The common 'pest' squirrel in the UK is the grey squirrel (Sciurus carolinensis).
 
Grey squirrels build their nests in the forks or hollows of trees, using twigs, leaves and grass. Occasionally nests are made in the roof spaces of houses. Squirrels retire to their nests during wet or cold weather, but remain active throughout the year.
 

Exclusion
 
As with rats and mice, the best way to solve squirrel problems is to stop them getting in to your premises in the first place.

 
Blocking holes that give access to roof spaces with mesh will discourage squirrels from entering the roof.

 
Treatment
 
Trapping is the usual method of capture of squirrels. This involves placing a cage with bait in it to trap and remove the squirrel.