Exterior Wall

How do I waterproof my exterior wall?

The golden rule in waterproofing is to stop water from getting in and not to try and stop it from getting out. This sounds pretty obvious doesn’t it, but you’d be surprised at the number of even experienced builders who start trying to seal leaks from inside. Mind you finding the point of entry may not be easy; water can travel a long way through a structure or even saturate it completely making finding the source a difficult task.

When exterior walls are exposed to rainwater or high humidity, water and moisture can travel through the masonry and affect your internal walls. This means that your walls may stay damp for a long time before drying, which may lead to mould growth and irreparable damage. In humid areas like Florida, wall damage due to water penetration isn’t a matter of IF, but a matter of WHEN.

How can you prevent water and mould from affecting your walls? By following the next seven steps to waterproofing exterior walls.

We have a wide range of external waterproofing services at Hitch Property Constructions.

Why do we get leaks?

The walls of most buildings these days have reinforced concrete vertical columns with reinforced ring beams along the top that provide the strength. The areas between the columns and beams have an infill of light concrete blocks or soft local red bricks with a skim of hard concrete on the surface. The reinforced concrete is often very poorly made with cracks and cavities in it, and the infill is like blotting paper (sorry you might not remember that, like a sponge).

This sort of structure is very rigid and the regular earthquakes we get in Bali (yes we get lots, usually so small we don’t even notice them but now and again one that will wake you up in the night) and these regular ground movements result in cracks in structures usually through the walls of buildings.

It is also very rare to find a tradesman who will work logically through the symptoms of a problem and accurately identifying the cause rather than taking the easy way out and treating the first thing he sees.

Exterior Wall

How Does Inadequate Waterproofing Harm Exterior Walls?

Exterior walls which are not adequately waterproofed will remain damp longer than those that are. Aside from the fact that this environment is the perfect breeding ground for mould, the damage may extend further and lead to unwanted water penetration.

Selecting The Correct Waterproofer

Choosing the right waterproofing paint is essential. The best brands are those who are breathable and that allows the exterior walls to “breathe” in a way that prevents and eradicates excessive moisture. You will also need a plaster additive. The right plaster is not only a good way to enhance the aesthetics of the exterior wall, but it can also make them more solid. The best coating is comprised of concrete which is specially designed for masonry as it can be added to virtually any surface.

The highest quality brands are silicate-based since they provide the strongest seals. The material is designed in such a way where it targets the very ingredients that are used in concrete masonry, forming a perfect coating that is versatile and can be used even for walls which are unpainted or unsealed.

While the majority of exterior plasters incorporate waterproofing characteristics, the infiltration of water and the problems that come with it can be avoided through the placement of waterproof additives inside the plaster.

Prepping The Walls For Waterproofing

To prep your exterior walls for waterproofing, it is essential to use high-quality filler, so that you can fix and patch holes or cracks which are present. The filler must be given enough time to dry out prior to grinding or sanding away any excess material, ensuring that the surface is even and free of dust. Once the walls are dried, you can then apply the waterproofing.

The best tool for applying to waterproof is a good brush or roller. Sometimes walls will need a second coat, and if so you will need to make certain the initial coat is completely dried before applying the second. The barrier you create must be able to resist moisture infiltration. The best way to make sure it works is through testing.

How do we stop water getting into walls?

So we have water in a wall, how do we deal with it?

First, check into a detoxification centre to deal with our alcoholic escapism, this will stop the DTs and the bloodshot eyes.

Next check into an ashram. Take a nine-month course in transcendental meditation where we learn to love for all living things (including cats) and acceptance of the water issues in our lives.

Finally, get a shave and a soothing massage.

Now we can return home, apologies to the cat, hide the bottle of gin and start thinking about our wall.

First – find where the water is getting in.

As we all know, it is a basic law of nature that water flows downhill, so we start at the highest point.

Is the wall open to the elements at the top or is the roof overhanging? If the roof is not overhanging look along the top of the wall and checks for cracks, even very fine cracks. Does the upper surface have a waterproof coating? Is there a concrete roof or a parapet wall? It may be that water is getting in where the concrete roof slab meets the wall or through the parapet wall and into the top of the wall below.

