Running Network Cabling Outside

I’ve been presented with the problem of networking a small business, only problem is it’s in an old house which really doesn’t lend itself to drilling holes. The owner of the house has sugested running a single Rj45 cable from the hub located downstairs to an upstairs room. However, I’m concerned, can I run a normal Rj45 cable outside – tacked to the wall?

Please help, thanks in advance.

Andrew Brown