INDUSTRY SEGMENT INFORMATION (Details) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 30, 2017 USD ($)	Sep. 30, 2017 USD ($)	Jul. 01, 2017 USD ($)	Apr. 01, 2017 USD ($)	Dec. 31, 2016 USD ($)	Oct. 01, 2016 USD ($)	Jul. 02, 2016 USD ($)	Apr. 02, 2016 USD ($)	Dec. 30, 2017 USD ($) item	Dec. 31, 2016 USD ($)
INDUSTRY SEGMENT INFORMATION
Number of industry groups in which the entity operates | item									2
Revenues from external customers	$ 40,193	$ 38,627	$ 39,887	$ 34,103	$ 36,996	$ 37,647	$ 42,721	$ 34,228	$ 152,810	$ 151,592
Depreciation, depletion and amortization	622	$ 617	$ 677	$ 638	539	$ 607	$ 651	$ 639	2,554	2,436
Operating income (loss)									3,016	5,841
Segment assets	82,489				78,008				82,489	78,008
Capital expenditures									5,781	4,405
Unallocated Corporate [Member]
INDUSTRY SEGMENT INFORMATION
Revenues from external customers									18	16
Depreciation, depletion and amortization									38	23
Operating income (loss)									(3,091)	(3,614)
Segment assets	2,670				3,653				2,670	3,653
Capital expenditures									$ 46	162
Construction Products Industry [Member]
INDUSTRY SEGMENT INFORMATION
Number of reportable segments | item									2
Revenues from external customers									$ 85,059	84,081
Depreciation, depletion and amortization									1,557	1,474
Operating income (loss)									4,517	4,996
Segment assets	46,380				39,691				46,380	39,691
Capital expenditures									4,701	3,406
Construction Products Industry [Member] | Concrete Aggregates and Construction Supplies [Member]
INDUSTRY SEGMENT INFORMATION
Revenues from external customers									66,407	67,091
Depreciation, depletion and amortization									1,405	1,340
Operating income (loss)									2,656	3,433
Segment assets	39,020				33,518				39,020	33,518
Capital expenditures									4,566	3,296
Construction Products Industry [Member] | Doors [Member]
INDUSTRY SEGMENT INFORMATION
Revenues from external customers									18,652	16,990
Depreciation, depletion and amortization									152	134
Operating income (loss)									1,861	1,563
Segment assets	7,360				6,173				7,360	6,173
Capital expenditures									$ 135	110
Heating Ventilation and Air Conditioning Industry [Member]
INDUSTRY SEGMENT INFORMATION
Number of reportable segments | item									2
Revenues from external customers									$ 67,733	67,495
Depreciation, depletion and amortization									959	939
Operating income (loss)									1,590	4,459
Segment assets	33,439				34,664				33,439	34,664
Capital expenditures									1,034	837
Heating Ventilation and Air Conditioning Industry [Member] | Heating and Cooling
INDUSTRY SEGMENT INFORMATION
Revenues from external customers									42,517	41,853
Depreciation, depletion and amortization									550	526
Operating income (loss)									2,140	3,046
Segment assets	21,543				22,381				21,543	22,381
Capital expenditures									804	655
Heating Ventilation and Air Conditioning Industry [Member] | Evaporative Cooling [Member]
INDUSTRY SEGMENT INFORMATION
Revenues from external customers									25,216	25,642
Depreciation, depletion and amortization									409	413
Operating income (loss)									(550)	1,413
Segment assets	$ 11,896				$ 12,283				11,896	12,283
Capital expenditures									$ 230	$ 182