How to waterproof terraces, roofs and coverings. Types of systems and materials?

Waterproofing terraces, roofs and coverings

With the arrival of the rains, infiltration problems in houses and buildings increase. If a protection of the rooftop or covering is not properly done, it causes significant damage.

In general, infiltration is due to problems in the waterproofing layer. A quality product must be chosen for the sealing of the covering, both when working on existing structures and in the case of new constructions.

Remember: Waterproofing sealer = Water-repellent material = Prevents leaks or moisture

Before delving further into waterproofing terraces or coverings, it is necessary to know the ways in which water presents itself concerning the building, the possibilities, and paths of penetration.

The attached diagram reflects the forms of rainwater infiltration. An infiltration is rainwater that penetrates the waterproofing (if it exists) and reaches the structure until it finds an escape route.

The “transport” and accumulation of moisture in construction materials and elements are complex phenomena that have components of liquid water and water vapor.

Today we have a lot to learn and how to waterproof a rooftop step by step…

What is the function of waterproofing coverings?

The main function of waterproofing a rooftop, covering, or terrace, is to protect from weather factors. They are water-repellent products used in construction or works whose objective is to prevent and stop the passage of water.

For example, excessive sun, leaks, moisture, rain, proximity to the sea, areas of high external humidity, physical or chemical reactions in industrial buildings, etc.

Undoubtedly, the waterproofing of terraces, roofs, coverings, balcony parapets, etc. are strictly necessary and essential. Doing them correctly depends on the future of a durable construction.

🟧 Note: Remember that we have a detailed article on condensation moisture for the interior of the home.

Waterproofing can and should be vertical or horizontal, in this case, we will talk about those that refer to all types of coverings:

• How to waterproof sloped coverings. With tiles, slates, sheets, etc.
• How to waterproof flat walkable coverings (Terraces with access)
• How to waterproof flat non-walkable coverings

From a project perspective (New Construction) and to situate ourselves in its phases, the different aspects and phases of development in a project are described below:

Remember that protecting terraces with carpentry enclosures (Aluminum, PVC, etc.), if applicable, is important, and for that, we have an extensive article HERE. Or the article on what advantages awnings bring to the home.

What are the moisture problems in a covering?

We cannot protect with any water-repellent product, nor treat a leak or moisture problem on a terrace, rooftop, or covering, if we do not know why that moisture and water dripping originate.

If we focus on the upper part of the building (Covering, rooftop, and terrace). The main origin of moisture in construction is:

From a more technical perspective, we provide the following diagram to clarify the possible causes of moisture and stains on coverings from a more detailed perspective:

Another aspect in the sealing of coverings is understanding what the objective and benefits of that protective membrane we are going to use are.

For this, we need to relate it to the possible problems that may arise in the construction element. We provide a diagram to understand the advantages of waterproofing a covering:

The previous diagram can be expanded from HERE (A new window opens).

Now that we have a clearer understanding of the problems water can cause in a construction, it’s time to learn the possible solutions…

What types of waterproofing systems for coverings are there?

Before starting to install a protection layer on the covering, the waterproofing system to be used must first be defined since each one has its particularities depending on the project or building to be rehabilitated and the selection of the product to be used.

The main systems for waterproofing would be:

It should be remembered that it is not always so easy to install from a technical perspective. So we could also divide them into:

• Simple installation. Can be executed and installed by anyone.
• Medium level installation. Some knowledge and minimum training are required.
• Special installations. Professionals and specialized equipment are required.

But… What are the characteristics of sealers for rooftops? Don’t worry! Keep reading…

What types of waterproofing for coverings and terraces are there?

As we will see now, due to the number of materials and types according to the necessary situation, the market offers us many purchasing possibilities. But don’t worry! We have prepared some diagrams to understand everything and choose the best option for waterproofing terraces.

From a general perspective, we can classify them into:

1.- Asphaltic waterproofing

They belong to a wide range of waterproofing products for the construction and works sector. For example, asphalt sheets, the queens of bituminous waterproofing.

They are manufactured with an asphalt mastic and various bases such as solvents, felt paper, water, felt paper. They can be preformed or liquid, applied cold or hot, on all types of surfaces.

The application of asphaltic waterproofing is with simple techniques, without the need for sophisticated installation means, and low costs, today they make up the largest share of installed surface, compared to other technologies. Classifying them into:

2.- Polymeric waterproofing

Polymeric waterproofing systems are products of natural, synthetic, inorganic, or organic origin. Today they are an important part of waterproofing solutions. They are divided into three large groups:

There are preformed solutions (also known as membranes) and liquid coatings in the form of paint (forming what is known as a “liquid membrane”), in addition to epoxy coatings.

