Freeze thaw damage on stucco through Illinois winters and how to stop it

Northern Illinois passes through freezing dozens of times each winter, and every pass takes a little water in a stucco wall from liquid to ice and back. Ice takes up more room than the water it came from. On a synthetic stucco (EIFS) wall that push lifts the finish off the base coat and crushes the foam behind a crack. On a hard coat cement wall it flakes the surface and works the cement loose from the lath. Joliet Stucco & EIFS does most of its sealant and crack work in the last weeks of the season for exactly that reason.

Why Illinois winters are hard on stucco

Freeze thaw damage needs three things: water, a way into the wall, and a temperature that crosses freezing often. The Illinois State Climatologist describes northern Illinois winters as cold with frequent passages through freezing, and puts the region at roughly 36 to 40 inches of precipitation a year, much of it driven against west and south walls by prairie wind. So the water and the cycles are given. A wall in Plainfield or Shorewood facing west takes rain in the fall, and then the January sun warms that same wall enough by afternoon to melt snow at its base, which refreezes after dark. The south and west elevations of a Joliet two story cycle more times than the north wall does, and that is where the damage shows up first.

The way in is the only variable. A tight wall with sound sealant and an unbroken finish sheds water and does not care how many times it freezes. The trouble is that most synthetic stucco in Will County went up between the late 1980s and about 2000 as a face sealed system with no drainage plane, which means every crack and every failed joint is a direct path to foam and sheathing that have no way to drain.

What freeze thaw does to EIFS

Four things, in order of how often we see them. Cracks widen. A hairline at a window corner in November has water in it. The water freezes, the crack opens, more water gets in at the next thaw. By March the same crack takes a fingernail. Our guide to stucco crack types explains how to tell which cracks are which.

The finish lifts. Water that gets between the finish coat and the base coat freezes as a thin sheet and pops the finish loose. In April this shows as blisters, then flakes, then bare patches of grey base coat on the sunniest wall. A recoat over a wall that is still flaking peels with it, which is why the prep on a freeze damaged wall matters more than the product.

The foam crushes. Water in the foam below a window corner turns to ice, crushes the foam cells, and when it thaws the finish sags into the void. From the sidewalk that is a soft spot or a slight belly below the window. Under a probe it is usually the wettest reading on the house.

The joints split. Sealant at windows, doors and penetrations is pulled hardest at the coldest point of the night, when the EIFS and the window frame shrink by different amounts. On 1990s houses the original joints were often painter’s caulk with no backer rod, and that material splits after ten or fifteen freeze thaw winters. A split joint above a window is the most common single source of a wet wall on the moisture inspections we write.

What it does to hard coat stucco

Cement stucco absorbs water into the cement itself, so the damage is at the surface and at the bottom. Spalling is the surface flaking off in thin scales, usually in the bottom two feet of a wall where snow sits against it. A white powder bloom, efflorescence, means water is moving through the cement and carrying salts out; it is a symptom, not the damage. Where a wall stays wet at the base through repeated cycles the lath behind it rusts, and a section eventually sounds hollow and drops. Snow shoveled against a stucco wall, mulch piled over the bottom edge and a downspout that dumps beside the wall all put the bottom two feet through more cycles than the rest of the house.

The five places water gets in

Walk the house in October and look at these, in this order.

1. 1

   Hairline cracks on the south and west walls, especially any that run off a window or door corner.

2. 2

   Sealant joints at every window and door, and at every hose bib, light, vent, cable and conduit that goes through the stucco.

3. 3

   Kickout flashing, or the lack of it, wherever a roof edge dies into a wall. On a 1990s two story that is usually where the garage roof or a porch roof meets the second floor. Without a kickout the roof water runs down inside the stucco.

4. 4

   The base of the wall: grade that has crept up against the stucco, mulch touching it, a splash block missing under a downspout, the place the snow gets piled.

5. 5

   Deck ledgers and railing posts that pass through the stucco, and any satellite dish or shutter that was screwed in without sealant.

How to stop it, in order of cost

Everything here comes from the published table, listed cheapest first because that is usually the right order to do it in.

What can still happen after the season closes

Inspections and moisture readings run all winter, and a March report puts you at the front of the line for an April recoat slot. Remediation that replaces sheathing is winter work if the wall is tented and heated. Some sealants tolerate cooler weather than finish coats do, so a split joint found in November is worth a call rather than a wait; we will tell you honestly whether it can go in or should be taped and scheduled. What cannot happen is a finish coat below the cutoff. A recoat sprayed on a cold wall in November is the one that peels by the third winter, and no warranty covers it.

Spring: what to look for after the thaw

Walk the south and west walls in April. Wipe a hand across the finish; powder means chalking. Run a fingernail along last fall’s cracks; if one catches, it widened. Look under every window for brown streaks and along the base of the wall for flakes on the ground. Push gently below the window corners for anything that gives. Any one of those on a synthetic stucco wall is the sign to get readings before the recoat, and all of them together on an elevation are the reason that elevation is priced by its condition and not by the square foot alone.