Stucco damage under a door threshold step down area is not uncommon, especially when the stucco is applied to the edge of a concrete slab or foundation. The stucco often looks like it is falling, peeling or flaking off and over time just gets worse and worse. Often when you go out the door and step down, it will be onto a concrete landing, sidewalk or patio. The damaged stucco is normally about 3/8 to 1/2 of an inch thick, but sometimes thinner. Homeowners or buyers will often worry that the stucco is defective and if this is a major issue or not, and often want to know what caused it.
What Causes Stucco to Flake Off Under Door Thresholds?
The stucco is often exposed to water. Water from storms and rain: some of which splashes back up off of a concrete step, walk or patio, thus the damaged area is getting hit by more moisture than the rest of the stucco on the home.
Water running off the roof or being blown against the stucco.
Snow or ice against the stucco in colder climates, freezing, then thawing and wetting the stucco. Since stucco is porous, when water seeps into it and then freezes repeatedly, thin coats (1/4 to 1/2 inch) of stucco will not stand up over long periods of time to this freeze / thaw cycle.
Spraying or washing down the step, sidewalk or patio adds more exposure of the stucco to wetting and getting soaked by water.
Capillary action and wicking up
When the stucco goes from the bottom of the door down to where it may be touching a concrete walk, landing, patio or even into soil if there is no walk, landing or patio, then moisture often wicks upward through capillary action.
Basically, the more water stucco is exposed to and for longer periods of time, the more the stucco will weaken, deteriorate, and flake or fall off.
#2 Mechanical Damage
Mechanical damage from the threshold being pushing down onto the stucco when stepped on. This occurs repeatedly over the months and years, ultimately this repeated pressure is like a little hammer, always hitting it lightly. Eventually the stucco will separate or pull away from the concrete.
Doors constantly opening, shutting, slamming, or banging
Vibration and jolts form doors opening, closing, or slamming is detrimental to these small areas of stucco. Day in, day out of being exposed to vibrations will weaken many materials, including stucco.
#3 Poor workmanship and improper preparation of materials
If the application of the stucco was improper, experienced extreme weather or not mixed properly, then problems may develop. For example:
- Stucco was applied on a day that was too hot or too cold.
- Right after application of the stucco there was a heavy rainstorm or freezing temperatures hit before the stucco hardened or cured.
- Wrong mix of materials. Perhaps too much sand or water was used, or not enough cement was used, then the mix will be deficient and often fail. At times the sand may have too much dirt in it, essentially not clean sand.
- Stucco was applied to the concrete before the concrete had sufficiently cured.
Note, the list of workmanship and preparation mistakes could take up this entire page.
The flaking or stucco falling off under exterior doors is very common and usually takes place over years, not days or months. Although it looks bad, it is normally not a structural concern but more of a cosmetic issue.
The majority of the time the cause relates to water, mechanical damage or workmanship.
Basically, it is a maintenance issue and generally not a time sensitive one. For home sellers, it would probably be wise to repair the stucco before listing their house, for some buyers might think the there is something majorly wrong with the house or stucco. Hopefully, a good home inspector would set their mind at ease about this issue.