Basement waterproofing works, but only when it is done right. Most people will rely too heavily on waterproof paints to do the heavy lifting or old school products like tar.

Here are the 2021 rules of basement wall waterproofing that should never be broken. And if they are, it almost always leads to a disaster.

This is a breakdown of the main DOs and DON’Ts of basement wall waterproofing that every homeowner should know.

Waterproofing Basement Walls

Basement flooding is a serious problem. The following are things that you should do when trying to keep moisture out of your basement.

1. Do wait - Confirm walls are to blame

The first step you should take is to investigate the source of the moisture problems.

The best way to do this is to cut out a piece of aluminum foil — a one-square-foot piece will do. Tape the piece onto your walls. After about a day, check the aluminum.

If it has moisture on the outer-facing surface, then you only have a high humidity problem in your basement. You can solve it by simply investing in a humidifier.

But if the moisture is on the inner-facing surface, then water is likely seeping into your basement from the outside. In this case, you will need to waterproof your walls.

2. Do wire brush or sandblast old paint away

Concrete sealers are designed to bond well with concrete or masonry walls. Therefore, you will get the best results by making sure that you apply the sealer directly to the wall.

Old paint can get in the way of sealer-concrete bonding. Therefore, it is always a good idea to remove every trace of old paint before beginning the sealer application process.

As far as techniques are concerned, using a sandblaster on the painted walls is the most efficient way to remove the paint.

However, wire brushing can also work. And for most homeowners, it is the most affordable, and convenient, way to prep the wall for sealer application.

3. Do use muriatic acid to remove efflorescence

After constant exposure to moisture, the interior walls of a finished basement will eventually start to develop white deposits. If you want the best results from your sealer, you will need to get rid of these deposits.

This is because if you apply the sealer over them, they will reduce the effectiveness with which the sealer adheres to the concrete wall. And the best way to get rid of this efflorescence is to use muriatic acid.

4. Do use hydraulic cement to seal off cracks on interior basement walls

Instead of using typical mixes to seal cracks and openings — like the ones that form along cold joints –, you should use hydraulic cement.

Thanks to the additives it comes pre-mixed with, it settles fast. When doing so, it also expands. This allows it to create water-tight seals that help eliminate any chance of water leaking into your basement.

5. Do install an interior drain tile

Hydrostatic pressure is the source of most moisture problems in a finished basement. This makes trying to relieve this pressure a key component of the basement waterproofing process.

Interior drain tiles are great at relieving hydrostatic pressure. When you install them on your basement floor, their perforated walls will let in water. These pipes will then guide the water to a central area where it can be pumped out of the basement by a sump pump.

Interior drain tiles are a must-have for any finished basement. This is because they help to prevent water problems before they happen. And given the fact that they don’t require regular maintenance, installing them on your own basement floor is prudent.

Waterproofing Basement Walls Before Finishing

6. Do install a sump pump

An interior drainage system is incomplete if there is no way to get rid of the collected water. To complete it, you will need to install a sump pump that will pump the water away out of your basement.

7. Do use a high-quality waterproofing paint

Waterproofing paints work. They are effective at covering surface holes. As a result, they can turn a porous wall into a water-resistant one. And when used in conjunction with other basement waterproofing techniques, these paints can eliminate basement water infiltration problems.

Unlike when applying normal paint, waterproofing paint needs to be applied generously.

The first thick coat should be to cover any surface holes and perforations. The subsequent coat will then be used as a finishing coat, designed to create a water-tight layer of defense against water seepage.

8. Do apply silicate-based concrete sealers on the basement wall

If you don’t want to use waterproofing paint, you can opt for silicate-based concrete sealers.

Unlike waterproofing paint, these sealers don’t just cover the concrete surface. They penetrate the concrete surface and then react with the concrete. This results in a durable waterproof surface. And what is even better is the fact that after applying these sealers, you can still paint the wall.

9. Do install an exterior waterproofing membrane

If the basement flooding risk that you are facing is extreme, then interior waterproofing will not be enough.

In some cases — like when dealing with porous walls or highly finished basements, it may even not be an option.

In such cases, installing an exterior waterproofing membrane is advisable.

Do so by first digging around the foundation wall. Cover the wall with the membrane. And then fill up the dug-out area. This will give the walls an added layer of protection against water infiltration.

10. Do add an exterior drain tile

While an exterior waterproofing membrane will be enough in most cases, you can go a step further by installing an exterior drain tile.

When installed, it will intercept any water and drain it away before it has a chance to get to your basement wall.

11. Do slope soil away from your house

You can protect your walls from moisture infiltration by making sure that soil gradually slopes away from your foundation walls.

Maintaining a steady slope of no less than 6 inches per 10 feet is recommended. And eventually, when the soil around your home settles, building back the crown is advisable.

DON'Ts of waterproofing concrete basement walls

When waterproofing your basement, there are things that you should never do.

Here are some of the most common mistakes homeowners make.

1. Don't use tar

While tar can form a water-tight seal, it is a poor material choice for waterproofing a basement wall. This is because when it cures, it becomes brittle.

