Necessary materials

Necessary materials and instruments: shims, masking tape, gloves and goggles, 1K polyurethane foam, fixing screws, caulk, knife, plumb, screwdriver, hammer, foam applicator, flashing strips and tapes.


Windows help to establish home's visual character, let in light and air and frame views from inside. On the market is a wide variety of the models and available kinds of installation which can be rather different, depending on the window type and searched insulation properties. Fitting installation of the window precisely guarantees the resilience toward consistent forces affecting the installation. The fine tolerances are needed to achieve this kind of performance and carpentry or masonry skills are must.
Most of all, before starting window installation checking manufacturer's instructions is nessecary.
Next step in window installation is checking the suitability of the window dimensions to the opening. The best way for checking this is leaving approximately 2 cm between the frame and while measuring opening. Then if the corners of the opening are at 90ş and walls plumb and if they are not right-angled and plumb, the walls and floor (basis) should be remodeled. Fix any problems in this phase.




  • Install the window according to manufacturer’s instruction. Window has to be mechanically fixed before PU foam is used for insulation. Once the opening is watertight and the window is set plumb and square, the gap between the window and the framing can be filled with PU foam. The foam serves only as insulation material in case of windows!
  • After installation double-check that the window is square by measuring the frame diagonally from corner to corner and that window sill is level.  If these two  dimension are identical, the sides of the window are plumb.
  • Installation of flashing depends on type of the house - e.g. wooden carcass houses or multi-storey concrete buldings have different approach. It may be required either before or after filling the joint with insulation foam
  • The connecting joints between the frame and the wall must be clean of residues and dust. The surfaces could be slightly moist, but they must not be wet. Remove big water drops.
  • Shake the foam can and attach it to the gun according to the instructions.



  • Fill the joints with foam, starting with upper horizontal joint. Keep the can in upright position, valve down. In order to reach inaccessible corners, it is possible for short time to held the can in horizontal position, when the can is full enough. Remember to shake the can after foaming horizontally.
  • Then spray the foam into the side joints going up from the bottom. After that do the same with the lower horizontal joint.
  • In case the joint between the wall and the frame is wider than 5 cm, apply the foam in 2 steps. In dry conditions, during winter time and in rooms with central heating, in order to get best foam structure and foam properties it is recommendable to fill gaps and joints in several layers by the application of smaller foam strings (up to 3-4 cm thickness) and slightly moisturizing between every layer.
  • Fill the gap to 2/3, the foam expands during the curing and fills the joint completely. If necessary, additional layer of foam may be applied later. Remember about moisturize the surface of the old layer with water before application.
  • In dry conditions, spray a small quantity of water on the fresh foam to support the curing. Do not use too much water, this may lead to foam shrinkage.
  • After full expansion, the foam should seal the space between the window/door frame and the wall. Overexpanded foam can be cut after 1 hour when humidity levels are above 50 % R.H. Dry rooms and winter conditions require longer, up to 24 hours, waiting time. Do not cut the foam before fully cured as this will deteriorate the foam structure and insulation properties. Remember - all the voids in the insulation layer are the thermal bridges.
  • The spacers must not be removed before the foam is fully cured, wait at least 3 h, depending the ambient conditions. In dry rooms and winter conditions 24 h waiting time may be needed.


  • Fix the window sill flashing outside the frame with the regular screws with flat nail-heads. Then foam the space under the sill flashing to provide sound insulation of the metal sill. Then install the sill inside and cover the slopes.
  • Insure that all PU foam layers are coated within a few days with suitable materials like a putty, sealant or paint to protect it from UV radiation. This is particularly important for the outer layer due to the sun light, but also the internal part must be covered within a few weeks.
    For window installation works our recommendation is to use only gunfoams with minimal curing pressure and low post-expansion characteristics.

Recommended products

For window installation works our recommendation is to use only gunfoams with minimal curing pressure and low post-expansion characteristics.

Makroflex Premium Window - long term flexibility
Makroflex Premium PRO - increased yield
Makroflex Low Expansion foam - joints with less than 3 cm width
Makroflex PRO - standard option