ノコギリは刃が40ｃｍです。ちょうど刃の後ろ部分の層が「かるかた雪」です。ここだけを使います。The saw blade is 40 cm long. The layer just behind the blade is the ideal “karukata snow.” We only use this part.
湯船から下一段切り出して、もう笹が出てきた。上一段目しかできていないので、切り出し場を求めて「廊下」を作り始めます。After cutting the first layer of blocks from the “bathtub” area, bamboo grass started appearing. With only the first layer completed, I needed another source for blocks, so I began extending a “hallway” to create a new cutting area.
イグルー側から見た廊下の先の「ブロック切り出し場」これまではサイコロ状を切り出し続け、最初の長細いブロックを切って転がしたところ。View from the igloo: The end of the hallway where blocks are cut. So far, I’ve been cutting cube-shaped blocks. Here, the first long block has been cut and rolled.
「切り出し場」からイグルーを「廊下」越しに見たところ。廊下を通って長いブロックを屋根として積む。View from the cutting area: Looking back at the igloo across the hallway. Long blocks are transported through the hallway and stacked as the roof.
手を使ってやさしく手前に転がした。スコップでやってはいけない。両脇がハの字に切れている。これを優しく立てて、ノコで縦切りRolling the block: Using hands to gently roll it forward. Never use a shovel for this step. The sides of the block are cut in a V-shape. Carefully stand it upright and cut it vertically with the saw.
窓はもちろん富士山側にして、最後まで夕景を楽しむ。日が暮れたらサムいから、この隙間を埋めておしまい。Of course, the window faces Mount Fuji, so I can enjoy the sunset until the very end. Once the sun sets, it gets cold, so I’ll fill in this gap and call it a day.
This Time, the Snow Depth Was 60cm
Last week, I had two consecutive igloo expeditions. One of them was in the Higashiyama area of Matsumoto City, on a mountain with an altitude of just under 2000 meters. This region does not have heavy snowfall, and since it is a cold area, the fresh snow never gets a chance to melt. Over time, it also doesn’t get compacted by the weight of more snow from above. The deepest snow I found was about 60 cm. However, that was still enough to build an igloo.
In our usual training sessions, we cut blocks only from the foot area of a 1.5m × 1.5m “bathtub” space and stack them. This method works when there is sufficient snow depth, with a usable snow layer of 30 cm stacked in two or three layers.
This time, the snow depth was 60 cm, but the top 10 cm was a loose powder layer, and the bottom 10 cm had become granular due to ground heat, mixed with bamboo grass and small twigs, making it unsuitable for blocks. That left a 40 cm thick middle layer that was usable for cutting blocks.
External Block-Cutting Method for Igloos in Low-Snow and Cold-Snow Areas
For a one-person 1.5m × 1.5m igloo, if the snow depth is insufficient, the first layer of blocks will be exhausted quickly, and after stacking the second layer, there will be no way to cut more blocks from inside.
To solve this, we extend a hallway outside the “bathtub” area of the igloo, allowing free movement in and out and placing the block supply point nearby. The blocks are cut as we extend the hallway. If the location is on a slope, it’s easier to transport the cut blocks if the supply area is placed uphill. Since the entrance is usually made on the lower slope side, it’s a good idea to create a separate back entrance.
Additionally, when the snow depth is shallow, there isn’t much room to expand below the snow surface. To ensure enough legroom, the igloo should be built slightly larger in advance, around 1.5m × 1.7?1.8m.
As long as the snow layer is good, working outside is much easier since there are no walls or ceilings to restrict movement. Long and sturdy blocks can be cut one after another. A recommended approach is to cut and transport multiple blocks in one go, place them in position, and then assemble the roof all at once at the end. The back “service entrance” can be quickly sealed with just a few large blocks.
Review: How to Cut Large, Long Blocks
Ensure the saw cuts align properly and fully separate the block.
Cut the sides in a V-shape, then tilt the block forward to roll it out.
A shovel is only used to create space for inserting fingers.
Using force with a shovel can break the block. Always roll it by hand.
Stand it up carefully.
Since it is heavy, lower your stance and bring your body close for control.
Cut it vertically with the saw.
Hold both sides with your left hand to prevent it from falling after the cut.
Building igloos requires different techniques depending on the season (December to May) and the snow conditions. There’s always something new to learn?it’s a deep and fascinating process.
