House Training an Adult Dog?

Six month ago we adopted an 8 year old border terrier called Brock. We already have an 11 year old Border Terrier called Tarka and two cats. Brock settled in very well except for the fact he will urinate everywhere in the house. He does this up my bin, kitchen cupboards, and my couch. This morning my daughter put her school bag on the floor to put her coat in and he urinated all over it.

I always have the back door open to allow both dogs access to the garden when needed. Brock will walk in from the garden and urinate in the house. I'm at my wits end now. We love Brock, but can't take the smell that it's now causing. Brock has been vet checked and he is a healthy dog. Can anyone please help?