Hello! Shoyan here. I'm a carpenter based in Japan. Today, I’m doing a renovation. I’m replacing the tatami mats with wooden flooring, and also the engawa. (veranda) The entire floor will be leveled. I will show you several videos of the renovation from this time. Today’s renovation is in a Japanese-style room. There are various types of renovations for Japanese style rooms: just plastering to renovate the walls, replacing the ceiling, and replacing the tatami mats with new ones. Those are common renovations, but this time, tatami mats are removed, and cedar planks will be installed for the flooring. Initially, the plan was to keep the threshold and replace the sliding screens called fusuma. However, the plan changed to create a room without sliding screens and a threshold to create a single room with more space. I haven’t asked why the owner is changing tatami mats to a wooden floor, but these days there are fewer and fewer tatami rooms. First, we remove the floorboards. The new floor will be the same height as the threshold. The height and size of the joists, can’t be determined until the floor is removed. If the wood is rotten, it must all be replaced. In the case of renovation, we don't know until we remove the floor, and that's what I'm afraid of. We have removed the boards, but nothing is damaged. In the past, we didn't use square sleepers and joists. Instead, we used timber, which was milled into 105mm or 45mm thick. (4' 1 1/8" or 1' 49/64" thick) It was called "taiko." Although it was not square, it usually contained the core of the wood. Even if it doesn't contain a core, it is still sturdy because it is just cut in two. The wood used in this house was not rotten, so it remains durable. None of the frames under the floor were damaged, but all the posts were loose, which means they had been shortened. So I only replace the wooden posts with plastic posts; they won’t be damaged by termites, and the floor height can be adjusted nicely. If timbers are not rotten from rain or humidity, their strength remains even if they are old. People often say, "It's not strong enough because the wood is old." However, wood finally shows its true strength after about 10 or 15 years of drying. After that, the strength does not decrease for decades. Therefore, if the wood is 40-to-50 years old, its strength will be completely unchanged. In fact, it will become harder and stronger. The same is true of concrete foundations. It takes years for them to harden and reach their maximum strength. In the case of beams, old wood is much stronger. The original joists were not damaged at all. So I build the frame using the same timber that is used for the ceiling called “nobuchi.” The nobuchi is short of the edge of the room by about 2mm.(5/64") So, I make a shim of 2.5 mm (5/64")-thick plywood, keeping the length; this makes the frame fit properly. Next, I install Styrofoam, a 30 mm (1' 3/16") insulation material, between the joists. When securing the joists, I first set the Styrofoam and secure the joists by using it as a reference. It may look like the order is different than usual, but this way, there is no gap between the insulation and the joists. For the engawa area, I won’t remove the original flooring since it’s not damaged at all. I firmly secure the original flooring with nails to hold it down and install the new floorboards over it. Therefore, the height of the existing engawa floorboards and the new joists will be leveled. The floorboards will be installed throughout the room and the engawa. More than half of the areas can reach the edge of the room with a 4-meter (13' 1 1/2") board. However, the 4-meter floorboard won't reach the edge of the room in the engawa area since there are two of them in a room. A 90cm (2' 11") -width area will not reach. Since I can’t use only one floorboard for a row there, I will stagger 180cm (5' 11") floorboards in that area which is the edge of the room. The floorboard is 30 mm (1' 3/16") cedar joistless. I always sort them by color before installing. They always fall into two categories: light sapwood planks with no knots or dark planks with knots. Unlike new construction, it is difficult to match the color with the old threshold. Also, the old pillars are thicker and uneven. If a pillar protrudes even a little, I cut the bottom off it. If the pillar runs the full height of the building from the sill plate to the roof, the strength could be weakened, so I only cut off about 1cm at the bottom. This makes the floorboard fit on the notch even if the pillar is uneven. It may also speed up the work. However, compared to a new construction, it still takes more than twice as long. Uh-oh... The house is over 30 years old, and the pillars are hardened. It’s hard cutting off the bottom of the pillar. Now let's install the floorboards. I measure the warp of the threshold and mark it onto the first floorboard. It’s very tricky to attach the first board neatly. I feel, as I believe every carpenter feels, that the first floorboard is so hard to install that it feels like you have already installed half of the floorboards. I install the planed floorboards. When renovating, it takes two steps to install the boards: measuring the warp and securing the boards. In new construction, floorboards may have grooves, or the edge may be designed to slope for ease of installation. it is very difficult to use floorboards without such joints, as in this case. I remove the insulation that I installed earlier. Then I get into the crawlspace and secure the floorboards from the bottom of the joist. If new floorboards are going to be installed over the old ones, you can use screws to secure them. At any rate, the first row must be secured accurately and properly, or it will affect the installation of the remaining boards. I first temporarily place all the remaining floorboards instead of securing them one by one. This way, I can check the color balance of the entire floor. I can’t sort colors in detail since there are only a few floorboards, but I will make sure to use the boards which have a similar color next to each other so that it looks comfortable. I arrange the boards with balanced color, stack them up, and start installing from the second board. This is the way I always do it. There is a variation in height between the engawa floorboard and the joists. I run an electric plane on that part. This makes them level with almost no step. Since the original plan for the floor has changed a little, the bottom of the doors will overlap the floor. If the floorboards are installed without allowing for the overlap, the floorboard can’t be removed. I place a piece of floorboard to be installed there, place a pencil, and draw a line on it. This way, there will be a margin of about 3-3.5mm above the floorboard. (1/8"–9/64") This will eliminate any overlap. For a door that has an outer frame and a plywood board in front of it with a hollow inner structure, it will definitely split if you initially use a circular saw. If the door is old, it would be worse than splitting: the panel could peel off. So, it’s better to use a ruler and a cutter or plane the edges with a hand plane. This way, the plywood won’t peel off. The bottom of the pillars at both ends is notched. Raise it more. Let's go a little lower. That’s too low! Raise it again. I can’t lower it anymore! Wait! Raise it! The space in that area is narrow, so it is not possible to slide it in. We are bending the boards to install them. It is challenging. I screw the last floorboard from the outside. Then I caulk between the window frames and the floorboards. This way, the water will not seep through to the floorboards if water drips from the window frame. Now I coat the floorboards with oil. Before that, I protect the baseboards, thresholds, and pillars with masking tape. If the oil gets on those existing timbers, I also need to coat them entirely, and that will be extra work. Sometimes in the past I have planned to oil only the floor but ended up oiling all the thresholds. It’s important to mask off the area with tape. This time, I’m using an oil available in Japan under the name “Gloss Clear Oil.” (KREIDEZEIT Wood Lazure) It is the type that you apply more, wipe it off, and polish it in. However, this oil requires special attention. It is inflammable— especially, the cloth that you use. If you leave the cloth in the back of your van, it will catch fire if it is exposed to direct sunlight. Therefore, it is important to properly dispose of each cloth in a bag after use. Gloss Clear Oil is a little expensive, but it is easy to apply— even I can apply it. I use a roller, applying it more generously than normal oil. It is not the type of oil that you can just leave on and finish, so I let it penetrate for a while, then wipe it off and polish. I had a cup of coffee after applying it. If you leave it too long, you will not be able to wipe it off. The oil left on the surface becomes hard, and it takes a lot of force to wipe it off. I allow time for the oil to be just right before wiping it off. I wipe it off thoroughly and fully, then polish it with force. The last time I used both hands and feet to wipe the floor was when I was in school. It’s been a while. I’ve finished renovating the tatami-mat floor. The threshold was intended to be kept, but we decided to use it to make the room more spacious. The room is usable in many ways. That's all for today. Thanks for watching!