Power Washing Before Painting:
Why It Matters

The Adhesion Problem

Paint adhesion is fundamentally a chemistry problem. For paint to bond properly to a surface, the binder in the coating needs to make molecular contact with the substrate. Anything sitting between the paint and the surface — salt crystals, biological films, loose chalk, dust, oil — breaks that contact and dramatically reduces bond strength.

In Bermuda specifically, three contaminants are almost always present on any exterior surface that hasn't been recently washed:

• Salt deposits — Salt is highly hygroscopic (water-attracting). Salt contamination beneath a paint film causes osmotic blistering — the film lifts as moisture is drawn through it toward the salt layer. In Bermuda's humid environment, this process is accelerated.
• Biological growth — Algae and mould colonies are common on Bermuda exterior surfaces, especially on north-facing walls and shaded areas. These organisms produce metabolic acids that weaken the substrate and prevent adhesion.
• Paint chalk — UV-degraded old paint leaves a chalky powder on the surface. Painting over chalk is essentially painting onto loose dust — you're bonding to the chalk, not the wall, and the chalk will delaminate.

What Power Washing Actually Achieves

A professional power wash before painting does several things simultaneously:

• Removes salt deposits and surface contamination that would compromise adhesion
• Kills and removes algae and mould (when combined with appropriate biocidal detergents)
• Strips loose and chalking paint film, revealing the stable underlying substrate
• Opens the surface profile of masonry, increasing mechanical adhesion for the new coating
• Reveals damage, cracks, and areas needing repair that were hidden under surface dirt

The Correct Process for Bermuda Exteriors

Professional preparation for a Bermuda exterior repaint follows a specific sequence:

1. Pre-treatment with biocidal wash — Apply a diluted biocide solution to the entire surface. Allow 15–30 minutes dwell time to kill biological growth.
2. High-pressure wash — Using appropriate pressure (typically 1,500–2,500 PSI for most masonry; lower for softer limestone). The pressure must be high enough to strip chalk and loose material without damaging the substrate.
3. Allow full drying time — Bermuda's humidity means this can take longer than expected. Applying paint over a damp substrate is a common cause of blistering and is as problematic as not washing at all. On humid days, 48–72 hours of drying time may be needed.
4. Inspect, fill, and repair — Once the surface is clean and dry, conduct a thorough inspection. Fill cracks, repair spalling areas, and treat any active moisture ingress points.
5. Prime — A penetrating masonry primer consolidates the substrate and ensures the topcoat has a consistent, stable base to adhere to.

Only after completing all five steps is the surface ready for the first topcoat.

Why Homeowners Should Not DIY the Wash

Consumer pressure washers are typically rated at 1,200–1,800 PSI and often lack the flow rate (GPM) needed to effectively remove salt and chalk from large areas. They also rarely have the detergent injection capability needed for biocidal treatment.

More importantly, inappropriate pressure — too high in the wrong location — can cause spalling on weathered limestone and damage to window seals and joint fillers. Too low, and the wash is ineffective. Professional equipment and technique matter.

T&H Painting includes full professional surface preparation on every exterior repaint project. It's not an optional add-on — it's the foundation of every job we take on. Explore our full services including power washing, or get a quote for your project.

The Cost of Getting It Wrong

A proper professional wash adds cost and time to a project. But consider the alternative: paint applied over a contaminated surface typically begins to blister, peel, or delaminate within 12–24 months under Bermuda conditions. You've paid for the paint, the labour, and the disruption — and you'll pay for it again much sooner than you should have needed to.

The preparation stage is where the quality of a paint job is actually determined. The final appearance may be set by the topcoat, but the durability is set by what happened before the first brush or roller touched the wall.

Read more on related topics: how often to repaint your Bermuda home and why roof painting in Bermuda is non-negotiable.