Why Does Stucco Crack


Stucco is used as a decorative covering for walls and ceilings. It is sometimes used over concrete and wood to make the wall or ceiling visually attractive. Stucco is one of the strongest materials out there but, despite its strength, stucco can and does develop cracks and decompose over time. Cracks around the edges of doors, windows and other sensitive areas are especially common.

Let’s take a look at some of the reasons why your stucco could be cracking.

1.Incorrect Mix
Stucco is made of water, a binder, and a construction aggregate. The most common type of stucco is cement plaster style stucco. If the cement and the sand base are not mixed in correct proportions, the end result ends up being weak. With the rise and fall in temperature, the weak stucco will develop cracks and begin to peel off the wall and ceiling. If the stucco on your wall has been applied in an even layer and you can’t find a problem with the application, the stucco has probably been mixed incorrectly. The old stucco may have to be peeled away and a new layer applied.
2.Faulty Install
It’s common to see small cracks in the surface of the stucco even if the stucco has been recently applied. But these cracks are sealed over as soon as the application is complete, usually by paint. While this may alarm you, it’s actually not an indication of a faulty install. If the cracks are too large, however, you should be worried. Also, if the paint starts to peel off early, it’s a sign of faulty install.

Faulty install of the stucco, in addition to the above, can mean several things like incorrect location of expansion joints, lack of control/expansion joints, a finish coat is applied before the base coat has had a chance to dry out, problems with the wall like an incorrect deflection criteria, loading or installing an interior drywall after the stucco has been applied, incorrect loading of the structure or the roof before the lath is installed, incorrect installation of the lath base, incorrect spacing between base sheathings, incorrect thickness of applied stucco or any one of these gaffes can cause your stucco to develop large cracks early in their lifecycle.
3.House Settling
House settling is a common cause of stucco cracking. House settling generally occurs in old homes, or homes built in areas with loose soil. The loose soil gives in to the pressure the weight of the house exerts, causing the house to settle lower. Incorrect backfilling techniques are also responsible for house settling.

Whatever the reason for settling, the phenomenon causes sudden pressure to accrue on the base of the house and its support structures, including walls and ceilings. The stucco in the walls and ceilings will crack under this additional pressure, because it has not been built to withstand it. Stucco cracks because of house settling are difficult to correct without professional help.

When a house settles it not only can affect the stucco but it can affect many aspects of your home. Steps around your home could end up being slanted, your driveway could end up having a crack formation, your floor in your kitchen could become uneven, doors that once opened and closed perfectly smoothly now open and close with distress, squeaks, and perhaps rub against the floor or carpet which will eventually lead to an issue there. This is the natural progression of things so when you first have a home built, if that is something you do, there is a solid chance that the cost of building a home goes a little bit passed that last nail being pounded in the joint or a gallon of paint being applied to the bedroom. Any home can settle though and these scenarios occur or others; it does not have to be a built home from scratch of your own design.
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4.High Winds
Stucco that has been recently applied is vulnerable to cracking because of high winds. High winds can suck away the moisture from the recently applied stucco. This causes the remaining stucco to shrink and develop small cracks, which can grow larger with time. This type of cracking is known as shrinkage cracking.

Stucco will also crack in extreme weather conditions. The strong winds will bring with them debris, like fallen branches, which can land against the stucco and cause it to crack. If the stucco is connected to a flexible joint, the winds will push the join inwards, which will exert pressure on the stucco and cause it to crack. High winds will also bring with them extreme moisture or heat, depending on local conditions. Stucco if exposed to either extreme will develop cracks and deteriorate over time.
5.Seismic Movement
It’s very difficult to protect your home walls from cracking during seismic movement, which can include earthquakes and seismic waves. During a period of seismic activity, depending on the fault, the tension under the ground may pull the ground apart, squeeze it together and strike and slide away. In some cases, the ground may fold over. In extreme cases, the energy may transmit in the form of a seismic wave, which is wave of force that travels through the ground, or cause an earthquake.

If your house is built near a fault line or a place with a higher-than-normal level of seismic activity, the seismic movement will cause your house to move around. The shock will transmit through the walls and cause the stucco to crack.
6.Man-Made Problems
Stucco can also crack because of man-made problems. Cracking can occur because of loud planes flying by your house, explosions taking place nearby and large vehicles driving by your home. Some planes are powerful enough to crack windows when they fly by, because of a phenomenon known as sonic resonance (sound waves). Loud explosions, apart from causing sound resonance, are also responsible for causing a shock to travel through the ground, which will cause your house to shake and stucco to crack. Powerful, heavy vehicles driving by your house can also transmit a shock through the ground. Other man-made problems include construction work going on near your house, excessive drilling and dropping of heavy loads nearby, among others.
Stucco, if applied correctly and with proper consideration for local conditions, will last for a lifetime.

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