At GOPAINT, surfaces are washed, scraped, sanded, caulked and primed before the finish coats. This guide explains what each of those steps does, why it matters in a climate like Ottawa's, and what you can look for when comparing quotes.
Washing: removing what paint cannot stick to
Exterior surfaces collect dirt, pollen, spider webs, chalky residue from old paint and, on shaded walls, mildew. Paint applied over any of these sticks to the contamination rather than the surface, and can start peeling far sooner than it should.
Washing is usually done with a pressure washer at a sensible setting or by hand with a cleaner suited to the surface. Too much pressure can force water into siding joints, damage soft wood or etch brick mortar, so the method depends on the material. Mildewed areas often need a mildew cleaner, not just water, or the growth comes back through the new paint.
After washing, the house needs time to dry completely before any paint goes on. Wood in particular holds moisture, and painting over damp wood is one of the most common causes of blistering and peeling.
Scraping and sanding: getting back to a sound surface
Any paint that is loose, flaking or lifting has to come off. Scrapers remove the loose material back to an edge that is firmly attached, and sanding then feathers those edges so they do not show as ridges under the new coat. Glossy areas are also scuffed so the new paint can grip.
Bare wood exposed during scraping needs attention. Wood that has weathered grey has a damaged surface layer that should be sanded back to fresh fibres before priming, otherwise the primer bonds to a weak base. Soft or rotten wood is a different matter: it needs repair or replacement, which is assessed separately from painting.
Older homes can have lead-based paint in their lower layers. If your house is older, ask how the existing paint will be checked and how scraping debris will be contained and collected; sanding or scraping lead paint without precautions spreads dust around the property.
Caulking: closing the gaps where water gets in
Caulk seals the joints between trim and siding, around windows and doors, and at corners. Over time it shrinks, cracks and pulls away, opening gaps that let rain run behind the siding and trim. Failed caulk is removed and replaced with a paintable exterior sealant before painting.
Caulking is not a cure for everything. Joints that are meant to drain, such as the bottom edges of some siding and the weep holes in brick, should be left open. Knowing which gaps to seal and which to leave is part of doing the preparation properly.
Priming: a stable base for the finish coats
Primer is applied to bare wood, repaired areas, new caulk where the product requires it, and surfaces that would otherwise not hold the finish well, such as some metals and very chalky old paint. It seals the surface, evens out how the finish coat absorbs, and improves adhesion.
Different surfaces need different primers: bare wood, knots that can bleed through, galvanised metal and masonry each have suitable products. Spot-priming only the areas that need it is common when the rest of the old paint is sound. Once primed, the surface is ready for the finish coats, which are what you see and what face the weather.
Protecting the property while the work is done
Preparation creates mess: paint chips, sanding dust, wash water and old caulk all end up somewhere. Gardens, decks, walkways and vehicles near the house are covered or moved, windows and doors are masked where needed, and debris is collected as the work goes rather than left for the end.
It helps to agree on a few practical things in advance: where the crew can park and set up, which outdoor taps they can use, whether pets will be in the yard, and any plants or features that need extra care. Trimming back shrubs and branches that touch the walls before the work starts also gives the crew room to prepare those areas properly.
When preparation is finished, the whole house is checked before painting begins, because a missed patch of loose paint or a forgotten gap in the caulk is much easier to fix at this stage than after the finish coats are on.
Preparation steps at a glance
| Step | What it does | Skipping it risks |
|---|---|---|
| Washing | Removes dirt, chalk and mildew | Paint bonding to grime and peeling early |
| Scraping | Removes loose and flaking paint | New paint lifting with the old |
| Sanding | Feathers edges and scuffs gloss | Visible ridges and poor grip |
| Caulking | Seals joints against water | Water behind trim and siding |
| Priming | Seals and stabilises bare areas | Uneven finish and weak adhesion |
Questions about exterior preparation
Why does preparation take so long?
Because it is where most of the durability comes from. Washing, drying, scraping, sanding, caulking and priming each have to be done in order, and some, like drying, cannot be rushed.
Can you paint over old exterior paint?
Yes, if it is clean, well bonded and dull enough for the new coat to grip. Loose paint must be removed first, and glossy areas are scuffed. Paint over failing paint will fail with it.
Do I need to be home during preparation?
Not usually. As long as the crew has access to the outside of the house, water and somewhere to work, most homeowners carry on as normal. Let the painters know about any days or hours when noise would be a problem.
Is rotten wood repaired as part of the paint job?
Rot is a repair rather than preparation. It is identified during the assessment and discussed separately so you can decide how to deal with it.
How does GOPAINT prepare exterior surfaces?
Surfaces are washed, scraped, sanded, caulked and primed before the finish coats, and we use premium exterior-grade coatings for the finish.