Exterior Wash and Prep Day Standard

Purpose

Produce a substrate that is clean, chalk-free, mildew-free, sound and dry enough to coat, and prove it with a reading rather than a feeling. Wash day is a separate day with its own deliverable, and treating it as the first hour of paint day is what produces the two most expensive exterior callbacks in this trade: a coat applied over live mildew that blooms back through in one season, and a coat applied over damp wood that blisters on the first hot afternoon. Both look perfect at final walk. Both are a full strip on the elevation that failed.

Scope

Residential and small commercial exteriors: wood siding and trim, fiber cement, previously coated masonry and stucco, soffit, fascia and rake.

It does not cover wood repair or bare-substrate priming (wood repair and substrate priming standard), joint sealant renewal (caulking standard), the meter method itself (moisture and adhesion testing standard), or containment on a pre-1978 exterior (RRP containment standard). Vinyl and aluminum siding are washed under this standard but coated under their own product-specific quote.

Roles and responsibilities

Procedure

1. Confirm the pre-1978 gate before any pressure hits paint. Establish the construction year and record it. Acceptance: a stated year, plus a work plan if pre-1978. What wrong looks like: a wand already running on 1950s clapboard. Stop rule: pre-1978 target housing whose paint the wash will remove is a regulated renovation under 40 CFR 745 Subpart E, so nothing starts until a certified renovator and that rule's containment are in place under the RRP containment standard, because pressure washing is not an approved way to strip lead paint and it puts lead chips and slurry into the customer's soil where children play. Hazard: lead reaches people here by ingestion off hands and soil, not only by breathing, so the crew eats away from the work zone and washes before eating whatever the day's task was.

2. Read the weather window and commit to it out loud. Check the forecast for the wash day plus the drying days, and get the customer's agreement that coating may slip. Acceptance: a written window naming the wash date, the earliest coat date and the temperature and rain thresholds you are working to. What wrong looks like: a crew washing Friday afternoon with a Saturday coat booked and rain Friday night. Stop rule: if the forecast breaks the window, the wash moves rather than the drying time shrinking, and the office sends the delay note the same day. Hazard: none, this is a decision made at a desk, and it is named so nobody assumes the weather call belongs to whoever shows up on site.

3. Protect plants, openings, meters and the ground before the pump is primed. Close and latch every window, cover exterior receptacles, light fixtures, HVAC condensers and the meter base, and either water plants heavily and cover them or tie them back. Acceptance: every opening on the elevation is closed, every powered device on the wall is covered, and no plant sits under an untented run. What wrong looks like: water tracking down inside a window stool an hour after the crew moves on. Stop rule: an opening that will not close or a fixture that cannot be covered gets washed by hand at that bay, not by wand. Hazard: water plus energized exterior circuits, so anything on that wall runs through a GFCI-protected supply, and if a covered fixture or receptacle takes water anyway, nobody touches it: that circuit gets shut off at the panel and looked at before work restarts on the bay.

4. Kill biological growth chemically before you move any water at pressure. Apply a cleaner labeled for mildew and algae on that substrate at the label's own dilution and dwell time, working bottom to top, keeping the surface wet for the full dwell. Acceptance: the dwell time on the label has fully elapsed and the treated area has not dried out mid-dwell. What wrong looks like: dark growth turning gray and returning as a shadow the same season. Stop rule: growth still visible after the labeled dwell gets a second application to the label, and growth that survives two applications means a wet-source problem that gets traced before anyone coats. Hazard: label directions are legally binding and hypochlorite solutions burn eyes, skin and airway, so chemical-resistant gloves, sealed goggles and a face shield go on before mixing, nothing is mixed with an ammonia or acid product, and a splash is flushed 15 minutes and evaluated rather than wiped off. Soffit work runs off a pole applicator so the run-back goes past you rather than into your face.

5. Wash at the lowest pressure that does the work, with the tip moving and angled. Start at the low end of the range for that substrate, hold the wand off the surface and increase only until soil releases, keeping the stream at a downward angle so water is not driven up under laps. Acceptance: no fuzzing or raised grain on wood, no eroded mortar joint, no lifted lap, and the rinse water runs clear off the bottom of the elevation. What wrong looks like: a bright, whiskered stripe on cedar where the tip dwelled, or water appearing on the inside of a wall. Stop rule: any raised grain or lifted lap stops the wand on that elevation and the rest is washed by brush and hose. Hazard: a pressure washer stream injects under skin, and an injection injury looks like a pinhole and needs surgical treatment the same day even when it barely hurts, so nobody clears a tip with a hand in front of it, the trigger is locked whenever the wand is set down, and nobody washes from a ladder, where the reaction thrust takes the tech off it.

