Technical Booklet C Site Preparation and Resistance to Contaminants and Moisture·Page 26·5.16
Ventilation pipes and grilles specification
Ventilation pipes must have a minimum diameter of 100 mm, and grilles must prevent vermin entry while allowing free air flow.
Any pipes needed to carry ventilating air should have a diameter of at least 100 mm. Ventilation openings should incorporate suitable grilles which prevent the entry of vermin to the subfloor but do not resist the air flow unduly.
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