Liquid rubber products have become the most searched flat roof coating solution in South Africa, and the appeal is easy to understand. The marketing is accessible, the price is low, and the DIY application suits a wide range of property owners. However, asset owners managing warehouses, shopping centres, factories and logistics facilities need to understand something important before they commit to a liquid rubber product as their flat roof coating in South Africa. Most of these products are water based acrylic coatings designed for tiled, fibre cement and pitched galvanised roofs. They were never formulated for industrial flat concrete decks. Furthermore, ponding water is the defining condition on every industrial flat roof in the country, and acrylic chemistry simply cannot handle it.
What Liquid Rubber Products Actually Are
Most products sold as liquid rubber in South Africa use water based acrylic resin as their base chemistry. The term rubber refers to the flexibility of the cured film rather than any true rubber or silicone chemistry. These products perform well on the surfaces they were designed for. Pitched roofs shed water quickly, and the coating dries thoroughly between rain events.
However, the moment that same product goes onto an industrial flat concrete deck, the performance conditions change completely. Consequently, the results change too.
The Ponding Problem That Changes Everything
Industrial flat roofs do not drain completely. Concrete decks on warehouses and shopping centres develop low spots as the structure settles and deflects under load over time. Water collects in those low spots after every rain event and sits there for hours or days before it evaporates.
In fact, research shows that nearly 70% of flat roof leaks come from ponding water caused by poor drainage and slope design. That statistic alone tells the story of what South African industrial roofs actually face.
Therefore, the coating on an industrial flat roof spends a significant portion of its life partially submerged. Acrylic based coatings are not designed for continuous water immersion. Water penetrates the acrylic film through osmosis over time, softening the resin, weakening adhesion and causing the coating to blister, lift and delaminate from the substrate. This failure does not happen all at once. Instead, it develops gradually and invisibly until the roof starts leaking again, often within two to three years of application.
Additionally, acrylic coatings shrink during cure and continue to shrink and expand with temperature changes throughout their service life. On a large industrial roof, that thermal movement creates stress across the coating film. As a result, cracks develop around penetrations, upstands and drainage outlets, and those cracks provide direct water pathways into the structure below.
Why South Africa’s Climate Makes This Worse
South Africa’s UV radiation levels rank among the highest in the world. The highveld subjects roof coatings to intense solar radiation combined with dramatic daily temperature swings. Acrylic coatings degrade under sustained UV exposure through photodegradation, where the resin breaks down at the molecular level. The coating chalks, loses flexibility and cracks.
Moreover, a large dark industrial roof in Johannesburg can reach surface temperatures above 70 degrees Celsius in summer and drop below 5 degrees on a winter night. Acrylic coatings become brittle in cold conditions and soft in extreme heat. That constant cycling between brittleness and softness accelerates cracking, particularly around flashings, penetrations and parapet junctions where movement concentrates.
Coastal industrial buildings in KwaZulu-Natal and the Western Cape face a further challenge. High humidity combined with salt air penetrates acrylic films faster than inland environments, shortening an already limited service life.
What SI-COAT 461 Does Differently
SI-COAT 461 is a 100% silicone roof coating manufactured by CSL Silicones. It uses moisture cure RTV silicone chemistry, and the cured film behaves in a fundamentally different way from any acrylic or polyurethane product on the market.
Silicone is hydrophobic at the molecular level. Water does not penetrate a cured silicone film through osmosis because the silicone polymer chain does not absorb water. Therefore, a silicone coating sitting under ponded water does not soften, does not lose adhesion and does not blister. The ponding problem that destroys acrylic coatings does not affect silicone chemistry.
Furthermore, silicone cures by reacting with atmospheric moisture rather than by water evaporation. This means it continues to cure even when the surface is damp, which matters greatly in South Africa’s summer rainfall regions where applying a coating between rain events is a practical challenge.
Silicone and UV Stability
Silicone chemistry is inherently UV stable. The silicon oxygen backbone of the polymer does not respond to UV radiation the way carbon based organic polymers do. As a result, a silicone roof coating applied in Johannesburg, Durban or Cape Town maintains its flexibility, adhesion and waterproofing performance year after year without the photodegradation that limits the service life of acrylic products.
In addition, silicone remains flexible across the entire temperature range that South African industrial roofs experience. It does not become brittle in winter or soft in summer heat. Consequently, it holds its integrity around penetrations, upstands and flashings where acrylic systems consistently fail first.
The Cost of Getting This Wrong
Water ingress into a warehouse damages stock, equipment and racking systems. In a food production facility, a roof leak can trigger a hygiene shutdown and product recall. In a shopping centre, it causes tenant complaints, lease disputes and brand damage.
