Sparrows eating mortar between bricks of neighbour's house


I feed the birds in my garden all year round. In addition to other types of bird, we now have between 30-40 sparrows who visit the garden on a daily basis. The foods placed in the garden are peanuts, sunflower hearts and dried mealworms. My neighbour has complained that the sparrows are eating the mortar between the bricks on her house. She says she has placed buckets of sand in her garden to act as a deterrent, but so far this has been ineffective. Also, both our gardens are regularly visited by a sparrowhawk who usually catches two or more sparrows. I should be grateful if anyone is able to offer advice or suggestions. With regard to sand, does it need to be a specific type? Thank you.