SANS 10400-L is the roofs Part. It covers roof coverings and waterproofing, the drainage and waterproofing of flat roofs, timber roof construction (the empirical truss and rafter rules), and fire resistance. SANS is the South African National Standard, published by the SABS, the South African Bureau of Standards, under the National Building Regulations and Building Standards Act 103 of 1977 (the NBR, or the Act). The brief works from SANS 10400-L:2011 (Edition 3).
A plain caveat first. The pitch figures, truss spans, coating grades and waterproofing rules below come from public summaries of the paywalled SABS SANS 10400-L text and from the gazetted regulations. They are an orientation, not a compliance spec. Confirm the exact current values with your local authority and the SABS SANS 10400-L text before you build or submit plans.
What this Part covers
Part L is the deemed-to-satisfy rule book for roofs. It sets minimum pitches for each covering, says when an undertile membrane is mandatory, sets flat-roof falls and the watertightness guarantee, deals with coastal corrosion of metal sheeting, requires anchoring against wind uplift, and gives empirical spans for timber trusses so a standard pitched roof can be built without an engineer.
Key requirements (plain English)
Keep the caveat in mind: these are orientation figures from public summaries.
Minimum roof pitches. As an orientation, for pitched roofs: corrugated metal or fibreglass profile at 11 degrees with sealed end laps (or 22 degrees without underlay); corrugated fibre-cement sheets at 11 degrees with a 200 mm end lap (or 26 degrees without underlay); fibre-cement slates at 11 degrees (or 17 without underlay); concrete and clay tiles and shingles at 17 degrees (or 26 without underlay); metal tiles at 11 degrees (or 15 without underlay); natural slate on open battens at 20 degrees (or 30 without underlay); and thatch at 45 degrees (35 at dormers). Sheeted roofs in Category 1 buildings without hips and valleys may go as low as 5 degrees if all end laps are sealed with a minimum 250 mm lap, with valley slopes no less than 11 degrees.
Undertile membranes. Mandatory for tiles, slates and shingles where the pitch is under 26 degrees or 45 degrees and over; within the coastal zone (between the coastline and a line 30 km inland, or the first mountain watershed if closer); and where no ceiling is installed. They are recommended in all situations.
Flat-roof fall. At least 1:80 where water flow is not interrupted, and at least 1:50 where there is an interruption such as a change of direction or a precast rib. In concrete, the design slope may need to be 1:50 to leave a finished 1:80 after deflection.
The five-year watertight rule. A flat-roof waterproofing system must stay watertight for at least five years with no maintenance other than cleaning gutters, downpipes and surfaces, and the installer must certify this in writing. Readily replaceable systems should last at least 10 years, and difficult-to-replace systems at least 20 years.
Coastal metal sheeting. Within 5 km of the coast or in aggressive environments, a minimum coating of AZ 150 or Z 275. Elsewhere, a minimum of AZ 100 or Z 200. Sheeting marked not suitable for coastal and aggressive environments may not go up within 5 km of the coast.
Wind anchoring. Every roof assembly must be anchored against wind uplift, with trusses and rafters tied to the supporting walls using galvanized steel straps or wire built into the masonry.
Timber truss empirical rules (Howe-type SA Pine, no snow). As an orientation: double-pitched trusses at a clear span up to 8,0 m; monopitched lean-to trusses up to 4,0 m; pitch of 17,5 to 35 degrees for tiles and slates, or 15 to 30 degrees for metal or fibre-cement sheets and tiles; purlin and rafter beams up to 8,0 m clear span where the pitch is under 26 degrees. Timber must be structurally graded, grade-stamped and treated to the relevant SANS standards. Upstand beams at flat concrete roof edges should be at least 170 mm high with corner fillets of at least 75 mm.
When you need a competent person
The roofing contractor owns pitched-roof compliance (pitch, covering, underlay and anchoring), the waterproofing specialist holds the five-year flat-roof guarantee, and the truss manufacturer must supply engineer-designed truss drawings for any non-empirical truss.
You need a competent person (built environment) or an engineer for flat-roof expansion joints unless the standard twin-kerb upstand joint is used, for any roof outside the Howe-truss empirical limits (spans over 8 m, hip and valley construction, scissor or A-frame trusses that generate horizontal thrust, or snow loading), and for flat roofs on framed buildings above the Category 1 limits.
Common mistakes
- Corrugated IBR sheeting under 11 degrees without sealed end laps, common on outbuilding lean-tos.
- No undertile membrane in a coastal area (within 30 km of the coast), whatever the pitch.
- Flat-roof screed fall under 1:80, where construction inaccuracy leaves ponding.
- No five-year written waterproofing guarantee from the waterproofing contractor.
- Coastal sheeting with only AZ 100 or Z 200 coating, marked unsuitable for the coast but installed within 5 km of it.
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