6. Test chalk and soundness after the surface dries, not while it is wet. Rub a clean dark cloth firmly over one square foot on each elevation, and press a screwdriver tip into any suspect wood at the same time. Acceptance: light or no powder transfer on the cloth on every tested elevation, and no probe penetration into wood beyond the surface. What wrong looks like: a heavy chalky white loading on the cloth from a south wall, which is a bond problem your topcoat will inherit. Stop rule: heavy transfer means the elevation gets re-washed with a cleaner labeled for chalk removal and re-tested, and if it still loads the cloth the job goes to the bonding-primer or strip decision with the customer before a topcoat is sold. Hazard: this test is done from the ground or a properly footed ladder, not by leaning off one, because the natural motion is to press hard with an outstretched arm.

7. Let it dry and record the reading that says it is dry. Allow the drying time your window committed to, then take moisture readings on each elevation with a meter used per the moisture standard. Acceptance: readings at or below 15 percent on wood, taken at three points per elevation including one low point within 2 ft of grade and one north-facing point, all three at or below the gate. What wrong looks like: 11 percent at eye level on the south wall and 19 percent at the bottom of the north wall, which is one elevation with one wet zone, not a dry house. Stop rule: any single point above the gate stops that elevation; nobody averages the three. Hazard: none at this step beyond ladder use to reach upper readings.

8. Remove what the wash loosened and feather what stays. Scrape only the film the wash lifted, and feather the shoulders of the remaining coating so the edge is not a visible ledge. Acceptance: run a bare fingertip across each scraped boundary and feel no step; sight along the wall in low sun and see no ridge line. What wrong looks like: a scraped patch with a hard rim that reads through two topcoats as a map outline. Stop rule: if scraping keeps opening new area beyond what was priced, stop and go back to the customer with a strip-versus-spot-prime decision rather than working through it. Hazard: scraping and sanding old exterior coatings generates dust in the breathing zone, so on a pre-1978 surface it runs under the step 1 RRP gate, and on any surface it is done with a fitted respirator under a written program per 29 CFR 1910.134 rather than a nuisance mask.

9. Restore everything you disabled, then release the elevation in writing. Uncover fixtures, condenser, meter and receptacles, restore any circuit you shut off at step 3, untie plants, and confirm each window that was closed still latches. Acceptance: every item covered at step 3 is uncovered and functioning, the condenser runs, and the elevation's three moisture readings and cloth result are entered against that elevation. What wrong looks like: a house released with a condenser still wrapped in plastic on a July afternoon. Stop rule: an item that does not restore or work stops the release, and a fixture or circuit that took water is looked at by an electrician before it is re-energized. Hazard: this is the step where energy goes back into things you covered, so the panel breaker is closed with the body to the hinge side of the panel door rather than square in front of it, and nobody restores a circuit they did not personally shut off.

The record this produces

Per elevation: construction year and lead determination; the weather window and any delay note sent; cleaner product, dilution and dwell used at step 4; wash pressure range and any wand-to-brush downgrade; cloth chalk result; three moisture readings with their locations; scrape and feather notes; the step 9 restore checklist with the tech's name and date. It files by elevation because failures are almost always one elevation, and the north wall's numbers are the ones that answer a bubbling call next spring.

One run of this procedure, filled in

A 1994 two-story with wood siding, four elevations. Step 1: 1994, RRP does not apply. Step 2: window written as wash Monday, earliest coat Thursday, no coating below 50 F or with rain in the prior 24 hours.

Steps 3 to 5 ran clean on all four elevations. Step 4 used a mildewcide at the label dilution with a 10 minute dwell, re-wetted once on the south wall to keep it from drying mid-dwell. Step 6 cloth test: south heavy white loading, the other three light. South fails, so the stop rule fired: it was re-washed with a chalk-removing cleaner and re-tested, and the second cloth came back light. The other three passed first time and did not get the second wash, which matters, because re-washing a sound elevation adds a drying day for nothing.

Step 7, Wednesday, three readings per elevation: south 10, 11, 12 percent; east 11, 12, 13; west 10, 12, 12; north 12, 14, 17 percent, the 17 taken 18 in above grade behind a shrub. The gate is 15 percent at every point, so north fails on one point. Not averaged: the north mean would have been 14.3 and would have released a wet wall. North was held, the shrub was tied further back and airflow opened up, and Thursday's north readings came back 11, 12, 13 percent, all three under the gate. South, east and west coated Thursday; north coated Friday.

Step 8 removed loose film on about a third of the west elevation, all feathered to no felt step. Step 9 restored the condenser cover, four exterior receptacle covers and two fixtures, and the one circuit shut off at step 3 was closed at the panel by the lead who opened it.

References

• 29 CFR 1910.134, OSHA respiratory protection, which gates every respirator behind medical evaluation, fit testing and a written program.
• 40 CFR 745 Subpart E, the EPA Renovation, Repair and Painting rule, for the pre-1978 determination at step 1.
• Cleaner, mildewcide and coating labels, which are the binding authority on dilution, dwell, rinse and any respirator the product requires.
• Pressure washer manufacturer manual for pressure range and tip selection on your machine and substrate.
• See related: the moisture and adhesion testing standard, the wood repair and substrate priming standard.