This post is a continuation from last week’s examination of earthen floors (土座床) in minka.
Even after the transition from the post-on-foundation stone method of construction to the use of a ground sill (dodai 土台堀立て柱) between posts and foundation stones, the tendency in doza-yuka dwellings was to use ‘half sills’ (han-dodai 半土台) internally, so that these members projected as little as possible above the ‘finished floor level’ of woven mats (mushiro 莚).
Doza-sumai. The earthen floors are covered with woven straw mats called mushiro.
The construction of the typical ‘floor living’ (doza-sumai 土座住まい) floor was a often more sophisticated than simply placing mats straight down on the earth. The ground was first dug out to a depth of around 100 to 200mm, then a soft ‘underlay’ layer, often of rice husks (籾殻, usually read momi-gara, but here read nuka), but alternatively some variety of straw (wara 藁) or thatch (kaya 茅), either of rice, Cyperacea species such as sedge, Miscanthus, speargrass (Imperata cylindrica) etc., or reed (yoshi or ashi, 葭), or millet husks (hie-gara or fue-gara 稗殻) was put down.
Rice husks, momi-gara.
Since straw and reed are hollow, they have an insulative effect and prevent damp, and are also unlikely to harbour fleas. Over time as they are walked on, however, the individual straws or reeds are broken and crushed, meaning both a relatively noisy floor and, as the subfloor packs down, a gradual subsidence of the finished floor level in the most trafficked areas. Because of this, and the vulnerability of these materials to insect damage, traditionally the subfloor was replaced every year.
On top of the subfloor layer went the ‘finish’ floor: mats (goza 茣蓙) of woven straw, thick mushiro (atsu-mushiro 厚莚) known as nekota or nekokata, bullrush or cattail mats (gama-mushiro 蒲莚), sedge mats (suge-mushiro 菅莚), or occasionally the rigid tatami (畳) mats that are still a characteristic feature of Japanese houses.
To minimise damage caused by flooding and the effects of ground moisture, a platform of compacted earth was sometimes built up above ground level within the perimeter of the external walls, to a height somewhat lower than or even as high as the typical timber-framed taka-yuka floor; indeed if the minka also had adjacent raised-floor areas such as a zashiki, building up the doza to this same level was logical and convenient. At first glance these raised earthen floors (taka-doza-yuka 高土座床) might appear to be timber-framed themselves, but lifting the mushiro and underlay or looking at the subfloor from the exterior would reveal an earthen base. Building up the floor in this way has the advantage that the underlay of husk or straw can be omitted, since raising the floor is similarly effective in reducing damp; it also eliminates the work of replacing the subfloor annually.
A raised doza or taka-doza-yuka.
Lifting the tatami and mushiro to reveal the raised earthen floor or taka-doza-yuka below, which is built right up to the underside of the sliding door sill (shikii, 敷居). There is no thick underlay of husks or straw; the mushiro is laid directly on the earth and serves as the underlay.
The raised earthen floor seen from the exterior of the minka, again showing how it is built up to the level of the underside of the shikii.