Rooftop Waterproofing and Sealing

The best sealing and waterproofing solutions. 

Many talk about roof insulation, but they mean the roof sealing (or else, waterproofing). These are two quite different concepts, equally helpful, but for different occasions. Basically when we want protection from temperature – that means that our house remains cool in the summer and warm in the winter – we need thermal insulation (no roof sealing or waterproofing), while when the problem deals with humidity (water running), then what is possibly required is roof waterproofing.

Do not confuse them and, above all, pay attention to what every craftsman or firm means, when they talk about insulation! The solution to distinguishing the two cases is simple. A thermal insulation without installing a thermal insulating material (Styrofoam) does not exist! So just remember that … Insulation = Polystyrene (Styrofoam)

IMPORTANT:Many times, we have a problem with humidity and we think that the solution is to seal the roof, but sometimes (depending on the causes that generate the humidity) only the thermal insulation will drive away the humidity.

The cases where the roof sealing is not enough, is when the phenomenon of liquefaction is generated (due to condensation). This means that when there is a large temperature difference between the external environment and the interior of the house, due to the temperature difference, vapours are generated. They accumulate in the ceiling, thus they gradually generate moisture. As you can easily understand, it is not to blame the water going on the inside through the roof, but the temperature difference. Therefore only a complete roof insulation will solve your problem.

In case you need something like this, the most effective and at the same time affordable option is the DUROSOL Light Roof lightweight roof insulation and waterproofing. But if your problem is purely a matter of waterproofing, below you will find all the necessary information and appropriate solutions for roof waterproofing.

And how do I know if I eventually need insulation or waterproofing?

To understand when you have insulation problem or a sealing problem, there are 2 to 3 useful tips. It is advisable to be visited by a technician for inspection of the site, but you can have a first impression. For more complete information you can also read the humidity on the wall and mold on the wall sections, where there is an extensive analysis of each case. However, in general, you should know that:

  • If the ceiling has signs of moisture and they are black (blackness), the problem is usually lack of thermal insulation while when they are yellow it may simply be a matter of waterproofing.
  • If there is moisture on the ceiling even when it does not rain on some days, it is almost certain that the problem is not solved with a simple roof sealing, but you will also need insulation.
  • To be even more sure, simply go up to the roof with a hose, thoroughly moisten an area. If, within hours, you see water running on the inside, you may need sealing.


Roof Insulation Systems

Options for Rooftop Waterproofing

Primarily, there are two options for roof waterproofing, felt paper and coating materials. Our company provides both options, but for many reasons we strongly recommend the solution of waterproofing with coating materials, which, as you will see below, have significant advantages. Possibly, other solutions will be proposed to you as well (lightweight concrete, tar, etc.), but the results will be either dubious or null!

Coating materials for roof waterproofing

The brushable sealants are materials that we pread on the roof and which offer waterproofing. Most of them are distinguished by reflective properties as well, assisting in the partial reflection of thermal radiation. Thus contributing, to a degree, in the summer, to not quite raising the temperature, which is based primarily on their colour (usually white), compared with the dark felt papers which are attracting radiation. In no case, however, you should not consider – or to be convinced by anyone – that with the coating materials or any other sealing solution, you will also have thermal insulation.

Useful Information on the spreadable coating materials

In order for the spreadable coating materials to have a good result, two coats should be applied – as appropriate – the consumption for two of these coats to be within 1-1,5kg per square meter. Consumption depends on the type of the brushable coating material, the methods of application and, mainly, the existing surface of your roof (how smooth or rough it is).

The work from a partner crew of ours is around 2-4 € / m² + VAT for the two coats that will be needed, the prices vary depending on the size of the surface and the condition of the roof (if cleaning is necessary).

As for the materials, there are 3 types of spreadable coating materals in the market. Each category is based on a different chemical composition, which ultimately determines the life, the technical specifications and the cost of each material. You will see their prices in detail below, but keep in mind that you will need a primer as well (which costs about 1-1,5 € / m²), unless you choose the silane resin coating materials, which we recommend as the most appropriate solution for roof waterproofing and primer is not required in most cases. Let’s briefly take a look at these three types of spreadable coating materials:


υλικό για στεγανοποίηση ταράτσας This is the simplest waterproofing solution, with low cost and a sufficiently transient effect. From that point on, the surface will begin to flake, which means that the sealing material must be applied again. The cost for acrylic spreadable coating material with an average consumption is around 2,9 € + vat / m², while primer is also necessary, that will ultimately drive up the cost around 4€+vat/m².


polyourethaniko-epaleiptikoThe polyurethane is a middle ground, although several claim that they are ideal. Their life span rarely exceeds 10 years, but after 1-2 summers, the chalking phenomenon will begin to generate, namely friction will produce a chalk-like powder. This over the years becomes more intense and the only way to avoid it is to add an aliphatic polyurethane, however, greatly increasing the cost. Generally the cost of polyurethane is around 3,9 € + vat / m², but with the primer you need, the price will rise to 5€+vat/m².

