Historic District Rules for Exterior Masonry in St. Louis

The surprise for most owners is not that review exists. It is that masonry is one of the things the city looks at most closely, because mortar and cleaning are where historic brick gets damaged permanently and quickly. A bad roof can be replaced. A sandblasted wall cannot.

Here is how the process works and what the rules actually ask for.

Who reviews what?

Two city offices sit between you and the scaffold.

The Building Division, inside the Department of Public Safety, issues the building permit. Tuckpointing and structural masonry repair are permitted work, and there is an application fee at the counter. Your contractor should be the one pulling it.

The Cultural Resources Office, inside the Planning and Urban Design Agency, is the city’s preservation agency. It reviews exterior work in local historic districts, on City Landmarks, in public parks, on public buildings and for encroachments into the public right of way. Its authority comes from Title 24 of the city code.

The two run together. In practice the permit application triggers the CRO review when the address is in a reviewed area, and the permit is not issued until the CRO signs off.

Is your building in a district?

This is where owners most often guess wrong, because there are several overlapping designations and they do very different things.

Designation	Who created it	Does it control your masonry work?
Local historic district	City ordinance, Title 24	Yes. CRO reviews exterior work against that district’s standards
City Landmark	City ordinance	Yes. CRO review applies
Preservation review district	City ordinance	Mainly demolition review. Check before you assume
National Register historic district	Federal listing	No direct control over private work by itself
Neighborhood association guidelines	Private	Not a city permit matter, but may bind you separately

The distinction that catches people is the last two rows. A National Register listing is an honor and a gateway to tax credits. On its own it does not require the city to review your tuckpointing. Plenty of St. Louis neighborhoods are on the National Register without being local historic districts, and plenty are both.

Do not assume from the neighborhood name. Check the address with the CRO before you scope the job. It is a phone call.

What do the standards actually require for repointing?

Each local historic district has its own ordinance with rehabilitation and design standards written for that district. They differ in detail. On masonry they converge on the same technical ground, which the CRO also sets out in its published standards for repointing and which matches the Park Service guidance on the subject.

Expect requirements along these lines:

• Mortar softer than the brick. New mortar must not be harder or stronger than the existing units. A portland-heavy mix on soft pre-1930 common brick transfers stress to the brick face and spalls it. Lime-rich mixes, or the weaker ASTM mortar types, are what these walls want.
• Match the original in color, texture and aggregate. Color comes mostly from the sand. A cured sample is the only fair way to judge it.
• Joint width unchanged. The finished joint should be the same width as the original. Grinder overcutting that widens joints changes the whole appearance of an elevation.
• Joint profile matched. Concave, weathered, flush or grapevine, whichever the building has.
• Depth of removal. Cut to roughly two to two and a half times the joint width, and further if the mortar behind is still soft.
• Hand tools on head joints. Circular blades do not fit short vertical joints without cutting the brick.
• No sandblasting, and no aggressive high-pressure washing. Abrasive cleaning strips the fired skin off soft brick and opens the body to water. This is the one that ends careers on a building.

What about cleaning, sealing and painting?

Cleaning is reviewed. The expectation is the gentlest method that works: low pressure water, a soft brush, and a masonry-safe detergent, with a test patch in an inconspicuous spot first. Chemical cleaners are approved case by case. Abrasive methods are generally out.

Painting previously unpainted masonry is usually not approved in local districts, because it changes the appearance and traps moisture in a wall that has to dry through its face. Removing paint from masonry is reviewed too, since paint stripping can be as damaging as sandblasting when it is done aggressively.

Water-repellent coatings sit in the same territory. A breathable penetrating repellent on sound masonry is a different proposition from a film-forming sealer, and the office will want to know which one you mean.

What does this mean for stone foundations, sills and piers?

Masonry review is not only about brick faces. On larger Central West End houses, the limestone foundation, the carved sills and lintels, the porch piers and the retaining walls at the sidewalk are all part of the reviewed exterior.

The technical points shift a little for stone. Joints are wider and more irregular, so the two-times-the-width rule yields a deeper cut. Limestone is soft and abrades easily, so a grinder near a carved face is a genuine hazard. Replacement stone has to be matched for type and color, and reusing sound original stone that has simply slipped is always preferred to cutting new. Where a pier has to come apart, the stones are numbered before they move so the wall goes back the way it came down.

We handle that kind of work through stone and foundation repair, and on a reviewed property the scope gets written to the district standard from the start.

How long does review add to the schedule?

Less than most owners fear, for straightforward work. Repointing that meets the standards can often be approved over the counter at the CRO, which turns review into a same-visit step rather than a hearing. Work that changes the appearance of a building, or that departs from the district standards, goes to the Preservation Board and follows its meeting calendar.

The way to keep it fast is to submit a scope that already meets the standard: mortar type named, sand source named, joint width and profile stated, cleaning method stated, cure sample offered.

Before you sign a masonry estimate

Ask three questions. Is my address in a local historic district or a City Landmark? Who is pulling the permit and handling the CRO submittal? Does the written scope name the mortar mix, joint depth and profile?

A contractor who cannot answer the first two has not checked. We check the address before quoting and write the scope to the district standard, so the permit and the review do not become your problem.