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How To Waterproof Your Basement The Right Way

I live in the Pacific Northwest and it rains a lot here in the winter time. One of the big problems people have is moisture and water in their basements. The problem is we get so much rain, over 100” in some areas, that the ground just gets saturated and the water needs to go somewhere. The best thin you can do if you are building a new house with a below ground living area is to apply extra sealer to the outside of any concrete walls. But what if you have an existing house water problems?

There are a lot of small things you can do that will help you to get rid of the moisture.

If your basement is damper than normal, water is dripping down the walls or even seeping through cracks you really need to waterproof your basement. In order to do any basement waterproofing the first thing you need to do is determine what is causing the water to enter your basement. A wet basement is usually caused by one of three different things, although it can be caused by a combination of these three things.

What Causes Wet Basements
Poor construction is one of the reasons why your basement might be leaking, although this is probably more common in newer homes that start leaking without warning. The house settling is another cause for a wet basement. When a house starts to settle the foundation often shifts a bit and that is what causes the cracks in the basement walls and sometimes the floor. The last cause would be water pressure that has built up outside the wall and is being forced inside the house through the walls. While all of these causes can be fixed, water being forced inside the walls due to excessive pressure is going to be the hardest.


Believe it our not, a lot of wet basement problems can be solved just by getting the ground water away from the walls. Usually when a home is built the soil around the foundation is sloped away from the the structure so that any water from rain and snow melt will actually run toward the yard and not puddle up next to the foundation. Over the years, the soil in this area can be compacted down and the water may actually be flowing toward the house from the yard and then puddling up and seeping down along the basement walls and finding its way inside.

If you can get this ground water away this may solve your problem. Another way that water can be introduced into the soil around the house is with a broken or poorly installed gutter and downspout system. There is a lot of water that falls on the roof during a rain storm and it needs to be channeled away from the house. This is the function of your gutters and downspouts. It used to be recommended that the rain water be be discharged at least 2′ away from your foundation but lately the feeling is more like 10′, especially in particularly wet areas like where I live.

Often time, if you can get rid of this water then you problem will be solved. But if not, there are several other methods to try.

Can I Use Waterproof Paint To Waterproof My Basement?
One question that many people ask is basement waterproof paint enough to fix any water leaks in the basement. Generally, if there is just not moisture collecting on the wall then this is worth trying. If the water leaks involve water seeping on through the walls of the basement a paint or internally sealer will usually not be enough. When using the paint you will want to follow the directions on the paint can to ensure you use the recommended spread rate. Also, most of these won’t adhere to the wall properly if it is wet. This is a project you should do during the driest part of the year.

When applying the paint use a roller on smooth surfaces and a brush for any masonry areas. Any pin-sized holes that you see should be covered with more paint; you do not want any holes showing through. Wait a few days for the paint to thoroughly dry and apply another coat. Two layers will usually fill in any tiny voids that are allow the water to migrate through the concrete or cement block wall.

Fixing Holes And Cracks
Before you can use any basement waterproof systems, you will need to fix the areas where water is leaking into the basement. Luckily, finding where the water is leaking through the basement walls or floors is easy to do. What you need to do is look closely at the walls and floors for any moisture that is coming through the walls or floors. Also, look for staining that usually occurs especially if your ground water has a high mineral content. This will mainly happen where the walls meet the floor, but also along any cracks that have formed due to shifting.

If the cracks you are trying to fix are bigger than 1/8 inch, you need to clean it out and apply a patch before you can waterproof. You can buy a patch made from epoxy and latex cement that works well. However, if you are on a tight budget you can make your own repair patch. To make your own patch you can just use mortar material and see if that works. Mix the dry mortar powder with a small amount of water till it gets sticky. When adding water you only want to add enough to make the mixture stiff, you do not want it to be runny or it will not stick to the walls and run down it instead.

