8. Appropriate air flow must also be taken into consideration when building a concrete drain with a flat roof. Suitable airflow is essential to avoid dampness buildup, which can lead to injury and deterioration from the roof. อ้างอิง-ภาพ : สำนักงานทรัพยากรน้ำแห่งชาติ Roof drains also are essential first ways in all drainage https://roof-drain29741.isblog.net/detailed-notes-on-ท-อน-ำฝน-48236059