The Truth about Rubber Coatings in the waterproofing industry

The last 4-5 years have seen a marked increase in the promotion and use of so-called ‘rubber’ coatings for waterproofing purposes. These products have been advertised extensively on radio and social media. Rubber coatings are touted as a cure for all roof and waterproofing issues. Popular brands include Eco Rubber, Duraflex, Hydro Rubber, Rubber Duck, Ecoproof, Suparubber, Rubberproof and many many more. 

However the whole ‘rubber’ coatings industry is at the very least, highly questionable for the reasons outlined below:

1. ‘Rubber’ is not rubber. Some superficial website research on any number of companies that manufacture or sell ‘rubber’ coatings will reveal quite clearly that the products are elastomeric acrylic or a similar type of description. Albeit there are a few solvent based ‘rubber’ coatings, but these are mostly vinyl based. The other variant of ‘rubber’ is Bitumen Emulsion which has been available for more than 70 years. 
2. This means that these suppliers and manufacturers are misleadingly claiming that their products are different from the many waterproofing acrylics that have been manufactured by most paint companies for the last 40 years or more which are all styrene or acrylic co-polymer based. 
3. Therefore they have taken an existing type of product and given it a different generic name. This is akin to calling your car a spaceship and pretending that it is something out of the ordinary when in reality it’s commonplace and the same as everyone else has. This has also been done to justify a much higher selling price. 
4. Home owners and unsuspecting ignorant contractors have been duped to believe that waterproofing is simple. Coat your roof with ‘rubber’ and all your problems are over. Unfortunately as will be discussed later, the problems are only just beginning. 
5. Promised guarantees range between 9-13 years depending on the supplier. ‘Rubber’ supply companies are not very forthcoming in actually supplying the warranty terms. 
6. Track records of these products, especially on concrete roofs are almost non-existent. Getting to view a concrete roof of a reasonable size which has been successfully sealed with ‘rubber’ that is more than 5 years old is the equivalent to finding the Holy Grail.

There are many problems that are caused by the use of ‘rubber’ products. Namely:

1. Metal roofs: Very often, the worst thing that can done to a metal roof is to unleash a waterproofing company onto it. This is because a waterproofing companies job is to apply waterproofing! This is not usually the most suitable way to repair a metal roof. This problem has now been compounded by having hundreds of would be entrepreneurs thinking that they have the skill to repair a leaking metal roof because of magic rubber! So what happens is, that they seal all the screws, flashings, ridge cappings, side overlaps and worst of all end overlaps with ‘rubber’ and membrane. This may be effective in the very short term, but very soon the roof starts to leak worse than before. This is because water gets trapped under the waterproofing for the following reasons:
2. Porosity of the membrane from weathering
3. Insufficient top coats during the initial application 
4. Cracking of the membrane due to thermal movement of the sheeting

Poor workmanship with the membrane not following the contour of the sheeting and creating gaps and holes. This will cause worse ingress through the roof than what was intended to fix in the first place. What’s more, after a few years, rust starts occurring under the waterproofing layer. This will require a partial and in severe cases full replacement of the sheeting. 

1. Tiled roofs: This is another situation where well meaning but ignorant rubber applicator ‘repair’ a tiled roof by using a ‘rubber’ coating. The causes of a leaking tiled roof are varied. But the most common in order, includes broken tiles, blocked valleys, cracked ridge cappings and faulty flashings. Smearing a ‘rubber’ coating very thick over tiles to seal all the joints and holes is destroying the roof. Once the tiles become glued together because of congestion by a coating, this once again causes water to get trapped under the paint layer, blocking escape of water, which has nowhere to run out and then penetrates on the inside. The thicker a ‘rubber’ coating is applied to a tiled roof, the more it will eventually leak. 
2. Concrete roofs: The most commonly used method of waterproofing of concrete roofs is torch on. This usually comprises of a 4mm thick modified bitumen sheeting which is applied to the substrate by heating the underside with with a gas burner. However competent torch on installers are hard to come by and as a consequence the cost of labour is higher as well. Application of a rubber coating to a roof which is paintable by unskilled labour now opens the doors of accessibility to anyone that has brushes, rollers and a ladder! Admittedly, torch on waterproofing is not infallible, mainly due to cheap and inferior quality of material, poor workmanship and lack of maintenance. However it is still currently the best waterproofing method available. The hero ‘rubber’ applicator now strips off the 4mm thick sheeting and replaces it with a paint on coating which is at best 0,25mm thick (16 x thinner). This is now somehow going to perform better! Within a few months, cracks in the screed cause the coating to crack as well and water penetration inevitably occurs. The contractor is surprised, because they thought it was highly flexible and elastic and then contacts the ‘rubber’ supplier. The ‘rubber’ supplier says that the surfaces weren’t properly prepared, the coating wasn’t applied thick enough and anyhow, it isn’t guaranteed against cracking of the substrate. Therefore, it’s not their problem. The contractor is unlikely to go back and repair because there simply isn’t a quick fix solution. The unlucky homeowner now sits with the problem whereby their reasonably good waterproofing system was removed which could have been repaired and burdened with leaks and having to fork out double for another company to rewaterproof the roof. The alternative is that the torch on is repaired and the ‘rubber’ is applied over. This gives the ‘rubber’ the credit, when meanwhile the existing torch on layer is doing all the sealing. 
3. Balcony decks: ‘Rubber’ coatings are frequently applied under floor tiles in order to waterproof balcony decks. This product is not suitable for this type of application. First of all, it will not cope with movement of the substrate. Second of all, ‘rubber’ products unless bitumen based do not cope well with continually moist below ground conditions. The coating will therefore will breakdown over a period of time and re-emulsify. 

