Cover Tatami with Sheet Vinyl OK?

[hanibi]

I am renting 2-floor house north of Osaka. There is a room
on the first floor with 6 tatami. My usage of that room is
not compatible with a tatami floor. (No need for comments
on tatami virtues; I know. Not for this room though.) I want
to buy from a building supply place a type of flooring we
call "sheet vinyl" in the USA. It is sometimes called one
piece "linoleum". I want to simply cover the tatami floor
with it. I want to know, over a year or more, how much
will the "not breathing" hurt the tatami? I do not know
what is under it. Does anyone have a guess. The house is 20
to 25 years old. Is there a "crawl space" and wood sub
floor under it, like a USA house? The shower near this room
is probably concrete slab under the tile. Is what is under
the tatami provide enough ventilation from below to keep
the tatami from mildew? Should I sprinkle a light dust of
boric acid powder on the tatami (inhibits insects including
dust mites, may inhibit mildew) before covering it?
It is a hassle to store, but should I remove the tatamis and
bind them vertically against a wall, covered in sheets, to
take better care of them? If I do, can I roll my sheet vinyl
out over the sub floor? What is under the tatami? I realize
eventually the house owners will need to be consulted, and
that if the tatami is damaged, I am responsible to pay for
new tatami. (What is that, maybe 2 man yen per tatami?).
Thank you for reading this, and for your advice. Hanibi

 

[undrentide]

Normally, the base is a kind of frame work (lattice?) and over it are wooden board. You can get some idea from the photos on the link below.
http://www.kenkoutatami-ueda.co.jp/p12.htm

People do say it is not good for tatami to cover it up, especially if the weather is hot and humid, you might get a lot of dust mite.
I'm not sure how long it would take that the tatami get mildewy or have those insects problem - it would depends on the climate and if you're living on the ground floor humidity can be high, then more possibility to damage the tatami.

I don't know if the wooden board below tatami is strong enough on its own.
When I was small, I once saw the board and if I remember correctly, the boards were rather thin.

If you have a special reason you need different flooring from tatami, I think the best way is to consult with the house owner. I checked about the price for new tatami, price range is something below JPY10,000 to over JPY30,000 per 1 jou.

Hope this helps a little.

 

[DoctorP]

You basically have two choices.

1) Leave them in place and cover them. Pros: easy, don't have to store anything. Cons: There will be mildew! One thing to consider is that tatami have to be thrown out and replaced over time. Are these new? Are they older? If so, then the homeowner has already figured on a time that they will be due for replacement and if it comes up early it won't be a huge problem to him. You may want to air them out every 3-4 months if this is possible.

2) Remove them and store them as you said. Pros: don't have to worry so much about mildew. Cons: There will be a 1/2" to 3/4" drop off when you step into this room. The tatami are usually made so that they will be flush with the flooring of the next room. Also, the surface on the bottom is not always that smooth. If you place vinyl over it you may notice it to be wavy or small bumps around.

I suggest option #2. It is the easiest in the long run, and you most likely will not need to replace the tatami when you move out.

 

[hanibi]

Thank you for the great answers. I am a little unclear yet, if the flat wood under the tatami, after weak thin vinyl is laid over it, is thick and strong enough for point-forces, like a table leg when there is 100 pounds of stuff on the table, or a chair leg. Also, in the fascinating link,
http://www.kenkoutatami-ueda.co.jp/p12.htm
I don't understand what the black sheeting material is, that the builder layed under the new tatami.

I have been watching answers twice a day. I got a lot from the two answers given, which are very clear. I want to thank undrentide and CC1 for providing such useful answers!

 

[cursore]

Vinyl flooring may seems a straight forward way to preserve natural flooring from heavy duties, but you'll might find yourself to throw the natural floor away.

That Material doesn't allow the natural floor to breathe therefore creating a warm and humid microclimate, usually the perfect place for woodworm like insect of fungal infestation.

As said before remove the tatami and store it in a cool dry place and if there is not concrete floor underneath replace it with treated chip wood (just in case) and then you can happily use the Vinyl floor.

 

[Mike Cash]

If you go to your local home center type store, you'll find products designed to easily and economically cover your tatami, and do it with at least a bit more style than a vinyl sheet.

This particular consumer need has already been perceived and is being commercially met, in other words.

 

[undrentide]

Thank you for the great answers. I am a little unclear yet, if the flat wood under the tatami, after weak thin vinyl is laid over it, is thick and strong enough for point-forces, like a table leg when there is 100 pounds of stuff on the table, or a chair leg.

That's what I'm concerned about. I think the real supporting strength comes from the frame under the wooden boards. The combination of these boards plus tatami on the frame is enough as a floor, yet I doubt if the boards on their own have enough strength to support point-forces, as you mentioned.
The thickness and strength of the boards under tatami should vary depending on the house, so I cannot say anything definite.

Also, in the fascinating link,
http://www.kenkoutatami-ueda.co.jp/p12.htm
I don't understand what the black sheeting material is, that the builder layed under the new tatami.

The sheet is treated with charcoal powder, to prevent excess humidity and keep tatami from getting mildewy.
According to the webpage, charcoal has effect of keeping insects and germs away, too.

As Mike Cash mentioned, there's some materials to convert tatami to wood flooring.
ﾆ脱ﾆ鍛ﾆ檀ﾆ谷ﾂーﾆ馳ﾆ鍛ﾆ暖 (wood carpet) is one of them.
Home and Garden

It says that the reverse side is coated with Polyester which was treated for anti-mites & antibacterial effect and "excels in sound-deadening, breathability, moisture-keeping, heat-resistance and low-temperature resistance". I'm not sure to what extent they are valid, but it should be better than removing tatami and covering the floor with thin vinyl sheets only.

If you are still concerned about tatami getting molds, how about removing the wood-carpet sometimes, maybe once or twice a year, for half a day, and let tatami breathe?

 

[mr.sumo.snr]

Before lifting old tatami release a bug-bomb in the room or get one of those sprays with the sharp point that you stick in the matting. Things 'exist' under tatami mats that are best NOT exposed to the outside world.

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