Rooftop Insulation with the Conventional method

For whichever method you select, the Durosol is the best insulation material. 

The conventional method is the traditional way for the insulation of roofs and is exactly reverse to the inverted one, as the insulating layer enters below the seal. The conventional roof insulation is the most common in our country, with the characteristic of the single and compact different layers that compose it. Indeed, because the seal is located above the insulation, it prevents the flow of water beneath the insulating layer, while it is important that usually the terraces hat are insulated by this method, and provide the possibility of compatibility, where you can walk on them. For this reason, the conventional roof insulation method is predominantly used for sealing the common commercial construction, which almost all have flat roofs or a low slope. However, this method has several disadvantages which you can read about below. For this reason we can not provide a guarantee for the method of conventional roof insulation. If you want guaranteed thermal insulation results with a 10 year warranty check the Durosol Light Roof insulation method here.

Important Information on roof insulation with the conventional method

The topcoat is basically felt paper, for this reason this solution offers you limited compatibility. A target price for the final cost, including all required materials together with the cost of application (work) from any of our partner crews of our company amounts to ≈26 € / m² + VAT. Finally, the weight of the insulation is ≈50 kg / m².

But regarding the conventional method for roof insulation, three are the main steps for their application, below we present the process in more detail, and we have also embedded a video about the application of the conventional roof insulation.

– Initially the surface of the roof is coated with Durosol insulating plates.
– Then flows are created, with lightweight cement.
– While, at the end, the insulation of the roof is completed with waterproofing.

Disadvantages of the conventional method for roof insulation

  • The conventional method is only applicable to flat or small-slope roofs.
  • The layers that compose it should ensure a balance of thermal stress developed due to the different expansion coefficients of the layers of materials, since most of them are exposed to the thermal variations. The main reason we use Durosol is the very low expansion coefficient.
  • Because the sealant layer is the most exposed one to thermal variations and thermal shocks, it typically results in faster aging.
  • The conventional insulation does not offer full compatibility, because the final layer is felt paper.
  • If the felt paper is damaged or when it is worn out with time, the water will pass under the cement mortar and water will appear on the walls. The restoration of the damage is very costly.

Συστήματα μόνωσης ταράτσας

For those interested, below you can see a video where the conventional roof insulation is applied, and then all the steps of the method are presented in detail.

Application stages the conventional method

1) Preparation of the surface:The surface must always be clean before beginning any procedure. Before the application you should have made the provision for mounting bases for solar water heaters, air conditioners or other mechanical equipment.

2) Creating a vapour barrier: The vapour barrier is created to stop the diffusion of water vapour from inside the premises of the lower floor to the insulation layer in order to prevent internal condensation moisture formation. Even if you do not use the Durosol third-generation thermal insulating material, it is possible that water vapour reaches the insulating layer, to be liquefied and eventually be absorbed by a common insulation material, thus losing its insulating ability. The vapour barrier varies depending on the hygrometry of the premises under the roof. Usually the common constructions are classified in areas with low or average hygrometry of ≤ 5,0 gr / m³ and do not require a vapour barrier. In areas of intense hygrometry of 5.0-7.5 gr / m³ a vapour barrier is required in the form of an adhered felt paper with a polyethylene film.

3) Placing an insulating layer: The insulating layer is positioned to protect both the base plate and the interior from the large temperature fluctuations of the environment. Their thickness is selected according to the project requirements. The Durosol insulating plates are placed freely on the roof plate.

4) Lightweight concrete layering: Before layering, the existing slopes of the construction are controlled. Then thread drivers are placed, defining the gradients to be created with the light weight concrete. The minimum slope requested is 0.7-1% for regions of the A climate zone, 1-1.5% for Zone B and 1.5-2% for the C and D zones.

5) Dismantling of the plaster:  After the drying of the foamed concrete, a perimeter dismantling of the plaster is done, to a height of 15cm for the boxing of the vertical edges of the sealant layer. This work is significant because the adhesion of the membrane is done on the stable parapet and not on the plaster which, in the future, may present some corrosions.

6) ) Local repairs: Surface preparation by local repairs and repairs with non-shrinking repair material during its setting on points where there is a rotten substrate, as well as in the gutter attachment points with the main roof or the supporting structure if necessary.

