Water Tables, Belt Courses and Caps: The Horizontal Stone Doing the Real Work on Your House

Look at any older masonry building in Chicagoland and count the horizontal bands of stone.

There is usually one low on the wall where the thicker foundation steps back. Often another at a floor line, or running beneath a row of windows. Caps on the porch walls. Sills under each opening. On a greystone or a substantial brick two-flat there may be five or six distinct projecting courses.

Homeowners read all of that as decoration. It is drainage. Every single projecting horizontal course on a masonry wall exists to throw water clear of the masonry below it, and when one stops doing that job it does not fail quietly — it concentrates water onto one strip of wall and takes the brick with it.

Paul Lally's Masonry Inc. is a family-owned, insured masonry contractor serving Chicago and the Chicagoland suburbs since 1988 — tuckpointing, brick repair and replacement, chimney repair and rebuilds, lintel replacement, masonry restoration, and waterproofing for residential and commercial properties. Built on Craftsmanship. Backed by Experience. Free on-site estimates — call (708) 448-8866.

The vocabulary

Water table. The projecting course low on the wall, typically where a thicker foundation or base section steps back to the wall above. It is the lowest and often the widest of the horizontal courses, and it protects the masonry immediately beneath it.

Belt course (also string course or band course). A projecting horizontal band higher up the elevation, frequently at a floor line or beneath a window row. Reads as ornament, functions as a drip.

Sill. The unit beneath a window opening.

Cap. The top course on a porch wall, a pier, a retaining wall or a freestanding wall.

Coping. The same idea at the top of a parapet.

Lintel. The unit spanning above an opening — carrying load as well as shedding water.

Six names, one shared mechanism: something projects, so water runs off it instead of down the wall.

How a projecting course actually works

Two features do all the work, and both are easy to lose.

The slope. The top surface is pitched outward so water runs off the front edge rather than pooling or running back toward the wall.

The drip edge. On the underside of the projection there is a groove or a lip. Water travelling along the underside reaches that groove, loses surface tension, and falls clear. Without it, water simply wraps around the projection and continues down the wall face beneath — which entirely defeats the purpose of the course being there.

That second feature is the one nobody knows about and the one most often destroyed.

Why horizontal stone fails first

Because water sits on it.

A vertical brick wall sheds continuously. A projecting horizontal surface holds water in every rain, every snowmelt and every thaw. Stone that is still saturated when the temperature drops goes into the freeze with water inside it — and limestone, being sedimentary, splits along its natural bedding planes when that water expands.

So on almost any Chicagoland masonry building, the horizontal stone is a generation ahead of the vertical masonry in deterioration. It is the first thing to need attention and the last thing anybody looks at.

The six failure modes

Delamination

Water between the bedding planes, freezing, lifting the stone apart in sheets. You see a flaking, layered face.

It is dramatically worse on a unit that was face-bedded — set with its bedding planes vertical rather than horizontal, exposing the layers directly to weather. That is an installation error from the original build, and it explains why one unit in a course can be falling apart while the one beside it is intact after a century.

Spalling

The face popping off in patches, concentrated where water sits longest — which on a water table is the top surface and the front edge.

Cracking through the section

Often mid-span on a longer unit, sometimes accelerated by a steel element corroding nearby, sometimes by settlement below.

Lost slope

Units settle over a century. And a well-meant repointing with a fat bed of mortar can level a course out entirely. A flat water table is a shelf that holds water — the exact opposite of its function.

Bridged drip edge

Repeated painting. A heavy parge coat. A bead of caulk run along the underside by somebody trying to stop a leak. Each of these bridges the drip groove and routes water back onto the wall. This is probably the most common and most avoidable failure on the list, and it is frequently caused by a previous attempt to fix a water problem.

Open joints

The bed joint under the course and the vertical joints between units. These are the direct entry points into the wall, and on a projecting course they are exposed to water sitting on the surface above them.

Reading the damage from the ground

Here is the diagnostic that makes this article useful.

Damage concentrated in a horizontal strip, with sound masonry above and below it, means the projecting course above that strip has failed.

Look for:

• Spalled or eroded brick in a band immediately beneath a stone course
• Staining running down from the underside of a projection
• Efflorescence — white mineral bloom — in a stripe below the stone
• Mortar joints eroded in the courses directly beneath, while joints elsewhere are sound
• Moss or algae on the wall below a course that is holding water
• The stone itself flaking, cracked, or visibly flat rather than pitched
• Paint or caulk along the underside where a groove should be open

Our post on why limestone sills and lintels fail covers the sill-specific version, and masonry around windows and openings the whole opening assembly.

The repair options, smallest first

A whole course rarely needs replacing. The right answer is usually the least invasive thing that restores function.