To fix the crack or hole where water is simply seeping through you will need to force the patch into the crack with a trowel; you can also use a putty knife. If the water is being forced through the wall due to pressure from the outside, you can try to chip out some of the crack to form a dovetail groove. When chipping the concrete you want to do so carefully, the dovetail groove is important because that is what allows the mortar mix to stick once it has dried. Chipping towards the crack to form a “V” does not work because once the mortar dries it falls right out. Instead, the dovetail is an inverted “V” which means the opening is wider inside the crack than it is on the surface. This way, when the mortar or patch material cures it will be locked in place.

Holes are fixed similar to cracks in the walls or floors. When fixing a hole the first thing you want to do is chip away the broken parts forming a dovetail. Once everything has been chipped away, fill the hole with the mortar mix making sure to smooth it out. When smoothing out the mortar you are making sure that there are no air pockets and that it is pressed into the entire hole.

Like the waterproof paint above, if you are going to try to patch these cracks and holes from the inside you need to be sure the wall is dry so the patch material will adhere and stick. If there is water present you will not have very good luck. Also, water from the outside that is being forced inside will be hard to stop with these internal patches. You may need to go outside and attack the water problem along your wall.

Inserting A Weep Pipe
If you have water being forced through the walls due to outside pressure then one way to get rid of the pressure is to install a weep pipe. Installing this kind of pipe allows the water on the outside to escape through the pipe into the basement so the pressure is no longer a problem. This probably sounds crazy because the whole goal of this project is to keep the water out. The idea behind the weep pipe is control where the water comes in and then you can more easily deal with it.

The weep pipe can be drilled into the wall to relieve the pressure until your sealing materials have a chance to set up and seal the cracks and holes. One of the best things about these pipes is they can be permanent or temporary depending on the situation. When leaving the pipe in place it will need to be drained into a sewer drain or via a sump pump.

Install the weep pipe where the wall and floor meet or where the water pressure is the highest. After installing the pipe, you will want to use water proof sealer or regular patching mortar to fill the crack from the top of the crack all the way to the bottom. Working from the top down enables better bonding with of the mortar. The mortar should be forced into the crack with a trowel up to the point where the pipe is installed. Allow the mortar to dry, which can take up to several hours or longer depending on how thick the application is. Once it has dried if the water is no longer coming through the pipe you can remove the pipe and fix the problem, but if water is still coming through you need to drain the pipe.

To remove the pipe you will need to fill in the hole and treat the cracked area all the way to where the wall and floor meet, even if the crack does not go down that far. Another option is to use a pipe with a threaded end and then just cap it off. This way, if you have any problems in the future you can take the cap off and drain the water that has build up along the wall. For a long term solution you can leave the pipe in and let the water drain into a sump and then pump it out.

Fixing A Leaky Floor Joint
Part of waterproofing basement floors involves fixing a leaky floor joint; in fact, this is probably the most common place to find leaks. If the leak is a minor one you can usually fix it by applying two layers of waterproofing mix with a trowel, where the joint is leaking. If it is a major leak, you will need to create a dovetail along the joint. Once you have dovetailed the entire leaking area you will need to clean it out. The best way to clean it out is to blow the dust and debris out of the newly chipped area. Using a trowel apply the mortar mix in small amounts, smoothing it out as you go along. When applying the mortar mix make a slight incline, slanting it upwards from the floor to the wall. This prevents any water from collecting in that same area in the future.

Remove The Paint For The Best Waterproofing Results
If your walls are already painted you will need to remove the paint before you can waterproof the walls. The reason for this is that the mixtures will not stick to the paint. To remove the old paint you can sand it away, scrub it off with a wire brush, or you can sandblast it away.

Waterproofing The Basement From The Outside
The last line of defense against a wet basement is to dig a trench around the foundation and apply the proper sealer to the outside of the walls. This is the most expensive fix but it also is the one that has the most chance of future success for years to come. This is usually not a job that a do it yourself homeowner can do because trench work can be very dangerous.
I would try to possible solutions above before you go to this extreme.

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