Exterior paint problem solver

Even the most professional painters can run into problems. But the good news is that there are solutions for almost all of them. For each problem you’ll find a guide to identifying it, its causes, solutions and in some cases, how to prevent the problem from happening altogether.

Exterior – Alligatoring

Have you spotted patterned cracks in the surface of your paint film that resembles an alligator’s scales?

This can be caused by several things:

  • The application of an extremely hard, rigid coating (like a solvent-based enamel) over a more flexible coating, like a water-based primer.
  • Applying your topcoat before the undercoat is dry.
  • The natural aging of oil-based paints as outdoor temperatures fluctuate – the constant expansion and contraction of the paint based on the temperature can result in a loss of paint film elasticity.

How to fix it:

Old paint should be completely removed by scraping and sanding the surface. A heat gun can be used to speed up your work on large surfaces, but be careful not to ignite the paint or substrate. Then commence painting following instructions on the can.


Exterior – Blistering

Have you noticed bubbles in your paint film? It’s called blistering and results from the loss of adhesion between the paint and its underlying surface.

Blistering can be caused by:

  • Painting a warm surface in direct sunlight.
  • Applying an oil-based or alkyd paint over a damp or wet surface.
  • Moisture escaping through the exterior walls (this is less likely with latex paint than oil-based or alkyd paints).
  • Exposure of latex paint film to dew, high humidity or rain shortly after paint has dried.

How to fix it:

If the paint is found to be unsound, it will need to be completely removed and stripped back to a sound substrate before any painting occurs. Old painted surfaces will require adequate surface preparation. The first step is to carry out a series of “adhesion tests” to clearly determine how sound or unsound the existing paint work is. To determine this, cut a small X through the existing paint with a sharp blade, press cellulose tape firmly across the cut and then rip off the tape. If the paint comes off, it is unsound and should be removed. Once the paint is deemed to be sound, the surface is ready to be painted.


Exterior – Dirt Pickup

The accumulation of dirt, dust particles and/or other debris on your paint film may resemble mildew and isn’t the best look.

It can be caused by the use of a low quality paint, by soil splashing onto the substrate or by general air pollutants like dust and exhaust fumes collecting on your house body and horizontal trim.

How to fix it:

Simply wash away all surface dirt before priming and re-painting. If you’re unsure whether the problem is dirt or mould, conduct a simple spot-test.

To clean off the dirt, use a scrubbing brush and some detergent solution, followed by a thorough rinsing with a garden hose. If the dirt is heavy, you may need to use a power washer.

Dirt pickup can’t be eliminated entirely but top quality exterior latex paints offer superior dirt pickup resistance and washability to minimise its impact. Higher gloss paints are also more resistant to dirt pickup than flat paints, which are more porous and can more easily entrap dirt. Diamond Weather Defender is recommended.


Exterior – Efflorescence & Mottling

Crusty, white salt deposits, leached from mortar or masonry as water passes through is known as mottling.

Generally mottling occurs when you fail to adequately prepare a surface by removing all previous efflorescence. This leads to moisture escaping through the exterior masonry from the outside leaving the unsightly, white salt deposits.

How to fix it:

Eliminate the source of the excess moisture by repairing the roof, cleaning out gutters and downspouts, and sealing any masonry cracks with a high quality, water-based all-acrylic caulk.

If moist air is originating inside the building, consider installing vents or exhaust fans, especially in kitchen, bathroom and laundry areas. Remove the efflorescence and all other loose material with a wire brush, power brush or power washer, then thoroughly rinse the surface.

Apply a quality water-based or solvent-based masonry sealer and allow it to dry completely. Then, apply a coat of top quality exterior house paint, masonry paint or elastomeric wall coating. Diamond Ace Duraflux is recommended.

Exterior – Fading & Poor Color Retention

Apply Is your paint work looking a little dull?

Apply Premature fading often occurs on surfaces with a sunny exposure. It can also be due chalking of the coating and can be caused by any of the following:

  • Using an interior grade of paint for an outdoor application.
  • Using inferior quality paint
  • Using a paint color that is particularly vulnerable to UV rays (most notably bright reds, blues and yellows).
  • Tinting a white paint not intended for tinting, or over tinting a light or medium paint base.

How to fix it:

Apply Color change due to the “fading” effect is irreversible once it begins to occur and the color can often become quite irregular or patchy in appearance. To eliminate the effect the entire surface will need to be pressure washed and/or scrubbed with a non-metallic scouring pad to remove all surface contaminants and chalking prior to repainting.

