Waterproofing a Basement on the Exterior: A Savage, MN Homeowner Guide

Exterior waterproofing means excavating around the foundation, sealing the wall and installing drainage along the footing. It treats water where it enters. It is also the most disruptive and expensive way to waterproof a basement. This guide explains how it works and when it is worth considering.

What exterior waterproofing involves.

1. 1

   Excavate.

   Soil is dug away from the foundation down to the footing, often along one or more walls.

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2. 2

   Clean and repair.

   The wall is cleaned and cracks are patched.

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3. 3

   Seal.

   A membrane or coating is applied to the wall.

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4. 4

   Drain.

   A perforated pipe in gravel along the footing carries water to a discharge point or sump.

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5. 5

   Backfill and regrade.

   Soil is replaced and sloped away from the house.

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The goal is to keep water from pressing against the wall and to give it somewhere to go.

Why it costs more than interior options.

Digging down eight feet or more around a house is slow and needs equipment. Decks, patios, landscaping, gas and electric lines and tree roots all complicate it. Restoration of the yard is part of the cost. Interior systems work from inside and leave the yard alone.

When exterior work makes sense.

• A foundation wall is cracked or failing and needs repair anyway.
• The wall is block with active seepage through the joints.
• The home is being excavated for another reason, such as an addition.
• Interior work is not possible, for example a finished slab with no access.
• A prior drain tile is clogged or broken.

If water enters only after storms and mostly at the floor edge, an interior system with a sump is often enough.

Cheaper fixes to try first.

Many wet basements have outside causes you can fix for little. Clean gutters, extend downspouts well away from the foundation and regrade soil so it slopes away from the house. A window well that fills with water needs a drain or a cover. These steps cost far less than excavation.

Rule out plumbing as well. A leaking pipe can look like seepage. Our leak detection service tests for it, and a meter test is free to do yourself.

What the membrane and drain are made of.

Exterior systems vary. A common one is a rubberized or polymer-modified coating or a sheet membrane bonded to the foundation wall. A dimpled drainage board then sits against the membrane to let water fall to the footing. At the base, a perforated pipe in washed stone catches water and carries it away.

Each layer has a job. The coating resists moisture, the board relieves pressure and the pipe moves water. Skipping one weakens the system. Ask the contractor to describe each layer and its warranty.

Warning signs that the wall needs more than waterproofing.

• A horizontal crack along a block wall.
• A wall that bows inward.
• Stair-step cracks in mortar joints.
• Doors or windows that bind for no clear reason.
• Efflorescence, the white powdery mineral crust, that returns after cleaning.

Those signs can mean structural pressure, not just moisture. A structural engineer should look before any waterproofing begins. A good contractor will tell you the same.

How long exterior work takes and what to expect around the house.

Expect machines in the yard, spoil piles of soil, plywood or fencing for safety and a trench that stays open until the membrane and drain are in and inspected. A small section might take a couple of days. A whole-house job can run a week or longer, and rain delays are common because water in the trench makes the work harder.

Ask what happens to shrubs, steps, decks and air conditioner pads. They often have to move and come back. Ask for the restoration plan in writing.

What to do before we arrive for a wet basement.

1. Stay out of standing water near electrical.

   Do not wade into water near the panel, outlets or a running sump pump.

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2. Move stored items off the floor.

   Cardboard and fabric wick water and grow mold fast.

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3. Note where the water enters.

   Wall seam, floor crack or window well. That detail steers the whole diagnosis.

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4. Call before anyone digs.

   Minnesota's Gopher State One Call (811) marks buried utilities for free before exterior digging.

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Code and sources.

Minnesota Rules chapter 4714 is the state plumbing code and the standard a licensed plumber works to. The Department of Labor and Industry states that it incorporates the 2018 Uniform Plumbing Code with Minnesota amendments. Your city building department decides when a permit or inspection is needed, so check with them before work begins.

Questions to ask a contractor.

• How deep will you dig, and on how many walls?
• What membrane or coating will you use, and what is its warranty?
• Where will the drain discharge?
• Who restores landscaping and concrete?
• Is a sump pump part of the plan?

Waterproofing contractors and plumbers overlap. Our sump pump repair page covers the pump side, and our Shakopee and Lakeville pages list nearby towns we serve.

Questions Savage homeowners ask.

Still have a question about your situation? The line is open around the clock. Call (952) 866-9120