Squirrels are always looking for secure places to nest. They can cause serious damage to both the fascia and soffit of a roof by chewing through them and to the interior by nesting, chewing up insulation and bringing in food and other foreign matter. When you repair holes made by squirrels, it is important not only to fix the damage, but also to change the materials so that it doesn't happen again.
Determine whether there are any squirrels inside of your roof before you repair the hole. If possible, do it at a time of year when there won't be any baby squirrels nesting inside. Babies are most likely to be present in the nest in early spring. Check the area around the hole, and then check all of the soffits and fascia on your house. Locate any squirrel damage and holes so that you can fix them all at the same time.
Repair a hole by covering it with a sheet of aluminium, nailed or screwed on over the hole, cut to have an overlap of 10 to 15 cm (4 to 6 inches) around the hole. Repair vinyl siding by either replacing the damaged sheet of vinyl or patching it with another piece of vinyl.
Repair an edge or corner either by shaping the patch to fit the profile the damaged area or by replacing the material in the damaged area entirely. Repair any rotted parts of the soffit by removing all rotted wood and enlarging the hole until there is only sound and solid wood present. If possible, cut away wood so that you leave a square or rectangular hole that you can then patch with a strong piece of wood. Cover this patch with a large piece of aluminium.
Prime and paint the patched area to prevent it from deteriorating further. Latex exterior primer and finish coat are good for wood. For aluminium or other metals, you will need an oil-based primer. Read the instructions on the can to be sure the paint is appropriate for your needs.
If the damaged area has trees in front of it, cutting them back may help to keep moisture off and to make access more difficult for squirrels. However, squirrels are incredibly agile, and if there is a tree anywhere near, they may still be able to access the roof. Metal soffit replacements are commercially available, though more expensive than a do-it-yourself fix. Soffits are most commonly made of wood, aluminium and vinyl. Of these, aluminium is the most difficult for a squirrel to chew through.
Always be careful when using ladders. Be sure that they are stable on the ground, and never lean far to the side while on the ladder. If you are at all unsure about the stability of the ladder, find someone to stand at the bottom and hold it for you.