Specifications for Lapa’s constructed by Style & Craft
General specification instructions

  • Uprights 150-200mm. (max span 3m apart)
  • Ring Beam 100-125mm.
  • King Post 100-125mm.(always bolted to tie beam and ridge collar)
  • Ridge Collar 100mm (always bolted to rafters)
  • Tie Beam 125mm (always bolted to rafters)
  • Rafters 75-100mm.
  • Battens / Laths 25mm.
  • Cape Reed is used as a “spray” (25mm) unless otherwise specified.
  • Total thatch thickness including Cape Reed 150-200mm.
  • All poles to be varnished / treated with 1 coat.
  • Bolts must be used at the main stress points (main tie beam, collar ties, scissor braces, ceiling joints etc.)
    • Site Positioning
    The layout should comply with the regulations of the local municipality (see SANS 10400), as regards building line restrictions and combustible material
    Roof Construction
  • All carpentry work must be neat and finished off to a high standard.
  • Roof construction must slope at 45 degrees with a min slope of 35degrees over windows etc.
  • Cracked and split pole ends within a distance of one pole diameter of a bolt location are not permitted and such poles shall be replaced.
  • Trusses must be spaced at a max of 700-800mm apart.
  • Any pole used longer than 9 m must be thicker than the prescribed 75-100mm.
  • In a span of less than 10m, all road points must be fastened with 12mm bolts, and with 16mm bolts on larger structures.
  • Anti-split plates of the correct size must be affixed to all sawn off pole ends (must cover 35% of the surface area of the end).
  • There must be a minimum spacing of 150mm between the first and last three laths, and 300mm between the remainder. The laths must be secured with 75-100mm nails to every truss.
  • All joints in rafters and trusses are spiked with 150mm to 200mm wire nails and bolted at the main stress points. Nails must not be used in joints in primary load-bearing members such as in top chords or bottom chords or webs except if used together with other connectors.
  • To prevent the thatch sliding down at the eaves level and to increase the tension of the stitching, it is recommended that a larger diameter bottom lath (tilting lath) be used to lift the thatch.
    • Grass
  • Grass must be cleaned of excess leaves and seeds, and the ends must be free of loose material.
  • Grass must preferably be yellow in colour.
  • A standard bundle of grass should have a diameter of 125mm and a circumference of 400mm.
  • Grass should have a cut length of not less than 0.8m, with a min diameter of 1.2mm and a max diameter of 2.5mm at the butt end.
  • Cape Reed should have a min cutting length of 1.2m, with ends ranging from 1.2 to 4 mm in diameter.
  • If no spray layer is used, it is recommended that ordinary clean (free of leaves) thatching grass be used as a bottom layer to create a neat surface on the inside of the roof.
  • Thatching grass must be attached to the laths with a treated sisal binding twine.
    • Ridges
  • Where the fibreglass ridging joins it should overlap a min of 75mm.
  • The area where the ridging is joined shall be sanded lightly to assist with bonding.
  • Resin shall be applied to the joining area and a layer of chopped strand matt shall be placed over the resin. A second layer of resin shall be applied to the chopped strand matt.
  • All ridging should be covered with an acrylic based waterproof paint and this paint shall be re-applied to the areas which have been joined. If the join is still visible it can be sanded and the water based acrylic paint can be re-applied.
  • Fiberglass, make sure that the roof is watertight.
  • Grass must be thatched and secured to at least the last two laths on the ridge.
    • Thatching
  • Spray layer ends must be tucked in behind laths and must not be visible.
  • Thatching must have a min thickness of 175mm at a min of 35kg/m2, which represents approximately 50 bundles of grass per m2.
  • Grass must be thoroughly compacted and layered. No loose grass or loosely layered grass is permissible.
  • Thatch twine must be tightly fastened, no further than 100mm apart as it is stitched around the laths, with no loops allowed.
  • Roof must be level and smoothly finished, layers in the thatching must not be visible. No bumps or dents are allowed.
  • No loose leaves or grass stems must be visible.
  • The overhang of the thatch projecting over the last lath must not exceed 300mm.
  • The kick battens must be 30-50mm thicker than the rest of the laths.
    • Bolts
  • Bolts differ from 12mm to 24mm in diameter depending on the size of the roof.
  • All the roof-timber joints of structural importance must be securely bolted together.
    • Building
  • Chimney stacks should be constructed in such a way that the outer faces in contact with the thatch do not become hot. A full brick thickness (9” double brick / 220mm) is normally sufficient.
  • No timber must penetrate the chimney or be closer than 200mm from the inside of the flue.
  • All mortar joints in the chimney must be properly filled.
  • The top of the chimney must extend to at least 1m (12 courses) above the highest point of the roof.
  • Install a spark arrestor, consisting of a piece of stainless steel wire mesh, fitted 700mm from the top, covering the full width of the flue.
    • Fire Safety
  • Thatches less than 20m2 must not be erected closer than 500mm (1/2m) from any boundary wall. (SANS 10400)
  • Thatches bigger than 20m2 shall not be erected closer than 4.5m from any boundary and 9m from another building unless designed and prepared by a competent person. (SANS 10400)
  • Thatch roofs must be treated with a fire-retardant system. This is the clients responsibility and a separate contractor specializing in fire proofing should be contracted.
  • Consider fire protection irrespective of size if the lapa is near an open stand, house or boundary wall.
  • If a lapa is built close to a boundary, it is advisable to construct a boundary wall, the top of which should extend at least 300mm higher than the bottom line of the lapa roof.
    • Thatch roofs covering a roof-plan area of less than 20m2
    According to the National Building Regulations, Part T, Clause TT 12.3, thatched lapas with a roof plan of less than 20m2 are regarded as non-combustible and, as such, will not have an effect on the determination of boundary distances. However, exceptions can occur.
    Thatch roofs covering a floor plan area of more than 20m2
    According to the National Building Regulation T1 subparagraph (2); if a thatched lapa with a roof plan area in excess of 20m2 is erected within 4.5m of any boundary or where the safety distance between the lapa and an existing house is insufficient, then such cases should form the subject of rational design. For detail on rational design criteria refer to pages 34+35 of ‘A guide to good thatching practice’.
    General
  • At the end of everyday clean up.
  • Remove bent nails.