個別イグルーを地下でトンネル続きにしています。迷路みたいだよ。The individual igloos are connected underground by tunnels. It’s like a maze!
Igloo workshop＠Nagoya rousan three groups
Impressions from This Session
Igloo-ski demonstrated the process in 36 minutes, and then everyone tried it on their own. I was worried about the low temperature, but the sun came out, and there was no wind, making it another great day for training.
Mizutani-san, in her second attempt, quickly succeeded in sealing the roof this time and was absolutely delighted. Many others followed, successfully completing their igloos one after another.
The snow depth was over 2 meters, and those struggling with block-making kept digging deeper. As a result, many couldn’t reach the ceiling. The trench-cutting method for making blocks wasn’t working well.
Key points for improvement:
Carefully align the saw cuts.
Don’t poke the blocks with a shovel until they start moving at the cut.
When stacking blocks, don’t just place them directly on top?push them inward as much as possible, testing the limits before they fall.
After demonstrating these techniques inside the hole, things progressed much more smoothly.
Many people were using 24 cm saws instead of the recommended 30 cm ones, resulting in blocks that were too small, making it impossible to close the roof. Later, those who had finished lent their saws to others, helping them realize the difference. It became clear that igloos cannot be built properly with short saws.
Failures lead to success. The lessons learned from mistakes are deeply ingrained, and if everyone applies them in their next attempt, I believe they will make significant progress.
Once the igloos were completed, people enjoyed ramen inside their own igloos. The aroma of ramen filled the air at the site.
どうすか？かるかた雪ってのは軽いからこんなに大きくても持ち上がるのです。固くて丈夫だからこんな無茶な積み方でもOKです。What is karukata snow?Because it’s light, you can lift large blocks like this.Because it’s firm and sturdy, you can stack them in seemingly impossible ways.
かるかた雪の長細ブロックなら、わずか数段で、見かけ上、背の低いイグルーができます。With long, narrow blocks of karukata snow, you can quickly build what appears to be a short igloo in just a few layers.
いちばんやりたいこと・イグルーの窓から飽かず絶景を見ることThe Ultimate Goals: Enjoying the stunning view through the igloo window
いちばんやりたいこと：イグルーの中でおいしいもん作って仲間とたべること これはですね、ベトナム屋台料理のエビバナナフライナンプラー浸しです。The Ultimate Goals:Cooking delicious food inside the igloo and sharing it with friends.This time, she made Vietnamese-style shrimp & banana fries soaked in fish sauce.
参加者29人、ひとり風邪で来られず。みな楽しそうで、うれしかったです。We had 29 participants, though one couldn’t attend due to illness. Everyone seemed to have a great time, which made me really happy!
Igloo Workshop @ Gakuto Matsumoto Mountain Forum in February
Thank you always for your inquiries about the igloo workshop! This past weekend, we held the first of two sessions as part of the “Gakuto Matsumoto Mountain Forum,” a mountaineering training series sponsored by Matsumoto City. This time, we conducted the workshop near Jizo-no-Kashira on the Tōmi Ridge in Hakuba Village.
The weather was perfect?clear skies with no wind?and we had a breathtaking view spanning from the Southern Alps to Kubiki and Mt. Naeba. The snow depth was about 2 meters, with the top 50 cm being soft, but underneath, we found the ideal “karukata snow” (light yet firm snow). I believe all participants experienced the joy of working with this type of snow. We were able to cut long blocks just as we wanted!
Key Learnings from This Session
Trench depth matters ? If it’s too shallow (e.g., 20 cm), building becomes difficult. Cut to the full length of the saw (30?40 cm) for better results.
Preventing broken blocks ? Make sure to cut all the way through with the saw before using a shovel to lift them out.
Starting size mistakes ? Some people made their initial igloo area too large, others too small. Giving early guidance could have helped, as both cases were doable but took extra time.
Dealing with soft snow layers ? The top 50 cm of soft snow tends to form potato-shaped blocks, so I had participants discard them liberally.
Stacking technique for second layers and beyond ? Blocks tend to be stacked vertically, but if you take a moment to reposition them slightly closer inward, you can quickly form a roof with a significant difference in structure stability.
竪穴の底は四角形。側面壁から三角柱を取り出したその下の部分の背面へのノコの入れ方を説明しています。The pit bottom is square, and after removing triangular prisms from the side walls, this video clearly explains how to saw the lower back section.
