Why do newly-made diagonal paintings of room windows crack easily?

Because the section of this wall is small, and the laying of concealed pipes for balcony light switches affects the quality of the wall to varying degrees, and some walls between doors and windows are built by core-cladding method or concealed joints, the bearing capacity of precast doors and windows on the lintel is insufficient, resulting in cracks. In the window-to-window wall at the junction of the external longitudinal wall and the internal partition wall, because the T-joint is not good during construction or the cantilever balcony beam extends into the internal wall, splayed cracks may appear at the root of the cantilever beam.

In building construction, cracks often appear in other parts:

1, cracks in the lower wall and parapet of the ring beam at the top floor of the building.

2. Cracks appear at the corners of the top gables and vertical and horizontal walls.

3. The cracks between balcony railing and balcony edge and cantilever beam.

4. Cracks appear in the cast-in-place floor slab.

5. Cracks appear on the door floor.

The causes of these cracks are:

1, cracks in the lower wall and parapet of the ring beam at the top floor of the building, cracks in the corner of the top gable and vertical and horizontal walls, horizontal or oblique cracks in the window at the junction of indoor longitudinal walls and gables, mainly temperature cracks. Because in structural design, only the load problem is usually considered, because of the different expansion coefficients of concrete and brick, horizontal temperature difference stress will occur between contact surfaces. When the temperature changes greatly and the stress is greater than the shear strength of the mortar at the joint of the two materials, cracks will inevitably occur, especially at the corner of the gable and parapet at the top floor of the house, when the longitudinal wall is longer than 50 m. However, due to improper operation in the construction process, such as there are many broken bricks when building to the top floor, the water is not permeable in high temperature season, and the ring beam template is stepped on the newly built wall when fastening, which makes the mortar loose, and the low label of the top mortar will aggravate the cracks.

2. The cracks between balcony railings (including aerated concrete railings) and balcony cantilever beams are usually caused by the different strength grades of railings and balcony cantilever beams, leaving no cracks at the joints, and mortar can not be squeezed in when plastering, resulting in cracks under the action of temperature.

3. The cracks in cast-in-place slab are mainly caused by design reasons and construction technical reasons, which are mainly manifested in: ① concrete materials; ② Poor protection of finished products; Special parts are not treated specially; ③ insufficient curing time; Bear the construction load prematurely; (4) reasons such as premature removal of bottom formwork support.