Objectives

The primary objective is to restore the structural integrity and weathertightness of a 750 m² roof slab by completely removing deteriorated waterproofing, correcting drainage deficiencies, and installing a durable, professionally finished membrane system. The project aims to eliminate future leakage risks, improve surface reflectivity for thermal efficiency, and extend the service life of the roof structure.

Scope of Work

The contract covers the full lifecycle of roof waterproofing replacement across the designated 750 m² area. Key activities include:

• Stripping and environmentally compliant disposal of the existing failed waterproofing layer.
• Correcting roof falls and outlet alignments to ensure proper water runoff and prevent ponding.
• Surface preparation and priming prior to membrane installation.
• Application of a 4 mm torch-on waterproofing membrane across the entire slab.
• Finishing with two uniform coats of silver (aluminium) reflective paint to protect the membrane and enhance solar reflectance.

Technical Requirements

• Execution strictly within the 750 m² roof slab boundary with minimal disruption to adjacent structures.
• Precise adjustment of roof gradients and outlet positions to meet engineering drainage standards.
• Use of a 4 mm thick bituminous membrane system compatible with torch-application methods.
• Application of exactly two coats of silver/aluminium reflective topcoat, applied according to manufacturer specifications.
• Adherence to occupational health and safety regulations, particularly regarding hot-work procedures and hazardous waste disposal.
• Provision of test patches or mock-ups where required to verify membrane adhesion and paint finish before full-scale application.

Skills Requirements

• Valid CIDB contractor grading of 1SN or higher, demonstrating verified financial capacity and managerial competence for structural projects.
• Proven track record in large-scale roof waterproofing, membrane installation, and surface remediation.
• Certified or experienced personnel skilled in torch-on membrane application, including flame control, overlap sealing, and edge detailing.
• Ability to accurately survey, cut, and regrade roof surfaces to achieve correct falls and outlet integration.
• Competence in applying industrial reflective coatings uniformly without blistering or uneven coverage.
• Strong site supervision and project coordination capabilities to manage sequential phases of stripping, disposal, preparation, and installation.

Explanation of Specialized Terms

Derbigum 4 mm torch-on membrane: A high-performance bituminous waterproofing sheet that requires heating with a controlled propane torch to melt its underside. This activates the adhesive layer, allowing it to fuse permanently to the prepared roof substrate. Torch-on systems demand trained applicators due to fire hazards, precise temperature management, and strict seam-sealing protocols to guarantee watertight integrity.

CIDB 1SN grading: A South African Construction Industry Development Board classification indicating eligibility for structural works up to a contract value of R10 million. The 'SN' suffix specifically denotes structural concrete and masonry works. This grading ensures the contractor maintains minimum financial turnover, owns or leases appropriate plant equipment, and employs qualified technical staff to deliver complex structural and waterproofing projects safely and to specification.