発寒の家Ⅲ 構造確認

 5/15（月）は二階の床組みを見上げながら飛栄建設さんと問題点の整理を行った「発寒の家Ⅲ」。一般的に昭和の家は現在から見れば構造的には決して強くありません。理由は手抜き云々とは関係なく当時はそれが技術的な標準だったからです。よく昔の仕事を指して現在の観点で批判ばかりする人がいますが当時の実情を充分理解しておらず的外れな場合も多いです。事実、今回は壁や天井の断熱も充分な量がありましたし、羽子板ボルトや梁受け金物等々金物も積極的に使われています。その一方で性能向上を目的とした改修ですから当時の標準を現在のものに引き上げることが目的です。そんな視点で現在の改修ポイントを探って行くと・・

On May 15th (Monday), we looked up at the second-floor flooring and sorted out the problems with Hiei Construction at ``Hasamu House III.'' Generally speaking, Showa-era houses are not structurally strong from today's perspective. The reason has nothing to do with cutting corners, it's because it was the technical standard at the time. People often point to old work and criticize it from a current perspective, but they often miss the point because they don't fully understand the reality of the time. In fact, this time we had a sufficient amount of insulation for the walls and ceiling, and we also actively used hardware such as battledore bolts and beam support hardware. On the other hand, since it is a modification aimed at improving performance, the purpose is to raise the standard at the time to the current one. If we explore the current improvement points from that perspective...

１本の梁に過大な負担が掛かっている。柱が大梁を受けていないために結果的に下に梁を追加して構造が成立。既存の根太が邪魔で室内側から防湿シートが通せない。外部から合板を張りたいが既存の間柱幅が狭すぎる等々・・・もうお分かりと思いますが、２階の床梁の上には二階の柱が、その上には小屋梁がその上には束＆母屋＆屋根垂木が載っている。安易に２階梁を撤去すればそれが支えていた上部構造も崩れるために撤去自体が難しく、構造に関しては補強法と歪み矯正が主な論点となります。もちろん断熱気密と矛盾することなく構造系を解決しないと後から非常に困るので頭をフル回転させて考えます。

Excessive load is placed on one beam. Since the pillars were not supported by the main beams, the structure was completed by adding beams underneath. The existing joists are in the way, making it impossible to pass the moisture-proof sheet through from the indoor side. I want to install plywood from the outside, but the width of the existing studs is too narrow... As you may have guessed, the second floor pillars are on top of the second floor floor beams, and the shed beams are on top of them. It has bundles & purlins & roof rafters on it. If the second-floor beams are removed too easily, the superstructure they support will also collapse, making removal itself difficult, and the main points of discussion regarding the structure are reinforcement methods and distortion correction. Of course, if we don't solve the structural system without contradicting the insulation and airtightness, we will be in trouble later, so we have to think about it with all our might.

注：今回は隣地が近すぎて外張り断熱＆外張り防湿シートが使えません。なので防湿は室内から・・

あらためて在来工法は間取り≒構造だなと感じます。それに配置・・隣地間距離が後の性能向上改修には特に大切。

Note: This time, the neighboring land is too close to use external insulation and moisture-proof sheets. So moisture proofing starts indoors...

Once again, I feel that with conventional construction methods, the floor plan ≒ structure. Additionally, the placement and distance between adjacent properties is especially important for later performance improvement renovations.

元々、梁成270ｍｍの梁に下から□105を追加補強している風に見えるが、お互いしっかり一体接合されていないのでほぼ効いていない状態。そこにスパン2.7ｍと3.6ｍの大梁が東西から掛かっている。本当は梁を全て架け替えたいところだが・・二階が落ちてしまうので補強法を考えます。

It looks like the 270mm beam was originally reinforced with □105 from below, but it is not really effective because they are not firmly connected to each other. Large beams with spans of 2.7m and 3.6m hang from the east and west. Actually, I would like to replace all the beams, but the second floor will fall down, so I will think about reinforcement methods.

手刻みの際に明らかに梁長さを短く誤ってしまった。その結果下の梁でなんとか構造的に成立させている。

When I carved it by hand, I obviously made a mistake in setting the beam length too short. As a result, we managed to make it structurally viable using the beams at the bottom.

構造補強と断熱化をいかに矛盾なく解決するかが論点。隣地間距離に余裕がなく、隣地側に壁厚が増す外張り断熱気密は限定的にしか使えない。

The issue is how to resolve structural reinforcement and insulation without contradiction. There is not enough distance between adjacent properties, and external insulation and air sealing, which increases wall thickness on the adjacent property, can only be used to a limited extent.