Stucco crack types in Joliet: hairline, map and structural, and what each one means

Cracks in synthetic stucco (EIFS) and in hard coat cement stucco fall into three families. Hairline cracks are a finish problem, sealed for $400 to $900 on one elevation or folded into a recoat at no extra line. Map cracks, the spiderweb pattern, are a base coat problem and still a coating fix on a dry wall. Structural cracks, the wide diagonal ones that run off a window corner or step across the wall, are a movement or water problem, and no coating fixes them. Joliet Stucco & EIFS reads the crack on the quote walk and prices it from the published table.

First, which stucco do you have

The same crack means different things on the two systems, so start there. Knock on the wall. Synthetic stucco sounds hollow and dull, because there is an inch or more of foam under a thin base coat. Hard coat cement stucco sounds solid and rings a little, because it is three coats of cement over metal lath. Most of the houses built in Joliet, Plainfield, Naperville and Frankfort between the late 1980s and about 2000 are synthetic. Older brick and frame houses closer to downtown Joliet and in Lockport are more often hard coat.

On EIFS a crack lives in a base coat that is a fraction of an inch thick, reinforced with fiberglass mesh. Where the mesh was lapped short or left out, usually at window and door corners, the base coat has nothing holding it and it cracks there first. On hard coat, cracks come from the cement shrinking as it cured and from the house moving underneath the lath. Either way the questions are the same: how wide, which direction, where on the wall, and is there water behind it.

Hairline cracks

A hairline crack is thinner than the edge of a credit card. You see it because dirt has settled in it, not because it has any depth. Hairlines show up as short random lines in the open field of a wall, sometimes following the texture, and they are thickest on the south and west elevations that take full sun and prairie wind.

The cause is the finish coat drying and shrinking, then expanding and contracting with every hot afternoon and cold night for fifteen or twenty years. They are cosmetic on the day you notice them. They stop being cosmetic in November, when water sits in the crack, freezes, and widens it by March. Our guide to freeze thaw damage on stucco covers that cycle.

The fix is a coating. An elastomeric finish stretches over a hairline and closes it; that is what the product is for. Sealing hairlines on one elevation runs $400 to $900 in the published table, and on a whole house recoat at $3 to $5.50 per square foot of wall the hairlines are included, not a separate line. If a contractor quotes you a structural repair for a wall of hairlines, get a second opinion. And one thing gets reported as a crack that is not one: the gap where stucco meets a window frame, door frame or hose bib is a sealant joint, designed to flex, and its fix is the sealant line.

Map cracks

Map cracks look like a road map or a dry lake bed: an interconnected web of fine cracks over a whole area of wall, with the pieces between them roughly the size of a hand. Some trades call the pattern alligatoring or crazing. It rarely appears in one spot; it covers an elevation or the part of one that gets the most sun.

On hard coat the cause is almost always the base coat drying too fast when it went on, a hot windy day with no curing water, or a mix too rich in cement. On EIFS the cause is usually a base coat that went on too thin over the mesh, or a finish that has chalked and shrunk so far that it is pulling itself apart. Either way the pattern tells you the layer under the finish is weak across that area, and that thousands of tiny openings have been taking water for years.

What it means for the quote is a two step check. First, surface meter readings across the mapped area and a probe below any window inside it, because a wall that has been drinking through a web of cracks for a decade is the wall most likely to read elevated. Second, a scratch test. If the base coat is firm, the fix is a bonding primer and an elastomeric recoat; a plain acrylic is the wrong product here because the map pattern telegraphs through it within a season. If the base coat crumbles under a putty knife, that area gets cut back and rebuilt with new mesh before the finish goes on. A rebuild of 10 to 40 square feet runs $1,200 to $3,500, and anything wet behind it moves to the remediation line.

Structural cracks

A structural crack is one you can fit a coin edge into, and it has a direction. The common shapes in Joliet are a diagonal crack running down and out from the corner of a window or door, a stair step crack that follows a line across the wall, a horizontal crack at the band between the first and second floor, and a vertical crack at an outside corner of the house.

Each shape has a usual cause. Diagonals off window corners on EIFS are the mesh problem above: the corner was never reinforced with the diagonal mesh strip the manuals call for, and the base coat split under normal movement. Diagonals on hard coat, and stair steps on either system, usually mean the foundation settled or heaved under that part of the house, a familiar story in Will County clay after a wet spring and a dry August. A horizontal crack at the floor line is the floor framing shrinking or deflecting behind rigid cladding. A vertical crack at a corner is two walls moving differently, often because there is no expansion joint where one was needed.

What every one of them means is the same: the wall has been open to water for as long as the crack has existed, and a crack that size at a window corner is the single most common place we find sheathing that reads above 30 percent. So the order of work is fixed. Find out whether the movement is still active, with a pencil mark across the crack and a return visit, or a call to a foundation contractor if the stair step runs into the block below. Probe the sheathing at the bottom of the crack, which is the moisture inspection with a written report, $450 to $850. If it reads dry, the crack gets cut back, the base coat rebuilt with mesh across the corner, the adjacent sealant joints replaced ($900 to $3,000 for a house), and the elevation recoated so the repair disappears, $1,800 to $4,500 for one elevation. If it reads wet, that section is a localized remediation, $4,000 to $12,000, and the recoat waits until the wall is dry and rebuilt.

How we read a crack on the quote walk

1. 1

   Width, against a card edge or a coin.

2. 2

   Direction and location, with a photo.

3. 3

   Depth, by running a knife point along it to see whether it stops at the finish or goes through the base coat.

4. 4

   Moisture, with a surface meter on the wall around it and a probe below if it sits at a window corner or reads elevated.

5. 5

   Activity, with a pencil mark across it and a date, so the next visit shows whether it has moved.

The result goes on your quote as a line from the published table, and if the crack is the kind that opens the wall, the photo of what we find behind it goes in your file whether or not you proceed.

Crack sealing and recoating need the wall above about 40°F for a day afterward, which gives Joliet a mid April to late October window. Inspection and marking run all year. Illinois issues no state license for stucco trades. The City of Joliet requires contractor registration; a like for like repair does not normally need a permit, and a repair that opens sheathing or framing usually does. The city’s residential permit page is the reference, and we confirm the category before quoting anything that opens a wall.