Exterior waterproofing stops water before it touches the wall. The foundation is dug out to the footing, the wall is repaired and covered with a membrane and drainage board, a new footing drain is laid, and the trench is backfilled with stone. It is more work than an interior system and is the right answer in specific situations.
Tell us what the Buffalo property is doing and we'll take a look.
Interior drainage manages water; exterior waterproofing protects the wall. That distinction decides which one a house needs. If a stone or block wall is deteriorating from the outside, with mortar washing out, parging gone and stones loosening, draining the base from inside will keep the floor dry but will not stop the wall from getting worse. If a poured wall has a crack that cannot be reached from inside because of a finished space or a utility, or a leak at a pipe penetration or a window well that keeps recurring, fixing it from outside is direct.
Exterior work is also chosen when an owner is already excavating for another reason, such as a porch removal, a new addition or a sewer lateral replacement, and the wall is exposed anyway. And it is the standard approach for a wall that is being rebuilt or straightened, since the outside face has to be accessible to relieve the load.
Digging in the Erie County lake plain means digging in clay. The soil survey describes the Odessa soils as very sticky when wet and cloddy when dry, and notes that substratum excavations in the Niagara-Canandaigua-Cosad soils are subject to slumping, sloughing and piping and that cut banks are unstable. In practice a trench beside a Buffalo foundation holds water, wants to close in on itself, and cannot be left open through a rain. The work is sequenced so the wall is exposed, treated and backfilled in as short a window as the job allows, and trench safety is not optional.
Frozen ground is another constraint. With around 124 days a year at or below freezing at the airport, exterior work is a spring-through-fall trade here. In the older parts of the city, lots are narrow and the neighbor's house may be a few feet away, so the excavation is sometimes done by hand along part of a wall or the exterior approach is ruled out for that wall entirely.
The backfill matters as much as the membrane. Putting the excavated clay back against the wall recreates the problem. The trench is backfilled with free-draining stone wrapped in filter fabric, capped with soil graded away from the house, so water that reaches the wall drops straight to the footing drain rather than sitting against the membrane.
The foundation is excavated to the bottom of the footing along the walls being treated, with utilities located first and shoring where depth or soil requires it. The wall is pressure-washed and inspected. Stone and block are repointed and parged with a compatible mortar; poured walls have cracks routed and sealed and tie holes filled. A waterproofing membrane is applied to the prepared wall from the footing to just below finished grade. A dimpled drainage board goes over the membrane to protect it during backfill and to give water a fast vertical path to the drain.
A new perforated footing drain is laid in washed stone at the base of the wall, wrapped in fabric, and pitched to an outlet: a sump inside the basement through a footing penetration, a storm sewer connection where permitted, or daylight where the lot has fall. Window wells get drains connected to the footing drain and, usually, covers. The trench is backfilled with stone and topsoil, graded away from the house, and the disturbed lawn or hardscape is restored.
The most common misunderstanding about exterior waterproofing is that it makes a basement dry. It makes the wall dry. Water that rises under the slab from a high water table still comes up through the cove joint and floor cracks, and no membrane on the outside of the wall touches it. On Buffalo clay, where the winter and spring water table sits in the upper subsoil, a house that has both a leaking wall face and a wet floor edge often needs exterior treatment on the failing wall and an interior drain and sump for the floor.
We will lay that out plainly on the assessment. Where a full exterior job would be spent mostly on protecting a wall that is in fact sound, and the real issue is the water table, we will recommend the interior system and save you the excavation.
Questions
A trench roughly two to three feet wide along the walls being treated, to footing depth. Landscaping, walks and decks in that strip come out and are restored or replaced afterward. Where a wall is inaccessible, an interior approach is used for that wall instead.
Not well. Frozen clay is slow to dig and membranes need a dry, above-freezing wall to bond. Exterior work is scheduled for the warmer months; interior drainage can be installed year-round.
The black asphalt coating on most older foundations is damp-proofing, meant to slow moisture, not to hold back water under pressure. A modern membrane with drainage board and a working footing drain is a different category of protection.
No. Floor water is the water table under the slab and is handled by an interior drain and sump. Exterior work protects the wall. Many Buffalo houses need one or the other, some need both, and the assessment tells you which.
Call the local line or send the form and we will set up a free on-site assessment with a written scope and no obligation.
Request a free estimate Call (716) 325-5837