7) Waterproofing: For the sealing of conventional roofs, what is recommended the use of bituminous membranes (elastomers, plastomers, etc.). The sealing starts with priming of the surface where the membrane will be placed, with asphalt varnish (priming). The sealing can be done by pasting 2 layers of film. The first layer is adhered spot on the substrate to allow commuting said expansion and contraction and expansion of the water vapor pressure diffusion. Instead, the second layer is adhered on the first total and placed parallel to the first and shifted by half of its width. Each bituminous membrane sheet affixed with a blowtorch. The membrane will get at least 15cm. height perimeter creating a completely watertight basin. Here enhance waterproofing membrane with additional tracks in all vulnerable points (angles, vents, aerials etc.). Final coverage of the membrane connections with the metallic elements, with special elastomeric mastic asphalt or polyurethane.

8) Ensure the roof compatibility: If your roof is not walkable but just visitable, the stratification may be terminated at the waterproof layer, which is coated with mineral chippings for sun protection of the membrane. But if the roof must be compatible, then on the waterproofing layer, geotextile is placed or a provision to be made and a film is applied, with a coating of polyethylene sheet so that can not be damaged from the occurring creeping tendency between the sealing-walking surface. Then the sealing is covered with pavement plates, ceramic tiles with cement mortar, industrial flooring, etc.

Cost for conventional terrace insulations

Material Prices / m²
Thermal Insulating MaterialDurosol eXternal Roof 5,75€
Foam Concrete 5€
Felt Paper 4,5€
Water Tar 0,4€
 Asphalt Varnish 0,9€
Total Material Cost 15,70€
Work Cost 10€
TOTAL COST 26,55€

Inverted Rooftop Insulation

What is the inverted insulation Rooftop Insulation?

Inverted insulation or thermal insulation of a roof, , is the insulation, wherein the insulating layer gets over the sealing, so somehow it protects it. The inverted insulation is a one-way street in the case of thermal insulation of a previously sealed roof. It has shorter application times and it is ideal for professional or industrial buildings. It also applies to buildings with average slope roofs. Finally it should be noted that the inverted method has several disadvantages which you can see below. For this reason, we can not guarantee for your insulation. If you want real insulated results with a 10-year guarantee you can be informed about the the Durosol Light Roof Plus insulation system.

Important information about the roof insulation with the inverted method

The topcoat is basically tile and for this reason this solution offers full compatibility. A target price for the final cost, including all required materials together with the cost of application (work costs) by one of the cooperating insulation crews of our company amounts to 37,8 € / m² + VAT. Finally, the weight of the insulation of the roof is ≈200 kg / m², therefore not suitable for very old buildings.

Precisely about this, what comes up to give the solution to roof insulation is the new and innovative method, the Durosol Light Roof Plus granite tile,, offered exclusively by our company after years of research. This is the most lightweight solution for roof insulation where the owner requires complete compatibility and the ability to fearlessly place heavy objects with spikes (chairs, dining rooms, etc.). Its weight is only 40kg / m², while the cost is more affordable than the inverted one, with the final price for all the materials and work not exceeding 37,8 € / m²!

Inverted insulation application stages

1) ) Preparation of the surface: The surface must always be clean before beginning any procedure. Before the application you should have made the provision for mounting bases for solar water heaters, air conditioners or other mechanical equipment.

2) Lightweight concrete layering: Before layering, the existing slopes of the construction are controlled. Then thread drivers are placed, defining the gradients to be created with the light weight concrete. The minimum slope requested is 0.7-1% for regions of the A climate zone, 1-1.5% for Zone B and 1.5-2% for the C and D zones.
* The above procedure for insulating a roof can be passed by if the flows of the roof are already in good condition and meet the minimum requirements.

3) Dismantling of the plaster: After the drying of the lightweight concrete, a perimeter dismantling of the plaster is done, to a height of 15cm for the boxing of the vertical edges of the sealant layer. This work is significant because the adhesion of the membrane is done on the stable parapet and not on the plaster which, in the future, may present some corrosions. This work is significant because the adhesion of the membrane is done on the stable parapet and not on the plaster which, in the future, may present some corrosions.

4) Local repairs: Surface preparation by local repairs and repairs with non-shrinking repair material during its setting on points where there is a rotten substrate, as well as in the gutter attachment points with the main roof or the supporting structure if necessary.

