Tuckpointing and Waterproofing: Should You Seal Brick Afterward?

Tuckpointing and waterproofing get lumped together because both are about keeping water out. Should you seal brick after tuckpointing? Usually not, and sometimes it does harm. Here is the reasoning, so you can answer the contractor who offers a sealer as an add-on.

Is tuckpointing already waterproofing?

Close, but not the same. Tuckpointing replaces failed mortar so the joints stop acting like open channels into the wall (Brick Industry Association). That is the main water defense of a brick wall: sound brick, sound joints, and a way for the wall to dry out.

Brick walls are not meant to be sealed shut. Water that gets in has to be able to leave. The National Park Service says repointing mortar must be more vapor-permeable than the brick and no harder than the original mortar, so the joints, not the brick, give up first and let moisture out (NPS Brief 2). The whole design is a wall that breathes.

Why can sealing brick make things worse?

Because a coating that blocks vapor on the outside of a wall that still holds water on the inside holds that water in. When mortar is less permeable than soft brick, moisture and dissolved salts leave through the brick face instead, and the salts crystallizing inside the brick can make the face spall or delaminate (NPS). A film-forming sealer does the same thing to the whole wall. You have moved the problem from the joints to the brick faces.

Salt is the common thread. Efflorescence, the white powder on brick, needs soluble salts, water and a path to the surface (BIA). Salt crystallizing under the surface, not on it, is the damaging form (BIA). Seal the surface and the crystals form behind the coating.

The BIA's position is plain: find and fix the moisture and salt cause, and do not rely on coatings alone (BIA). The NPS adds that water-repellent coatings are appropriate only after a building has been made watertight and dried (NPS). That guidance is aimed at early American brick, not Chicago common brick specifically, but the reasoning carries: seal a wet wall and you seal the wet in.

What should you fix before thinking about a sealer?

Most "waterproofing" problems are water-management problems. Work down this list first:

1. Gutters and downspouts. Water pouring down a brick face from an overflowing gutter will outwork any sealer. Downspouts should discharge well away from the wall.
2. Roofline details. Parapets, copings and chimneys sit in the most exposed spots. Caps and copings should channel water away, and brick caps with many joints can be a poor choice (BIA).
3. Flashing. Through-wall flashing collects water that got behind the brick and sends it back out. It belongs at the bases of walls, the heads of openings, parapets and chimneys, among other places (BIA).
4. Grade and splash. Soil that slopes toward the wall and bare downspouts dumping against it keep the base of the wall wet. Sloping soil away from the foundation and extending downspouts help (University of Minnesota Extension, general building science, not Chicago specific).
5. Open joints. That is where tuckpointing comes in. See how to tell if your brick needs tuckpointing.

Do those and most walls need nothing more. The City also treats joints that are not weather resistant or water tight as an unsafe condition under the exterior maintenance code (City of Chicago), so tuckpointing is the repair that matters.

When is a coating a fair question?

There is a narrow case. If a building has been made watertight, joints repointed, flashing and caps sorted, the wall dried out, and the brick is so soft or porous that it keeps eroding, a water repellent can be a legitimate conversation. The NPS says exactly that: only after watertight and dried (NPS).

If someone proposes one, ask these questions:

• What problem is it solving, and what did you fix first?
• Does the product let water vapor out of the wall, or does it form a film?
• Is the wall dry now, and how do you know?
• What happens to the brick if the coating fails or peels?
• Is it reversible?

If the answer to "what are you fixing" is "the white stuff," see efflorescence on brick. A coating does not stop efflorescence. Fixing the water does.

What about caulk and other quick fixes?

Caulk on mortar joints has the same problem in a smaller form: it sits on the surface and hides a joint that has already failed. We answer that in can you caulk mortar joints instead of tuckpointing. And if water is already coming through the wall, start with water coming through a brick wall.

The bottom line

Tuckpointing is the waterproofing that old brick needs. Sealing is a rare, late, conditional step, not a standard add-on. Get the joints right with mortar that matches the brick, fix the water sources, and let the wall dry. For the wider picture, see our Chicago tuckpointing guide. If a contractor wants to seal your brick as part of the quote, our tuckpointing team will give you a second opinion on whether it belongs in the job.

Common questions

This article explains general rules and common situations in Chicago. It is not legal advice, and City rules change. For a specific property, check with the Chicago Department of Buildings or a licensed professional.