What ‘Surface Preparation’ Actually Includes (and Why Two Quotes Differ)

Two quotes for the same house can differ by thousands. Almost always, the gap is not the paint — it is how much preparation each painter has actually allowed for. Prep is invisible once the job is finished, which is exactly why it is the first thing cut.

Here is what proper preparation involves, so you can read a quote and see whether it is in there.

Why prep decides how long the job lasts

Paint does not hold a wall together. It sticks to whatever is on the surface. If that surface is dusty, chalky, greasy, damp or already flaking, the new coat is bonded to the failure underneath — and it takes the failure with it when it goes.

This is why early paint failure is nearly always a prep failure. Peeling within a couple of years, patchy sheen, filler edges showing through, cracks reopening: none of those are the tin’s fault.

What a full preparation actually includes

1. Clean the surface

Interiors: wash down where there is grease or residue, particularly kitchens, bathrooms and anywhere near a heater. Exteriors: remove dirt, chalking and any mould or lichen growth, and let the surface dry properly before anything else happens. On older homes, cleaning method matters — high-pressure water is not appropriate on every substrate.

2. Deal with what is already failing

Loose, flaking or blistered paint has to come off back to a sound edge, and the edge feathered so it does not telegraph through the finish. Painting over a flaking edge produces a visible ridge and a coat that lifts at that ridge first.

3. Repair the substrate

• Cracks cut out and filled properly rather than skimmed over
• Holes, dents and old fixing points filled
• Damaged or drummy plaster patched
• Rotten or split timber addressed — paint does not fix timber
• Rust cut back and treated before coating, so it is stopped rather than covered

4. Find out why, not just fix what

Recurring mould in a bathroom, a stain that keeps coming back through the ceiling, bubbling on one wall only — these are symptoms. Painting over them buys a few months. If there is a leak, a ventilation problem or rising damp behind it, the cause needs fixing first or the new coat fails in the same spot.

5. Sand

Sanding levels the fillers, knocks back the gloss on existing coatings so the new paint has something to grip, and takes out brush marks and grit from the last job. On pre-1970 homes this step comes with real constraints — dry sanding lead paint is not acceptable, and asbestos cement must never be dry-sanded or water-blasted. We have written separately about that.

6. Prime and seal

Bare substrates, patched areas, new plaster, timber knots and stained surfaces all need the right primer or sealer. Skipping this is what causes patch flashing — where every filled spot shows through the finish as a different sheen. A stain blocker is a different product from a general primer, and using the wrong one means the stain arrives back through both top coats.

7. Mask and protect

Floors, fixtures, glass, hardware, gardens and paving. This is not just tidiness — overspray and drips on someone’s floor are the most common complaint in the trade, and they are entirely preventable.

How to see it in a quote

The phrase to be wary of is “prep as required”. It sounds thorough and commits to nothing. A scope you can hold someone to names the work:

• Which surfaces are being washed, and how
• What repair work is included — and what will be treated as a variation if it is found once work starts
• Where primer or sealer is going, and what product
• How many finish coats, of what product
• What is explicitly not included

That last one is worth asking for directly. A painter who will put exclusions in writing is a painter who has actually thought about your job.

The honest bit about variations

Some things cannot be seen until work starts. Rot under a windowsill, plaster that turns out to be drummy across a whole wall, a leak that only shows once the old coating comes off. Nobody can quote those accurately from the front yard.

What we can do is tell you before we start which parts of the house we are unsure about, and what the likely cost is if the worst case turns up. A surprise you were warned about is a variation. A surprise you were not warned about feels like something else.