There should be a gap between the astragal bar and frame to allow for movement. If there was no gap, the bar would just pop off. PVCu or UPVC expands in heat and by including a gap we’ve made room for any potential expansion you may see during hot summer months. The PVCu will turn to its original form when it cools down.
Required gap: 0.8mm | Tolerance: +/- 0.1mm