What is the minimum recommended roof pitch for slating?

For moderate exposure, it's 25 degrees; for severe exposure, it's 30 degrees (Table 1).

What kind of nails should be used for fixing slates?

Copper nails or aluminium alloy nails are recommended for durability (Clause 4.3).

How is the batten gauge calculated?

The gauge is calculated as (Length of Slate - Head Lap) / 2. The Head Lap is determined from Table 1 based on roof pitch (Clause 5.4).

Is an underlay required for a slate roof?

Yes, an underlay of roofing felt (conforming to IS 1658) should be laid over the rafters before fixing the battens (Clause 5.2).

IS 5119

: 2000

Code of Practice for Laying and Fixing of Sloped Roof Covering, Part I: Slating

CurrentSpecializedCode of PracticeBIMArchitectural · Building Construction Practices incl. Painting, Varnishing

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This standard provides guidelines for the laying and fixing of natural slates on sloped roofs. It covers materials, roof pitch, lap requirements, fixing methods using nails, and detailing for eaves, ridges, and valleys to ensure a weather-tight finish.

Code of Practice for Laying and Fixing of Sloped Roof Covering, Part I: Slating

Quick Reference Values

Minimum roof pitch (moderate exposure)25 degrees

Minimum head lap for 25° pitch roof80 mm

Minimum side lap50 mm

Recommended nail materialCopper or Aluminium

Typical batten size for 400mm rafter spacing38 mm x 25 mm

Key Formulas

Batten Gauge = (Length of Slate - Head Lap) / 2

Practical Notes

Ensuring correct head lap and side lap is critical for weather-tightness, especially in areas with high rainfall or wind.

Use of non-corroding nails (copper or aluminium) is essential for the longevity of the roof, as steel nails will rust and fail long before the slate.

Proper selection and spacing of battens are crucial to support the weight of the slates and prevent sagging.