Leaks from cracked concrete roof gutters

A very common problem in Bali is leaking concrete gutters. It is regarded here that it is very bad form to allow water from your roof to run off onto a neighbour’s property or into a street. If a building is built right against the property line, and very many are, then usually a concrete gutter is built along the top of the wall to catch water from the roof and take it away. These concrete gutters have two basic problems:

  1. Ground movement often results in cracks across the gutter which allow water into the wall. If the cracks are small, this can be fairly easy to fix. The gutter must first be cleaned thoroughly then waterproofed in the inside, and it is best to do the whole gutter while you are at it.
  2. Wall gutters are often built with the outer wall higher than the inner wall so that if the gutter fills with water, it will overflow into your building either across the ceiling or down the inside of the wall. In Australia, roof gutters are made of plastic or aluminium and purposely have the outer side of the gutter lower than the inner side, so if they fill up, they will overflow outwards. To solve this problem first make sure that the drain pipe from the gutter is large enough to take the roof area it has to drain and that the outer side of the gutter has low points cut in it to provide overflow points. These should, of course, be lower than the inner side of the gutter. It is also a good idea to make sure that downpipes have a gap between the gutter and the ground so that water cannot back up in the pipe.

Check the surfaces of the wall.

When you have checked along the top of the wall next look at the surface of the wall. Carefully check it from top to bottom. Is it open to the weather? Note that if you are in a windy place, the wind can drive rain at steep angles against the wall. Sensibly designed buildings have good roof overhangs which are designed to keep the rain off the walls. Roof overhangs also keep sunshine off walls and so keep inside room temperatures down.

If you have a wall exposed to rain you can waterproof it to stop water getting in. Take particular note of any cracks in the wall which will need special treatment, and we’ll come to that in a minute.

A word of warning, a wall needs to breathe so that if water does get into it, it can evaporate out again. Do not waterproof both inside and outside surfaces of a wall. If you do, you may well always have damp walls.

Rising damp

The last thing to check for is rising damp. This is very common in Bali where damp proof courses are not installed, but it can be fixed if you are know-how. Like poaching an egg, this is not something you would trust to people who don’t know what they are doing. The solution is to cut out a horizontal slit right through the bottom of the wall and the full length of the wall � yes this needs great care, and for obvious reasons, you don’t do it all at once. You then fill the slit with high-density cement. This is known as a sloof and will stop water rising inside the wall from the ground beneath. Techniques widely marketed in Britain (usually of very dubious efficacy) such as injecting silicone solutions are not available here. They would probably not work because of the high porosity of the batako blocks in the walls.

Looking for external waterproofing Melbourne? Check out Hitch Property Constructions.

Sealing the leaks

Alright so we have found the cause, how do we treat it? The traditional method is to use a skim of high-density waterproofing cement, but this is not a method I recommend. This type of waterproofing film is very brittle and can crack. On a surface exposed to sunshine, the excess surface heat will crack the concrete skim away from the wall beneath, allowing water to enter which can travel between the concrete skim and the surface beneath.

My treatment of choice is a thick polymer paint applied with a brush. It comes in different colours. There are cheaper local versions, but I suspect you get what you pay for. Cracks need special treatment as they are likely to suffer further movement. Raintite comes with a membrane material, rather like a thick bandage. Paint the Raintite polymer along both sides of the crack, stick the bandage over the crack along its length then paint the bandage to saturate it with the polymer fully. If the crack moves, the bandage will stretch a bit and maintain the waterproof film. It should be noted that these polymers do not like water.

Before applying a waterproofing polymer, the surface must be very clean and dry. Any loose paint, moss or dirt must be removed first, and the surface must be dry. Wait for a day when the surface and any cracks have fully dried out before you waterproof.

For general waterproofing of walls in good condition Dulux Weathershield is the universally respected waterproof paint for outside walls but again, make sure the wall can breathe.

Now we have dealt with the difficult stuff we can move on to easier things. Show the chimpanzee how to stand on one foot while holding the pan in the other and, taking the egg in its one hand and a spoon in its teeth.

Simple Steps to Waterproofing Exterior Walls

Check walls for faults. 

Waterproofing external walls are the best solution only if the walls become damp as a result of rainwater or moisture. Before shopping around for waterproofing products, it’s important to eliminate any other causes of structural dampness. It could be anything, from cracks in your bricks or condensation within the wall to a burst water pipe. Once you fix the issue, you can apply a waterproofer as a preventative measure. 

Clean your gutters 

The problem with clogged gutters isn’t only that they may flow over the edge, down your walls; they also retain rainwater, which is gradually absorbed by the roof’s wood or fascia boards, potentially leading to a series of problems, including rotten wood, leaks, and mould. You can avoid all these and keep your home healthy by simply cleaning your gutters twice a year.  