Apply To minimise the “color fading” effect:

  • Diamond Ace Weather Defender is recommended as it exhibits UV protection and high performance color durability
  • Select lighter colors as they absorb less heat and UV radiation


Exterior – Lapping

Have you noticed that there are areas of denser color or higher gloss where wet and dry layers overlap during painting?

This is caused by not maintaining a ‘wet edge’ while painting.

How to fix it:

To maintain a wet edge, apply your paint towards the unpainted area and then back into the just-painted surface. Brushing from “wet to dry,” rather than the other way around will help produce a smooth, uniform appearance. It’s also wise to minimise the area being painted and plan for interruptions at a natural break, such as a window, door or corner.


Exterior – Chalking

Chalking is the formation of fine powder on the surface of the paint film during weathering, which can cause color fading. Although some degree of chalking is a normal, desirable way for a paint film to wear, excessive film erosion can result in heavy chalking which is never a good look.

Generally there are two things that cause chalking: the use of a low-grade, highly pigmented paint or, using of an interior paint for an outdoor application.

How to fix it:

To eliminate the effect completely, the entire surface will need to be pressure washed and/or scrubbed with a non-metallic scouring pad to remove all surface contaminants and chalking prior to repainting.

The use of a water based 100% acrylic latex topcoat provide superior exterior durability and gloss retention relative to many alternative coatings systems, especially oil based enamels. A number of Diamond® decorative paint products could be considered but for maximum gloss retention, the Diamond Weather Defender range provides the best performance.


Exterior – Nail Head Rusting

Reddish-brown stains on the paint surface are caused by nail head rusting.

Nail head rusting can be caused by any of the following:

  • Non-galvanised iron nails that have begun to rust, causing bleed-through to the top coat.
  • Non-galvanised iron nails that have not been countersunk and filled over.
  • Galvanised nail heads that have rusted after sanding or excessive weathering.

How to fix it:

If you’re painting a new exterior construction where non-galvanised nails have been used, countersink the nail heads, then caulk them with a top quality, water-based all-acrylic caulk. Each nail head area should be spot primed, then painted with a quality latex coating.

When repainting exteriors where nail head rusting has occurred, wash off all the rust stains then sand the nail heads and follow the same surface prep procedures as you would for new constructions.

Exterior – Peeling

Peeling may involve one, some or all coats of paint from the primer right through to the topcoat.

It can be caused by any of the following:

  • Seepage of moisture through uncaulked joints, worn our caulk or leaks in the roof or walls.
  • Excess moisture escaping through exterior walls (this is more likely if paint used is solvent-based).
  • Inadequate surface preparation.
  • Use of inferior quality paint.
  • Applying a solvent-based paint over a wet surface.
  • Previous blistering of paint .

How to fix it:

First, try to identify and eliminate the cause of moisture . Then, prepare the surface by removing all loose paint with scraper or wire brush. Sand rough surfaces and prepare surface as per label instructions prior to painting.

Exterior – Poor Alkali Resistance

Poor alkali resistant is the loss of color and overall deterioration of paint film on fresh masonry.

It occurs when oil-based paint is applied to new masonry that has not cured for a full year. Fresh masonry is likely to contain lime, which is very alkaline. Until the lime has a chance to react with carbon dioxide from the air, the alkalinity of the masonry remains so high that it can attack the integrity of the paint film.

How to fix it:

Always allow fresh masonry surfaces to cure for at least 30 days, but ideally for a full year, before painting. If this is not possible, apply a quality, alkali-resistant sealer or water-based primer. Diamond Ace Acrylic Primer Filler, Sealer and Undercoat followed by Diamond Weather Defender is recommended.

Exterior – Poor Gloss Retention

Poor gloss retention is the deterioration of paint film that results in excessive, or rapid loss of lustre in the topcoat.

This can occur when an interior or inferior quality paint is used outdoors. It can also occur when solvent-based paints are used in areas of direct sunlight.

How to fix it:

Use a high quality paint. While all types of paint will lose some degree of lustre over time, lower quality paints will generally lose gloss much earlier than better grades. The binder in top quality acrylic latex paint is more resistant to UV radiation. Surface preparation for a coating showing poor gloss retention should be similar to that used in chalking surfaces .

The use of a water based 100% acrylic latex topcoat provide superior exterior durability and gloss retention relative to many alternative coatings systems, especially oil based enamels. A number of Diamond® decorative paint products could be considered but for maximum gloss retention, the Diamond Weather Defender® range provides the best performance.

