Standard Specifications on thatched Roof Structures
Wood
All wood is C.C.A. treated S.A.B.S. approved, eucalyptus.
Pole thickness will vary in accordance to roof structures. Minimum thickness will be
100-125mm diameter, measured at thin end of pole. Lath thickness will vary between 25mm-40mm, measured at thin end of lath. Laths will be spaced at intervals, not exceeding 300mm.
Frame Construction
All poles are bolted together by means of mild steel threaded rods in accordance with load at stress points. Bolts will be fixed with mild steel hexagon nuts and round flat washers. All pole ends will be sanded to prevent sharp corners & splinters. All laths will be drilled prior to nailing to prevent laths from cracking when fixed by wire nails. All tie beam ends will be gang nailed.
Supporting points will be no larger than 3.5 meters apart. All joints on poles will only be bolted and no tongue and groove or any other type of similar joints will be made.
Anti-skid blocks will be inserted on top of beams and walls to prevent rafters from sliding on supporting surfaces. Horizontal load will be eliminated by means of double tie beams or scissor truss designs. All trusses will be designed by Prothatch Namibia for approval by engineer if applicable.
Dual ridge poles will be used in all cases apart from round roofs, on round roofs, no more than four (4) poles will be drilled and fixed to king posts. No poles will be fixed by means of nails to structures. Ridge tie beams will be used on both sides of king posts to support ridge beams.
In all cases, struts will be installed where distances in access of 3.5 meters are exceeded. All eaves will be finished horizontally, to prevent uneven staining of eave thatch.
All supporting king posts will be removed before thatching commences to prevent sudden load on structures.
All roof structures are constructed at 45ยบ pitch or more, but not less, to avoid water penetrating the thatch to such a level that may cause the twine to get wet.
All hips are constructed with dual hip rafters to obtain a solid thatching radius.