10 Steps for Waterproofing an Existing Outside Wall


The old stone house that I was renovating and planning to move into, was built from a barn on a Pennsylvania property originally deeded in 1696. The north side of this building was built into the ground and when it rained heavily, the groundwater came in at floor level inside. The heavier it rained, the bigger the wave of water that ran through the building that would be my home.

Solution: We put together a successful plan with the help of a Construction Contractor, who was a good friend of mine. This was what we came up with.

  1. Exposed the outside of the wall – The dirt and fill used to originally back-fill against the wall need to come out. Along with the old field tile or any drainage pipe that was being used, it has to be removed down past the footer.
  2. Clean the dirt and debris from the wall- The caked-up dirt on the house has to be cleared away so that the next couple of steps will work better. Broom or brush the wall cleaned and then with a power washer finish it off.
  3. Plug any holes or cracks with Hydraulic cement after the wall is clean. Use hydraulic Cement to plug any holes or large cracks in the wall. Follow directions for the cement and clean out loose stones or cement before applying this product.
  4. Paint the Outside Wall with a Cement Waterproofing Sealer- After the wall dries brush on a waterproof paint-sealer used for outside walls. This needs to be dried thoroughly.
  5. Pitch the Wall with a Tar-based product- Use a Tar-based Pitch and trowel the product onto the wall.
  6. Add a Thick Heavy Duty Membrane 6 Mil or Above– Roll out a thick plastic Heavy Duty plastic or rubber Membrane and lay it up on the wall with some help on the pitch over the footer and apron it outwards away from the wall.
  7. Add a few inches of 3/4 inch gravel base for the Drainage Pipe to lay on in the trench below the Footer. A base of gravel in the trench is needed to support the plastic perforated drain pipe.
  8. Lay Perforated Drainage Pipe-Cover with Gravel- At about or near the footer level with the holes face down. Then back-fill gravel and cover the pipe with at least a 3-4 inch cover.
  9. Cover the perforated plastic pipe with a Fabric Barrier– This is an important step to ensure that dirt doesn’t get back into the pipe and clog the system
  10. Back Fill Dirt-Back-fill the dirt back into the trench and build the top of the dirt high enough to allow for settling. Try and slope the ground away from the house to allow for the runoff. Adjust the rain gutters to move water from the roof away from the house.

Lay your Drainpipe (holes down) on a bed of gravel-cover the pipe with a sock and cover it with gravel

Waterproofing Exterior Wall Products

The cost of the project would depend on a few extra options that would include a Bobcat or a Trencher. This could cost up to 200 to 300 dollars a day more, plus the delivery cost. Because of the proximity of the trench against the wall, a Bobcat, Trencher, or Mini-Excavation equipment would be hard to operate. Especially if you don’t normally operate this kind of equipment. We found that the best way was the old-fashioned way. Get in there and dig by hand.

Afterward, about a month later, and after the ground settled, I rented a small Bobcat to landscape the trench against the wall adding fresh topsoil and a few bushes. Now you would hardly know that anything happened there.

The cost of this job without the Excavator or Bob Cat was approximately: 1000.00 dollars but it would depend on the size of the wall that you are waterproofing. If you dig by hand and assume that your shovels, post hole diggers, and wheel barrels, then the materials needed are:

  • Waterproofing Paint Sealer

(Thoro-seal which is a cement-based paint that has been around for years) is 50.00 dollars for 5 gallons. There are newer products at 250.00 dollars for a 5-gallon bucket. Newer technology products like Krystol T2 are surface-applied water block that prevents hydrostatic pressure. The product grows microscopic crystals that fill the pores and voids in concrete. It can replace faulty membranes and give years of added protection. This amount will normally cover up to 300 square feet of a wall. It can be sprayed or painted on.

  • Plastic Heavy Duty Membrane

6 mil and over is under $50.00 for a 10x 50-foot roll or about 500 square feet. You can double it up for better protection

  • 4.75 Gallons of Tar Pitch like Henry

Their products are designed for above and below-grade outside walls and will provide about 100 square feet of coverage for around 50.00 dollars. This product is meant to be applied on all masonry walls including cinder block and concrete.

  • Trowels and brushes for the application

of these products would be approximately between $50- 75 dollars. They are necessary to apply the products on these types of surfaces.

  • Hydraulic Cement

can block running water in cracked concrete and block other masonry surfaces. Hydraulic Cement is Good for above or below grade and sets in 3-5 minutes at 5500 lbs. PSI. Can fix golf ball size holes in your wall. It can harden and set underwater and is what you need to patch any holes or cracks before painting it.

  • Bulk 3/4 inch

is around 30-40 dollars a ton and approximately $100.00 for delivery. Have the truck deliver it during the week. It will be cheaper than the weekend rate. If you try and pick it up yourself, it will just use up too much time and might mess up somebody’s pickup.

  • 4″ Polypropylene Drain Pipe

with socks is about 25.00 dollars a length no need to add the fabric barrier with the added sock. This size pipe is the normal size for drainage. Make sure to use some kind of barrier.

