Revenue Recognition - Schedule of Disaggregation of Revenue (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jul. 04, 2026	Jun. 28, 2025	Jul. 04, 2026	Jun. 28, 2025
Disaggregation of Revenue [Line Items]
Total revenues	$ 233.5	$ 228.1	$ 456.2	$ 438.6
Product revenues
Disaggregation of Revenue [Line Items]
Total revenues	197.9	190.9	386.7	366.6
Janus International
Disaggregation of Revenue [Line Items]
Total revenues		28.4		49.6
Janus International \| Product revenues
Disaggregation of Revenue [Line Items]
Total revenues		28.3		49.4
Operating Segments \| Janus North America
Disaggregation of Revenue [Line Items]
Total revenues	202.9	200.3	398.8	391.0
Operating Segments \| Janus North America \| Product revenues
Disaggregation of Revenue [Line Items]
Total revenues	167.7	163.2	329.9	319.2
Operating Segments \| Janus North America \| Self storage - new construction
Disaggregation of Revenue [Line Items]
Total revenues	84.2	68.8	155.5	132.6
Operating Segments \| Janus North America \| Self storage - R3
Disaggregation of Revenue [Line Items]
Total revenues	54.1	49.6	111.9	108.0
Operating Segments \| Janus North America \| Commercial and other
Disaggregation of Revenue [Line Items]
Total revenues	64.6	81.9	131.4	150.4
Operating Segments \| Janus International
Disaggregation of Revenue [Line Items]
Total revenues	31.1	28.4	58.4	49.6
Operating Segments \| Janus International \| Product revenues
Disaggregation of Revenue [Line Items]
Total revenues	30.7	28.3	57.8	49.4
Operating Segments \| Janus International \| Self storage - new construction
Disaggregation of Revenue [Line Items]
Total revenues	28.8	25.1	53.9	45.0
Operating Segments \| Janus International \| Self storage - R3
Disaggregation of Revenue [Line Items]
Total revenues	2.3	3.3	4.5	4.6
Intersegment eliminations
Disaggregation of Revenue [Line Items]
Total revenues	(0.5)	(0.6)	(1.0)	(2.0)
Intersegment eliminations \| Product revenues
Disaggregation of Revenue [Line Items]
Total revenues	$ (0.5)	$ (0.6)	$ (1.0)	$ (2.0)