Why does the exterior wall paint finish crack?

Soon after the completion of many buildings, the exterior wall paint finishes cracked, which seriously affected the appearance of the building; and the wall water seepage caused by the cracking not only affected the function of the house, but also affected the structural safety of the building, which became a project Quality hazards.

So, what is the reason for the cracking of the exterior wall paint finish? What are the preventive measures?

Causes of cracking of exterior wall paint finish

1.

The base layer of exterior wall paint finish is cement mortar plastering layer, which will produce dry shrinkage and temperature difference shrinkage during the setting process.

The phenomenon of hollow cracking on the outer wall

The phenomenon of hollow cracking on the outer wall

2.

Due to defects in the quality of the external wall putty used, poor crack resistance; or due to improper construction operations, the putty shrinks and cracks after being scraped onto the wall, which affects the coating surface.

3.

Due to poor crack resistance or improper construction, some paints with quality problems are prone to shrinkage, cracks and other quality problems after being painted on the wall shortly after being blown by the wind and sun.

External wall cracking

Construction preventive measures for cracking of exterior wall paint finish

1.

(1) The proportion of cement mortar used for exterior wall plastering should be selected appropriately, generally 1:2.

(2) Strictly follow the external wall plastering operation regulations and process construction.
Before plastering, the dust, dirt, oil stains on the surface of the base layer and the ear dust on the brick wall must be carefully removed.
The wall must be watered the day before construction, and 24 hours after the construction is completed, it must be watered and maintained.
The number of watering per day should be determined according to the weather conditions, at least twice a day, and the maintenance time shall not be less than 7 days.

Cement maintenance for exterior wall construction

(3) If construction is carried out in a sunny season, the construction time should be arranged scientifically, and construction should be avoided under the sun, or effective shading measures should be taken to ensure that the mortar surface is dry and prevent the plastering mortar layer from shrinking too quickly due to sun exposure.
Caused by cracking.

(4) The division of the cement mortar plastering surface layer should not be too large, and the shrinkage of the cement mortar can be adjusted by making full use of the division.
Use triangular or trapezoidal cross-section wooden strips to divide the cement mortar surface.
No joints of construction joints are allowed in the same construction section.
The joints should be caulked with caulking paste.

The external wall construction divides the seam

2.
Construction of external wall putty layer

(1) The exterior wall putty layer construction should start after the plastering layer has reached the maintenance period.

(2) The plastering mortar layer should be inspected before the putty scraping, and the hollows and cracks should be repaired 2 to 3 days in advance.
Remove the dust and floating sand from the plastering surface and keep the plastering surface clean.

(3) Construct in strict accordance with the requirements of the construction specification and product description to ensure that the putty layer and the plaster layer are firmly bonded without cracking.
At the same time, avoid working under the sun during construction to ensure that the putty layer is in a dry state.

Putty for exterior wall

(4) The polishing process of the putty layer should be maintained in time after the construction is completed.

3.
Construction of coating surface layer

(1) Before construction of the coating surface layer, the putty layer should be smooth, firm, clean, free from sparseness, chalking, peeling and other defects.

(2) According to the paint finish construction specification and paint product requirements, the base layer of putty has a moisture content of 8%-10% before the paint surface coating can be applied.
Drying of the putty base layer during construction is the key to ensure that the coating surface layer is firmly bonded and does not crack.

Paint exterior wall latex paint

(3) The paint surface layer is applied in several layers with different materials according to different functions.

(4) According to the construction technology and product requirements, the pH value of the grassroots is required to be below 10.

(5) The construction of the paint surface layer should not be carried out in an environment where the wind is above 4, or in rainy, foggy and relative humidity above 85%, to prevent the dust raised by the wind from polluting the paint surface, and to ensure the dryness of the construction surface.