Designing our house

26 May 2025 | #housing | #money | #japan

We recently wrapped up the design of our house. I will share how it went in this post.

Before meeting with the architect

This is different by house maker, but Ichijo only lets you meet with their architect once you bought the land. This makes sense: lands in Tokyo are usually small, so it is rare that a house designed for one land will fit another one. So while we were choosing the land, we only worked with our sales guy from Ichijo. He prepared some reference layouts, but as we later realized they were more for visualizing the size of the house, as most of them would have failed the earthquake resistance rules (e.g. having too wide open spaces, putting a door too close to the corner). They were still helpful, but the architect didn’t even consider them when starting the design.

May 7: we closed on the land

We closed on our land on May 7th. Officially we were only allowed to enter the land from this point, so after this date Ichijo went and measured the land. This didn’t change anything for us, as the previous owner already measured it (after taking down the old house and splitting the land into two), but if the land was sold with an old house on it, it can happen that the size of the land was last measured when the old house was built, and might be incorrect affecting the size of the new house.

Initial schedule

We met with our architect on June 6th for the first time. He collected our requirements, wishes, and ideas, and outlined the following schedule (he asked for 2-3 weeks between the steps, and then we agreed on the exact dates):

• June 6: First planning meeting (初回プラン打合せ)
• June 26: Basic plan (基本プラン)
• July 10: Electrical and lighting meeting (電気・照明打合せ) - final deadline: November 28
• August 9: Final specification meeting (最終仕様 打合せ)
• August 26: Consent to start construction (工事着手承諾) - final deadline: January 12

Due to Ichijo’s backlog of houses, our actual deadline for the electrical and lighting meeting was November 28, and the Consent to start construction had to be signed by January 12. If these deadlines are met, then the construction would go as follows:

• Mid March: groundbreaking ceremony (地鎮祭)
• End of March: construction starts (着工)
• Mid May: walls and roof done (上棟)
• End of August: moving in (お引渡)

This schedule assumes that we mainly accept the first plan he comes up with, and only make a few minor modifications. The extended deadlines gave an additional 4 months of leeway, but in the end we asked for an additional extension of 2 months, pushing out all the construction dates by that. This extension didn’t cost anything extra (other than the additional 2 months of rent we need to pay at our current place).

With the 2 months delay our final schedule looked like this:

• June 6: first meeting - discussing our requirements and ideas
• June 26: 1st layout - living room on the first floor as we asked. Outside shape of the house is already the same as the final one. Requested bunch of changes
• July 10: 2nd layout - many of the changes ended up worse than original, so reverted them. Made other requests (e.g. move bathroom to the 2nd floor)
• July 22: 3rd layout - bathroom didn’t work on the 2nd floor, so asking to move it back.
• August 9: 4th layout
• August 26: 5th layout
• September 12: 6th layout, finalizing details (like window sizes and stronger walls)
• September 26: 7th layout. It feels that we are getting the most out of the space, but the kitchen-dining-living spaces feel too cramped
• October 17: 8th layout. Can we move the living-dining-kitchen to the second floor? This restarts much of the designing.
• October 24: 9th layout. Second floor living-dining-kitchen works much better, every starting to come together
• November 13: 10th layout. Started working with the lights and electrical stuff. Layout is mostly fixed
• November 28: 11th layout. Slowly finalizing the minor details.
• December 9: 12th layout. Almost there, finalizing lights.
• January 9: 13th layout. We spent New Years with the in-laws, and they pointed out that the kitchen is only about 2m away from the toilet door. We spent the rest of the holiday coming up with new layouts until we found one that was the best, and shared it with the architect on January 9.
• January 23: 14th layout, based on our new idea. Works really well.
• February 7: 15th layout. Still figuring out the kitchen counter a bit, and moving some doors, but the walls are the same as in the final design. Meanwhile working hard to finalize all the electrical stuff (as we kept changing the layout until now and we care about lights). We had two sessions with a lighting designer to get advice.
• February 19: 16th layout, final meeting to confirm everything. Usually at this point only minor changes are made, but we make like 200 requests (including adding a new window to the bathroom, and redefining the floorheating zones).

This concluded the design phase, and we are looking at a construction schedule of:

• Mid May: groundbreaking ceremony (地鎮祭)
• End of May: construction starts (着工)
• Mid July: walls and roof done (上棟)
• Early November: getting the keys

Dragging out the design phase this long is uncommon, but overall I’m happy that we did it. With each iteration we got closer to a better use of the limited available space, and I’m confident that we are getting the most out of what we have. We were very lucky that both Ichijo’s sales guy and our architect were totally cool with our process taking longer than usual, and supported us throughout this extremely patiently.

Rules, rules, rules

As we started the design, we quickly realized that there are a lot of rules that one has to follow.

