(1)
Where a crawl space is unheated, a ground cover shall be provided consisting of not less than
(a)
50 mm of asphalt,
(b)
100 mm of 15 MPa Portland cement concrete,
(c)
Type S roll roofing, or
(d)
0.10 mm polyethylene.
(2)
Joints in sheet-type ground cover required in Sentence (1) shall be lapped not less than 100 mm and weighted down.