Silane Resins

epaleifomenostThe roof sealing with silane resin spreadable coating materials is the most effective solution. First, for the application of these surface coatings, no primer is required (where in other solutions raises the cost by 1,5 € / m²), while the life span usually approximates 15 years. It is a material that remains completely unaffected by exposure to sunlight and temperature variations, also, for the FGL-Flex ST, a 10-year warranty is also provided! As for the material cost, it will approximately reach 3,9 € + vat per surface square meter onto which it will be applied.

Therefore as we see above, silane resin spreadable coating materials are superior in all respects to all other options for roof waterproofing. Not only because they have the longest life span, but they are also more beneficial economically, they do not require priming the surface with a primer! Indeed especially the ST spreadable coating material is given by 10-year warranty, is the most suitable for the complete sealing of your roof. The final cost of materials and work for roof waterproofing with brushable ST from one of our partner crews will be at 7-7,5 € / m², plus material vat and work vat.

Here, we should note that if there are capillaries on the roof (cracks), we will also need to put some reinforcement (fibreglass mesh), which will also increase the consumption of the brushable coating materials by approximately 0,5kg / m², in order to box into this fibreglass mesh.

Felt Papers

στεγανοποίηση ταράτσας με ασφαλτόπανοOne option for roof waterproofing which was especially selected routinely a few years ago is waterproofing with felt papers. It is about rolls of asphalt material which is properly armed and which is affixed to the roof with a blowtorch the and relative asphalt glue-varnish. As we shall also see below, however it has several disadvantages compared to the spreadable coating materials, so in recent years it is chosen less and less frequently.



Useful Information on roof waterproofing with felt papers

To make the roof waterproofing with felt paper, the felt paper itself is required, the blowtorch which will be available by the craftsman and bituminous adhesive (bituminous varnish) for the gluing. The consumption of felt paper is about 1.1 square meter of material per surface square meter (calculate a deviation for folding, joints, etc.), while consumption in bituminous varnish is about 0,4-, 0,5Ltr / m².

With regard to the prices of materials, this time we have a good enough felt paper in offer at only 2,99 € + vat / m², while the bituminous glue costs about 1,1 € + vat / m². Thus with just over 4 € + vat / m² the material costs are covered. On the other hand, work costs by one of our partner crews is around 4-4,5 € / m² + vat, so the final cost of materials and work will reach 8-8,5 € / m² plus vat of materials and vat for works.

From that point on there are different types of felt papers, depending on the circumstances in which they need to be applied. Therefore they are distinguished by their weight per square meter, the minimum temperature they can resist to (the maximum ones exceed the normal environmental conditions) and the final surface, whether it will have chippings and what colour this chipping will be.

Eventually, which sealing solution to choose?

We have also mentioned earlier that as a company with over half a century of experience in insulating materials, we recommend roof waterproofing with spreadable coating materials, although we have all the necessary materials available for both options, at very good prices. The reason we prefer the spreadable coating materials is because over the years we have noticed that they have significant advantages compared to the felt papers. Let’s take a more specific look at the advantages and disadvantages of the two options for roof waterproofing:

  • One of the key advantages of roof waterproofing with spreadable coating materials over felt papers is that they have a longer life span, as especially silane resin coating materials will continue to protect you for about 15 years, while the felt paper usually begins to wear quite earlier.
  • Equally important is the difference in cost. A roof sealing with spreadable coating materials is more economical, both for work and for materials. As seen in the above analysis, the silane resin spreadables cost 4 € + vat / m² and the work for their application at 3-3.5 € + vat / m², while the materials for felt papers (felt paper and adhesive) reach € 4 + vat / m² with others at 4-4.5 € + vat / m² per application cost.
  • The spreadable sealants are characterized by a high rate of transpiration, meaning that they let the roof “breathe”. Instead the felt paper acts as a vapour barrier, so that the terrace does not breathe and it is likely to increase the humidity inside the house. Namely, if we choose the felt paper, we may not have the desired effect on the roof sealing.

  • Because the felt paper does not breathe, if for any reason water passes underneath, it will not be able to dry and thus it will create humidity in the ceiling. On the other hand, the spreadables breathe so any water that passes through will quickly dry.

  • Also, if the felt paper undergoes damage and water passes, it requires a great process for the repair. Unlike the spreadables, you simply apply 1-2 coats again locally!

  • The colour of felt papers is always dark (even on a white mosaic, the effect is dark gray), which significantly absorbs more solar radiation and significantly raises the temperature in the house. Namely, they essentially increase the temperature inside the house while the coating materials which have reflective properties also help to maintain more normal temperatures.

Summing up the above we conclude that the roof waterproofing with spreadables has several advantages over the felt papers!

Closing up the section of roof sealing we should point out that in any case neither the spreadables nor the felt paper offer any insulation. If what you want is protection against extreme temperatures and want your house to be cooler in the summer and warmer in the winter, you need roof insulation.