  • Pressure Washer

Most places like Home Depot run about $100.00 per/day or buy one. A pressure Washer has all kinds of uses. Besides the wall, there are a hundred uses for one. We had a built-in pool and decided to buy one and it was a great investment. By the time you add the cost of renting one every year, you’ll see what I saw it makes sense to buy one.  Generac has many gas-powered ones that work great you can find them on Amazon. Check here for an updated price. Generac 7901 – 3100 PSI Gas-Powered Pressure Washer with PowerDial Gun

Dig down past the footer to expose the entire exterior wall

Lay your Drainpipe on a bed of gravel cover the pipe with a sock and cover it with gravel. Square Foot is generally Length x Height. So an 8-foot wall 30-foot length is approx. 240 square feet. these products give you pretty much exactly what you need to perform the task.

How to waterproof foundation walls from the outside

“If you have food and beer they will come”

We planned the project on a Fall weekend with good dry weather and we were blessed with it. We also decided to give the whole project a party-type of atmosphere. I found that good friends will work hard if they eat and drink well.

My wife and I knew that this job would require a lot of back to dig the trench. So we scheduled a weekend or 2 days and invited over as many friends as we could. My wife made huge amounts of breakfast for everyone so no one had an empty stomach. We started early.

The wall was about 30 feet long and we needed to get down past the footer which was almost 8 feet deep. Working in shifts, we found it incredible how fast we were able to dig the trench. It was almost fun with lots of music playing and snacks that my wife was serving up.

By dinner time we were cleaning the wall. Dinner was a huge barbecue and keg of beer that was strategically brought out after the blunt of work was done. By nightfall, I and a few others were patching and painting the completely exposed wall.

Waterproofing foundation walls from the outside is critical for preventing water infiltration into basements or crawl spaces, which can lead to structural damage and mold growth. Here’s a general guide on how to waterproof foundation walls from the outside:

  1. Excavation: Excavate around the perimeter of the foundation to expose the exterior walls. The depth of the excavation will depend on the foundation type and the extent of waterproofing required. Typically, the excavation should extend below the level of the footings.
  2. Clean the Surface: Thoroughly clean the exterior surface of the foundation walls to remove dirt, debris, and any existing waterproofing materials.
  3. Repair Cracks and Holes: Fill any cracks, voids, or holes in the foundation walls with hydraulic cement or epoxy mortar. Ensure that the surface is smooth and free of any protrusions that could affect the waterproofing membrane’s adhesion.
  4. Apply Waterproofing Membrane: Apply a waterproofing membrane to the exterior surface of the foundation walls. There are several types of waterproofing membranes available, including asphalt-based, rubberized asphalt, and polymer-modified bitumen membranes. The membrane should be applied according to the manufacturer’s instructions, typically with a trowel or roller.
  5. Install Drainage System: Install a drainage system at the base of the foundation to collect and divert water away from the building. This may include perforated drainage pipes surrounded by gravel, a French drain system, or a combination of both. Ensure that the drainage system slopes away from the foundation to facilitate proper water flow.
  6. Backfill: Once the waterproofing membrane is in place and the drainage system is installed, backfill the excavated area with soil. Compact the backfill soil in layers to minimize settling.
  7. Protective Barrier: Install a protective barrier, such as a dimpled membrane or drainage board, over the waterproofing membrane to provide additional protection against soil pressure and mechanical damage.
  8. Landscaping: Grade the soil around the foundation to ensure that water drains away from the building. Avoid landscaping features that could trap water against the foundation, such as flower beds or retaining walls.
  9. Inspect and Maintain: Periodically inspect the exterior foundation walls for signs of damage or deterioration. Maintain the drainage system to ensure proper function and clear any obstructions that may impede water flow.

By following these steps, you can effectively waterproof foundation walls from the outside, protecting your building from water damage and ensuring a dry and stable foundation. If you’re unsure about any aspect of the waterproofing process, consider consulting with a professional waterproofing contractor for guidance and assistance.

Add Hydraulic Plug Inside and Outside Walls

Hydraulic Plug

By the next morning, I could get in close and inspect everything and the wall was looking good. We started the pitch which was pretty messy like I anticipated and troweled it into the wall making a coat over the freshly dried sealer paint.

A few of us laid out a plastic sheet that was doubled up and laid it up against the wall that was freshly tarred.

Next came the bed of gravel for the perforated drain pipe to lay on. The trench went deep to shallow with a natural slope, along the wall, so we didn’t have any problems laying the pipe for drainage. Next came a few more inches of gravel that covered the pipe than we backfilled.

Make sure that rain gutters on the roof are working and capable of accommodating the water from the roof. I added bigger wider gutters in case it was happening, it would help. It was worth a little more time and some money.

Besides the groundwater that I knew was coming in, the water coming off the roof could have been an issue too, and attributed to some of the problems in that area of the house.

Pay attention to all suspected cases. All water is the enemy. Add wider gutters and if you can use the vinyl more expensive kind that snaps together.

Take the downspouts and run them away from the wall away from the house. This can make the difference from that water puddling up against the outside wall and possibly finding another way in.