This makes it more prone to cracking. And it is something that definitely compromises its ability to protect your basement space from moisture infiltration. As a result, it increases the odds of ending up with entire basement floods.

2. Don’t use limestone as backfill

It is a bad idea to backfill with limestone.

This is because it does not have good drainage qualities. It is in fact more likely to clog any adjacent drainage structures. Gravel is a better backfilling material choice.

3. Don’t start repairs on a flooded basement

You should never start doing repairs on interior basement walls while the basement is still flooded. This is because doing so increases the risks of electrocution.

Therefore, before repairing cracks, holes, or gaps in the walls, you should get rid of all the water in the basement. The best way to do so is to use a sump pump.

4. Don’t over-rely on waterproofing paint

Waterproofing paint can work, but only when it is used in conjunction with other basement waterproofing techniques. When used alone, it is usually no match for hydrostatic pressure.

And while it can help to create a water-tight seal on the surface of concrete, this seal will easily break off when used in a seeping basement.

Therefore, thinking that you can skip external waterproofing just because you have waterproofing paint, is a mistake that you should never make.

5. Don’t seal the cove joint to stop water seepage in a finished basement

The joint that forms where the basement wall meets the floor is often a weak link. When there is too much hydraulic pressure, it tends to let in water into the basement.

Trying to seal this joint as a way of stopping water infiltration is a bad idea. It is something that you should never do simply because it will increase hydraulic pressure buildup against your walls. This is bound to cause more damage as the pressure looks for another outlet.

Therefore, sealing the cold joint with hydraulic cement as a way of stopping water infiltration is a definite waterproofing “DON’T”.

6. Don’t forget to install a window well drainage system on a basement window

Window wells usually form an easy entry point into the basement. Therefore, if water is allowed to collect in your basement’s window well, chances of water seepage will increase. This is what will happen if you forget to install a drainage system beneath the window well of your basement window.

This is a mistake that can be remedied by doing two things. The first is to cover the window well with a sloped cover. And the second is to dig around the window well — about two feet deep — and then fill the hole with gravel.

7. Don’t drain your basement too quickly

If your basement is flooded, draining it too quickly can be disastrous. This is because the process will lead to an almost-instant pressure imbalance that will result in outside water rushing in trying to fill the void left. It can end up damaging your foundation walls.

When is basement waterproofing necessary?

It is time to start basement waterproofing as soon as you notice obvious signs of water infiltration. These signs include the following.


Efflorescence. Efflorescence is a common sign of constant moisture exposure. It usually appears as white stains that tend to sparkle and it is usually created by mineral deposits that are left behind after moisture evaporates from the concrete surface.


Water puddles. If you notice water puddles in your basement, then you should definitely start investigating whether they are a result of moisture infiltration through the walls. And if this is the case, you should start waterproofing your walls immediately.


Rusty nails. If you have nailed items like family pictures on the walls of a finished basement and they start showing obvious signs of rust, then you probably have a moisture problem.

Water may be seeping through the foundation wall and waterproofing your walls may be the only way to stop further damage.


Accumulating water outside your home. If a pool of water forms outside your home, especially near your foundation, you should definitely think about waterproofing.

This is because this water might find its way into your basement through cracks. It may even generate enough hydrostatic pressure to a point where it forces itself through cold joints.

As a result, waterproofing the walls may be the only way to stave off an impending disaster.


Musty smell and mold staining. If your basement has a distinct earthy and musty smell, chances are that you have a mold problem. In such a case, you should investigate the source of excessive moisture by using a piece of aluminum foil.

If the test confirms that your basement wall is the source, you should start thinking about waterproofing them.


Water stains. Stains on a basement wall are commonly caused by water seeping through cracks in the wall. And if there is no other explanation as to why the stains keep forming, chances are that the walls need to be waterproofed.


It is better to waterproof your basement from the outside. This is because it allows you to intercept the infiltrating water before it has a chance to damage your walls.

Furthermore, you will have more space, hence more freedom, when waterproofing from the outside. This plays a role in increasing your options as far as waterproofing techniques are concerned.

You can waterproof your basement without digging by using waterproofing paints or silicate-based concrete sealers.

Adding soil around your home to create a sloping crown will help. And so will sealing any cracks, gaps, or openings on walls with hydraulic cement.

Yes, inside waterproofing works.

When you install internal drain lines and a sump pump drainage system, you will be able to stop any infiltrating water from flooding your basement.

Sealing cold joints with hydraulic cement helps to close off weak links. And applying waterproofing paint and concrete sealers are effective ways to reduce the permeability of concrete walls.

Yes, waterproofing a basement is worth it because it helps to prevent water damage.

It can save your home from structural damage. It can prevent premature cracking and splits. And it can also save your valuables from moisture damage.

As a result, when you consider the potentially disastrous effect that water infiltration can have on your home and your valuables, waterproofing basements is totally worth every penny.

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Timothy Munene
Author: Timothy Munene - Timothy is a freelance writer and an online entrepreneur.