## 2 Literature Review
### EIFS Specifications Related to Adhesion Quality  
As mentioned earlier in the introduction, many factors influence adhesion quality. However, this paper specifically focuses on the specifications related to the quantity and shape of adhesive, which can be evaluated using CV. To this end, a literature review was conducted on EIFS specifications concerning the quantity and shape of adhesive as applied in construction sites. There are several specifications concerning EIFS. In the USA, the American Society for Testing and Materials International (ASTM) covers board sizes through ASTM E 2430 [18] and the minimum requirements for EIFS adhesives through ASTM C 1397-13 [19]. According to ASTM regulations, insulation board size is designated as a length of 48 in. (1219 mm) \(\pm\) 1/16 in. (1.6 mm) and width of 24 in. \(\pm\) 1/16 in. (1.6 mm). In the ribbon and dab method, ribbon thickness is 2 in. (50.8 mm), the diameter of the ribbon is 4 in. (101.6 mm), and intervals of the dabs are 8 in. (203.2 mm). The European Organization for Technical Approvals (EOTA) issued the ETAG 004 [20], which is in Section 6.1.4.1.3. \"Bond strength between adhesive and insulation product\" specifies the area calculation formulas for the bonding performance of each adhesive (Table 1 and Equation (1)). However, it lacks detailed descriptions regarding the application methods (shapes) of the adhesive. To comply with the minimal admissible bonded surface requirement described below:  
\[\text{S}(\%)\ =\ \frac{0.03}{B}\times 100 \tag{1}\]  
where S is the minimal bonded surface, which shall exceed 20%. \(B\) is the minimum failure resistance of the adhesive to the insulation product in dry conditions for all failure modes (MPa), and 0.03 MPa is the minimum requirement. According to the table and equation in ETAG-004, in the case of the minimum bonding strength of 0.03 MPa, a 100% bonded surface area is required. Even with an increase in bonding strength, a minimum bonded surface area of 20% is still mandated. In the Republic of Korea, the Korea Land & Housing Corporation (LH) defined requirements for EIFS by the specification for Housing Projects 46030 in 2012 [21]. In 2020, it was revised to align with the Korea Construction Standard and rebranded as LHCS. Figure 1a shows the previous version of the specification. LH46030 stated that insulation boards should not exceed 600 \(\times\) 1200 mm, the adhesive should cover at least 40% of the surface, and the specified ribbon width should comprise 50 mm and 100 mm diameter of six dabs, with distances between each dab. \begin{table}
\begin{tabular}{c c c c} \hline \hline  & \multicolumn{3}{c}{**The Minimum Failure-Resistance Values After Each Conditioning in N/mm\({}^{2}\) (MPa)**} \\ \cline{2-4}
**Mode of Failure** & **Dry Condition** & \multicolumn{3}{c}{**After Effect of Water**} \\ \cline{3-4}  & & **At 2 h After Removing the** & **At 7 Days After Removing the** \\  & & **Samples from the Water** & **Samples from the Water** \\ \hline Adhesive rupture & 0.08 \({}^{*}\) & Adhesive rupture in adhesive & 0.08 \({}^{*}\) \\ \hline Cohesive rupture in insulation & 0.03 & Cohesive rupture in insulation & 0.03 \\ \hline \hline \end{tabular} \({}^{*}\) One single value lower than 0.08 but higher than 0.06 \(\text{N}/\text{mm}^{2}\) (MPa) is admissible.  
\end{table} 
Table 1: Specification of ETAG 004. In the revised specification LHCS 41 42 00 15 [22] Figure 1b, following the LH specification for Housing Projects 46030, the insulation board size of 600 \(\times\) 1200 mm, the adhesive area, the ribbon thickness of 50 mm, and the dab diameter of 100 mm were maintained. On the other hand, the number of dabs increased to eight, while the distance between each dab was removed. Table 2 provides a summary and comparison of regulations for adhesion quality in the countries mentioned above. While many factors contribute to EIFS adhesion quality, most regulations emphasize performance tests, such as insulation durability and bonding strength tests, among other criteria [23].