Debris between slates and membrane

It is generally recommended to remove any loose debris that is trapped between the slates and the membrane during a roof installation. Leaving the debris in place can potentially cause problems in the future. Here are a few reasons why it's important to remove the debris: Water Drainage: Debris can obstruct the flow of water on the roof, leading to water pooling and potential leaks. Proper water drainage is crucial for maintaining the integrity of the roof. Moisture Retention: Debris can hold moisture, which can lead to rot and deterioration of the roof membrane over time. This can weaken the roof's structure and reduce its lifespan. Weight and Stability: Accumulated debris adds unnecessary weight to the roof, which may strain the supporting structure. Over time, this extra weight can lead to sagging or structural damage. To ensure the long-term durability and performance of your roof, it is best to have the contractor remove the loose debris before continuing with the installation. If you have concerns or questions about the process, it is advisable to consult with the roofing professional working on your project.

All debris should be removed you will get very small amounts left behind but if it is clearly visible I would ask your roofer to remove the slates and clear it off before continuing with the works.

This is Standard whilst working with slate and unavoidable due to the constant cutting of slates the debris should only been fairly fine and wont do any harm to the roof.

Yes it should be removed. Many roofers scrim on skips by 'burying waste'.