Things You'll Need
Nature’s Miracle in spray bottle, or other liquid enzyme-based odor neutralizer
Cat spray is very pungent and the scent can last for a long time. Once a cat has sprayed an area, he will often re-spray the same area when the smell dissipates. Cat spray smell is notoriously difficult to get rid of and even after cleaning the area with strong scented cleaners, although humans no longer pick up the spray odor, cats still may. One solution is to use an enzyme-based cleaner formulated especially for biological odors such as urine and cat spray. These not only mask the scent, the enzymes neutralize the odor-causing substances in the cat spray.
Rinse the siding with gentle stream of water from a hose. This will get off some of the excess cat spray, which will allow the cleaner to work more effectively.
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Allow the siding to dry thoroughly. This type of odor remover works better full-strength--moisture may make it less effective.
Spray a generous amount of the cleaner on all areas of the siding the cat has sprayed. Let the cleaner sit for an hour or so, then wipe the areas with a clean absorbent towel.
Spray an additional layer over the area or areas the cat has sprayed and leave it on. This will help neutralize any remaining scent.
Allow the siding to dry fully. Reapply the product liberally if the cat still shows interest in the area.
To prevent cats from revisiting your siding, try using a cat and dog repellent around the base. These are granules you sprinkle and leave on the ground. If you touch a towel to the untreated areas and then use that towel again elsewhere, even if you've rinsed it, you are doing him a favor. Be sure to use clean towels.
Test a small area of siding before using on painted siding. Painted siding may need special care to keep paint from peeling.