Exterior foundation waterproofing for Jersey City homes

Exterior waterproofing is the only method that keeps water from soaking into the foundation at all. That matters most in three situations. The first is a finished basement, where cutting the floor and opening walls from inside would mean tearing out drywall, built-ins or flooring. The second is a wall whose outer face is failing: old parging falling off, mortar washed out, or soil packed against bare block. The third is a wall that's wet across its whole height, not just at the bottom.

It's also the right call when the problem sits right at grade. A rear wall where the yard slopes toward the house, or a front wall below an areaway that collects water, often leaks from the top down. Fixing the outer face and grading the soil away from it solves the cause instead of collecting the result. If the same yard holds water everywhere, grading and yard drainage may be part of the fix too.

Exterior work also makes sense during other projects. If the yard is being dug up anyway for a new patio, a rear addition or underground leader drains, adding membrane and a footing drain while the trench is open costs far less than coming back later. The same goes for a front areaway being rebuilt. On the other hand, if water only appears at the floor edge and the basement is unfinished, an interior drain usually solves the leak for less money and with less disruption to the property.

Many foundations already have a thin black coating on the outside. In most cases that's damp-proofing: a sprayed or brushed asphalt layer meant to slow soil moisture, not to hold back water under pressure. It cracks when the wall moves, it doesn't bridge gaps, and it was never designed for a high water table. When we dig up a leaking wall, we often find that coating intact and the wall wet anyway.

Waterproofing is a different product. We use either a rubberized sheet membrane, lapped and sealed at the seams, or a thick liquid-applied membrane built up to a measured thickness. Both stretch over small cracks and stay stuck to the wall under water pressure. Sheet goods give a very consistent thickness; liquid membranes wrap around pipes, corners and irregular old masonry more easily. We choose based on the wall surface we uncover, and then protect the membrane with drainage board so backfill stones can't puncture it.

The wall comes clean first. We dig down to the footing, scrape and wash the wall, and repair what we find: open joints repointed, cracks sealed, loose parging removed and replaced. Tie-rod holes on poured walls get plugged before membrane goes on. Any problem left under the membrane would sit there for decades, so this is the slow, careful part of the job.

After the membrane comes dimpled drainage board, which holds an open air gap against the wall so water drops straight down instead of pressing on it. At the footing we lay perforated pipe in washed stone, wrapped in filter fabric, and run it either to a sump or to daylight where the lot slopes enough. On many Jersey City lots there's no low point to drain to, so a sump is the normal answer. We then backfill in layers, compacting as we go, and finish the grade sloping away from the wall.

Leaders get rerouted while the ground is open. A downspout that used to dump at the wall gets a solid pipe carried away from the house, never tied into the perforated footing drain, because roof water poured into that pipe would flood the very system meant to keep the wall dry. Window wells along the dug wall get their own drains connected to the footing line, so they stop filling during storms. These small details are what keep an exterior job working for decades instead of a few seasons.

Attached houses change the math. On a downtown rowhouse or brownstone, the side walls are party walls shared with the neighbors, and there's no way to dig along them from outside. Usually only the front wall, often under the areaway or stoop, and the rear wall facing the yard can be excavated. Front work may involve the sidewalk, so we plan staging, sidewalk protection and any city approvals that apply before we start.

That's why many of our rowhouse jobs combine methods: exterior membrane on the rear wall where the yard allows, and an interior perimeter drain along the party walls from inside. Detached two- and three-family houses in the Heights and Greenville usually give us more room, though tight side yards and neighboring fences still shape the dig. We walk the property with you and show you exactly which walls we can reach before we price anything.