TL;DR
Soffit vents are deliberate openings into your attic, so any spray aimed upward puts water directly into the roof structure. Clean soffits and fascia with a detergent on a soft brush and a downward-angled rinse only, worked from the ground with an extension pole. Never operate a pressure wand from a ladder.
What these parts are and why it matters
The fascia is the vertical board running along the roof edge, usually where the gutter is mounted. It is a face, and it can be washed like any other exterior face.
The soffit is the underside panel between the fascia and the wall. It is almost always vented -- either with slotted panels or with individual vents -- and those openings are not a flaw. They are the intake side of the attic ventilation system, drawing air in at the eaves so it can exhaust at the ridge.
That is the whole problem. Aiming water up at a soffit is aiming water into an attic through a hole designed to let air in. Insulation soaks, framing gets wet, and nothing up there dries quickly or gets inspected.
The one rule that governs the job
Spray downward and across. Never upward.
Everything else on this page follows from that. On a wall you can angle down easily. Under an eave, gravity works against you, so you have to consciously position yourself so the water is moving away from the openings rather than into them.
The practical version is to stand back from the house rather than directly beneath the eave, so the spray reaches the soffit at a shallow angle from the side and drains outward.
The lap joint version of this same problem, on siding, is covered in washing vinyl siding without forcing water behind it.
What accumulates up there
Soffits and fascia collect a specific mix.
Dust and pollen bind into a grey film, heaviest on the shaded side of the house.
Algae and mildew grow in that film, particularly under trees and on north-facing eaves that stay damp.
Cobwebs and nests. Eaves are prime real estate for spiders, wasps, and birds. Check before you spray. A wasp nest hit with water at close range is a serious problem, and stinging insects are a pest control question, not a cleaning one.
Gutter runoff staining. Dark vertical streaking on fascia often comes from gutters overflowing or leaking at the seams, which is a repair signal rather than just a stain.
Tiger striping on the gutter face is a different residue entirely, and it does not come off with house wash -- see removing tiger stripes from gutters.
The method
1. Check for nests and insects from the ground before anything is sprayed. Deal with stinging insects separately and safely, or have pest control handle them.
2. Prep. Cut power at the breaker to any eave-mounted lighting. Move furniture and grills clear. Close nearby windows.
3. Soak the plants below with plain water and keep them wet.
4. Apply detergent with an extension brush. A soft-bristle brush on a telescoping pole, dipped in a bucket of mild exterior cleaner, gives you contact and control that spraying does not. Work along the soffit panels rather than jabbing up into the vents.
For heavier growth, a low pressure spray from a pump sprayer with a wand extension can apply the cleaner, aimed across rather than straight up.
5. Dwell. Five to ten minutes, out of direct sun, never to dryness. Chemistry does the work here, which is the logic in soft washing and when it applies.
6. Brush the fascia and the soffit panels. Long strokes, light pressure, following the panel direction.
7. Rinse gently, downward and outward. Garden hose with an adjustable nozzle is enough for most homes. Stand back so the water reaches at an angle and drains away from the openings.
8. Do the walls below afterward, since runoff will have dirtied them. That sequencing is part of whether to work top down or bottom up.
Source: attic ventilation and roof edge maintenance guidance
Ladders, and why this section is short
Do not operate a pressure washer wand while standing on a ladder. The wand pushes back when the trigger is pulled, and a ladder gives you nothing to brace against. This is one of the most common serious injuries in exterior cleaning.
Extension poles for brushes and hose wands exist precisely so this work can be done from the ground. Use them.
If your eaves are too high to reach safely from the ground -- most two-story homes -- that is the point at which the job goes to someone with proper access equipment. The result is not worth a fall.
Material differences
Vinyl soffit panels are the most common and the most forgiving. Mild detergent, soft brush, gentle rinse.
Aluminum soffit and fascia cleans the same way but can oxidize into a chalky surface. Washing removes the loose powder; heavy oxidation is a refinishing question.
Wood soffit and fascia needs the gentlest treatment. Water forced into end grain and seams stays there, and painted wood adds a coating that lifts if the paint bond is weak. Test in a hidden area.
Fiber cement trim follows the manufacturer limits, which are low -- a garden hose and a soft brush.
Avoid abrasive pads, wire brushes, and strong solvents on all of them. Vinyl and painted surfaces scratch, and scratches hold dirt permanently.
What cleaning will not fix
Sagging fascia, soft spots in the wood, or staining that reappears within weeks all point at water rather than dirt. Common causes are gutters overflowing, a failed gutter seam, missing drip edge, or a roof edge detail that lets water run behind the gutter.
Persistent mildew on one section of soffit with dry sections either side usually means moisture is coming from inside the attic, which is a ventilation problem.
Cleaning those areas removes the evidence for a season. It does not remove the cause, and mold or rot in a roof structure is a repair trade rather than a cleaning one.
FAQ
How do you clean soffits and fascia?
Apply a mild exterior detergent with a soft-bristle brush on an extension pole, let it dwell several minutes out of direct sun, brush along the panels, then rinse gently with the spray angled downward and outward from a position back from the house. Wash the walls below afterward.
Can you pressure wash soffits?
Not upward, and preferably not at all. Soffit vents are openings into the attic, so a stream aimed up puts water into insulation and framing. If a machine is used, it is at low pressure with the widest tip, aimed across rather than up, from a stance well back from the eave.
Why do my soffits keep getting mildew?
Usually because that section stays damp -- deep shade, overhanging trees, or splash from an overflowing gutter. Mildew on one section with dry areas either side can also mean moisture is escaping from inside the attic, which is a ventilation problem rather than a cleaning one.
Should I clean soffits before or after the walls?
Before. Everything you loosen at the roof edge runs down onto the walls, so cleaning the walls first means doing them twice. The general sequence is roof edge and gutters, then walls by elevation, then decks, then flat surfaces last.
Can I clean soffits from a ladder?
Brush work from a properly footed ladder is possible, but never operate a pressure washer wand from one -- the recoil is a genuine fall hazard with nothing to brace against. Extension poles let this be done from the ground, and eaves out of safe ground reach should be hired out.
If the wider house needs the same attention, that is what house cleaning services cover.
Roof-edge work is where a small cleaning decision meets attic ventilation and ladder safety at the same time. If your eaves are beyond safe reach from the ground, get a quote and we will look at the whole roof line with you.