Quarterly report pursuant to Section 13 or 15(d)

Document and Entity Information

v3.10.0.1
Document and Entity Information - shares
 9 Months Ended
Jun. 30, 2018
Aug. 10, 2018
Document Information [Line Items]    
Document Type 10-Q  
Amendment Flag false  
Document Period End Date Jun. 30, 2018  
Document Fiscal Year Focus 2018  
Document Fiscal Period Focus Q3  
Trading Symbol ROAD  
Entity Registrant Name Construction Partners, Inc.  
Entity Central Index Key 0001718227  
Current Fiscal Year End Date --09-30  
Entity Filer Category Non-accelerated Filer  
Class A Common Stock [Member]    
Document Information [Line Items]    
Entity Common Stock, Shares Outstanding   11,950,000
Class B Common Stock [Member]    
Document Information [Line Items]    
Entity Common Stock, Shares Outstanding   39,464,619