Window Keystone
Polure window keystones form prominent crown focal points atop window and door architraves, bringing classical masonry architecture to interior and exterior facades. Molded from high-density rigid polyurethane (150-220 kg/m³), these keystones offer wood-like mechanical durability while remaining lightweight for easy, secure wall positioning. The closed-cell material matrix keeps water absorption below 1%, guaranteeing zero swelling, rot, or moisture degradation when installed outdoors. Rated B2 for fire safety and capable of withstanding temperatures from -100 °C / +80 °C, each piece arrives pre-primed in factory white acrylic primer. Installation requires applying continuous polyurethane assembly adhesive to contact backs and securing with countersunk screws; silicone bonding is strictly prohibited. Joint seams and countersunk screw locations are filled with exterior or interior acrylic putty, sanded smooth with 180-220 grit paper, and finished with UV-resistant facade paint for exterior applications.
Frequently Asked Questions
What material is Polure window keystone made from?
It is molded from high-density rigid polyurethane (150-220 kg/m³), providing wood-like strength and a B2 fire safety rating.
Can window keystones be installed on exterior building facades?
Yes. Water absorption is under 1%, ensuring the keystone will not rot, freeze-thaw crack, or dent under hail.
How is a window keystone properly installed?
Apply continuous PU assembly adhesive to contact backs and fix with countersunk screws. Silicone is forbidden. Fill gaps with putty and sand smooth.
What paint finish works best on window keystones outdoors?
Exterior installations require elastic, UV-resistant facade paint to prevent sun yellowing and weathering.