Getting Your Washitsu Right
I spent three days trying to replace tatami in a client's bedroom back in 2018 and learned enough to never skip the inspection phase again. The room was in Kyoto, old building, uneven subfloor. Most guides gloss over what happens when you actually try to lay new mats down. This is more about the stuff nobody mentions until it's too late. Tatami isn't one product. It's a system. The mat itself is a compressed core of rice straw, bound with cloth, wrapped in woven rush called igusa. The standard dimensions are tied to a measurement unit called the ken, but not every shop uses the same variant. You'll see 910x1820mm mats, or 955x1910mm, or smaller guest-room sizes around 818x1636mm. Order wrong, and your last row becomes a sliver you can't hide with furniture. Here's what nobody tells you: measure the actual floor space first, then work backward to determine mat count. Don't assume the room matches standard dimensions. I had a situation in Nagoya where the room was 2.7 meters wide. Standard mats would've left a 40mm gap on one side. Better to use slightly thinner mats or switch to a different layout pattern. A custom-cut edge mat looks fine if it's on the wall side, tucked behind a sliding door track, but it'll drive you crazy if it's visible.
The rush surface comes in different weaves. Hoya-gushi is the standard diagonal weave you see everywhere. Fuki-omi is a tighter, flatter weave that feels smoother under bare feet but shows wear patterns faster. If you have kids or pets, avoid the lighter-colored natural igusa. It stains. I've seen coffee spills turn permanent within an hour on untreated mats. There are synthetic alternatives now. Polyethylene tatami exists and it's not terrible. It won't crack, won't develop mold, and costs roughly half as much. The downside is it lacks the humidity-regulating properties of real straw cores. In a space without climate control, that matters more than you'd think. Real tatami absorbs and releases moisture, which keeps the room from feeling stale. Synthetic mats just sit there. Installation is straightforward if your subfloor is flat. Old wooden joist systems in Japan are usually forgiving because the mats sit directly on the joists with small gaps for airflow. But if you're retrofitting into a modern apartment with a concrete slab, you'll need a leveling layer first. I recommend a vapor barrier underneath, then treated plywood slats spaced 300mm apart. Without that, moisture from the concrete will wick into the straw core within a year, and you'll be dealing with black mold you can't see until it's too late.
The border fabric, or tsugike, is where aesthetics show. Dark green borders are traditional but dated. Navy, brown, and grey options exist now, and they look significantly better in contemporary settings. Just know that dyed borders fade differently than the rush surface. A mat with a bright new border and aged igusa looks worse than an evenly aged one. Costs in 2024 run roughly ¥8,000 to ¥15,000 per standard mat for good quality natural tatami. Imported or specialty weaves push past ¥20,000. Synthetic runs ¥3,000 to ¥7,000. Labor for a full room replacement in the Tokyo area averages ¥30,000 to ¥60,000 depending on scope. Buying online from Chinese suppliers will save money upfront but you're looking at shipping costs that can double the price, plus zero ability to check quality before payment. Here's the edge case I ran into last spring: ordering replacement mats for a room that already had aged tatami. New mats have a bright green surface. Old mats are olive-brown. Even if you buy the same brand, the color mismatch is obvious within the first month. The workaround I use now is to recommend clients either replace all mats in a room at once, or intentionally age the new ones. I've soaked new mats in weak tea solutions before installation to pre-darken them. Takes two days of drying time but saves the visual clash. It sounds crude and it works.
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Maintenance is simple but specific. Vacuum weekly with a soft brush attachment. Never use water on the surface. If something spills, blot immediately, then use a slightly damp cloth only on the affected area, followed by thorough drying. Direct sunlight fades igusa. Rotating the mats every six months evens out wear if your room has a window on one wall. I rotate mine clockwise so each mat gets equal exposure over the year. If you're considering tatami for a room that will see heavy foot traffic, like a hallway or entryway, skip it. The rush surface compresses and tears. It's beautiful in bedrooms and formal rooms, not high-traffic zones. For those spaces, cork or engineered wood with a Japanese aesthetic works better and won't require replacement every five years. One more thing about the core material. Straw-core tatami lasts about ten years before the compression drops and the surface loses firmness. I've seen some last fifteen with careful use. Rush-only mats with synthetic cores claim twenty-year lifespans but feel different underfoot, softer and less resilient. If you're doing a long-term renovation, the straw-core version is worth the replacement cost over time. The feel is distinct and hard to replicate.
Check the JIS standard if you're ordering from a domestic supplier. JIS A 4601 covers tatami specifications in Japan. Anything below that standard is likely cheaper materials and shorter lifespan. Overseas sellers rarely comply with this standard, which is another reason to be cautious about foreign purchases. The room size calculator most people use online assumes perfect rectangular rooms. Yours probably isn't one. Take photos of your space from multiple angles, measure each wall at floor level and at 900mm up, and note any obstacles like heater units or built-in shelves. That detail about the heater is important. Traditional washitsu rooms sometimes have concealed heating. If yours does, make sure your tatami order accounts for clearance around the unit. Mats placed directly over warm areas dry out faster and crack along the edges.
