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Restrictions on Roof Structure in Japan


What is a Non flammable Roof Area (building standard Law 22. Areas)?

I will explain what is Article 22 area in the Building Standards Law Of Japan.

Hello! My name is Yamaken.

Read this article.
Then you will be able to understand the definition of “building” in Japan.

Now, let me explain.

First, what is Section 22 of the Law?

The conclusion of Article 22 of the Building Standards Law is as follows.

“Make the roof of the building Non flammable material.”

[Points of Roof Non flammable Areas under the Building Standards Law]

○The structure of the roof of a building in a district designated in an urban(downtown) area shall be as follows

・ Comply with the technical standards specified by Cabinet Order, corresponding to the classification of the structure and usage of buildings, with regard to the performance required for roofs in order to prevent the occurrence of fires of buildings caused by sparks in the event of an ordinary fire.
・ Those using the structural method specified by the Minister. It shall also be certified by the Minister.

As a general rule, roofs must be made of Non flammable materials (Non flammable materials such as tile roofs and steel plates).

See what kind of area is designated next.

Article 22. Right holders to designate areas?

The city designates the area after hearing the opinion of the Municipal City Planning Councilsthe.

Basically, it is designated in areas other than Fire prevention districts or quasi-fire prevention districts in City Planning areas.

So, it is not designated outside “the City Planning area”.

What’s the structure of the roof?

The standards must conform to (1) and (2) with some exceptions.

Standards specified by Cabinet Order
⑴ To have a roof which does not generate fumes harmful to fire prevention due to sparks from an ordinary blaze.
⑵ To have a roof which does not cause melting, cracking or any other damage which is harmful to fire prevention and reaches the roof due to sparks generated by an ordinary fire.

*) Exceptions
Some exceptions are cases where only (1) needs to be conformed, such as warehouses for storing non flammable goods. The details are described in the Minister’s Notice (Notification of No. 693 of 2016), but the explanation is omitted in this blog because the explanation becomes complicated.

Summary of this article

I explained what kind of area is Article 22 of the Building Standards Law and what kind of restriction is it.

Basically, you can think of the roof as an area that must be made of non flammable materials.

That’s all for this article. I hope it helps.

Photo by Jonathan Ybema on Unsplash

【資格】1級建築士、建築基準適合判定資格者、宅建士など 【実績・現在】元役人:建築・都市計画・公共交通行政などを10年以上経験 / 現在は、まちづくり会社を運営:建築法規・都市計画コンサル,事業所の立地検討,住宅設計など