Cleaning Vinyl Siding, Stucco and Hardie Board Safely

Most siding damage from cleaning is not caused by dirt or age. It is caused by someone using a pressure washer on a surface that needed a gentler approach.

The mistake behind almost all siding damage

A pressure washer in the wrong hands forces water upward and behind siding. Siding is designed to shed water running down it, not to resist water driven up under it at high pressure. Once water gets behind the panel it sits against the sheathing, and what starts as a cosmetic job becomes a mould and rot problem inside the wall.

This is why every material below is best cleaned with soft washing rather than high pressure. The cleaning is done by the solution, not the force.

Vinyl siding

Vinyl is the most common siding in the newer St. Johns County communities and the most forgiving of the three, but it has two specific weaknesses.

First, the seams. Vinyl panels lock together and there are gaps by design. Pressure aimed upward drives water straight through them. Second, oxidation. Older vinyl develops a chalky surface layer, and aggressive cleaning can leave it blotchy where the chalk has been stripped unevenly.

Correct approach: a cleaning solution applied top down, dwell time to kill the mildew, then a low pressure rinse. Nothing aimed upward under the laps.

Stucco

Stucco is common on the Mediterranean style homes around St. Augustine and Ponte Vedra, and it is the least forgiving material of the three.

Stucco is porous and relatively soft. High pressure will pit the surface, blast out the texture and, on older or already cracked stucco, force water deep into the wall assembly. Hairline cracks that were harmless become water entry points.

Correct approach: the lowest practical pressure, a solution suited to a porous surface, and careful attention to existing cracks. Any contractor who approaches stucco the same way they approach a concrete driveway should not be on your property.

Hardie board and fiber cement

Fiber cement is durable and increasingly popular, and it tolerates cleaning better than stucco. The vulnerability is the factory finish. Fiber cement is usually pre painted with a baked on coating, and that coating is what makes the warranty worth anything.

Aggressive pressure dulls and can strip that finish. Manufacturers of fiber cement products generally specify low pressure and a soft brush or cloth rather than a pressure washer.

Correct approach: soft wash with a solution, low pressure rinse, no abrasives.

Brick and painted wood, briefly

Brick looks tough but mortar is not. Pressure erodes mortar joints, and repointing is expensive. Painted wood will simply lose its paint under pressure, and on older homes there are lead paint considerations. Both belong in the low pressure category.

What to ask a contractor

• What pressure will you use on my siding specifically?
• Do you soft wash, or do you pressure wash everything?
• How do you protect landscaping and outdoor fixtures?
• Are you insured for damage to the structure, not just liability?

The answer to the second question is the one that matters most. A company that only owns one method will use it on everything.

How often siding needs it in Florida

Once a year for most homes here. North facing walls and anything under tree cover grow mildew faster and are usually the first to look dingy. If one side of your house looks noticeably worse than the others, that is normal and it is the shade doing it.

We clean siding of every type across St. Johns, Fruit Cove, Oakleaf Plantation, Orange Park and the surrounding areas.

Frequently asked questions