Cat urine odor can be nasty. It's persistent, strong and seems to get worse every time it gets moist or damp outside. Fortunately there is relief. We have two products which would work well for this problem. Both work equally as well; the NNZ has no odor and the N7C has a slight sweet smell. These products are non hazardous and ideally suited for the situation you have. Each 1/2 gallon of concentrate will be able to cover 500-1000 sq/ft. Be sure to treat the entire area. Generally, it's easiest to spray with a good pump sprayer but if the area is hard to access, use a BG Fogger. If used properly, one treatment will knock the odor out. If the smell is persistent after 1 week, treat again. You'll find all these items listed in our cat control products page here along with some other good tools that might be needed. Good luck!