Diagnostic Level	Method	Condition Index classification	Determine the grade	Proposed renovation principle
Stage 1	D.E.R Visual Diagnostic Method	83 ≤ CI	1 (Good)	Healthy, no immediate harm, regular check once a year
		61 ≤ CI ≤ 82	2 (Not bad)	R = 1, check once a year. R = 2, 3, partial external wall tap tone diagnosis (top and ground floor) R = 4, comprehensive external wall tap tone diagnosis
		38 ≤ CI ≤ 60	3 (Attention needed)	R = 2,3, partial external wall tap tone diagnosis (top and ground floor) R = 4, comprehensive external wall tap tone diagnosis
		CI < 38	4 (Bad)	External wall renovation are recommended
Stage 2	Tap Tone Method	no significant peak		Check once a year
Stage 2	Tap Tone Method	frequency peaks in between 240 - 760 Hz		Based on user demand, overall renovation