Igloo Workshop Video by Gaku-To Matsumoto Alpine Forum
You can find it on the website of the Gaku-To Matsumoto Alpine Forum.
Every year in February and March, the “Gaku-To Matsumoto Alpine Forum” (organized by an executive committee including Matsumoto City) holds igloo workshops for individuals.
The English subtitles for the video could not be added. Please understand the content from the visuals. Sorry about that.
This year, the workshops are scheduled for February 15 and March 8. However, registration, which opened in mid-December, quickly filled up. I apologize for that.
For those who can attend, this video will serve as a good preview. For those who couldn’t join this year, watching this will give you a clear understanding of the process, almost as if you participated. The video is approximately 40 minutes long?about the same duration as the explanation given by Igloosky while actually constructing an igloo.
Nearly Unedited Footage with Helpful Visual Aids
The video is mostly uncut, but additional explanations and red lines have been added to clarify difficult-to-understand aspects, such as the direction of the saw when making cuts angled outward. You can grasp the key techniques just by watching.
New Features in This Video
1. Square Bath-Like Pit
Filmed in March 2024, this latest version features improved construction methods. One notable change is shaping the pit as a square (approximately 1.5m × 1.5m) instead of a circular one.
Although igloos appear round, blocks are rectangular, and human living spaces are more efficiently used when square. Imagine an oversized bathtub.
If the pit is too small, it becomes difficult to extract blocks.
If it’s too large, construction takes too long.
The ideal size is around 1.5m per side?or maybe 1.3m?
2. Emphasis on Trenches
Trenches are crucial for cutting clean, stable blocks, much like cutting tofu precisely.
Square blocks with flat surfaces stack more stably.
Cutting long blocks is a key skill in igloo construction.
Though digging a trench may seem like extra work, it is essential for preparing good blocks.
Additionally, this time we emphasized:
Cleaning loose snow from the bottom before sawing.
Keeping the saw horizontal and ensuring cuts connect properly.
3. Cutting Blocks from the Side
A key improvement in this version is demonstrating how to cut blocks from the lower section after extracting triangular prisms.
The rear-side sawing technique is now explained in more detail.
Hold the saw handle with both hands and rotate it to cut efficiently.
This method addresses a frequent question from workshop participants.
Other Covered Techniques
This video also includes nearly all the workshop content:
Smoothing the ceiling edges.
Expanding the side walls from the inside.
Using loose snow as flooring.
Sealing gaps from the outside.
One part we forgot to film was how to seal the entrance. However, if you stack blocks to close the entrance after entering, it will stay warm while you sleep.
Even if you can’t attend the workshop, watching this video will give you tips to reduce your igloo construction time.
信大山岳会は、アロハが制服とのことで、イグルスキーも一着、賜りました。ポリエステル製が良いとのこと。The Shinshu University Alpine Club’s unofficial uniform is the aloha shirt, so they gifted me one as well. Apparently, polyester is the preferred material.
4人用炊事集会イグルーは座って鍋を囲むサイズ。２〜３人なら横になれるサイズThe four-person cooking and gathering igloo was big enough for everyone to sit around a hot pot. If there were only two or three people, they could lie down comfortably.
こんなにたくさん誰が食うんだよ〜と思いましたが食ってしまったシチュー。Initially, I thought, “Who’s going to eat all this?” but we ended up finishing the stew.
シンヤさん！もうすぐ届くぞ、頑張れよ〜！という声かけが迫真。これ埋没者には効くんだよ。Hearing someone shout, “Shinya! We’re almost there! Hang in there!” was incredibly intense?it really works for the buried victim.
First Time with Shinshu University Alpine Club and Igloos
I held the first workshop to encourage the Shinshu University Alpine Club to incorporate igloos more into their activities.Participants included one third-year student, six second-years, four first-years, plus four alumnus and friends. We built an igloo village on the gentle slopes of Kaminotanbo in Tsugaike. Each team of four constructed a communal dining igloo in the center, surrounded by individual igloos. Everyone quickly mastered the technique, cutting out massive tombstone-sized blocks and finishing their structures in no time. Young people learn fast?no complaints at all!
For over 30 years, I’ve had many close climbing friends from Shinshu University. It’s a bit late, but I was really happy to finally connect with current students through igloo building.
