1. Analysis of common shedding quality problems

The building exterior wall insulation system is a composite structural layer. Shedding generally occurs at the junction of different structural layers. Such as between the bonding layer and the base layer, between the insulation layer and the bonding layer, and between the plastering layer and the insulation layer. Common shedding phenomena mainly occur in the shedding of the insulation board and the plastering layer. The main reasons for the shedding of the exterior wall insulation system are as follows:

1. Adhesive factors

Among the quality problems of the exterior wall insulation layer shedding, the insulation shedding problem caused by adhesive factors is the most common.
(1) The quality of the adhesive is too poor.
The insulation material of the wall insulation system is mostly polymer foam board. In order to ensure the adhesion of the insulation material to the base wall, a polymer mortar with polymer emulsion or dispersible glue powder is used. The polymer content in the adhesive will affect the adhesive’s adhesion, water resistance, etc. However, the cost is relatively high. Some companies will reduce the amount of polymer used, sacrificing quality in exchange for low cost. This directly leads to the adhesive performance failing to meet the 0.1MPa requirement specified in the standard.
(2) Improper glue application or insufficient glue application results in too small an area for the insulation board to be pasted.
Adhesive pasting of insulation boards is the main method for fixing insulation systems. The bonding area of the insulation boards directly affects the bonding firmness of the insulation system. Insufficient adhesive application during construction or incorrect application method will result in the effective bonding area between the insulation board and the base wall failing to meet the specified requirement of more than 40%.
(3) Construction factors or base wall reasons lead to false pasting of the insulation board.
Due to the operation of the construction workers or the large deviation of the wall flatness, the insulation board is falsely pasted. Secondly, incorrect application method can also easily lead to false pasting.

2. Quality problems of external wall insulation layer materials

(1) The adhesion of the insulation board surface is too poor.
Due to the forming process or material characteristics of the insulation board, the surface finish of the insulation board is relatively high. The adhesion with adhesives or plastering mortar is too poor, such as XPS board, PU, etc.
(2) The insulation board has too low strength.
If the insulation board has too low strength, the insulation system will be damaged and fall off from the insulation layer. Therefore, national standards or industry standards have set requirements for the tensile bond strength of insulation materials. For insulation materials with low strength, such as rock wool, certain reinforcement measures should be taken. In addition, materials such as insulation mortar and foamed cement board will have their own strength greatly reduced after absorbing water. This should also be noted when used in exterior wall insulation systems.
(3) The insulation material quality is unqualified.
Taking EPS board as an example, the industry standard clearly stipulates that the bulk density per cubic meter should not be less than 18 kg. The tensile bond strength should not be less than 0.1 MPa. In fact, many projects cut corners and use low bulk density EPS boards when applying them. This results in the insulation board having too low tensile strength. It cannot meet the requirements of the insulation system’s self-weight and resistance to negative wind pressure. The insulation board is damaged and falls off in the middle.

3. Base wall factors

The base wall strength is too low. Or there are floating dust, oil stains and other materials on the surface that affect the adhesion of adhesives. This causes the insulation material to not bond firmly to the base wall. It falls off on the surface of the base wall. Secondly, when the flatness deviation of the wall surface is large, it is easy to cause the insulation board to fall off.

4. Anchoring problem

(1) Anchor bolts are not designed or the number of anchor bolts is insufficient.
For the external insulation system of the building exterior wall, insulation auxiliary fixation is usually used. Especially for coastal areas with large negative wind pressure and projects using insulation materials such as rock wool, XPS, and phenolic board. Relying solely on the bonding of bonding mortar. There is a risk of insulation board falling off.
(2) The anchor bolt anchoring depth is not enough or the anchoring method is incorrect.
When designing and constructing anchor bolts, the base wall type is not considered. For example, special walls such as aerated concrete or hollow block walls. Ordinary expansion anchor bolts are selected or the anchor bolts are not deep enough into the wall. This leads to insufficient anchoring force between the anchor bolt and the base wall, resulting in the insulation system falling off.

5. Unreasonable design of the finishing layer, and the falling off due to excessive weight

The external insulation system of the wall is a systematic project. In the classic EIFS system, the external finishing is a coating system. In China, in order to emphasize the decorative effect, heavy finishing such as bricks and stones will be constructed on the outside of the plastering layer of the external insulation system. When the weight of the finishing layer is too large, the shear force generated on the insulation material will cause the insulation system to fall off, and when the adhesive quality of the finishing layer itself is poor or deformed, it will cause the finishing layer to fall off.