Select the right waterproofer 

A series of waterproofing products are available today to help homeowners protect their homes from external moisture. Here are a few products you should consider:

  • concrete waterproofing coating, which is a cement-like product that adheres to concrete and masonry permanently; it can be applied to any surface, including painted walls;
  • silicate-based concrete sealer, which reacts with the ingredients in masonry and concrete to form a waterproofing coating; this sealer can only be used on unsealed/unpainted walls;
  • Waterproofing paint, which is similar to acrylic wall paint, with the main difference that it delivers better waterproofing performance. It’s very important to choose a breathable formulation that is specially designed to allow walls to breathe and eliminate moisture. The product can be applied to surfaces previously painted.

Use plaster waterproofing additive. 

Plastering can help improve aesthetics, make walls more solid, and protect them against moisture ingress. Though most exterior plasters have waterproofing characteristics, you can eliminate water infiltration problems and prevent reoccurrence by simply adding a waterproofing admixture to the plaster.

Prepare your walls for waterproofing. 

Irrespective of the product chosen for waterproofing exterior walls, you have to bring your walls in good condition first. This means that you need to use a good-quality filler to repair cracks and patch holes. Allow the filler to dry optimally before grinding. Then sand away rough, uneven areas, remove dust by cleaning the surface with water and let the walls dry completely to ensure good adhesion between the waterproofer and the substrate.

Apply the waterproofer 

You can use a roller or a brush to apply the waterproofer. If a second coat is required, allow the first coat to dry and then apply the second coat fully. Use enough product to create an impenetrable barrier against infiltration.


Conducting a water-tightness test is very important to evaluate the effectiveness of the products used for waterproofing exterior walls. For this test, water should be sprayed on the wall surface for a couple of hours, keeping the nozzle at a 30-degree angle. Your home will pass the test only if a moisture meter shows there is no moisture. By waterproofing exterior walls, you’ll not only prevent serious damage but also boost the value of your home.  

Proper Exterior Waterproofing

The number one thing needed to properly waterproofing the exterior of a structure is – care. Yes, you must care. You must use proper materials, take your time and have pride in the workmanship. Without these things, your home will not be waterproofed correctly.

Moisture is transferred from the outside of the building to the basement interior by four primary mechanisms—first, water flow. Water takes the path of least resistance, if this is into your basement, then that is where the water will flow. Second, capillary action. Concrete is a porous material, and it is very hard yet porous. Think of capillary action being like a wick. As concrete sets in water, this water is absorbed by the concrete until it becomes complete saturated and then disperses moisture and water vapour to the inside of the home.

Next is vapour diffusion. Vapour diffusion is much like capillary suction, except with water vapour. Water vapour only needs the smallest of openings to penetrate a structure and raise humidity levels. Lastly, air movement. Any time that a door or window is opened not only are you bringing air into the home, but you are pulling air from the basement to the upper living levels. This is known as the stack effect. Your home acts like a chimney drawing air from the bottom toward the top. 40% of the air we breathe in our homes comes from the basement.

At Hitch Property Constructions, we offer Melbourne external waterproofing services. 

What should you do?

If exterior water is making its way into your basement or crawlspace, you are in need of proper exterior waterproofing. To properly waterproof your home, it will need to be excavated. The footing will need to be exposed, and all exterior issues will need to be dealt with.

Foundation walls will need to be cleaned, and then a spray or roll on polymer waterproofing product will need to be applied. Once dry, this coating will need to be covered with a dimple board product that protects your newly sealed surface and also allows better water flow downward. The next step is to install a drainpipe system that is properly sloped for continuous drainage. This slope can be to a sump pit or daylight, depending on the site layout. The drain pipe is then covered with a ¾” clean rock. This rock backfill can be from 1′ up to 60% of the wall height, depending on the soil conditions. On top of the rock, non-woven geotextile material is wrapped to help filter soil without clogging. After the geotextile material installation soil backfill can begin, this soil needs to be native clayey soils that resist water intrusion. Backfilling with loose soils creates a highway for the water opposed to clay soils that force water away.

Proper exterior waterproofing is no small chore and should not be attempted by unqualified people. You are protecting your home, and the job should be done correctly and provide a permanent solution to your home. Remember, though, and exterior wall waterproofing cannot prevent water from moving deeply below your foundation walls. This water can move through your basement or crawlspace floor. In these cases, an interior drainage system will complement your exterior efforts, not replace them. An interior drainage system is not waterproofing. Interior drain systems are water management agents that relieve excess water from around and under your foundation.

Also, keep in mind that if you are moving the exterior water to a sump pump system, this system must be up to the task. Modern sump pumps, battery backup sump pumps and high-quality sump basins are available to remove this collected water away from your home.

Foundation drain tile systems are the means by which groundwater can be transported away from your basements foundation and floor. If you want a dry basement and a sound foundation, you must have an adequate foundation drainage system.

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