Exterior foundation waterproofing cost

Exterior foundation waterproofing costs $100 to $220 per linear foot of wall, typically about $160. That buys digging the wall out to the footing, a membrane on the concrete or block, a new footing drain in stone, and the backfill.

The rate is set less by the membrane than by what is standing in the way of the trench. A bare lawn on a one-story house sits near the bottom. A wall behind a paver patio, a stoop, the gas meter and the air conditioner sits at the top, and some of those items are not in the per-foot price at all.

What it costs

Most homeowners do not dig out the whole house. The usual job is one or two elevations, the wall that leaks, measured in linear feet along the outside of the foundation. A 40 foot wall is a very different check from a 160 foot perimeter.

What the per-foot rate is made of

Most of the money is excavation. The trench has to reach the footing, which on a full basement is commonly seven to nine feet down, and it has to be wide enough for a person to work against the wall. A trench that deep is a confined space with collapse risk, so crews slope it back, bench it, or shore it, and that is why a deep basement costs more per foot than a shallow one even though the wall is the same.

Once the wall is exposed, the crew pressure-washes or scrapes it, cuts out loose parging, and fills tie-rod holes and cracks from the outside. Then comes the membrane. On a proper job it is a true waterproofing layer, a fluid-applied rubberized coating or a self-adhered sheet, usually covered by a dimpled plastic drainage board that keeps soil off the membrane and gives water a path straight down.

At the bottom, a perforated pipe goes alongside the footing in washed stone wrapped in filter fabric, sloped to an outlet. The trench is then backfilled, ideally with free-draining material against the wall, and rough graded so the surface falls away from the house.

Dampproofing is not waterproofing. A thin sprayed asphalt coat, the black layer most houses got when they were built, resists soil moisture but not water under pressure. A quote that lists "foundation coating" without naming the product may be selling that. Ask for the membrane by type and thickness.

When exterior is worth the premium over interior

Interior drain tile at $50 to $120 per linear foot is roughly half the price, and for most wet basements it is the sensible answer. The basement waterproofing guide covers that choice in general. These are the cases where exterior earns its cost.

The wall itself is deteriorating. A block wall that stays saturated spalls and loses mortar over the years, and an interior system collects the water only after it has gone through the block. Stopping it at the outside face is the only way to keep the masonry dry.

The basement is finished, or about to be. Interior drain tile means breaking the slab along every treated wall, which means removing flooring, stud walls and drywall. Digging outside leaves the finished room alone.

The leak is high on the wall. Water entering at a pipe penetration, a window frame or a crack halfway up runs down the inside face before an interior drain ever sees it.

You want no pump in the system. Where the lot slopes enough for the footing drain to run to daylight, exterior work can be gravity-only, with nothing that fails in a power outage.

You are digging anyway. An addition, a new egress window, a sewer lateral or foundation insulation all expose the wall, and adding the membrane then costs a fraction of a separate job.

Before any of this, rule out the surface water. Clear gutters, downspout extensions and a grade that falls away from the house solve a large share of wet basements for very little, and the drainage and grading guide is the place to start.

Access, landscaping and the things the trench meets

Two quotes for the same 50 feet of wall can be thousands apart, and the gap is nearly always on the surface.

Machine access. A mini excavator needs a path roughly the width of a small car. A side yard between two houses, a fence with no gate or a slope too steep for the machine means hand digging, which is slower by a wide margin.

Hardscape against the wall. Patios, walkways, stoops and driveway edges have to come out and go back. Pavers can usually be lifted and relaid; poured concrete is broken out and repoured. Decks are worse, because their posts often sit in the zone being dug.

Utilities. Gas meters, electric service entries, condenser units and hose bibs are all on the foundation wall. Some can be worked around, and some need the utility or another trade to disconnect and reset them. That is quoted separately, and it should be named on the quote.

Planting. Foundation beds, shrubs and anything rooted within about six feet of the wall rarely survive. Most contractors backfill and rough grade only; replacing beds and lawn is your cost.

Settlement afterward. Backfill sinks over the first year or two. Expect to top up the soil along the trench at least once, and to check that the grade still falls away.

A worked example: one leaking wall behind a walkway

A one-story house with a full block basement takes water along its 40 foot rear wall after heavy rain. A paver walkway runs along that wall, and two cracks show from the inside. The owner wants the wall dug out, sealed and drained, with the walkway relaid.

• Excavation, membrane and footing drain: 40 linear feet × $100 to $220 per foot = $4,000 to $8,800
• Crack repair: 2 cracks × $350 to $1,000 each = $700 to $2,000
• Walkway lifted and relaid: 30 square feet × $15 to $35 per square foot = $450 to $1,050
• Total: $5,150 to $11,850

The excavation line is most of it, and where it lands in its range depends on depth and on whether the machine can reach the back of the house. The crack line can often drop off: once the wall is exposed, cracks are sealed from the outside under the membrane, and many contractors include that. Ask before paying for both. The walkway line is a reminder that the per-foot rate rarely covers what sits on top.

Done from inside, the same 40 feet of interior drain tile would cost less, but the water would keep going through the block, and the drain would need a sump and a pump that has to run in every storm.

How to read an exterior waterproofing quote

• What membrane, by product type and thickness, and is there a drainage board over it?
• How deep is the excavation, and is the price per foot at that depth?
• Where does the footing drain discharge: daylight, a dry well or a sump?
• Are cracks repaired from the outside before the membrane goes on?
• What is excluded: patios, stoops, decks, utilities, planting, final grading?
• Who calls in the utility locate before digging, and who pulls any permit?
• What does the warranty cover, and does it transfer to a buyer?

If the wall is bowed or has a horizontal crack, stop and get an engineer first. Digging out a wall that is already pushed in removes the soil holding it, and the wall needs bracing or anchors as part of the same job. An independent $400 to $1,500 report is small money against that risk.

Frequently asked questions

How much does exterior basement waterproofing cost per linear foot?

$100 to $220 per linear foot, typically about $160, including excavation, membrane, footing drain and backfill. Deep basements, hand digging and walls with block that needs repair push it to the top. Patios, decks and landscaping are usually priced on top.

Is exterior waterproofing better than an interior drain?

It stops water before it reaches the wall, which an interior drain does not, and it can work without a pump on a sloped lot. It also costs roughly twice as much and disturbs the yard. It is better value when the wall is failing, the basement is finished, or the leak enters high on the wall.

How long does exterior foundation waterproofing last?

A true membrane with a drainage board and a footing drain in filter fabric is built to last decades, often the remaining life of the house. Sprayed dampproofing breaks down far sooner and was never meant to resist water under pressure. The footing drain usually fails first if it was laid without fabric and silts up.

Can exterior waterproofing be done in winter?

Usually not well. Frozen ground is slow to dig, most membranes need a dry wall and temperatures above a minimum to bond, and backfill should not go in frozen. Most contractors schedule exterior work from spring through fall.

Related guides

• Basement waterproofing cost — interior and exterior compared across the whole job
• Wet basement repair cost — the cheap outside fixes to try first
• Foundation crack repair cost — reading the cracks the trench will expose
• Bowing basement wall repair cost — the wall to brace before anyone digs
• Drainage and grading cost — keeping surface water off the wall afterward