Painting and Damp Explained

The "how to" painting guide


When should we call in a  professional painting contractor or when is it easy enough for us to take on the job ourselves? Whatever your decision is, the main objective is to get the maximum out of our selected paint by ensuring that the correct preparation is followed.


The first step that needs to be done upon any project is identification. Taking time out to notice the condition of a property or surface area is crucial. The second step is to find out what the correct preparation method is to treat the area, not following through with proper preparation can lead to your paint problems reoccurring not to long after the job has been completed. 


PAINT
Identifying and solving the paint problem:

Crocodiling

This refers to patterned cracks in the surface of the paint film that resemble the scales of a crocodile.

POSSIBLE CAUSES 
  • Applying an extremely hard, rigid coating, like a solvent-based enamel, over a more flexible coating, like a water-based primer.
  • Applying a topcoat before allowing adequate drying time of undercoat.
  • The natural aging of solvent-based paints as temperatures fluctuate. The constant expansion and contraction results in a loss of paint film elasticity.


SOLUTION
Remove the old paint completely by scraping and sanding the surface. A heat gun may be used on large surfaces to quicken the process, but be careful and avoid igniting the paint or substrate. 
Prime the surface with a high-quality water-based or solvent-based primer, and follow with two coats of a top-quality exterior water-based paint.

Chalking

The formation of fine powder on the surface of the paint film during weathering can cause the paint colour to fade. Although some degree of chalking is a normal, desirable, way for a paint film to wear, the paint film can become excessively eroded through heavy chalking.

POSSIBLE CAUSES
  • Previously using a poor quality paint
  • Using an interior paint for an outdoor application.


SOLUTION
Remove as much of the chalk residue as possible by scrubbing the surface with a stiff bristle brush and sugar soap and rinse the area thoroughly. Alternatively, use power-washing equipment to clean the surface.  Repeat this process if necessary.

Check for any remaining chalk by running a hand over the surface after it has dried. If a noticeable amount of chalk is still present, apply a quality solvent-based or acrylic water-based primer (or comparable sealer for masonry), then repaint the surface with a quality exterior coating. If little or no chalk remains and the old paint is sound, no priming is necessary.

Chalk Run-Down

This occurs when chalk from excessively eroded paint washes down onto another area below it (a brick foundation, for example), ruining its appearance (see Chalking).

POSSIBLE CAUSES
  • Using a lower-quality paint
  • Using an interior paint for an outdoor application.


SOLUTION
Remove as much of the chalk residue as possible (see Chalking). Scrub any stained areas with a wire brush and a detergent solution, then rinse the surface thoroughly. In cases of severe staining, an acid wash may be necessary. 

If the affected area dries to a different colour, consider repainting it with a quality water-based paint.

Dirt Pickup

This refers to the build up of dirt, dust particles and/or other debris on the paint film that may resemble fungus or algae.

POSSIBLE CAUSES
  • Using a low-quality paint, particularly lower grades of satin types.
  • Air pollution, car exhaust fumes, and flying dust.


SOLUTION
Wash off all surface dirt before priming and painting, using a scrub brush and detergent solution, followed by a thorough rinse. Heavier dirt accumulations may require the use of a power washer. While dirt pickup can't be eliminated entirely, top quality exterior water-based paints typically offer superior dirt pickup resistance and washability. Also, higher gloss paints are more resistant to dirt pickup than matt paints, which are more porous and can more easily entrap dirt. Regular wash down will give longevity to the paint film. 

Remove all dirt from the surface using a scrubbing brush and a detergent solution, and rinse thoroughly. A heavy accumulation of dirt may require the use of a power-washer. 

Prime and repaint the surface using a top-quality exterior water-based paint. While this type of paint will not entirely eliminate the accumulation of dirt, it typically offers superior resistance against dirt pickup, as well as greater washability. Higher-gloss paints are more resistant to dirt pickup than matt paints, which are porous and trap dirt more easily. 

Wash the surface down regularly to improve the longevity of the paint film.

Fading

Premature and/or excessive lightening of the paint colour can occur on surfaces that are regularly exposed to the sun. Fading, or poor colour retention, can also be caused by chalking.

POSSIBLE CAUSES
  • Using an interior paint for an outdoor application.
  • Using a lower-quality paint, leading to rapid degradation (chalking) of the paint film.
  • Using a paint colour that is particularly vulnerable to UV-radiation (certain bright reds, blues, and yellows, for example).
  • Tinting a white paint not intended for tinting, or over-tinting a light or medium paint base.


SOLUTION
If fading or poor colour retention is a result of chalking, remove as much of the chalk as possible by scrubbing the surface with a stiff bristle brush (or a wire brush for masonry), and rinsing thoroughly. 

