Unable to Clear Cobwebs

[Doctor Who]

While cleaning the outside of a property I encountered two cobwebs that I can't clear. They are at a corner of the roof and, even with a ladder or scaffold, they can't be cleared because the 'cleaning' option is not available outside a property.

[A Bi Supreme]

Can you try doing them from the inside? The cleaner will often get things through the wall if they're close enough and you give it a bit of a wiggle.