The Ultimate Guide to Waterproofing Concrete House Roofs

Concrete roofs have been an integral part of modern architecture for decades. Although they are typically seen as rooftops for commercial buildings, with changes to styles and architecture for residential buildings, homes are now also being constructed using this roofing method, with concrete shingles also starting to become popular in residential home structures. Even though concrete has been chosen as a superior material for both housing and commercial structures, it doesn’t mean that it is not susceptible to damage from the elements.

Waterproofing is one way you can help avoid damage from occurring earlier than anticipated and will inevitably help your concrete roof to last a lot longer. Adding waterproofing to your roof is a great way to protect your building and is well worth the investment.

Take measures to prevent concrete cancer

Concrete cancer can be devastating, but what causes it? The term itself is a bit of a catch all for a variety of problems associated with concrete embedded with steel.

During construction, concrete is reinforced with steel bars or, in some cases, mesh. As a metal, steel can corrode after exposure to the elements, like water or air. Steel that is corroding is forced to expand. This expansion causes the surrounding concrete to crack and even break. Cracking exposes even more of the steel which leads to increased oxidation and further damage to the concrete.

The belief that steel rods won’t come in contact with water because they’re surrounded by concrete is simply wrong. It’s important to understand that concrete is porous, and can absorb water. Also, a failure to adequately waterproof can increase the likelihood of concrete cancer. That’s why it’s essential to take the proper precautions to prevent concrete cancer. In situations that demand remediation, there are also things you can do.

The phases of concrete cancer

According to the Australian Concrete Repair Association (ACRA) there are four stages of concrete cancer progression. In general terms, the cost to fix concrete cancers multiples by roughly five through each stage of the cancer’s progression in the concrete. This is sometimes referred to as the ‘Law of Fives’.

  1. Design, construction and curing of concrete
  2. Corrosion has initiated, but damage propagation hasn’t started.
  3. Deterioration begins to propagate through the concrete.
  4. Advanced propagation concrete cancer and significant damage.

By the fourth stage, a complete knock down of the structure might be the only solution. So remember to act early and if you think your premises has concrete cancer.

Concrete cancer assessment

In circumstances where concrete cancer is potentially affecting your structure, it’s best to call a professional. The first step in preventing or repairing concrete cancer is to have the structure analysed by a specialist. From here, recommendations can be made for remediation of the structure and ongoing prevention. In most cases, if you act early enough, the structure won’t need to be knocked down.

Choosing the proper sealer for your concrete

All exposed concrete should be protected with a sealer. A failure to use the right sealer, or to properly apply the sealer, increases the risk of concrete cancer to your structure, leading to expensive maintenance, repairs and replacements down the track. Sealers protect from moisture and prevent the build up of mould and fungus on the concrete.

How long should a sealer last?

A good concrete sealer will last around five years before reapplication is required. Resealing should be completed as regularly scheduled maintenance works and prioritized to prevent damage.

How does concrete sealer work?

When waterproofing concrete, a topical sealer is applied to the surface of the concrete. The sealer is impermeable (provided it is applied correctly) and forms a waterproof membrane around the concrete, preventing moisture from entering the concrete. Topical sealers can be made from acrylic, epoxy and polyurethane based materials. Many are decorative in colour and style.

Are there permanent sealers?

Permanent sealers do exist, though they leave a matte finish and are not available in decorative colours. Permanent sealers work by filling all the tiny holes in the concrete. They are made from silicate, silanes or siliconate and are also referred to as penetrating concrete sealers.

Concrete flat roof construction and issues

It is now more common to see home designs which incorporate a flat roof in order to make it look both appealing and elegant in style. However, proper design of such a roof style is required in order to ensure rainwater is drained away from the roof as soon as possible. ‘Water-ponding’, or the stagnation of water due to rainfall on such roofs, is the leading cause of deterioration of concrete materials in roofing.

Variations in both temperature and moisture levels can lead to differential thermal movement. Combined with the potential acids left by rain that has evaporated, this can lead to the serious deterioration of what should be a stable, concrete roof.

Protecting your roof top

Concert rooftops are exposed to the elements 24/7, so it’s essential that they are properly designed and waterproofed to prevent leaks through the roof. Rooftop leaking can cause ongoing issues in the home. Beyond water damage to the interior, it can also affect electrical components, lighting and insulation. Ideally, you want preventative measures in place from the get-go, but if you think your concrete rooftop could be leaking or letting moisture in, it’s better to take action sooner rather than later.

Roof membrane systems

When looking at ways to waterproof a concrete roof, a waterproofing membrane is considered to be the most important aspect of a roofing system, as it is the key to keeping water out of the building. There are varying types of roof membrane systems on the market, so it’s important to understand the differences in order to choose the right system for you and your construction needs.

Pre-formed sheet membranes

Pre-formed sheet membranes are an excellent choice for waterproofing your roof and there are two versions available in the market. These membranes are supplied as a waterproof sheet and require them to be welded/joined together to form a watertight membrane.

You may find Polyvinyl Chloride (PVC) pre-formed sheet membranes on the market. They are well designed to deal with the pressures of high winds, excessive rainfall and other weather-related stresses including being UV Stable. Some products are also modified to be fire retardant, so they can also provide a good fire rating to help protect your building in case of an emergency.

Wolfin Waterproofing Systems

One such polymeric PVC waterproofing system is the Wolfin sheet membrane system. Wolfin can be laid loosely on the surface or bonded (Wolfin GWSK) and due to its high quality composition, has outstanding properties to enable greater longevity & service against all climates and conditions and are used in new & remedial applications. Wolfin is used on most substrates and areas and is compatible for a number of installations including over bitumen, asphalt, sheet and liquid membranes and is used in critical areas (Over Habitable Spaces) where waterproofing is of the highest importance. This German-manufactured product also has a high tear and puncture resistance, making it one of the most trusted and reliable products on the market to date.

Cosmofin Waterproofing Systems

Cosmofin is known in the industry as being a reliable and long-term product that provides great performance in a number of applications. This product is a PVC waterproof membrane that includes a central glass non-woven inlay. Cosmofin is often used for a wide variety of building structures such as residential, commercial, civil and marine construction projects. It is also used for many applications, not exclusive to rooftops, such as balconies, terraces, retaining walls and planter boxes. With its clean application, and any waste being recyclable, Cosmofin waterproofing systems are also extremely high tear and puncture resistant.

Both Cosmofin and Wolfin products are versatile enough to be used on a number of materials. Not limited to concrete roofs, these products can be utilised to waterproof other building materials including steel, timber, CFC, masonry etc.

Designed to withstand chemicals in domestic and industrial constructions, they’re highly durable, UV stable and in the event it is required, easy to repair.

Waterproofing a concrete roof for safety and longevity

Whether it’s a concrete rooftop that you’re concerned about, or perhaps there are other construction materials you want to ensure are stable and waterproof for years to come, there’s no doubt that investing in superior waterproofing systems is the best way to protect your assets. Not only can you protect your roof from the extreme climates Australia endures, you can also have the peace of mind that you are doing the best that you can to protect your building and constructions from unnecessary damage.

And remember, if you’re having any other water problems in the home it’s best to consult with a plumber before taking action.

Need to waterproof the concrete in your home? It’s time to talk to Projex

Water damage to concrete in your home can lead to expensive consequences down the line. Why delay, when a solution could be as easy as contacting the experts. With extensive experience in waterproofing commercial, industrial and residential builds, Projex is ready to help you. Contact Projex today.