Check for any remaining chalk by running a hand over the surface after it has dried. If a noticeable amount of chalk is still present, apply a quality solvent-based or acrylic water-based primer (or comparable sealer for masonry), then repaint the surface with a quality exterior coating. If little or no chalk remains and the old paint is sound, no priming is necessary. 

When repainting the surface, be sure to use a quality exterior house paint in colours that are recommended for exterior use

Frosting

This refers to a white, salt-like substance on the paint surface. Frosting can occur on any paint colour, but is less noticeable on white paint or lighter tints. On masonry, it may be mistaken for efflorescence.

POSSIBLE CAUSES
  • Protected areas (under eaves and on porch ceilings, for example) that do not receive the cleansing action of rain, dew and other moisture.
  • Using dark-coloured paints that have been formulated with a calcium carbonate extender.
  • Applying a dark-coloured paint over a paint or primer containing calcium carbonate extender.


SOLUTION
Frosting can be a stubborn, albeit uncommon, problem, and is often difficult to remove by washing alone. Moreover, the condition can recur, bleeding through to the surface even after a new topcoat has been applied. In extreme cases, it can interfere with paint adhesion. 

The best remedy is to remove the frosting from masonry using a wire brush, or from wood surfaces by sanding, and rinsing them thoroughly. Apply a solvent-based primer before adding a coat of high- quality exterior paint.

Fungal / Algal Contamination

This manifests as black, grey, or brown areas of fungal or algal growth on the surface of the paint or sealant.

POSSIBLE CAUSES
  • Areas that tend to be damp, and receive little or no direct sunlight (North-facing walls and the underside of eaves are particularly vulnerable). Algae forms in the presence of light and moist environments.
  • Using a lower-quality paint, which may contain an insufficient amount of fungicide or algaecide.
  • Failing to prime a bare wood surface before painting.
  • Painting over a surface or coating from which fungus or algae has not been removed.
SOLUTION
To distinguish fungus or algae from dirt, apply a few drops of household bleach to the discoloured area. If it disappears, it is probably fungus or algae. 

Treat the contamination with a fungicidal wash, or apply a diluted household bleach solution (one part bleach to three parts water). Leave it on for 20 minutes, applying more as it dries. Ensure that you wear rubber gloves and eye protection while doing so. Scrub and rinse the surface thoroughly, and prime it using an exterior water-based primer. Apply a premium exterior water-based paint in a matt, silk, or gloss finish, depending on the desired appearance.

Nailhead Rusting

This is identified by reddish-brown stains and spots on the paint surface.

POSSIBLE CAUSES
  • The rusting of non-galvanised iron nails, causing bleed-through to the topcoat.
  • Non-galvanised iron nails that have not been countersunk and filled over.Galvanised nailheads beginning to rust after sanding or excessive weathering.
SOLUTION
When painting a new exterior construction where non-galvanised nails have been used, it is advisable to first countersink the nailheads, then seal them with a top-quality, water-based all-acrylic or siliconised acrylic sealant. Each nailhead area should be spot primed, then painted with a quality water-based coating. 

When repainting exteriors where nailhead rusting has already occurred, wash off the rust stains, sand the nailheads, then follow the same surface preparation procedures outlined above.

Paint Incompatibility

This refers to the loss of adhesion that may occur when a water-based topcoat is applied over several coats of old, solvent-based paint.

POSSIBLE CAUSES
Using water-based paint over more than three or four coats 
of solvent-based paint may cause the old paint to lift off the substrate.

SOLUTION
Repaint the surface using another coat of solvent-based paint. Or, preferably, remove the existing paint and prepare the surface by cleaning, sanding, and spot-priming where necessary. Then paint the surface with a top quality water-based exterior paint





Peeling
When a primer and a topcoat, or multiple coats of paint, have been applied to a surface, the paint film may begin to peel in some or all layers due to poor adhesion.

POSSIBLE CAUSES
  • Moisture seeping through unsealed joints, worn sealant, or leaks in roof or walls.
  • Excess moisture escaping through the exterior walls (more likely if paint is solvent-based).
  • Inadequate surface preparation.
  • Using a lower-quality paint.
  • Applying a solvent-based paint over a wet surface.
  • The earlier blistering of the paint.

SOLUTION
Identify and eliminate the source of the moisture. Then prepare the surface by removing all loose paint with scraper or stiff wire brush, sand any rough edges, and apply an appropriate primer. Repaint the surface with a top-quality acrylic water-based exterior paint to ensure maximum adhesion and water resistance.

Poor Alkali Resistance

This refers to a loss of colour and overall deterioration of the paint film that may occur on fresh masonry. A problem often seen.
POSSIBLE CAUSES
Applying solvent-based paint or water-based paint (vinyl acetate co-polymers-type) 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.



