3.2 – Roof details and joints – 4. Construction of valleys 239 This solution requires a specific arrangement in the substructure and offers greater safety in terms of: • protection against the penetration of stagnant water; • movement space to compensate the thermal expansion of the sheets and sheet metal work valley. Box-shaped valley with a depth ≥ 30 mm for roof cladding with slope ≥ 20° Box-shaped valley with depth ≥ 60 mm ≥ 15* ≥ 100 ≥ 100 ≥ 150 ≥ 150 ≥ 60 ≥ 30 * Movement space to compensate the thermal expansion of the sheets; a value of ≥ 20 mm is necessary with sheet lengths of more than 10 m. 1 2 EXCERPT
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