Get a gallon of Petzyme (available at Petsmart stores) enzymatic
cleaner meant for cat urine and have her SOAK her balcony with it. She
may need to cover the balcony with plastic to allow the cleaner time
to work (read the instructions on the bottle).

Also, you might want to bring him into your vet's office for a check
up (and bring a urine sample). If he's never done this before, he
might be having urinary problems.

Rene