Why Using Liquid Rubber Roof Paints/Waterproofing To Paint Your Roof is a Bad Idea!

Many of the newer “rubberised” roof paints and waterproofing liquid rubber systems on the market sound impressive in marketing, but in real-world applications they often create more problems than they solve, especially in the South African climate.

One of the biggest concerns is that many of these liquid rubber products are still relatively new to the industry and simply have not stood the test of time yet. A product sounding innovative does not automatically mean it will perform over:

• 5 years,
• 10 years,
• or 15 years

under real South African weather conditions.

Many of these systems have only been on the market for a short period of time, meaning there is often limited long-term performance history available regarding:

• UV resistance,
• ponding water resistance,
• adhesion longevity,
• elasticity retention,
• and movement performance.

This is extremely important on sectional title complexes, commercial buildings, and flat concrete roofs where waterproofing failure can become very costly.

Another major issue is that many rubber coatings trap moisture instead of allowing the roof structure to breathe properly. If there is already:

• damp,
• trapped moisture,
• porous concrete,
• hairline cracking,
• or failed waterproofing underneath,

the rubber coating seals the moisture in.

Over time this often leads to:

• bubbling,
• blistering,
• peeling,
• delamination,
• and coating failure.

Concrete roofs especially can build up moisture vapor pressure beneath the coating, eventually pushing the membrane off the substrate. Many roofs look good for the first few months after application, but then begin failing once heat, UV exposure, and trapped moisture start affecting the coating system. A further problem in the industry is that many roof leaks are not actually caused by failed paint systems in the first place.

Most leaks are caused by:

• • structural movement,
  • expansion joint movement,
  • failed flashings,
  • ponding water,
  • cracked parapet walls,
  • failed detailing,
  • poor falls,
  • rusted roof screws,
  • or deteriorated waterproofing systems.

 

 

Rubberized paints often temporarily hide these issues instead of resolving the actual waterproofing defects. This is why many roofs:

• stop leaking briefly,
• then begin leaking again shortly afterwards.

In many cases, the coating simply acts as a cosmetic band-aid over an underlying structural or waterproofing problem. Although many rubber coatings advertise “high flexibility,” buildings constantly move due to:

• heat expansion,
• cooling contraction,
• settlement,
• vibration,
• and structural movement.

Over time, prolonged UV exposure and extreme roof temperatures can cause many liquid rubber coatings to:

• harden,
• lose elasticity,
• become brittle,
• or tear at stress points.

Once elasticity is reduced, cracks reopen and water begins tracking underneath the membrane again. South African roofs are subjected to extremely harsh UV conditions, especially flat concrete roofs and metal roofing systems. Another major concern is ponding water. Many rubberized waterproofing systems do not perform well under permanent standing water conditions.

Flat roofs commonly suffer from:

• blocked outlets,
• poor drainage,
• inadequate falls,
• or low spots where water accumulates.

Over time ponding water:

• weakens adhesion,
• accelerates UV degradation,
• causes swelling,
• and deteriorates the coating system prematurely.

This is one of the main reasons many liquid rubber systems fail far earlier than expected. The industry also has a growing problem with misleading marketing.

Many liquid rubber products are promoted using phrases such as:

• “paint directly over leaks,”
• “instant waterproofing,”
• “one coat solution,”
• “paint over old waterproofing,”
• or “10-year fix.”

Real waterproofing does not work that way. Proper waterproofing generally requires:

• substrate preparation,
• crack routing,
• joint treatment,
• reinforcement membranes,
• primers,
• detailing work,
• correct film thickness,
• and proper application procedures.

Most failures occur because contractors skip preparation and rely purely on the product’s marketing claims. Film build thickness is another serious issue. Many contractors apply rubber coatings too thinly or unevenly. The roof may visually appear waterproofed while not meeting the required dry film thickness for long-term protection.

This allows:

• UV penetration,
• weak membrane performance,
• and premature waterproofing failure.

This is why properly specified systems from manufacturers such as Dulux often include strict film thickness requirements, specifications, and inspection procedures. Clients and body corporates also need to understand that not all rubberized waterproofing products on the market have been independently tested to recognized standards.

Before selecting a waterproofing system, clients should request:

• technical data sheets,
• independent laboratory testing,
• application specifications,
• maintenance requirements,
• warranty terms,
• and proof of compliance with relevant standards.

Where applicable, clients should specifically ask whether the liquid rubber system complies with relevant South African Bureau of Standards (SABS/SANS) requirements or internationally recognized testing standards.

A major concern in the industry is that some products are marketed aggressively with:

• “lifetime guarantees,”
• “miracle waterproofing claims,”
• or extended warranty promises,

without sufficient long-term real-world performance history behind them. Waterproofing systems should never be selected purely on marketing claims or price alone.

The correct approach is to assess:

• the roof structure,
• substrate condition,
• drainage,
• movement,
• existing waterproofing failures,
• compatibility of systems,
• long-term track record,
• and testing/compliance documentation.

It is also important to understand that roof paint and waterproofing are not the same thing. Roof paint is primarily designed to:

• protect surfaces,
• improve appearance,
• and provide UV resistance.

Waterproofing is designed to:

• stop water ingress,
• accommodate movement,
• and seal critical junctions and detailing areas.

A properly specified waterproofing system with correct preparation, detailing, reinforcement, and maintenance will often outperform many of the newer “miracle” rubber coating systems currently being pushed into the market.