Mortar for bonding and rendering thermal insulation boards

Fiber reinforced and flexible cement based mortar used for the application of various types of thermal insulating boards such as EPS, EPS NG, XPS and MW. NOVABOND PS FLEX  is suitable for substrates such as: concrete, bricks, plaster, aerated concrete, cement board, gypsum boards (properly primed), as well as for the creation of a base coat layer before applying the final decorative coating of external thermal insulation composite systems. It is flexible with high adhesion to thermal insulating boards and adequate slip resistance in order to be easily applied on vertical surfaces. It has an extended open time in order to be applied outdoors. Part of the  External Thermal Insulation Composite System (ETICS), NOVATHERM SYSTEM.

Consumption: 1,4 kg/m²/mm of thickness
Color: Grey, White
Package: Paper bags 25 kg
Pallet: 1350 kg


  • NOVABOND PS FLEX is suitable for:
    • bonding thermal insulating boards such as:
          • expanded and extruded polystyrene
          • expanded polyurethane
          • mineral fiber boards, rock wool
    • levelling thermal insulating boards prior to the application of:
    • application in various substrates such as:
          • concrete, cement screeds, brick walls
          • renders and wall brick mortars
          • cement and gypsum boards (properly primed)
  • Form: powder
  • POT life: 4 hours
  • Application temperature: from +5°C up to +35°C

Substrate preparation:

Cement based substrates must be compact, without cracks, free of dust, salts, grease and any other materials that could reduce adhesion of NOVABOND PS FLEX to them. Existing cracks on the substrate should be patched up with the fluid epoxy resin EPO FLUID. On the still fresh EPO FLUID surface, scatter S 500 silica sand or similar to create a mineral surface. Concrete substrates should be mechanically prepared, for example, by grinding to achieve a uniform surface of open porosity without protruding edges. For gypsum-based substrates, it is necessary to prime the substrate with NOVAPRIMER prior to the rendering of the insulating boards. Nonabsorbent substrates are recommended to be primed with PLANO CONTACT or PLANO BOND.

In case the application is done upon absorbent substrates such as concrete, cement screeds etc. properly saturate the substrate with water, avoiding the presence of standing water. For additional information, refer to the corresponding Technical Data Sheets of the products.

Preparation of the mix:

Mix the contents of a NOVABOND PS FLEX (25 kg) bag with 6,0 – 7,0 liters of clean water by means of an electric stirrer at low speed (500 rpm) for at least 3 - 5 minutes. Mixing should be done until a uniform mix free of lumps is obtained. The product is ready for use. The mixture has a pot life of approximately 4 hours. During hot weather it is advised not to expose the materials before their use in the sun (powder and mixing water) otherwise the open time of the mixture is reduced. In any case, avoid mixing by hand.


On flat substrates apply NOVABOND PS FLEX as adhesive mortar directly onto the back of the thermal insulation board with a trowel. With a toothed trowel spread evenly the adhesive so that the back side of the board is totally covered with mortar, throughout the surface. On uneven substrates, apply the mortar by using a trowel pointing to the center and the perimeter of the thermal insulating board.

By applying firm pressure, place the thermal insulating board in the correct position. When NOVABOND PS FLEX is applied as a levelling coating, spread the mortar over the entire surface with a toothed trowel and in the fresh layer incorporate the fiberglass mesh NOVATHERM NET. Ensure an overlapping of ≥ 10cm between the rolls of the mesh. Integration of the NOVATHERM NET must be performed as long as the mix is still fresh with the flat side of the trowel.


  • Do not apply when ambient temperature is less than +5°C or higher than +35°C
  • Do not exceed 10 mm of thickness in one single layer
  • Do not apply upon metallic, wood or deformable surfaces
  • Do not apply upon surfaces such as polyurethane coatings, paints, acrylics and substrates subjected to big movements
  • Do not apply upon PVC and bitumen membranes and in general materials which polymerize in the long run
  • Do not apply upon loose substrates or substrates not properly cured
  • Do not apply upon non-absorbent substrates not properly primed
  • Do not apply upon existing expansion or movement joints of the substrate
  • Do not apply the mixture under direct sunlight exposure and/or strong winds
  • Do not exceed the recommended quantity of mixing water
  • Protect the application surface from rain or frost the first 24 hours
  • Do not add cement, gypsum, lime or other materials that might affect the properties of the mortar
  • The application must be performed by a professional installer


Tools, buckets, coverings etc. can be cleaned with water as long as NOVABOND PS FLEX is still moist. Once the material dries, cleaning can be done only by mechanical means.

Legal Notice:

The technical data and recommendations included or listed are the outcome of laboratory measurements combined with our current knowledge and expertise. All information and specifications should in any case be considered as indicative. The Company makes every effort to ensure the accuracy of the information provided herein. Product specifications are subject to change without notice and may differ from product images. Due to printing and application procedures, the colors displayed here should be considered as indicative. In particular, variations in materials, substrates and on-site application conditions are such that no warranty can be given or implied reference to the suitability of the materials for trading or use for a particular purpose and conditions of any given project. Anyone interested in using the product must ensure beforehand that the product is suitable for the intended use and in any case, the user is solely responsible for any outcomes associated with the use of product. Among other things, the Company is not responsible for any normal wear or tear from environmental or any other unsuitable conditions. We reserve the right to revise or change the data herein without prior notice. Restrictions and disclaimers apply to the extent permitted by applicable law. The Company has a Technical Support Department, which has exclusive responsibility for providing technical advice and solutions, addressing relevant issues. Requests to the Technical Support Department are addressed and answered, only in writing. For the latest and valid version of the Technical Data Sheet, the user of the material must refer to our website