Other interesting factors about ‘rubber’: 

1. The way ‘rubber’ is advertised is misleading and false. A video will show water leaking into a bucket. The product is then shown being applied to a tiled roof which implies to the homeowner that it seals a tiled roof. This is patently incorrect and as mentioned above will ruin a perfectly good roof. 
2. The claims of its elasticity and elongation are untrue. One product cites a value of 1000% full recovery. In practical application this is completely false. To demonstrate, take a rubber band by each end and stretch it out. The elasticity is impressive. Then put your fingers next to each other in the middle of the band and then stretch it, there is very little elongation at all. This is precisely what happens over a crack. When the coating is fully bonded either side of a fissure it can withstand very little stretch over an extended period of time. 
3. Roof coatings do not require an excessive amount of stretch. After the stretchy rubber coatings have been in the sun for a year or two, they dry out and can become quite brittle in some instances. 
4. When the sales representative shows the customer a cut out sample of the product it is usually 3-4 times thicker than it is generally applied to the roof, giving a false impression as to the actual thickness. Furthermore the sample is usually cut into longer strips. When the product is a little warm from being on the car dashboard or in one’s pocket then it appears very stretchy and flexible. Even an experienced waterproofing contractor could have doubts thinking that this product is the real deal. However the reality is, that once this coating has been on the roof for two or three years in the hot sun, as well as cooling and alternating wet and dry conditions, the plastics in the product leech out. A simple experiment can be undertaken by cutting out a piece of waterproofing which has been on the roof and then trying to stretch it. This will show that there is very little elongation remaining and in fact it actually becomes brittle. 
5. There is no advantage in applying ’rubber’ as a paint coating to a tiled or metal roof. ‘Rubber’ products have a higher resin content and lower pigment concentration. This gives good waterproofing and flexibility properties, but will not be as UV resistant. A roof paint has a lower resin content and higher pigment concentration. This makes it not so waterproof, but long term lifespan and colour fastness against UV is excellent. Manufacturers of paint products always tread a fine line to get the best of both worlds, but there will always be a sacrifice on the one side or the other. 
6. The rubber applicators as well as many of the suppliers come and go. If the product was so brilliant and amazing , why the constant turnover of companies that don’t last? I’m sure many a well meaning entrepreneur has lost their life savings by investing in a rubber waterproofing business. A typical scenario is retirement in one’s sixties with a good pension payout. This is invested into a rubber application business, because it looks simple, easy and foolproof. After a year, the comebacks begin to mount and then the doors close with major loss of financial investment. 
7. Most ‘rubber’ suppliers and applicators typically have no or very little experience in the traditional waterproofing methods. Therefore lack of experience and ignorance would mislead them into thinking that applying a ‘rubber’ coating is an easy solution for all roof and waterproofing problems. 
8. Learning the roofing industry requires years of experience. A spray or brush applied coating to all roof types is very far from being the answer to all the roof and waterproofing problems out there. 
9. Homeowners use ‘rubber’ products in order to save money and as an easy solution to solve problems. It therefore would come as a rude surprise to find that not only are the ‘rubber’ products not successful, but that their roof has been ruined and that repairs are now much more costly and extensive than what was required in the first instance. 
10. ‘Rubber’ products are now starting to lose their shine and grip on the market. The chickens are coming home to roost as comebacks on roofs mount to a level beyond being able to cope and continually coming up with excuses as well dealing with litigation. Some of the big players in the market are on shaky ground legally and financially. One company is in liquidation and another is in a legal battle over product naming rights. Experienced and established contractors have always shunned these products, but the other players in the market are starting to realise that the performance promises and back up are non existent and are turning away from the product. 

Where can ‘rubber’ be used?

In simple terms, it should be used anywhere the standard acrylics are used, together with polyester membrane. 

• Tops of walls
• Parapets
• Tops of chimneys
• Window cills
• Flat roofs
• Flashings 
• Ridge cappings

Hopefully this article will put ‘rubber’ products into perspective and one should be cautious about where and how they are used. Rather stick with tried and tested cementitious, Torch on, cementitious and acrylic products which have a proven track record in South Africa. The old maxim ‘If it sounds to be good to be true, then it is too good to be true’ is very applicable when it comes to rubber products.