Interior vs. Exterior Paint: What's the Difference?
Call (604) 417-6483Interior and exterior paints are engineered for completely different conditions, and using whichever can you have on hand leads to premature failure, safety issues and wasted money. Here's Texora Painting & Drywall's breakdown of how they differ, and why it matters for your next project.
For a room repaint, see our interior painting in Delta service.
The three core components of any paint
Every paint has a binder (the resin that holds the dried film together and sticks it to the surface), pigments for colour and coverage, and additives that control mildew resistance, flexibility, UV protection and dry time, and interior and exterior paints differ in how each of the three is formulated.
Binders: the most important difference
Exterior paints use softer, more flexible binders, typically acrylic or vinyl-acrylic resins, so the dried film can expand and contract when BC temperatures swing from near-freezing on a winter morning to 25°C on a summer afternoon. Interior binders are firmer so the film is scrubbable on a kitchen wall or a busy hallway, but that hard film on an exterior surface in a BC climate will crack and peel within a season or two.
Why exterior binders are not safe indoors
Exterior paints release higher levels of volatile organic compounds (VOCs), and many include fungicides and mildewcides made for open-air application that off-gas into living space indoors and can cause headaches and respiratory irritation. Some BC municipalities have restrictions on applying certain high-VOC coatings indoors altogether.
Exterior paints contain biocides and other additives that are not safe for enclosed living spaces, and even with good ventilation they will not give a better result inside a BC home than a quality interior product.
Pigments: coverage and UV stability
Exterior paints carry more titanium dioxide and other UV-stable pigments, and south-facing walls in BC's Lower Mainland take the full force of summer UV that would fade interior paint within a single season. Exterior pigments also have to resist leaching and colour bleed in a climate like Tsawwassen or Delta, where annual rainfall can exceed 1,000 mm.
Additives: what's extra in each formula
Exterior paints carry additives that have no place in an interior product:
- Mildewcides: anti-fungal biocides that stop mold growth on exterior surfaces, and a health concern indoors.
- UV absorbers: protect the binder itself from UV, which interiors don't need.
- Freeze-thaw stabilizers: help the paint survive temperature extremes during application and after curing.
Interior paints have their own:
- Blocking agents: stop tannin, nicotine or water stains bleeding through from old surfaces.
- Scrubbability enhancers: let the finish be cleaned repeatedly without burnishing.
- Low-VOC formulations: premium interior paints are formulated to meet BC's indoor air quality expectations.
Interior vs. exterior paint compared
| Property | Interior Paint | Exterior Paint |
|---|---|---|
| Binder flexibility | Firm, hard film | Soft, flexible film |
| VOC levels | Low to very low | Moderate to high |
| UV resistance | Low | High |
| Mildew resistance | Basic | High (biocides) |
| Scrubbability | High | Moderate |
| Price range (per 3.78L) | $50–$90 | $60–$100+ |
Paint brands for BC's climate
Not all paints perform equally in the Lower Mainland's wet coastal climate. These are two brands that hold up well here:
Benjamin Moore
Benjamin Moore's Aura Exterior and Regal Select Exterior lines perform well in high-moisture environments, and the Color Lock technology in Aura resists fading on the wood and fibre-cement siding common in BC. For interiors, Aura Interior is Benjamin Moore's premium zero-VOC line, with a finish that cleans without burnishing.
Sherwin-Williams
Sherwin-Williams' Duration exterior line is a thick, self-priming formula that builds more film than standard exterior paints, which suits the weathered wood siding on older Tsawwassen and Ladner homes. For interiors, Emerald offers mold-resistant properties suited to BC bathrooms and basements.
Help choosing the right paint
Not sure which product is right for your project? The Texora Painting & Drywall team is happy to walk you through product selection as part of our free quote process in Delta, Tsawwassen, Ladner, Port Coquitlam and Port Moody.
One of the two partners walks the job with you, and the written estimate names the scope and your 1, 2 or 3-year warranty term. Call (604) 417-6483.
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