't provide any additional support actually.

Sadly, the BeNippon site is shut down due to the earthquake a few years ago. Why they haven't reopened since the dangers passed, I do not know.

1 reply

Hey I just wanted to thank you for your great instructions and pictures. I have searched many a blog about building my own "Kotatsu" and yours by far is the best, I am mostly a visual learner and your instructions are very clear. My boyfriend and I built our table this past fall, with free wood that was thrown out in the woods by our maintenance guys. We only bought stain and sand paper. I am going to be using a king size faux shearling blanket, its super soft and warm! Yeah I was totally lazy this past winter and did not get a heater wish I did. I will now for sure, I have decided on the cozy legs heater, for safety reasons! Also still need a table top, for over the blanket. Then we will REALLY get to try it out, we have just been using the table as a coffee table, since I did not have one. Thanks again, this blog really helped inspire my own "Kotatsu" table. Sorry I tried to up load the pics of my table but it did not work.

1 reply

Hey there and thanks for the kinds words! I'm glad to hear that things worked out for you. I'd love to see the pictures of your completed kotatsu. Try imgur.com for free image hosting.

Also, I don't know much about the Cozy Legs heater, but be sure to read the safety manual to double check that there's no safety risk with keeping objects so close to it. I know that traditional space heaters have this stipulated.

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