5) Waterproofing: For the sealing of conventional roof terraces, we recommend using a coating sealant based on silane resins. The seal starts by filling the cracks with acrylic sealant for an outdoor space. After sealing the surface with primer or polyurethane or 2-component water epoxy. We prefer polyurethane since below the surface there are perishable materials in solvents, such as polystyrene, for example. Primer is used if the surface is rotten or dirty and quite dusty. Then we apply the silane resin coating material in 2 layers, crosswise. The waiting time between coats is at least 3 hours and the application is done by spraying or a roller (sponge). The application of surface coatings for roof insulation is performed only on dry surfaces. There is also the option of felt paper use instead of the spreadable. It is worth noting that for the insulation of roofs, the use of felt paper is not recommended since water may penetrate it and we will not have the desired thermal insulation effect for the roof insulation.

The creation of a vapour barrier is deemed unnecessary for the roof insulation, since the silane resin coating material has a water vapour permeability of 30gr / m2 / hr thus allowing the application to “breathe” and to create healthy living spaces. * The vapour barrier is created in insulation solutions that do not “breathe” to stop the diffusion of water vapour from inside the premises of the lower floor to the sealing and insulating layer, to prevent internal condensation moisture formation. It is usually used in combination with polystyrene that does not “breathe” and it is in no way recommended.

6) Placing of the insulating layer: The Durosol plates are positioned freely on the roof plate except where that is inclined more than 40% where point fastening of the insulation plates is made. The Durosol plates have a perimeter flange (on the 4 sides) and nest together for a neat roof insulation.

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7) Ensuring the compatibility of the roof: If the roof is accessible and it is used quite often, the protective layer is cement mortar where the flows are taken in as well, with a minimum thickness of 4 cm. What is recommended is the strengthening with a metal structural mesh of 10cm x10cm, polypropylene fibers and latex. After the cement mortar has dried for at least 1 day / cm thickness, waterproofing is performed with a cementitious base brushable sealing mortar. When the cementitious mortar has dried as well, we place tiles of the customer’s choice, with external space acrylic adhesive. For a neat roof insulation it is necessary to seal the cement mortar because otherwise if water passes through the joints of the tiles and there is no waterproofing underneath, the water penetrates the cement and the insulating layer and it is trapped underneath the original waterproofing layer so we do not have the desired thermal effect. The application of the cement mortar and the tile creates a stylish and fully compatible roof surface, which, at the same time, protects the Durosol plates of insulation so it is not grabbed from the air, from the ultraviolet radiation of the sun and temperature changes. So the roof insulation has greater durability.

 All that is really suitable for a quality inverted roof insulation is Durosol.

The insulation protects the waterproofing coverage by:

  • large temperature changes: +80°C έως -20°C.
  • corrosion due to weather conditions.
  • mechanical damage during use and maintenance.

The insulating material of the inverted insulation must:

  • resist to water absorption.
  • withstand high pressures.
  • protect the waterproof layer for a long time.
  • be protected from UV radiation and mechanical damages.

Cost for inverted roof insulation

Material Prices/m²
Thermal Insulating MaterialDurosol eXternal Roof 5,75€
Cement Mortar 10€
Mesh 3€
Tile of your choice 3€
Tile Adhesive 1€
Felt Paper 4,5€
Asphalt Varnish 1,4€
Total Material Cost 27,80€
Work Cost 10€
TOTAL COST 38,65€

Advantages and Disadvantages of the Reversed Insulation 

Advantages for the Inverted Roof insulation

  • The waterproofing layer is fully protected from any mechanical abuse: pedestrians, falling objects, etc.
  • Also does not exposed to harmful UV rays and other atmospheric aggravating factors that accelerate aging.
  • The thermal insulation protects the waterproofing against extreme temperatures and especially their quick changes (thermal shock) that accelerate aging and depreciation of the membrane.
  • The roof can become compatible with the appropriate protection layer / ballast.

Disadvantages  for the Inverted Roof insulation

  • The control is much more difficult in the case of the sealing layer failure. This means that the seal must be extremely well-made and – if possible – to be comprised of two layers.
  • The insulation material should be resistant to moisture, compression and frost. That is why our only option is Durosol.
  • It takes a more responsible and detailed work regarding the slopes.
  • Very important: In winter, the rainwater (or melted snow) passes through beneath the filling and it is interposed between the heat-insulating and sealing layer, thereby significantly reducing the heat insulation as the plate is “heating up” from the water which results in the sewer and this cycle continues as it rains and until the water below the insulation evaporates (3-4 days after the rain).