Shinshu University students come from Matsumoto (Faculty of General Education, Science, Humanities, and Medicine), Nagano (Education and Engineering), and Ina (Agriculture). Most students are from outside the prefecture and chose Shinshu University because they love the mountains. The club members are overwhelmingly “mountain people” or “nature lovers,” and the similarity to Hokkaido University is striking. One participant was the daughter of a close climbing friend from my Aomori days, which led to this whole event happening.
Immersed in the Students’ Cheerful Atmosphere and Serious Beacon Training
Living together in the igloos with students and sharing their routines was fascinating?rice topped with stew thickened with flour, zenzai (sweet red bean soup) for breakfast, the “atocha” pot-washing tradition, and the secret stash of special treats everyone brought.
The next day, we joined an avalanche burial rescue training session. It had been over 30 years since my last formal training.
My beacon experience had stopped at the old Ortovox models with just arrows and lights. This was my first time updating my knowledge on the latest beacons and search procedures. Modern beacons are amazing!
After their realistic voice-call excavation drills, the students openly discussed what was unclear and how to improve, which was incredibly valuable. The training was laser-focused on shaving off even a single second in rescue time. It was the first time in a long while that I felt the urge to record a video.
Snow Conditions This Time
This time, there was a 60cm layer of fluffy new snow, making it tough to walk. Even compacting it with skis wasn’t enough, and the first layer of blocks we dug out was too crumbly. These weak blocks ended up being a liability in the igloo walls, so we abandoned them and moved to the second layer sooner. Once we hit a good layer, massive tombstone-sized blocks were easy to cut. However, digging too deep meant we couldn’t reach high enough to place the second row of blocks effectively. The key was to start sealing the roof with long blocks as soon as possible. Snow conditions change every time, so adapting to the situation is crucial.
Ski Descent and Student Gear Reality
We skied down from the site. At Shinshu University, mountain skiing is considered an “extra” to regular winter mountaineering with snowshoes, so not everyone owns backcountry skis. Some students carried their alpine skis up. These days, mountain skis are too expensive for students. If you have unused ones, consider donating them!
There was even a rare sight of someone climbing on a splitboard while carrying an 80L Gasherbrum pack?balancing that must have been seriously tough.
The Joy of Down-Mountain Meals
We celebrated our descent with a meal at Donmaru. Then, we had an ice cream showdown at Tsuruya, where each person was allowed up to 151 yen. The fact that everyone played rock-paper-scissors to decide who would pay reminded me so much of Hokkaido University?it was nostalgic.
An Igloo Workshop at Norikura – Organized for the Suzuran Mountain Club
I was asked by a senior member of the Hokkaido University Mountaineering Club to serve as an instructor for an igloo workshop organized by the Suzuran Mountain Club. However, due to scheduling conflicts, I couldn’t make it. Instead, three representatives from the club came to Norikura-dake for an intensive pre-training session. The senior member mentioned that while they had built igloos several times before, it took them about three hours each time. They wanted to learn how to build one in under an hour. So, I taught them the world’s fastest “Igloosky Method.”
The Suzuran Mountain Club has been around for decades. Back in the 1990s, they were very active in mountaineering and backcountry skiing, producing excellent activity reports one after another. I believe they were one of the clubs that pioneered backcountry skiing among social clubs during my generation. I once organized an igloo workshop expedition for Suzuran members I had met through PC communication networks back then. It was a trip that started from Shiratori-yama and ended with skiing down to the Sea of Japan.
One of those members, Mr. Furumoto, later passed away in an accident while climbing a stream on Mt. Zaru.
Reducing the construction time from 3 hours to 1 hour.
As expected, those with prior experience in building igloos picked up the technique quickly. They cut long, neat blocks and finished the igloo in about an hour. The key to speed lies in refining the block-cutting technique. Once the first layer of cubic blocks was completed, they swiftly moved on to cutting longer blocks.
We built a central igloo with space for three people to gather and connected it via tunnels to three smaller personal igloos surrounding it. The senior members planned to stay overnight and aim for the summit tomorrow. As for me, skied down , taking only 20 minutes to descend before catching a bus back to Matsumoto.
The weather was clear, with weak winds and a pleasant atmosphere, but the temperature dropped considerably. By the time I sped downhill on skis, my? body was chilled.
On the way home, I bought tonkatsu and some sake from Niigata.
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