When waterproofing exterior walls, adding hydraulic plugs can be an essential step to prevent water infiltration through cracks and gaps. Hydraulic plugs are materials specifically designed to seal leaks in concrete and masonry structures, including both inside and outside walls. Here’s how hydraulic plugs can be applied:

  1. Inside Walls:
    • Identify any cracks, voids, or gaps in the interior surface of the walls where water may penetrate.
    • Clean the area thoroughly to remove any debris, dust, or loose particles.
    • Mix the hydraulic plug material according to the manufacturer’s instructions. This typically involves blending the plug powder with water to create a workable paste.
    • Apply the hydraulic plug paste to the cracks or gaps using a trowel or putty knife, ensuring thorough coverage and a smooth finish.
    • Allow the hydraulic plug to cure completely according to the manufacturer’s recommendations.
  2. Outside Walls:
    • Inspect the exterior surface of the walls for any cracks, holes, or other openings where water may enter.
    • Clean the exterior wall surface to remove dirt, grime, and loose debris that could interfere with adhesion.
    • Prepare the hydraulic plug material as instructed by the manufacturer.
    • Fill the cracks or gaps in the exterior walls with the hydraulic plug paste, ensuring it completely seals the openings.
    • Smooth out the surface of the plug to create a uniform appearance and improve waterproofing effectiveness.
    • Allow the hydraulic plug to cure thoroughly, taking into account environmental factors such as temperature and humidity.

When applying hydraulic plugs, it’s essential to follow the manufacturer’s guidelines regarding mixing ratios, application techniques, and curing times to ensure optimal performance. Additionally, proper surface preparation is crucial for achieving a strong bond and effective waterproofing. If the cracks or gaps are extensive or structural in nature, it may be necessary to consult with a professional waterproofing contractor for a more comprehensive solution.


After 20 Years The House is Dry

I found this procedure to work well and now am confident that waterproofing the outside existing wall was not only long-term successful, but inexpensive (as long as no corners are cut) and the right decision. You don’t want to do this project again 10 years from now down the road. After 20 years or so I can say with pride, not a drop comes in from where we waterproofed or any other place around my home. A couple of tips I can relate to anybody who is thinking of doing this themselves to save money would be:

Invite friends with strong backs and make it a party. We had so much fun, it was hard to imagine that we saved so much money.
Pre-plan right down to the weather. Talk to a professional contractor who knows the details and equipment you will need. Talking to him gave me not only the right information but confidence as well. When those cold nights come, you want to make sure your heating system performs at a higher efficiency lowering heating costs and saving you money.

How  Do You Waterproof a Basement Wall from the Inside?

Prep the wall of old paint
Wash dirt & dust off the wall
Plug Holes & cracks with Hydraulic Cement
Seal Openings in doors, windows & window wells using waterproof caulk
Apply a coat of waterproof masonry cement to your wall
Install a Sump pump
Use a quality dehumidifier
Vent Dryer outside-Cover H2O pipes ……………………………………………………………………………. Read more

JimGalloway Author/Editor




Why are waterproofing exterior walls important? Waterproofing exterior walls is important because it prevents water infiltration, which can lead to structural damage, mold growth, and other issues. It helps to protect the building’s integrity and prolong its lifespan.

How do I know if my exterior walls need waterproofing?  Signs that your exterior walls may need waterproofing include water stains, peeling paint, efflorescence (white, powdery residue), cracks, or dampness on interior walls. Additionally, if you notice water pooling around the foundation or basement leaks during heavy rain, it may indicate a waterproofing issue.

What are the common causes of water infiltration in exterior walls?  Common causes of water infiltration in exterior walls include cracks, gaps, deteriorated mortar joints, poor drainage around the foundation, inadequate waterproofing materials or techniques, and hydrostatic pressure from groundwater.

Can I waterproof exterior walls myself, or do I need to hire a professional?  While some homeowners may choose to waterproof exterior walls themselves, hiring a professional waterproofing contractor is often recommended, especially for more complex projects or severe water issues. Professionals have the expertise, equipment, and knowledge to ensure effective waterproofing and long-lasting results.

What are the best materials for waterproofing exterior walls? The best materials for waterproofing exterior walls depend on factors such as the wall substrate, climate, and level of waterproofing required. Common materials include liquid waterproofing membranes, sheet membranes, cementitious coatings, polyurethane coatings, silicone sealants, and waterproofing paints.

How long does waterproofing exterior walls last? The longevity of waterproofing exterior walls depends on factors such as the quality of materials used, environmental conditions, and maintenance. Generally, well-installed waterproofing systems can last for many years, but periodic inspections and maintenance may be needed to ensure continued effectiveness.

What maintenance is required for waterproofed exterior walls?  Regular maintenance for waterproofed exterior walls may include inspecting for cracks or damage, cleaning gutters and downspouts to ensure proper drainage, reapplying sealants or coatings as needed, and addressing any landscaping or grading issues that could affect water flow away from the building.

How much does it cost to waterproof exterior walls?  The cost of waterproofing exterior walls varies depending on factors such as the size of the building, the extent of waterproofing required, the chosen materials, and labor costs. It’s best to obtain quotes from reputable waterproofing contractors to get an accurate cost estimate for your specific project.

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