Building laws

There are restrictions on the size, and shape of the building that are written in law. These depend on the city and the zoning of the land. For us the main ones were the following:

• maximum 40% of the land can be covered with a house
• floorspace of the house is maximum 80% of the size of the land
• minimum 50 cm between the outside of the wall and the edge of the land
• don’t block the sun from your neighbor to the North (北側斜線制限, see below)

The first two means that for a 120 m2 land you can build a 2-story house with overall max floorspace of 96m2. These two percentages are one of the main information that people check when looking for a land as it defines the size of the potential house, and it depends on the zoning of the area. The 40/80% is pretty common for low-rise residential areas (lot of single-family homes, but most places will have a few 2-story apartment buildings with small, 1-room apartments as well).

‘Don’t block the sun from your neighbor’ regulation 北側斜線制限

With houses built very close to each other, Japan wants to ensure that every house gets some amount of sun. Most of the sun comes from the South, so the North side of the houses are required to stay under a ~45 degree plane in order to let their neighbor to the North get enough sun.

Our land is long in South to North direction, so this affects how close the house can be moved to the North side (back of the land). Also as the land is not exactly South-North, but about 15 degree off, so the rule applies to the West side too (as it is technically West-NorthWest). This resulted in the West edge of the second floor have a sloped ceiling. The lowest point of this is 170 cm, and we put the stairs under it, where it doesn’t matter that much. These types of sloped ceilings are pretty common in Tokyo.

These rules are non-negotiable (the house won’t get the building permit if any is violated), so they don’t depend on the builder company.

Rules of earthquake resistance

The next type of rules are to ensure the house won’t collapse in case of an earthquake. Things like:

• maximum size of open spaces
• big living room having to have a ~1 m long wall coming in from the side in the middle

These depend on the builder for multiple reasons:

• material of the house: steel frame is stronger than wood (Ichijo uses wood)
• targeted earthquake resistance rating (Ichijo targets a pretty high grade)

So working with Ichijo made these rules more of an issue for us, but other than having to add an extra small wall in the living room, it was fine in the end.

Rules of the builder

Then there are the rules of the house builder.

Semi-order and full-order houses

Some companies have semi-order and full-order houses, where the latter is more expensive, while the former restricts the outside shape of the house to one from their set of designs. Luckily Ichijo wasn’t like this, and they let us build the house in any shape.

Size of a section of wall

As the houses are mainly built from wood, the walls consist of pillars and space between the pillars (filled with insulation). Usually this unit of pillar-space-pillar has a pre-defined size, and the wall has to be a multiple of this. The most common size for this is 1マス which is a square of 3尺（910mm）× 3尺（910mm）. So all walls have to be multiples of 91 cm.

Ichijo also allows wall sections of half this size, so in practice you can have walls of multiples of 45.5 cm. This limitation is less visible in bigger rooms, but pretty much decides the width of corridors, stairs, and toilets.

Some builders offer 100 cm unit instead, which however means that more space is wasted on corridors, stairs, and toilets (or more spacey corridors, stairs, and toilets, depending on how you look at it).

Central air circulation system (ロスガード)

This system is one of the selling points of Ichijo. It is mandated by law to provided sufficient air circulation in the house, which often means an air intake in each room where outside air can come in. This makes all heating and cooling systems having to run stronger, as outside air keeps coming in.

Ichijo’s solution to this is a central air circulation system that sends and collects air from each room via pipes, and then makes the incoming and outgoing air pass next to each other exchanging heat. They claim a 90% heat exchange efficiency.

This is all great, but finding a place for the central unit for this system was a major headache, as it has many rules:

• The unit takes up one square (91x91 cm)
• It has to be on the second floor, next to an outside wall
• The wall can’t be sloped (ruling out one of our walls)
• In front of it there has to be an empty square (as the door of the system needs to be opened for maintenance), and this square has to have at least one side open (no door or wall on at least one side)

It took a lot of work to find a place for this where it is not in the way, but still follows all these rules.

Summary

Those were most of the rules of designing the house. Our architect was excellent at knowing about these and guiding our design to ensure we follow them. However He was less strong in suggesting us good design ideas. Apart from the initial design, he mainly waited for us to come up with ideas, and then he would work those into the layout.

Towards the end of the design we were running out of time, and were also slightly frustrated with the lack of advice about design (e.g. about lights). So we consulted with a freelancer lighting advisor and had a one hour call with him twice. These were super helpful. He had a lot of concrete advice, and he worked with us on figuring out what works for our design. I can highly recommend him. (He does not speak English though.)

Things we would do differently next time:

• hire an additional architect or interior coordinator to advice on the design. Probably a freelancer like the lighting advisor would be enough
• bring concrete layout ideas from the early meetings, instead of just telling our opinions about the layout. It could have saved a lot of back-and-forth, as e.g. we thought about moving the bathroom to a different floor, architect comes back in 3 weeks, shows the design, it just doesn’t work there, so we ask to revert it. By the end of the design phase, we were coming up with layouts ourselves, and that allowed a much faster iteration on ideas, letting us only bring more polished ideas to the architect