The grey squirrel was brought over from America and has all but displaced the lovely native red squirrel.
A good indication that you have a squirrel problem is noise: if they’re in the attic, they’ll quickly start to build a drey (nest) using both materials in your loft and sticks or other materials brought in from outside.
The harm they do
Aside from a pox that grey squirrels can carry, the most serious problem they’re likely to cause is house fires as they’ll happily chew through the insulation on electrical cables. In addition, they will open the property to further damage from the elements, leading to rot and possibly water damage. Anyone who’s had them in a loft will also mention the noise they make as a serious issue.
As with most rodents, the point of entry needs to be located and sealed – squirrels will show very determined effort trying to get back into a loft or roof void so the materials have to be suitable for the job. Once entry has been denied, any squirrels that are then trapped in the building have to be removed. A job that is best left to a professional; it is illegal to release a grey squirrel into the wild because they are not classed as a native species in the UK.