Mildew and Grime on a Pool Cage
A screen enclosure sits in the most humid microclimate on the property — directly over evaporating pool water, usually with limited airflow. It is the single fastest-growing surface on most Florida homes.
Why cages grow mildew so quickly
Pool water evaporates continuously, and a screen enclosure holds that moisture against the frame and mesh. Add pollen, oak debris and lawn clippings blown through the screen, and you have a constant food supply sitting in permanent damp.
The black you see is mildew and algae growing on and through the mesh. On the aluminum frame it shows as a dull grey-green film, heaviest on the shaded side and along the bottom track where water sits.
Screens also collect a fine grey oxidation from the frame itself, which is why a cage can look tired even where mildew has not taken hold.
Why the enclosure is the wrong place for pressure
Screen mesh has almost no tolerance for pressure. A standard pressure washer at working pressure will stretch, dish or tear panels outright, and rescreening a single large panel costs more than the cleaning did.
Pressure also drives water into the frame channels and screw bosses, accelerating corrosion in exactly the places you cannot see or reach.
The spline holding the mesh in the track is the other casualty. Once pressure lifts a spline, the panel bellies out and has to be respined.
What not to do
Do not pressure wash the mesh. There is no safe pressure setting that also cleans effectively — by the time it removes the mildew it is damaging the screen.
Do not scrub panels with a brush. Mesh stretches under lateral force and will not recover its tension.
Do not let cleaning solution run into the pool untreated. Runoff needs controlling, or you will be rebalancing chemistry for days.
How we clean an enclosure
The whole cage is soft washed — frame, mesh, kick plates and screen door — at low pressure with a solution that kills mildew and algae rather than blasting it off.
We manage runoff away from the pool and rinse the deck, coping and surrounding surfaces as part of the job. The bottom track gets flushed, since that is where debris and standing water concentrate.
Frames come back to their proper finish, mesh returns to an even colour instead of a blotchy grey, and the enclosure lets noticeably more light through.
Questions we get about this
Will cleaning damage or tear my screens?
Do you clean the pool deck at the same time?
Will the chemicals affect my pool water?
How often should a pool cage be cleaned?
Related: Pool deck cleaning · Soft washing explained · all FAQs