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Demolition and Renovation of Japanese Houses

As I mentioned in “Part 6: Vacant houses and garbage problems” in this series, Japanese wooden houses are very flexible. Even if part of the house collapses, it can be repaired, and the layout can be easily changed. For major renovations, you can remove all the old walls, leaving only the pillars, and then rebuild the house with a new layout.

In Japanese houses, there are two types of columns: some are structurally important, while others aren't. The less important ones can be removed to create larger rooms. Even the important ones can sometimes be taken down if the house is reinforced―like by making the beams thicker or adding new columns in other places.

However, it's dangerous for someone without experience to decide which columns are safe to remove. Always get advice from a professional before starting any work.

Usually, the pillars in a Japanese wooden house hold up most of the structure, so as long as they remain in place, it's safe to remove old walls. But in some cases, termites or other damage may have weakened the pillars, and the walls might be supporting more weight than expected. If you take down a wall without checking the condition of the house first, it could collapse or lead to serious accidents.

Columns mainly support vertical loads, but the walls help protect the house against sideways forces from earthquakes and strong winds. If you remove the walls, the house could become unstable, so you need to install temporary supports or reinforcements. Again, always consult an expert.

If any columns are damaged, you’ll need to either replace them or cut out the damaged parts and connect new wood. This is also difficult for an amateur to do on their own.

Compared to concrete, mud walls are much easier to break down with tools like a hammer or crowbar, but they create a lot of dust. So, wearing protective gear like work clothes, goggles, and dust masks is essential. Since clumps of dirt can be heavy and dangerous if they fall, safety shoes and helmets are also a good idea.

If you’re not familiar with demolition work, it's safer to break the wall down slowly, starting from the top, rather than trying to knock it all down at once. You should also cover any nearby items or rooms you don't want to get dirty. Be careful about opening windows and doors while you're demolishing, as dust could blow outside and bother your neighbors.

The bamboo mesh (竹小舞: Take-komai) and the wooden boards connecting the pillars (貫: Nuki) that make up the framework of mud walls can be easily removed with a saw or crowbar, so there’s no need for power tools when dismantling them.

Mud walls often emerge from beneath printed plywood. While most walls in modern houses are made of wallpaper over plywood or plasterboard, mud walls were commonly used in houses built before the 1980s. In many cases, thin printed plywood was added during renovations by previous owners to cover up these old clay walls.

Mud walls are made by attaching a woven bamboo net to a board called Nuki, which connects the pillars. Mud is then applied to the net, allowing it to get tangled and stick in place. As explained in “Life in an Old Japanese House Vol. 10: Japanese Houses Walls Part 1”, the Nuki plays an important role in supporting the house against sideways forces.

Temporary bracing should be installed in areas where walls have been removed or where the building is structurally weak to prevent collapse from earthquakes or strong winds during construction.

The ceilings of Japanese wooden houses are often made of thin boards attached to lightweight wooden beams, making them relatively easy to dismantle. However, because the materials are thin, they can easily collapse if someone steps on them. Additionally, like with mud walls, dismantling ceilings can produce a lot of dust.

Interestingly, materials used in older houses are often of higher quality than what's sold today. In the past, ceiling boards were made from natural wood, while today, thin printed plywood or plasterboard is more common. These modern materials, including plywood, wallpaper, and plasterboard, typically last 10 to 30 years before needing replacement. In contrast, older houses built with natural materials like wood and mud walls tend to have a longer lifespan if properly maintained.

A thin wooden board is attached to a narrow stick called a 竿縁: Sao-buchi using small nails. If the wooden planks are carefully removed, the Sao-buchi can remain in place, allowing a new plank to be reattached. However, it’s difficult to remove the old boards without breaking them, making reuse challenging.

The ceiling of a Japanese house is fragile and will collapse if stepped on, so if you need to move around up there, make sure to step on the beams.

As the demand for traditional Japanese-style rooms decreases, the price of materials rises, and fewer craftsmen remain who can do this type of work. Rebuilding an old interior to match its original style can be very expensive.

So, before demolishing a room just because it looks old, carefully consider which parts should be preserved and which can be rebuilt.