What Repairs Should Be Done Before Painting a House?

One of the most common reasons paint jobs fail early is not the paint. It is what was — or was not — done to the surface before the paint went on.

Painting over a cracked surface does not fix the crack. It covers it temporarily. Painting over mould does not solve the moisture or contamination problem beneath it. Painting bare timber without primer does not properly protect it — the topcoat has a weaker bond and is more likely to peel.

Surface repairs before painting are not extras to consider after the scope is set. They are part of the scope. Here is what typically needs addressing before any repaint — interior or exterior — and why.

Repairs before painting are not optional extras. They are one of the biggest factors in whether the finished paintwork holds up over time.

Interior Repairs Before Painting

Plaster cracks and holes

Hairline cracks in plaster walls and ceilings are common in Melbourne’s established homes — particularly around door frames, window reveals and cornices where building movement concentrates. These need to be filled with appropriate flexible filler, allowed to cure fully, sanded smooth and spot-primed before painting.

Larger cracks — step cracking around windows, separation at cornices, cracks wider than 3mm — may indicate ongoing movement and need assessment before filling. Filling a crack that is still moving will result in the same crack reappearing through the new paint within months.

Holes from removed fixtures, hooks and nails need filling and sanding flush. A filled hole that is not sanded smooth will be visible in the finished paint under raking light.

Mould staining

Mould on interior walls and ceilings — common in bathrooms, laundries, south-facing rooms and spaces with poor ventilation — should be treated before painting. Painting over mould with a standard topcoat does not address the underlying moisture or contamination issue, and staining, blistering or peeling can return if the surface is not properly treated.

Treatment involves applying a biocidal wash, allowing adequate dwell time, cleaning the surface, and applying an appropriate stain-blocking primer before topcoating. Bleach wiped over a surface and painted over is not adequate mould treatment.

Water stains and bleed-through

Water stains on ceilings from roof or plumbing leaks can bleed through standard topcoats — sometimes through multiple coats — unless the stain is sealed with an appropriate stain-blocking primer. The stain should be confirmed dry and the underlying leak addressed before painting, or the stain may continue to develop.

Surface contamination and adhesion

Kitchen walls and surfaces near cooking areas accumulate grease and silicone residue that prevents paint adhesion. These need cleaning and degreasing before painting — not just wiping down. Bathroom surfaces may have silicone residue from sealant work. Both need specific preparation before new paint will adhere.

Timber doors, frames and skirtings

Bare timber — exposed by sanding, damage or stripping — needs priming before topcoating. Timber that has been painted without primer will show adhesion failure at the bare sections. End grain on door edges and frames is particularly important to seal.

Exterior Repairs Before Painting

Render cracks

Render cracks on brick veneer homes are common — particularly around windows and at control joints. Hairline cracks usually need flexible fillers that can accommodate minor movement. Wider or step cracks should be assessed before filling to determine whether they indicate ongoing structural movement that needs addressing before any cosmetic repair.

A filled render crack that is not primed will show through the topcoat — the different porosity of the filler versus the surrounding render creates a visible patch. Correct spot priming after filling prevents this.

Mortar deterioration

Brick homes with deteriorating mortar between courses or around window reveals may need repointing or mortar repair before painting. Painting over deteriorating mortar does not properly solve the issue — water may continue to penetrate and accelerate deterioration beneath the paint.

Timber fascia, eaves and frames

Timber fascia, eaves, window frames and exterior joinery with surface cracking, UV damage or early rot need assessment before painting. Soft or rotted timber usually needs to be repaired or replaced — painting over deteriorating timber does not properly protect it, and the failure can continue beneath the new coat.

End grain on fascia boards and window sills is a common entry point for moisture. These sections need to be sealed and primed appropriately before topcoating.

Moss, lichen and biological growth

Exterior surfaces with moss or lichen growth — common on south-facing walls, under trees and in shaded areas — usually need biocide treatment before washing and painting. Pressure washing can remove visible growth, but it may not deal with embedded spores. Without treatment, regrowth can occur and contribute to early coating failure.

Weatherboard specifics

Weatherboard homes require more pre-paint assessment than brick or render. Peeling paint needs to be removed — not just painted over — to prevent the new coat from lifting with it. Gaps between boards need filling with flexible caulk to prevent moisture entry. Bare timber sections need priming before topcoating. End grain on cut boards needs sealing.

Multiple accumulated paint layers need adhesion testing before new coats are applied. Incompatible paint systems — oil-based over water-based — can cause delamination if not correctly managed.

For homes with timber cladding, see our weatherboard painting service for how we assess peeling paint, gaps, bare timber and end grain before painting.

Why Painting Over Problems Fails

The physics of paint adhesion are unforgiving. Paint bonds to surfaces, not to problems beneath surfaces. When the surface moves — as cracks do — the paint over it moves too and eventually breaks. When mould grows beneath a coat, the biological activity disrupts the adhesion and the coating lifts. When moisture is present behind a stain, it migrates through the new coat over time.

None of these failures are the fault of the paint. They are the predictable result of applying a coating over conditions that prevent it from performing.

The reliable way to get a result that holds up is to address the surface conditions before paint goes on. This adds time and cost to the job, but it is one of the main factors that determines how long the finish performs.

One Team, One Scope

At Melbourne Renovation Experts, visible surface repairs are scoped as part of the painting job where relevant — not treated as an automatic add-on after quoting. We assess the surface on-site before quoting, identify what needs addressing, and include the agreed repairs in the written fixed-price scope.

This means you do not need to organise a plasterer before the painter can start, or discover mid-job that the quote did not include obvious repairs that were visible during inspection.

• See how we approach interior painting
• See how we approach exterior painting
• See our weatherboard painting service
• Understand realistic painting costs

Frequently Asked Questions

Do I need to fix cracks before painting?

Yes. Painting over unfilled cracks usually produces a temporary result — the crack can reappear through the new paint, especially if movement continues. Cracks should be filled, cured, sanded and primed before topcoating.

Should mould be treated before painting?

Yes. Painting over mould with standard paint does not address the underlying moisture or contamination issue. Mould should be treated, cleaned and sealed with an appropriate primer before any topcoat is applied.

What repairs need to be done before exterior painting?

Exterior repairs before painting typically include filling render cracks, treating moss and lichen growth, repairing or replacing deteriorated timber, sealing end grain on fascia and window sills, and filling gaps in weatherboard. The specific scope depends on the property type and surface condition.

Can a painter do repairs and painting in the same job?

Yes — for minor plaster, timber and surface repairs, this is usually the most efficient approach. A painting company that can assess, scope and include relevant surface repairs in the same job can reduce the need to coordinate multiple trades before painting begins.