INDUSTRY SEGMENT INFORMATION (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 02, 2016 USD ($)	Jul. 04, 2015 USD ($)	Jul. 02, 2016 USD ($) item	Jul. 04, 2015 USD ($)	Jan. 02, 2016 USD ($)
INDUSTRY SEGMENT INFORMATION
Number of reportable segments | item			2
Revenues from external customers	$ 42,721	$ 34,865	$ 76,949	$ 65,550
Depreciation, depletion and amortization	651	651	1,290	1,297
Operating income (loss)	2,830	631	3,682	412
Segment assets	78,167	75,755	78,167	75,755	$ 75,755
Capital expenditures	1,694	427	$ 2,776	520
Number of industry groups in which the entity operates | item			2
Concrete Aggregates and Construction Supplies
INDUSTRY SEGMENT INFORMATION
Revenues from external customers	20,912	14,090	$ 33,111	24,655
Depreciation, depletion and amortization	357	340	704	677
Operating income (loss)	2,065	(128)	1,871	(856)
Segment assets	36,382	31,791	36,382	31,791
Capital expenditures	1,314	178	2,233	178
Doors
INDUSTRY SEGMENT INFORMATION
Revenues from external customers	4,890	4,681	8,745	8,869
Depreciation, depletion and amortization	32	32	63	63
Operating income (loss)	537	456	847	794
Segment assets	7,272	6,471	7,272	6,471
Capital expenditures	30	32	52	32
Heating and Cooling
INDUSTRY SEGMENT INFORMATION
Revenues from external customers	6,635	5,874	17,785	15,020
Depreciation, depletion and amortization	139	143	277	285
Operating income (loss)	(237)	(195)	797	302
Segment assets	19,025	22,628	19,025	22,628
Capital expenditures	259	149	376	209
Evaporative Cooling
INDUSTRY SEGMENT INFORMATION
Revenues from external customers	10,279	10,216	17,299	16,998
Depreciation, depletion and amortization	119	123	238	246
Operating income (loss)	1,365	1,245	1,818	1,696
Segment assets	13,343	12,730	13,343	12,730
Capital expenditures	91	68	115	101
Unallocated Corporate
INDUSTRY SEGMENT INFORMATION
Revenues from external customers	5	4	9	8
Depreciation, depletion and amortization	4	13	8	26
Operating income (loss)	(900)	(747)	(1,651)	(1,524)
Segment assets	2,145	2,135	2,145	2,135
Construction Products
INDUSTRY SEGMENT INFORMATION
Revenues from external customers	25,802	18,771	41,856	33,524
Depreciation, depletion and amortization	389	372	767	740
Operating income (loss)	2,602	328	2,718	(62)
Segment assets	43,654	38,262	43,654	38,262
Capital expenditures	1,344	210	2,285	210
HVAC Industry
INDUSTRY SEGMENT INFORMATION
Revenues from external customers	16,914	16,090	35,084	32,018
Depreciation, depletion and amortization	258	266	515	531
Operating income (loss)	1,128	1,050	2,615	1,998
Segment assets	32,368	35,358	32,368	35,358
Capital expenditures	$ 350	$ 217	$ 491	$ 310