Prior to commencement, all projects have detailed structural drawings that serve to determine the timber and other material required to complete the project. Waterfront Thatchers will assume that it has been brought to the attention of the owner that the supporting structure for the roof is capable of supporting the roof and has been checked by a competent person for horizontal and vertical forces, on its supports. Prior to the laying of thatch, all roof structures are inspected by a certified engineer. On completion of the project, an engineer’s certificate will be issued for the thatch roof.
The following are general specifications subject to each project:
1. TIMBER STRUCTURE
- The poles used for the structure comply to SANS 457:1994 (SABS 457-3). All poles must be CCA treated and meet the SABS 457 specification for Eucalyptus & Pine wood.
- All timber used for the erection of roof structure are treated in compliance with SANS 1288:1994 (SABS 1288) and SANS 10005:1994 (SABS 05)
- The structure of the roof is built in compliance with SANS 10160 (SABS 0160) and SANS 10163-2 (SABS 0163-2)
- The standard diameter of the poles used in the construction of the roof are as follows; rafters – 100-125mm; ridge 100-125mm, hips & valleys 100-125mm, beams 150-175mm & columns 200-225mm
- All major stress points of pole connections are bolted with galvanised threaded rods, nuts and washers
- All the ends of the poles are to be fitted with anti-split plates (gangnails)
- Laths are laid at 300mm centres, except for the first three rows at the eaves and the last three rows at the ridge where they are laid at 150mm centres.
2. “SPREI” OR CEILING
- Albertinia Cape Reed (Thamnochortus Species) is used or alternatively “Tamboekie” grass can be used to thatch the bottom layer (ceiling)
- The ends of the reed/grass is blocked below the lower edge of the lath
3. THATCH LAYER
- Common or fine thatching grass (Hyperhenia Hirta and Hyparrhenia Phillependula) is used for the thatch layer and must be free of excess seeds and leeves
- Grass must be cut when fully mature and have minimum moisture content. Butt ends to be clean cut and straight
- Thatch layer to be 175-200mm thick
- Thatch layer stitched between laths and 3.15 galvanised wire with tarred sisal twine
- Ridging are cast in cement, with 250 micron plastic, 25mm wire mesh and 50mm x 50mm welded mesh as base
- All cement ridges must be sealed with a waterproofing membrane
- Our patterned cement ridging give a unique detail to our roofs and a perfect finishing touch