SOLUTION
Allow new masonry surfaces to cure for at least 30 days, and ideally, for a full year before painting. If this is not possible, apply a quality, alkali-resistant sealer or water-based primer to the masonry, followed by a top-quality pure acrylic exterior water-based paint. The acrylic binder in these paints resists alkali attack

Poor Galvanised Metal

Colour loss and overall deterioration of paint film on fresh masonry. 

POSSIBLE CAUSES
Solvent-based paint or water-based paint (vinyl acetate copolymers type) was 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.






SOLUTION
Allow masonry surfaces to cure for at least 30 days, and ideally for a full year, before painting. If this is not possible, the painter should apply a quality, alkali-resistance sealer or water-based primer, followed by a top quality pure acrylic exterior water-based paint. The acrylic binder in these paints resists alkali attack.

Poor Gloss Retention

A deterioration of the paint film may result in excessive or rapid loss of lustre of the topcoat.

POSSIBLE CAUSES
  • Using an interior paint outdoors.
  • Using a lower-quality paint.
  • Using a gloss, solvent-based paint in areas of direct sunlight.


SOLUTION
While all types of paint will lose some degree of lustre over time, lower-quality paints generally lose their gloss much earlier than better grades of paint. The binder in top-quality acrylic water-based paints is especially resistant to UV-radiation, while solvent-based paints actually absorb the radiation, causing the binders to break down. 
When preparing the surface of a coating displaying poor gloss retention, follow the techniques outlined under Chalking

Tannin Staining

A brownish or tan discoloration on the paint surface may be due to the migration of tannins from the substrate through the paint film. This typically occurs on ‘staining woods’, such as redwood, cedar and mahogany. It can also appear over painted knots in certain other wood species, such as pine.
POSSIBLE CAUSES
Failure to adequately prime and seal the surface before applying the paint. Use of a primer that is not sufficiently stain-resistant. Excess moisture escaping through the exterior walls, which can carry the stain to the paint surface.

SOLUTION
Correct any possible sources of excess moisture (see Efflorescence and Mottling). After thoroughly cleaning the surface, apply a high-quality, stain-resistant solvent-based or acrylic water-based primer. Severely staining boards are best treated with a solvent-based stain-resistant primer. In extreme cases, a second coat of primer may be applied after the first coat has thoroughly dried. Finish with a top-quality water-based paint

Wax Bleed

This refers to stains that appear as a result of a waxy substance in reconstituted wood products like chipboard or MDF. When these products are painted, these staining substances can bleed through the paint – even through some ordinary primers. This can cause dirt pickup, fungal or algal contamination, and/or poor paint adhesion.

POSSIBLE CAUSES
Failing to apply a proper primer to hardboard before applying a topcoat.

SOLUTION
Apply a quality water-based acrylic primer, followed by two coats of quality acrylic paint







Blistering

These tell-tale bubbles are usually due to a loss of adhesion in areas, and the subsequent lifting of the paint film from the underlying surface.

POSSIBLE CAUSES

  • Applying solvent-based paint over a damp or wet surface.
  • Moisture seeping into the home through the exterior walls (less likely with water-based paint).
  • Exposure of the water-based paint film to high humidity or moisture shortly after the paint has dried, especially if the surface was not adequately prepared.

SOLUTION
If the blisters do not extend all the way down to the base material, remove the blisters by scraping and sanding. Then repaint the surface with a quality acrylic water-based interior paint. 

If the blisters do extend down to the base material, first locate and remove the source of moisture, if possible. Repair loose sealants and consider installing vents or exhaust fans. Finally, remove the blisters by scraping and sanding, followed by a coat of the appropriate primer. Finish it off with a top-coat of quality acrylic water-based interior paint.

Cracking / Flaking

This generally occurs as paint ages. The dry paint film splits through at least one layer, ultimately leading to the paint not being able to adhere to the surface. This condition first manifests as hairline cracks. As the problem worsens, flaking may occur.

POSSIBLE CAUSES
  • Using a low-quality paint that is not adhesive or flexible enough.
  • Over-thinning or overspreading the paint.
  • Inadequate surface preparation, or applying the paint to bare wood without first applying a primer.
  • Excessive hardening of solvent-based paint as the coating ages, resulting in it becoming brittle.


SOLUTION
Remove loose and flaking paint with a scraper or wire brush. Then sand the surface, taking care to feather the edges so that no ridges are visible. 

If several layers of paint are flaking, you may need to use a surface filler, for example Polyfilla Fine Crack Filler. If the flaking occurs in multiple layers of paint, a face filler may be necessary. 