Repair	When it applies
Repoint the joints	Joints are the failure; stone is sound
Clear the drip edge	Groove bridged by paint, parge or caulk
Patch localised spalling	Shallow damage, unit otherwise sound
Dutchman insert	A portion has failed, rest of the unit is good
Reset the unit	Stone sound but slope lost or settled
Replace the unit	Cracked through, or delaminated across its depth
Rebuild the masonry below	Where the failed course has already destroyed it

Clearing a bridged drip edge deserves emphasis because it is cheap, frequently overlooked, and immediately effective. Cutting a bead of caulk out from under a projection and restoring the groove can stop years of concentrated water damage on the wall beneath.

How the work is done

1. Identify the material. Quarried limestone, cast stone, or precast concrete — they fail differently and repair differently. Cast stone is a moulded concrete product that can look convincing and sometimes reveals internal reinforcement as it spalls.
2. Trace the water path, above and along the course, including gutters and anything discharging onto it.
3. Repoint the bed and vertical joints with matched, appropriately soft mortar.
4. Restore the drip edge where it has been bridged.
5. Patch, Dutchman, reset or replace units as their condition requires.
6. Restore the slope on any unit that has gone flat.
7. Repair the masonry below that the failed course has been feeding.
8. Clean down gently — no sandblasting, no high-pressure washing, both of which permanently strip the weather-resistant outer skin from stone.

Materials and the governing rule

Stone matched in colour and finish. Repair mortars formulated for stone rather than generic patching compound, tinted and textured on site. Mortar matched in type, colour, sand and joint profile.

And the rule that outranks everything else on historic masonry:

Mortar must always be softer than the stone it surrounds.

Mortar is the sacrificial element — it takes the movement and weathering so the units do not, and it gets renewed periodically. Put hard modern mortar around soft limestone or century-old brick and the stress goes into the units instead, spalling faces that cannot be replaced. On this stock that generally means Type N or softer rather than Type S. See type N versus type S mortar.

Where you find this on Chicagoland buildings

Greystones. Defined by their stone — water tables, belt courses, window surrounds, entry detail, all in quarried limestone. The horizontal courses are the first thing to go and the most expensive thing to get wrong.

Chicago brick bungalows. Limestone or cast stone sill courses, a water table at the base, and decorative bands. On a great many of them what people call "the limestone" is actually cast stone.

Two-flats and three-flats. Stone bands at floor lines, porch caps, and stone bases taking splash and salt.

Post-war ranches and split-levels. Cast stone sills on wide picture windows, and cast caps on planters and low walls — sixty-plus years into an Illinois climate.

Commercial storefronts. Water tables at the base, belt courses at the second floor, and coping at the parapet.

Chicagoland conditions

Freeze-thaw. A Chicago winter thaws and refreezes dozens of times a season, and each cycle is an expansion event inside wet stone. Horizontal surfaces take the worst of it because they hold the water.

Snow load. Snow sits on a water table or a cap for weeks, melting and refreezing in place — a far longer wetting event than rain.

De-icing salt at grade, working on water tables and porch caps near walks and drives.

Slow-drying elevations. North walls and narrow gangways keep horizontal stone wet long after the sunny side has dried.

Maintenance that actually helps

• Look at the undersides of every projecting course once a year, for a clear drip groove
• Never run caulk along the underside of a projection, and remove any that is there
• Keep the tops clear of soil, mulch, planters and debris — anything that holds water against stone
• Check that gutters and downspouts are not discharging onto a course
• Watch for damage in bands on the wall below, which is the early warning
• Do not pressure wash stone trim

What drives the cost

Linear footage of stone involved. Whether the work is repointing, drip-edge restoration, patching, Dutchman inserts, resetting or replacement. How much brick must come down and go back up around a replaced unit. Height and access. Whether stone can be matched from stock or must be cut. Whether the masonry below needs repair as well. Weather windows, since mortar needs workable temperatures to cure.

We publish no figures, because a number that means anything requires seeing the stone. Free on-site estimate, in writing — call (708) 448-8866.

The short version

If you have damage in a horizontal band on your wall, stop looking at the damage and look at the stone above it. Nine times in ten the course is cracked, flat, or has had its drip edge caulked shut by somebody trying to help.

Fix the stone and the wall below stops losing ground. Fix the wall and leave the stone, and you will be back.

Paul Lally's Masonry Inc. is family-owned, insured, and has worked Chicagoland stone since 1988. Our name is on every job. Related services: limestone and sill repair, masonry restoration, tuckpointing and repointing, brick repair, and parapet wall repair.

Built on Craftsmanship. Backed by Experience. Get a free on-site estimate or call (708) 448-8866.