Stucco waterproofing in NYC starts with an unhelpful fact. Stucco cannot be made waterproof, and products sold as though it can are usually the ones that cause the damage. What can be done is treating the details where water actually enters and choosing a repellent that leaves the wall able to dry.
Waterproof and water resistant mean different things, and the gap between them is the whole subject. A waterproof layer stops liquid water completely and it belongs below ground where nothing has to dry outward. A water resistant wall sheds most of what hits it, absorbs a little, and lets what got in leave again as vapor. Stucco is the second kind and it was designed to be.
As a stucco waterproofing contractor in NYC we work on that basis rather than against it. That means treating the heads, sills, roof junctions and penetrations where water genuinely enters a New York wall, and where a repellent is appropriate, using one that soaks in rather than one that forms a film across the face.
Almost none of it comes through the field of the wall. Water enters at the places where the stucco stops, changes direction, or has something passing through it.
These five account for most of what we are called to look at, and none of them is solved by coating the surface.
The top of an opening is where water running down a NYC stucco wall meets an interruption. Failed or missing flashing here puts water straight behind the finish.
Water sits on a stucco sill rather than running off it. Where the slope is wrong or the joint has opened, it soaks into the wall from below.
Roof edges, step flashings and the junction at a lower roof. On a New York building this is the single most common entry point we find.
An open or cracked coping lets water into the top of a stucco wall, where it runs down inside and emerges several floors below on a New York building.
Conduit, vents, hose bibs and old fixings through a NYC stucco wall. Each is a hole sealed once and moving ever since.
Four things worth knowing before anybody puts a product on your wall.
A waterproof layer stops liquid completely and is meant for below ground. A water resistant wall sheds most water and lets the rest leave as vapor. Above grade on a NYC stucco wall you want the second.
Silane and siloxane repellents soak into the stucco and line the pores rather than covering them. Water beads and runs off, vapor still passes through the wall, and there is no film to peel.
A sealer that lies on the face stops water getting in and stops vapor getting out. On a New York wall carrying any moisture at all, that is the mechanism behind most of the coating failures we are called to.
Foundation waterproofing is a membrane system designed for permanent contact with soil. It is not an above grade product and using one on an exposed wall is a common and expensive mistake.
Heads, sills, roof junctions, copings and every penetration on the elevation. On a New York stucco wall the field is rarely the problem, and a survey that only looks at the wall face has looked at the wrong thing.
An existing film sealer on a NYC stucco wall changes everything. A repellent will not absorb through one, so the honest sequence is often removing what is there before anything useful can go on.
Flashing, coping and sealant work first. A repellent applied over an open detail is money spent on the part of the stucco wall that was not letting water in.
A wall that is letting water in is also letting water out. Seal the face and you stop both, but only one of those was helping you. Whatever moisture is already in the masonry, and whatever continues to arrive through the flashing detail nobody fixed, now has nowhere to go. It collects behind the film, and in a New York winter it freezes there. The coating comes off in sheets, usually within a few seasons, and the wall underneath is worse than it was. That is the mechanism behind most of the failed waterproofing we are called to remove.
Where water enters depends on the building type, and the details that fail on a pre-war walk-up are not the ones that fail on a rowhouse or a detached house.
See stucco contractor NYC for the full range of stucco systems and how each one is built.
Browse our gallery to explore the outstanding projects we’ve successfully completed, highlighting our expertise.
No, and it was never meant to be. Stucco is water resistant, meaning it sheds most of what hits it, absorbs a little and lets that leave again as vapor. A genuinely waterproof wall cannot dry outward, which on a NYC building creates more problems than it solves.
By treating the details rather than the wall. Flashing at heads and roof junctions, sills that shed properly, sound copings and sealed penetrations. Where a surface treatment is appropriate we use a penetrating repellent that leaves the wall vapor open, not a coating that seals it.
The question is worth reframing, because the best product for most NYC walls is not a sealer. A penetrating repellent based on silane or siloxane soaks into the surface and repels water while letting vapor through. A sealer that forms a film does the opposite and is why most treated walls fail.
Rarely. A paint marketed as waterproof is a film, and a film over a stucco wall stops moisture leaving as well as entering. On any New York wall carrying damp, that traps it. If the wall needs painting, the specification should be about vapor transmission rather than about waterproofing.
Old stucco can be made more water resistant, which is a different promise. On a pre-war NYC wall the useful work is repairing the details and, if the surface is sound and unsealed, applying a penetrating repellent. Anything sold as making a century old wall waterproof should be treated with suspicion.
