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Foundation Waterproofing

Foundation Waterproofing Cost Guide 2021

It's hard to pick any one part of your house as the most important.

Floors and walls? Definitely important.

Roof? Of course.

Doors and windows? Yes and yes.

A home is like an industrial production line where all parts work together to provide shelter, comfort, and warmth, so no individual pieces of the system can function without the others. However, an argument can easily be made that the foundation is the basis of it all, and without it, the rest of the house would be deprived of a strong standing base that supports the entire structure.

Most homeowners would never ignore a broken window, leaking roof, or a sunken floor, but many will ignore a basement leak until it wreaks havoc on the home's foundation. 

Whether you decide to renovate or build your dream home, it's always prudent to waterproof your foundation. Avoid foundation leaks, mold growth, and musty basements by ensuring the waterproofing of your foundation walls.

Are you looking for accurate cost information related to foundation waterproofing? Perfect, you're in the right spot. In this guide, you'll learn:

  • What it means to waterproof a foundation
  • How to waterproof a foundation
  • How to save money when waterproofing your foundation

Let's dive right in!

What Does it Mean To "Waterproof" Your Foundation?

Concrete block foundations are typically strong and sturdy. Even so, eventually, soil and hydrostatic pressure can overwhelm the mortar, causing it to erode. The breakdown may allow groundwater to seep into hollows and joints, making its way into your basement. In severe cases, the foundation walls can begin to cave in. Due to the porous nature of concrete blocks and crawl spaces, they are particularly susceptible to mold. To avoid issues in the long run, experts always recommend waterproofing your foundation.

Basically, foundation waterproofing is the process of preventing water from seeping into a basement from the outside. It typically involves putting in place a system that can prevent water ingress into the structure and effectively control hydrostatic pressure. 

The question is not so much about stopping water from entering your basement, but rather what approach you should use to prevent it. The extent of the damage, the level of disruption the waterproofing solution causes, and the financial costs are all factors to consider when weighing your options.

Below are four major types of foundation waterproofing solutions available:

1. Dampproofing

The first solution is dampproofing. This entails applying tar, solvent based acrylic sealer, or acrylic-modified cement to the outer surface of a wall. This entire process's main goal is to stop the transference or wicking of water vapor through your concrete walls by creating a strong waterproofing membrane.

It's worth noting that dampproofing is not intended to keep all the moisture and liquid water out. It's a process that only works by blocking out moisture for a while. However, with the absence of hydrostatic pressure to drive water seepage and correctly installed foundation drains at the footing, dampproofing can offer long-lasting protection for your basement and crawl spaces.

Your dampproofing cost can vary from as little as $200 per wall to upwards of $2,000 per wall. To be sure of the cost, have a waterproofing contractor assess your foundation first.

2. Waterproofing Paints and Primers

If your home is under construction or renovation, waterproofing paints and primers might be your best bet. This solution involves applying a sealant (which in our case is a waterproofing paint/primer) to any problem areas where mold grows or where cracks allow water to seep in. Interior sealants will not only prevent condensation from forming but also protect your foundation walls against water that originates from melting ice and snow.

Waterproofing primers go for as low as $30, while elastomeric coatings can range between $1.30 to $1.80 per square foot. So if you are confident in your DIY abilities, it shouldn't cost you an arm and a leg to waterproof your home's foundation.

3. Exterior Drainage Systems 

Unlike the other two strategies, an exterior drainage system seeks to move water out of the ground instead of simply blocking it. Even if you're a do-it-yourself kind of person, it's prudent to leave the installation of drainage pipes in the hands of professionals. This arrangement is quite costly, with French drains, for example, going for $20 to $30 per linear foot—more on this solution below.

4. Interior Drainage Systems

An interior foundation drainage system looks a lot like an exterior French drain, only that it is made of perforated pipe littered with stones to prevent it from blocking/clogging. It works by collecting water from the water table and runoff that might infiltrate the basement. The system then drains this water into a sump pump, which channels it out of the basement. This ensures your foundation remains super dry.

Here are the costs for the different sections of an internal drainage system:

  • Sump pump: $500-$1,000
  • Crawl space interior drain: $800-$300
  • Basement interior perimeter drain: $4,000-$12,000

Want to learn more about how to install an internal drainage system? Check out this series of YouTube videos from AskBuilder: 

How To Waterproof a Foundation

Step 1- Dampproofing

First off, it's important to note that proper waterproofing always starts with the home's exterior. We're looking to answer: What can be done to help keep away water from the home's foundation from the outside?

Often, this can be achieved with dampproofing. It all starts with excavation. Here, all soil will be dug away from your home's foundation up to a depth of 7-8 feet. The team will then dig a trench around the concrete foundation and fill it with gravel and drain material. 

What follows is the actual process of dampproofing. Depending on your home's exact issue, the crew will apply a waterproofing membrane and/or chemical sealant to the exterior foundation walls. 

Step 2- Installing an Interior or Exterior Drainage System

Next up, the team will line the trench with a drainage mat that has molded dimples. Ideally, the mat should be cut out to the exact depth of the foundation. 

Now it's time to complete the weeping tile or French drain. The pipe (mostly 4") will be installed at the footing weeping the water table below the basement floor. To complete the French drain installation process, the crew will backfill the trench with gravel. 

As for interior drainage systems, you can have a drain tile system and sump pump installed. Or, if you are a DIY enthusiast, you can jackhammer the floor, install the entire system, and replace the floor in a matter of days. However, it's best to leave the job to foundation specialists as they have a better grasp of where to install the system. Often, drain tile systems in pre-existing homes are installed under the concrete slab.

Step 3: Grading 

Grading plays a vital role in where the water ends up on your property. It's one thing to dampproof and install drainage systems, but without proper grading, you're staring down at more foundation leaks in the future.