Here the classification extends over different types of membranes such as; PVC membranes, thermoplastic TPO, CSPE (chlorosulfonated polyethylene), TPA (Tri-Polymer Alloy), EPDM membranes, etc. A long list, with particularities for each material.

3.- Mineral-based waterproofing

Those based on minerals are varied and their uses depend on the constructive solution required in work or rehabilitation.

• Cementitious
• Betonic
• Crystallizers

There are waterproofing – for example – composed of Portland cements mixed with silica sand and special chemicals, also others with bentonites that are clays of volcanic origin, or cementitious, to which crystallizer systems are added.

🟧 Note: As a fact, we have an excellent article on green roofs with several useful manuals, in case you’re interested.

What type of sealer – protection to apply, according to the type of covering – rooftop

But… When can I use one protective coating or another? or What is the best coating on rooftops? Although we always have to check the manufacturer’s specifications and professional advice, we will clear up doubts easily.

We have excellent diagrams to recognize the sealing material to use, according to circumstances and type of covering – rooftop of the building or home.

From a perspective of the relationship between the system, type of product, and difficulty in installation on the roof, we would have the following diagram for the waterproofing of rooftops:

Well! We have advanced quite a bit. From what their objectives are, the possible moisture problems, or the types and when we can use them. We just need to know how to install them…

Tips for requesting a waterproofing budget for coverings

Some key points must be considered when requesting a budget to waterproof a covering:

• The asphalt sheet is one of the best solutions available, but also one of the most expensive. It can be placed both on top of the existing one or remove the defective one and add a new one.
• In most renovations, in addition to covering the flat part of the covering, it will be necessary to repair damage to edges, ventilation ducts, or adjoining joints – party walls – with buildings, this will increase the final cost! Keep it in mind.
• In the case of estates, homeowners’ associations, the VAT on applications is 10% (Spain) always ask for an invoice!
• Remember that in most cases a building permit will be required, which will increase the budget, always demand the building permit!

The company that comes to repair our covering must have the relevant building permit

How to waterproof rooftops, terraces, or coverings?

Here we could write three whole books. Instead, we have decided to provide the documentation and key elements to understand how to waterproof a rooftop.

We start with a video on how to correctly place the asphalt sheet, as it is useful for many users who need a “quick fix” and want to practice DIY.

The waterproofing product is used to prevent water from passing to the underlying layers and, generally, must be placed after thermal insulation (which is found after the sloped screed and any vapor barrier) and before the top layer.

They usually appear in the form of cracks or fissures in the layer – membrane, or in the joints between different materials, or in the singular points where stress concentrations occur. They are caused by many reasons that are generally:

• Mechanical (settlements, breaks, cracks).
• Thermal (expansions, slides, thrusts).
• Atmospheric (rain, hail, snow, wind).
• Frosts in combination with infiltrated moisture (causing volume increase and damage).
• UV radiation (degradation effect by UV radiation).
• Chemical (attack by organisms, effect of chemical products).
• Aging of materials (including fatigue from cyclic loading).
• Corrosion of metal roofs.
• Traffic on coverings or non-suitable areas.
• Inadequate interventions, for example, incompatible remodels and modifications.
• Incompatible or inadequate maintenance work.

At the time, we wrote an article on tips for rehabilitating roofs and coverings in homes where we already talked about a series of very interesting manuals with technical details on the construction process of all types of coverings and terraces. They are very very good and with quality information:

Another starting point that will be very useful is to go to a manufacturer specialized in waterproofing and insulation (Coverings, roofs, walls, and floors). We have been looking, and we liked CHOVA.

On their website, they have a specialized section and, apart from finding documentation, we will have the technical detail drawings in Autocad and BIM. So great! Because it can serve us for our projects.

And finally, the best manual currently available online on waterproofing roofs, rooftops, and terraces. And it’s no joke! It’s a compendium of technical recommendations with a quality that surprised us.

It is 81 pages with details of all kinds; from recommendations and tips, uses for each type of protective sheet, advantages and disadvantages of all sealers, and technical placement drawings, even for singular elements.

The manual is from the Chilean Chamber of Construction (CDT – Technological Development Corporation) and can be accessed from HERE in PDF (Due to the size of the document, it takes a while to load)

Maintenance and prevention

Repairing a covering is not cheap and if we have had some water leaks in the building that have affected the homes. The homeowners’ association can be quite expensive.

Preventive maintenance activities are necessary and can be carried out by own staff or an external company. In the case of waterproofing large coverings, it is advisable to hire a company specialized in these tasks to save us from troubles.

As a reminder and what we should do, we leave the following diagram:

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