All burnt clay bricks demonstrate irreversible expansion after extended exposure to moisture. The extent of the expansion will vary according to brick type. Movement related to irreversible expansion can be accommodated through the insertion of vertical movement joints into horizontal lengths of walling.
SABS 0249 recommends design for potential movement due to moisture expansion, in mm/m:
Category I bricks– 0.5mm/m
Category II bricks – 0.5-1mm/m
Category III bricks – 1-2mm/m
THE BUILDING’S EXPOSURE ZONE
Southern Africa can be divided into four exposure zones, which are defined in SABS 0164 Part 2.
Zone 1 – Protected
All areas 30km or more inland from the coast.
Zone 2 – Moderate
The coastal belt extending up to 30km from the coastline, but excluding the spray zone.
Zone 3 – Severe
Sea spray zone. This includes areas at sea level on the east and north seaward sides of the Durban Bluff and other similarly exposed coastal headland areas.
The 15km coastal zone which extends from Mtunzini to the Mozambique border. This includes Richards Bay and St Lucia.
The coastal belt of Namibia.
Zone 4 – Extremely Severe
Area such as Walvis Bay, where the moisture from sea mist and high ground water tables, high soluble sulphates in the soil, and / or rapid temperature changes, combine to create the most severe exposure and weathering conditions in Southern Africa.
Industrial areas where high acid and or alkali discharges occur.
