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Commentary on standards for stairs in detached houses in the Building Standards Law (Japan)

Hello it is Yamaken.

This article introduces the rules of “stairs” for a detached house for those looking to build a detached house.

First, the width of the stairs and tread of stairs are stipulated in the Building Standards Law. If individual design freely, stairs that are extreme and may not be secure can be created possibility, so they are stipulated by law.

Outline of staircase standards for houses

In the case of a house, standards such as the width of stairs and landings, the height of tread, treads, and the location of landings are specified.

Stair type Width of stairs and landing


Tread/Going/Run Stairs landing Step width of stairs landing
Detached house 75㎝ or more (outdoor stairs: width 60cm or more) 23㎝ or less 15㎝ or more Every 4m or less in height 120㎝ or more

About the installation of handrails

Handrails must be installed on the stairs (not applicable for stairs less than 1m in height)

>> By the way, as the handrail installation compulsory is from the Building Standards Law enforcement order enforced on June 1, 2000, some houses before this may have no railings. (In that case, it doesn’t violate the law, but it needs to be improved in the future)

Side walls need to be installed on both sides of stairs and landings (excluding the side with handrails)

Is the handrail height on the stairs more than 1.1m?

It is a common question, but it is a misunderstanding about the standard of handrail height.

No conclusion required (however, generally installed around 750㎜)
>> The wording “1.1 m” is stated in Article 126 of the Enforcement Ordinance, but this only applies to buildings to which Section 2, Chapter 5 applies (In the case of a house, it is a building with more than three stories or a building without a window for lighting.). Furthermore, since the wording “stairs” does not appear, there is no clear basis for setting the handrails of stairs to be 1.1 m or more.

>> However, as stipulated in Article 126 of the Cabinet Order, “balconies and other similar structures”, it is desirable to provide handrails of 1.1m or more for staircases facing stairwells to prevent falls.

[Article 126, Paragraph 1 of the Order for Enforcement of the Building Standards Law] Handrails, fences or wire mesh with a required height of at least 1.1m must be installed around the rooftop square or balcony on the second floor or higher.


How was the article? This time, I explained the steps of the house. thank you for reading it until the very end. I hope it helps.٩( ‘ω’ )و

【資格】一級建築士、一級建築基準適合判定資格者、宅建士など 【実績・現在】元国と地方自治の役人:建築行政・都市計画行政・公共交通行政・まちづくりなどを10年以上経験 / 現在は、地元でまちづくり会社を運営し、都市に関わるコンサルタントや住宅設計、執筆活動を行っています。