Sparrows have been on the decline for decades and as a result are on the red list for conservation, requiring the highest level of protection. They are rarely a problem in domestic situations, being of much greater concern in commercial properties such as warehouses and bakeries. However, if you do get sparrows nesting, they can damage roof tiles, cause unsightly mess with their droppings and attract insect pests to their nests.
Measures for dealing with sparrows are limited to deterrents and can only be installed after the breeding season in the autumn. In a domestic property bird gels and bird spikes are usually enough to prevent the birds from roosting.