SANS 10407 Thatched Roof Construction

SANS 10407 is the South African National Standard for the construction of thatched roofs. The edition cited in the 2016 industry guide is edition 2 of 2015. It sits alongside the National Building Regulations, published as SANS 10400, in particular Part L (roofs), Part T (fire protection) and Part V (chimneys). The Thatchers Association of South Africa (TASA) published A Guide to Thatch Construction in South Africa in 2016 to explain good practice; the guide states that it is not itself a specification.

Materials

The guide identifies these South African thatching materials:

• Common thatching grass, Hyparrhenia hirta.
• Fine thatching grass, Hyparrhenia filipendula.
• Cape thatching reed, Thamnochortus species (Afrikaans dekriet).

It does not recommend Chondropetalum tectorum or Phragmites australis.

Key figures (TASA guide)

Item	Requirement
Minimum pitch	45 degrees
Finished thickness, grass	175 mm (6.9 in), at least 70 mm (2.8 in) over the sway
Finished thickness, reed	180 mm (7.1 in), at least 80 mm (3.1 in) over the sway
Rafter spacing	Not more than 900 mm (35 in) centres
Truss spacing	Not more than 2.7 m (8.9 ft)
Battens	At least 38 x 38 mm (1.5 x 1.5 in)
Laths	At least 25 mm (1 in) top diameter
Binding spacing	Not more than 110 mm (4.3 in)
Sway wire	Galvanised, at least 3.15 mm (0.12 in)
Chimney height above thatch	At least 1 m (3.3 ft)

Valley liners must be at least 0.4 mm copper, 0.5 mm galvanised steel or 0.7 mm aluminium. A 50 mm (2 in) gap between laths and ceiling is recommended for ventilation. Below 45 degrees, thatch decays rapidly.

The SANS 10400 guidance site summarises Part L thatch rules as a 45 degree slope (35 degrees at dormers), 175 mm of fine grass or reed, 200 mm (7.9 in) of coarse grass and 300 mm (11.8 in) of water reed, and pole rafters of 100-125 mm (4-5 in) diameter for spans up to 4 m (13 ft).

Fire and lightning

Under clause 4.12.2 of SANS 10400-T, thatched buildings with a roof area over 300 m² (3,230 sq ft), or closer to a boundary than 4.5 m (14.8 ft), need additional fire-retardant systems; small free-standing thatched shelters (lapas) under 20 m² (215 sq ft) must be at least 1.0 m (3.3 ft) from any boundary. Lightning protection to at least protection level III (SANS 62305-3) is required where ground flash density under SANS 10313 exceeds 7, or 3 where wire sways could act as conductors, with masts at least 1,000 mm (39 in) clear of the thatch.