Furthermore, the cost of recoating after an acrylic failure is not simply the cost of the new coating. The failed system typically needs removal or encapsulation before a new coating can go on. That adds time, cost and disruption to what should have been a straightforward maintenance project.
A silicone roof coating applied correctly from the start avoids this cycle entirely. Moreover, because silicone is chemically inert, it does not interact with most existing roof surfaces and applies over many substrates without the compatibility testing that some systems require.
SI-COAT 461 Application Summary for Industrial Flat Roofs
Substrate: concrete, screed, existing waterproof membranes, metal roof sheeting, polyurethane foam. Surface preparation: clean, dry and structurally sound surface free of loose material. Application method: brush, roller or airless spray. System: single coat or two coat depending on substrate and required film thickness. Cure: moisture cure RTV at ambient temperature. Ponding resistance: permanent, silicone does not absorb water. UV stability: excellent, silicone chemistry does not photodegrade. Thermal range: remains flexible from below zero to above 150 degrees Celsius. Service environments: industrial, commercial, coastal, highveld, high UV.
Frequently Asked Questions
Are liquid rubber products suitable for warehouses and shopping centre flat roofs in South Africa?
Most liquid rubber products sold in South Africa use water based acrylic chemistry and are designed for tiled, fibre cement and pitched galvanised roofs. Industrial flat roofs accumulate standing water after rain events, and acrylic coatings deteriorate under sustained water immersion through osmosis, leading to blistering, delamination and coating failure. For industrial flat roofs, a 100% silicone coating such as SI-COAT 461 provides the correct chemistry for the environment.
What is the best flat roof coating for industrial buildings in South Africa?
The most appropriate flat roof coating for industrial buildings in South Africa is a 100% silicone system. Silicone does not absorb water, does not photodegrade under UV radiation and remains flexible across the full temperature range that South African roofs experience. These properties make it specifically suited to the demanding conditions on large flat concrete roofs where acrylic and polyurethane systems consistently underperform.
Why does my roof coating keep failing after a few years?
The most common cause of premature coating failure on industrial flat roofs is ponding water. Acrylic films absorb moisture over time, which weakens the resin and causes adhesion loss, blistering and delamination. UV degradation and thermal cycling on large industrial roofs accelerate cracking in acrylic systems. Switching to a silicone based coating eliminates all three failure mechanisms.
How long does a silicone roof coating last in South Africa?
On a correctly prepared substrate, SI-COAT 461 silicone roof coating provides a service life significantly longer than acrylic or polyurethane alternatives. The silicone chemistry does not degrade under UV exposure, does not crack under thermal cycling and does not blister under ponding water. In South African conditions this translates to a coating that maintains its waterproofing performance across multiple maintenance cycles rather than requiring recoating every two to three years.
Can SI-COAT 461 go over an existing failed coating?
In many cases, yes. Provided the existing coating has adequate adhesion to the substrate and the surface is clean and structurally sound, SI-COAT 461 applies as an overcoat. Areas of active delamination or blistering should be removed and the substrate prepared correctly before application. The chemical inertness of silicone means it does not react adversely with most existing coating systems.
Does silicone roof coating work in South Africa’s coastal environments?
Yes. Silicone resists salt air, humidity and the marine environment without degrading. It does not hydrolyse in high moisture conditions. Coastal industrial and commercial buildings in KwaZulu-Natal and the Western Cape that experience high humidity combined with high UV radiation benefit significantly from silicone chemistry compared to organic coating systems that deteriorate rapidly in the same conditions.
What causes ponding water on industrial flat roofs in South Africa?
Ponding water develops on industrial flat roofs because concrete decks settle and deflect under load over time, creating low spots where drainage cannot remove all standing water. Nearly 70% of flat roof leaks in South Africa trace back to ponding water. The coating system chosen for an industrial flat roof must therefore tolerate continuous water immersion, which eliminates most acrylic based products from consideration.
Conclusion
Liquid rubber products dominate the search results and the hardware store shelves across South Africa. However, they were not designed for industrial flat roofs. The ponding water that is a permanent feature of warehouse, factory and shopping centre roofs is precisely the condition that acrylic based coatings cannot handle.
SI-COAT 461 silicone roof coating addresses the actual conditions on South African industrial flat roofs. It does not absorb water. It does not photodegrade. It does not crack under thermal cycling. Moreover, it does not require stripping and replacement every few years when the system fails again.
For asset owners, facilities managers and roofing contractors working on industrial and commercial buildings across South Africa, the flat roof coating decision comes down to one question. Do you want a product designed for a domestic pitched roof, or one built for the environment your roof actually operates in?
To find out more about SI-COAT 461 for industrial flat roofs in South Africa, contact Technical Solution Supplies.