Qicai Bangyuan

What are the common causes of deformation and cracking in exterior wall insulation panels?

Release time:

2023-05-22 16:42

Repairing deformation and cracking in exterior wall insulation panels has long been a major headache for contractors, as it is both time-consuming and labor-intensive. In this issue, Shandong Bangyuan New Building Materials Co., Ltd. will discuss with you the causes of such problems, hoping to provide you with some useful insights.

Exterior wall insulation board

1: The insulation board settled due to the absence of anchor bolts for anchorage.

 

2: Insulation layer work should not be carried out on frozen surfaces, at excessively low temperatures, or on substrates with excessive moisture that have not been treated with a moisture‑proof coating, as freezing or the warming of such substrates in spring can cause water to form an impermeable barrier or lead to gas expansion.

 

3: The adhesive used for insulation boards is of poor quality (e.g., with insufficient polymer content), low‑priced, provides an inadequate bonding area, exhibits poor anchorage performance, or has poor compatibility with the accompanying interface agent, thus failing to withstand positive and negative wind pressures.

 

4: When the surface of the insulation board is not treated with an interface agent as required or when a spot‑and‑frame bonding method is used, and when no venting channels are provided in the adhesive applied to the frame or when a moisture‑proof primer is not applied to the substrate, the system is susceptible to moisture‑induced degradation.

 

5: The substrate has insufficient strength or is excessively dirty, resulting in weak bonding at the interface between the adhesive mortar layer and the substrate.

 

6: The adhesive used for bonding the panels has been stored for an extended period, resulting in insufficient bond strength with the wall substrate.

 

7: Gaps between insulation boards shall be directly filled with skim coat mortar.

 

8: The insulation boards are not firmly bonded, resulting in only a surface adhesion on the wall.

 

9: After production, the insulation boards do not undergo sufficient curing, resulting in dimensional instability and deformation upon installation.

 

10: Use boards that have undergone deformation (warping).

 

11: Causes of cracking between foam boards. Differences in the flatness of the exterior surface of the base wall, variations in insulation board thickness, and uneven side‑face flatness can lead to gaps or height differences at the joints when installing the boards. If foam strips are filled unevenly, applied intermittently, or left out entirely, and if the surface is not properly smoothed, localized irregularities may develop after mesh reinforcement and skim coating. Over time, these surface irregularities can cause differential shrinkage, resulting in cracks and sharp edges at the joints, which, in the long run, may allow rainwater to penetrate.

 

12: Design Reason

 

What measures can be taken to prevent cracking and deformation of exterior wall insulation panels?

 

1: Insulation boards must undergo the required curing period, and the board adhesive, mesh reinforcement, anchor bolts—along with their specifications and quantities—shall be selected in accordance with the design requirements.

 

2: If the substrate has high moisture content, apply a moisture‑proof primer to ensure the substrate is dry and that the ambient temperature meets the requirements for application.

 

3: The adhesive quality must be ensured, and the bonding area shall be no less than 40%. Anchor bolt specifications and quality shall comply with design requirements; the number of anchors used shall be determined according to the building height, and the embedment depth into the base wall shall be no less than 25 mm.

 

4: If the substrate has high moisture content, apply a sealing primer and use the spot‑and‑frame adhesive application method.

 

5: The substrate for adhering the panels shall be sound, smooth, dry, and clean, and moderate pressure should be applied during installation.

 

6: The adhesive must be used within its shelf life; adhesives that have expired must not be reconstituted with water for further use.

 

7: Gaps between insulation boards shall be filled with foam; mortar-based finishing plaster shall not be used to seal these gaps.

 

8: After production, insulation boards must undergo adequate curing and aging to ensure dimensional stability and prevent deformation—this is the most fundamental requirement. Otherwise, even high‑quality adhesives and complementary materials will be difficult to apply, and any temporary mechanical fastening will eventually deform, leading to a reduction in bond strength.

 

9: To prevent cracking between insulation boards, after the substrate has been properly prepared, apply adhesive mortar to the underside of each board and affix it to the wall. During installation, ensure that a 5–15 mm joint remains between adjacent boards. Fill these预留板缝 with single-component polyurethane foam to seal them, then sand down any excess foam protruding into the joint until it is flush with the surface of the insulation board, achieving both expansion‑based sealing and structural integration before proceeding with the next standard construction steps.

 

10: Provide expansion joints at structural deformation joints.

 

11: Reinforcement mesh should be added around windows and at their corners to distribute stress.

 

12: Layer-by-layer gradient design, stress relief, and prevention of cracking and leakage in the external insulation layer. Surface cracks are primarily caused by material deformation; as long as stress can be effectively dissipated through controlled deformation, thereby reducing stress concentrations under constrained conditions, cracking can be effectively controlled. Therefore, materials used in wall insulation systems must possess adequate flexibility, and an reinforcing mesh capable of dispersing stresses should be incorporated into the crack-resistant protective layer.

 

The thermal insulation system employs flexible soft connections, creating a flexible deformation mechanism that progressively releases stress and thereby mitigates cracking, effectively controlling the formation of surface cracks in the insulation layer.

 

13: Thermal bridge mitigation in exterior walls. In the envelope of exterior walls, components such as metal elements, reinforced concrete beams and columns, projecting balconies, sunshades, and protruding moldings can, under the influence of indoor–outdoor temperature differentials, create areas of concentrated heat transfer with relatively low inner-surface temperatures—these constitute thermal bridges. Such thermal bridge zones are prone to delamination and cracking of the insulation layer, leading to water infiltration. Therefore, the external insulation must fully encase all exterior surfaces, ensuring a continuous, closed‑cell insulation system.

 

Shandong Bangyuan New Building Materials Co., Ltd. is located at No. 17 Kunming Road, Linyi Economic Development Zone. “Qicai Bangyuan” is the company’s brand name. Bangyuan Building Materials is a comprehensive enterprise integrating research, development, production, and sales of building materials. It operates modern production facilities across China and maintains numerous stable project‑based partnerships. Leveraging state-of-the-art manufacturing equipment and a dedicated R&D team, the company continuously develops a wide range of high‑quality, environmentally friendly new‑generation building materials.

 

　The main products include molded polystyrene boards, graphite‑enhanced polystyrene boards, lost‑foam molds, polymer‑based bonding mortars, polymer‑modified skim coats, adhesive‑powder‑filled slurries, lightweight machine‑sprayed plaster gypsum, alkali‑resistant fiberglass mesh fabrics, and other innovative building materials.

 

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