Exterior – Surfactant Leaching

Have you noticed a blotchy, sometimes glossy appearance with tan or brownish casts? This is surfactant leaching – a concentration of water-soluble ingredients on water-based paint, that’s more likely with tinted paints than with white or factory-colored paints.

Causes of surfactant leaching include:

  • Painting in cool, humid conditions or just before they occur. The longer drying time allows the paint’s water-soluble ingredients – which would normally evaporate, or be leached out by rain or dew – to rise to the surface before paint thoroughly dries.
  • Contact of mist, dew or other moisture with the painted surface shortly after it’s dried.

How to fix it:

Avoid painting in the late afternoon if cool, damp conditions are expected in the evening or overnight. If the problem occurs in the first day after painting, the water-soluble material can sometimes be rinsed off easily. Fortunately, even more stubborn cases will generally wear off in a month or so.

Generally, the leached surfactant does not lessen the durability of the paint film, it just looks unsightly. On exterior surfaces, surfactant leaching will usually weather off over a short period (approximately a month) without the need for intervention. Rinsing with fresh water can help to wash it away.

Under severe conditions, surfactant leaching may reappear once or twice until all the surfactant has been removed. The effect will be less noticeable each time and can be removed by washing in the same manner as prescribed above. On rare occasions, the leached material may stain the paint surface. This would require a repaint once the surface has been thoroughly washed and the paint film has cured.

Exterior – Tannin Staining

Tannin Staining is the brownish or tan discoloration on a painted surface due to migration of tannins from the substrate through the paint film. Typically, this occurs on ‘staining timbers,’ such as redwood, cedar and mahogany, or over painted knots in certain other types of timber.

Causes of tanning staining include:

  • Using a coating that is not sufficiently stain-resistant
  • Excess moisture escaping through the exterior walls and carrying the stain to the surface.

How to fix it:

First, correct any possible sources of excess moisture. After thoroughly cleaning the surface, apply an exterior top coat with tannin blocking properties. Diamond Weather Defender is recommended following application instructions on the can. For severely stained boards an oil based primer such as Diamond Duraflux Primer, Sealer and Undercoat is recommended before applying the top coat.

Exterior – Wrinkling

We all know the sun can give us wrinkles, but did you know it can do the same to your paint? Wrinkling is a rough, crinkled paint surface that occurs when paint forms a ‘skin’.

In addition to hot weather, wrinkling can also be caused by:

  • Paint being applied too thickly (more likely when using solvent-based paints).
  • Painting a hot surface or in very hot weather.
  • Exposure of uncured paint to rain, dew, fog or high humidity levels.
  • Applying the topcoat to insufficiently dried first coat.
  • Painting over contaminated surface (e.g., dirt or wax).

How to fix it:

Scrape or sand substrate to remove the wrinkled coating. Then, repaint with an even coat of top quality exterior paint. Apply paints at the manufacturer’s recommended spread rate (two coats at the recommended spread rate is better than one thick coat). If painting during extremely humid, cool or damp weather, allow extra time for the paint to dry completely.

Exterior – Cracking / Flaking

Cracking or flaking is the splitting of a dry paint film. This is a problem that needs fixing as it can lead to complete failure of the paint. Initially, the problem appears as a hairline crack, before evolving to flaking of paint chips.

Cracking and flaking is caused by:

  • Use of a lower quality paint that has inadequate adhesion and flexibility.
  • Over thinning the paint or spreading it too thin.
  • Poor surface preparation, especially when the paint is applied to bare timber without priming.
  • Painting under hot or windy conditions that make water-based paints dry too fast.

How to fix it:

If caught early, it may be possible to correct superficial cracking by simply removing the loose or flaking paint with a scraper or wire brush, sanding to feather the edges, then priming any bare spots and repainting. However, if the cracking goes down to the substrate, you’ll have to remove all of the paint by scraping, sanding and/or using a heat gun prior to painting.

Exterior – Mould

If you’ve noticed black, grey or brown areas on your painted surface, chances are you’re dealing with a mould problem.

As with mould anywhere else, exterior mould is caused by moisture. It’s often found on areas that are damp, and receive little or no direct sunlight (the underside of eaves are particularly vulnerable). Mould is more likely to occur after use of a lower quality paint, failure to prime bare wood before painting, or if you’ve painted over a coating of mould without removing it.

How to fix it:

First, test for mould by applying a few drops of household bleach to the discolored area. If it disappears, it is probably mildew. Remove it by scrubbing with a diluted household bleach solution (one part bleach, three parts water). Be sure to wear rubber gloves and eye protection. Power washing is also an option. Then rinse thoroughly prior to applying exterior top coat. Diamond Weather Defender is recommended.