Prime bare wood areas before repainting. Use a top-quality primer and topcoat to prevent the problem recurring.

Foaming / Cratering

Foaming refers to the tiny bubbles that may form in the paint film during the application process. As the paint dries, these bubbles may break and leave small depressions, known as cratering.

POSSIBLE CAUSES
  • Shaking a partially filled can of paint.
  • Using a low-quality paint or very old water-based paints.
  • Applying paint too rapidly, especially with a roller.
  • Using a roller cover with the incorrect nap length.
  • Excessive rolling or brushing of the paint.
  • Applying a gloss or satin paint over a porous surface.


SOLUTION
All paints will foam to some degree during application. However, higher-quality paints are formulated to ensure that the bubbles break while the paint is still wet, allowing for good flow and appearance. 

Avoid excessive rolling or brushing when applying paint, or using paint that is more than a year old. Apply gloss and satin paints with a short nap roller, and always apply an appropriate sealer or primer before using these paints on a porous surface. Problem areas should be sanded before repainting

Efflorescence / Mottling

This refers to the crusty, white salt deposits that may be leached from mortar or masonry as water passes through it.

POSSIBLE CAUSES
  • Failing to adequately prepare the surface by removing all previous efflorescence.
  • Excess moisture escaping through the exterior masonry walls from behind.


SOLUTION
If excess moisture is the cause, eliminate the source of the problem by repairing the roof, cleaning out gutters and drainpipes, and sealing any cracks in the masonry with a high-quality, water-based all-acrylic or siliconised acrylic sealant. 

If moist air is originating from inside the building, consider installing vents or exhaust fans, particularly in the kitchen, bathroom and laundry. 

Remove the efflorescence and any 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 or primer, and allow it to dry completely. Follow this with a coat of top-quality exterior house paint, masonry paint, or elastomeric wall coating.

Wrinkling

This refers to the rough, crinkled, appearance of the paint surface that occurs when uncured paint forms a ‘skin’.

POSSIBLE CAUSES
  • Applying paint too thickly (particularly when using solvent-based paints).
  • Painting during extremely hot weather or cool damp weather, which causes the paint film to dry faster on top than on the bottom.
  • Exposing uncured paint to high humidity levels.
  • Painting over a contaminated surface (dirt or wax, for example).


SOLUTION
Scrape or sand the surface to remove the wrinkled coating. If using a primer, allow it to dry completely before applying a topcoat. Repaint the surface, applying an even coat of top-quality interior paint. Try to avoid painting in extreme temperatures or humidity.

DAMP

Identifying the cause of damp:

 Rising Damp

  • Builders not installing DPC correct)
  • Lack of a dpc in old houses
  • Failure of the dpc (poor materials used initially)
  • Ground levels that are higher than the internal floor level (Moisture the by passes dpc)

  Penetrating Damp

  • Cracked masonry allows water to ingress
  • No waterproofing on parapets
  • Defective gutters or down-pipes

  Condensation

  • Poorly ventilated rooms
  • Areas of high humidity e.g. bathrooms
  • The appearance of mould on the walls

  Lateral Damp

  • Higher ground level behind a problem wall
  • Problem area behind a wall (Shower not well sealed)

Treating Damp correctly can be very labour intensive often requiring skilled experts within the industry. It is always advised that you consult a reputable contractor as damp can get tricky. Most reputable contractors use two methods, either injection or slurry or even both on one surface. Both methods work well if completed correctly.


Removing Contaminated Plaster
The slurry Process: This includes removing the contaminated plaster off the brickwork, allowing the brickwork adequate drying time, applying a chemical to the brickwork with two coats of slurry (check for pinholes) and then re-plastering the area with a good bond agent alongside another damp proofing chemical within the mix. Contractors also cut a v-joint into the plaster (rising damp) and reseal the gap between the paving bricks and wall.


Re-plastering


Applying the Slurry

















Drilling Holes into Brickwork
The Injection process: 
1.This includes removing the contaminated plaster off the brickwork, 2. Allowing the brickwork adequate drying time
3. Drilling into the brick at a sufficient height + distance from one another, creating the holes to which the chemical will be entered into. 
4 Injecting The chemical into the wall
This will form a chemical DPC which will prevent damp from rising.

Injecting Chemical DPC


Illustration of DPC line

The use of an instrument:
14.1%
A damp meter will illustrate moisture readings within the surface allowing you to know exactly where the damp is coming from and how bad the damp build within the plaster is. All reputable contractors should be able to issue you with a damp report on your property alongside your quotation. This will give you some great insight to the problem.



Always Remember
                

Painting and damp proofing is all about the preparation, followed by a quality top coat. Understanding the problem is half the battle won.


  Identify - Preparation - Paint.

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