Futon or Bed in a Small Japanese Apartment? How to Choose (and Avoid Mould)
In a room under about 8 tatami, a futon frees up floor space in the day, but it must be aired or lifted often because moisture builds up underneath and causes mould. If you will not fold it away every day, put the mattress on a slatted base (すのこ) or a low bed frame. A single in Japan is about 97–100 cm wide.
The real issue: moisture
Japanese summers are humid and winter rooms are often cold, so condensation forms between a futon and the floor. A futon left on the floor for weeks can grow mould on its underside. Airing it on the balcony, folding it during the day, or raising it on a slatted base solves most of this.
Futon: when it works
- Small rooms where you want the floor back during the day.
- Tatami rooms, which breathe better than flooring.
- People who are happy to fold and air bedding regularly.
Bed: when it works
- You will not fold bedding away every day.
- You want storage space under the bed.
- You have back or knee pain and prefer to sit down onto a raised mattress.
Japanese bedding sizes
- Single (シングル): about 97–100 cm wide.
- Semi-double (セミダブル): about 120 cm — a roomy size for one person.
- Double (ダブル): about 140 cm.
- Futon and bed mattresses use slightly different measurements, so check the 寸法 (dimensions) on each item page.
Picks with checked prices
-
Slatted bed base (single)
【20時~5％引クーポン】 19万台突破＆楽天1位 ワンタッチ 折りたたみ ベッド 折り畳み 耐荷重300kg 床傷防止PUキャスター シングル シングルワイド
¥11,999（タンスのゲン Design the Future · checked 2026-10-24）
Why this one: Raises the mattress so air flows underneath — the simplest way to stop mould.
Check on the item page: すのこ = slatted base. 桐 (paulownia) is light and absorbs moisture. 折りたたみ = folds for drying.
View on RakutenOther price levels: Budget ¥5,580Premium ¥17,999
-
Tri-fold mattress (single)
【20時~5％引クーポン】 確かな品質で6年連続No.1 マットレス ｢純｣ 高反発(R) 全部洗える 10cm厚 3つ折り メッシュ/パイル 折りたたみ ベッ
¥5,555（タンスのゲン Design the Future · checked 2026-10-24）
Why this one: Folds into thirds so you can stand it up to dry or store it during the day.
Check on the item page: 三つ折り = folds in three. 高反発 = firm, supportive foam. 厚さ = thickness; 8–10 cm feels close to a bed.
View on RakutenOther price levels: Budget ¥4,680Premium ¥18,598
-
Dehumidifying sheet
洗える除湿シート 豊富な7サイズ シングル セミダブル ダブル キング ファミリー ベビー 布団 からっと寝られます 除湿マット センサー付き 結露 カビ対策
¥1,680（スリーププラス · checked 2026-10-24）
Why this one: Goes under a futon or mattress and absorbs moisture; many have a colour sensor that tells you when to dry it.
Check on the item page: 除湿シート = dehumidifying sheet. センサー付き = colour-change sensor. 洗える = washable.
View on RakutenOther price levels: Budget ¥1,580Premium ¥4,378
-
Futon dryer
【選べる】布団乾燥機 アイリスオーヤマ カラリエ ダニ対策 コンパクト シングルノズル マット不要 梅雨 湿気 靴 乾燥 布団あたため 花粉 部屋干し 衣類乾燥
¥9,980（OA’Z · checked 2026-10-24）
Why this one: If you cannot air your futon outside, a futon dryer blows warm air through it in about an hour.
Check on the item page: マット不要 = no mat needed (easier). ダニ対策 = dust-mite mode. 靴乾燥 = can also dry shoes.
View on RakutenOther price levels: Budget ¥6,980Premium ¥12,700
FAQ
- Why does my futon get mould?
- Moisture from your body and the room collects between the futon and the floor. Air it often, fold it away during the day, or use a slatted base (すのこ) or a dehumidifying sheet (除湿シート) underneath.
- What size is a single bed in Japan?
- About 97–100 cm wide and 195–210 cm long, depending on whether it is a bed mattress or a futon.