Hello Sharon my name is ***** ***** I will help you with this.
Just to be clear, you can't tell if it shared? Does it have a T in the deed please?
Thanks. Do you know where the tenants have moved to?
if is a joint boundary then yes they are jointly liable. It may be that their tenant has done it and as such, they need to pursue the tenant.
But they are liable for the fence as it was done by their tenant.
Can I clairfy anything for you about this today please?
If I could ask you to rate my answer before you go today, otherwise the site does not pay me for the time spent with you today. Thank you in advance and good luck!