When looking at the grading, you should be looking at all the areas around your house, including the gardens, paved areas, the lawn, and the landscaping directly surrounding the perimeter.

All water that falls within 10 feet of your house (rain or snowmelt) without pooling (water only runs downhill). Generally speaking, the ground should drop 1 inch for every 1 foot that you move away from the house for the first 5 - to - 10 feet around your property.

To improve or fix the grading, add soil next to the foundation such that it slopes away from the house. However, you should have at least 4" of your foundation (stone, block, or concrete) showing above the soil. This ensures that water continues to flow away from the house instead of pooling.

Keep in mind that improper grading can be just as bad as not grading at all. If you're a little skeptical about your grading skills, it's best to leave the task to a professional. 

Your landscaping specialist will be able to ascertain whether the ground is uneven and whether it's contributing to poor basement drainage. Then, they'll eliminate the topsoil to shape the ground below it so that there'll be enough drop in the grading as you move away from the house.

Step 4: Applying Waterproofing Paint or Primer

As we said, a waterproofing primer or paint creates a barrier between the actual wall of the house and moisture. While waterproof paint is best applied on basement walls or inside the house, it can also be applied on the exterior of the house on the foundation. Here's how to properly apply it:

  • Remove excess mortar - Use a stiff brush to brush away any chunks of mortar that appear loose or crumbling. 
  • Patching - Fill any gaps with fresh mortar. Remove excess mortar with the trowel and allow the mortar to properly cure.
  • Nix the moisture - Set up the dehumidifier and run it for days prior to painting or priming.
  • Painting/Priming - Use a paint sprayer when working on the exterior walls of your home. You can also use a paint sprayer on the inside of the house for vast areas, but a paint roller will help you access even the tightest of spaces.

Step 5: Install Gutters & Downspouts

Another important step in waterproofing your foundation involves installing downspouts and/or gutters.

These two systems are unsung heroes, so it pays to get it right from the word go. Below, we tell you how to install gutters and downspouts correctly:

  • Cover the basics of the project - Ensure you have all the tools you need for the job, including step/extension ladder, work gloves, power drill, 25-foot tape measure, screws, gutter brackets, gutter sealant, caulking gun, and tin snips.
  • Prep your fascia and soffits - Perform a thorough inspection of the flat boars underneath your roof (fascia) as well as the area between gutters and the wall (soffits). Replace any soffits or fascia that are rotten, damaged, or otherwise missing.
  • Get a helping hand - Request a friend or family member to give you a hand holding gutters/downspouts in place for drilling.
  • Direct your drainage - It's prudent to install all gutters with a slight angle for water to drain towards the downspouts and out to the yard. For gutter runs shorter than 40 feet, select one direction for the water to drain, and pitch the "high" end of the gutter run on the opposite side of the run from the downspout. As for the runs that are 40 feet or longer, pitch your gutter such that its highest position is in the middle of the run. Then slope it downward in the direction of the downspouts positioned at both ends of the run.
  • Measure carefully - Hang your gutters based on the manufacturer's instructions. Always measure twice before cutting.
  • Attach the downspouts - Our assumption is that you've already marked the location of the downspout on the low end of the gutter. If so, go ahead and secure the downspout outlet to the gutter with pop rivets or screws. 

Step 6: Installing an Interior Drainage System

This process is very similar to installing an external drainage system.

Start by laying out an internal French drain along walls that meet on the corner where the sump pump is situated. If your basement floor is sloped towards opposing corners, it's best to install two French drain pipes, each directed towards the low-lying corners. This goes a long way in improving drainage. 

Use an electric jackhammer to dig up a runoff trench that extends 10-12 inches below the base of the concrete floor slab. Install a waterproofing membrane (such as tar paper, acrylic polymer, and so on) around the basement walls from where it extends to the runoff trench to the top of the wall. Pour at least 2 inches of gravel into the base of the runoff trench. Follow it up with fitting a French drain inside the runoff trench. Make sure the French drain is well centered. Then attach a PVC elbow to the end of the French drain that is on the opposite end of the runoff trench from the sump pump. 

Lay the French drain inside the trench, making sure it's well-positioned. Then fill the trench with more gravel until it's on par with the base of the concrete slab. Ideally, the French drain and trench should span the entire length of the walls, with the PVC elbow on the opposite side as the sump pump. Again, this job is best left to professionals.

How To Save Money When Waterproofing Your Foundation?

There's no reason why homeowners with the skills (and the waterproofing products and tools) can't install a French drain or pitch a gutter. It's important, though, that you know your limitations and don't take on a foundation repair project you can't handle. If you take on a foundation waterproofing project only to abandon it midway, you've wasted whatever you spent on waterproofing materials and tools, not to mention your time. You'd have been better off to have called in a professional from the word go.

Talking about professionals, don't call the handyman, general contractor, or plumber to fix your wet basement. They might be good at what they do, but that doesn't mean they know the ins and outs of basement waterproofing. A foundation specialist is your best bet in this regard.

What's more, you need to be picky when selecting a waterproofing company. There's no such thing as "one-size-fits-all" solutions. If you hire a basement waterproofing company that provides a full range of services, you'll get what you are looking for, not what they sell.

Again, desist from spending on what you don't need. The most common source of foundation seepage in your area might be wall cracks, which can be swiftly and permanently fixed by injecting polyurethane into and through the cracks. This repair might only cost you a couple of hundred dollars. Don't spend thousands of dollars for a French drain or some other waterproofing system when you don't need it.

On the other hand, if your foundation is almost sinking or you notice other signs of water seepage in your foundation, don't slap a cheap "bandage" repair on a severe problem. Call in a pro right away. They can possibly fix the issue much more economically now than later when it gets worse.


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