Segment Data and Foreign Operations (Details) $ in Thousands	3 Months Ended							6 Months Ended			9 Months Ended
	May 31, 2020 USD ($) segment	Feb. 29, 2020 USD ($)	Nov. 30, 2019 USD ($)	Aug. 31, 2019 USD ($) segment	May 31, 2019 USD ($)	Nov. 30, 2018 USD ($)	Aug. 31, 2018 USD ($)	May 31, 2020 USD ($)	Feb. 29, 2020 USD ($)	Aug. 31, 2019 USD ($)	May 31, 2020 USD ($) segment	Aug. 31, 2019 USD ($)	May 31, 2019 USD ($)
Segment data
Number of operating segments | segment	3			2							3
Revenue	$ 64,871				$ 72,112						$ 197,255		$ 211,246
Income before income taxes	12,527				12,188						33,403		30,928
Interest	67				91						178		457
Depreciation											2,989		3,634
Amortization											8,724		9,339
Gain on sale of property	760										760
Severance Costs	183										183
Exit costs related to facilities	268				193						977		453
Pension related settlement costs	(75)				(11)						(75)		(484)
Impairment of goodwill													2,410
Total assets	333,870			$ 307,968				$ 333,870		$ 307,968	333,870	$ 307,968
Granite Falls Location
Segment data
Exit costs related to facilities	0	$ 60			193				$ 559	526	559		193
Pawtucket, RI manufacturing facility
Segment data
Gain on sale of property	760										760
Exit costs related to facilities	85					$ 260	$ 1,272				85	0	260
Adhesives, Sealants and Additives
Segment data
Revenue	22,922				26,009						73,184		78,814
Income before income taxes	6,704				7,509						20,936		20,530
Interest	26				34						68		172
Depreciation	199				356						791		1,121
Amortization	2,340				2,341						7,033		7,020
Impairment of goodwill					2,410								2,410
Total assets	134,353			135,583				134,353		135,583	134,353	135,583
Industrial Tapes
Segment data
Revenue	31,752				33,704						91,931		98,324
Income before income taxes	9,011				6,929						24,050		20,980
Interest	33				38						87		193
Depreciation	428				410						1,247		1,304
Amortization	450				450						1,350		1,350
Total assets	70,489			77,085				70,489		77,085	70,489	77,085
Corrosion Protection and Waterproofing
Segment data
Revenue	10,197				12,399						32,140		34,108
Income before income taxes	4,149				4,817						12,240		11,667
Interest	8				19						23		92
Depreciation	144				161						449		500
Amortization	108				323						341		969
Total assets	31,722			32,478				31,722		32,478	31,722	32,478
Reportable segments
Segment data
Income before income taxes	19,864				19,255						57,226		53,177
Total assets	236,564			245,146				236,564		245,146	236,564	245,146
Corporate and common costs
Segment data
Income before income taxes	(7,337)				$ (7,067)						(23,823)		$ (22,249)
Total assets	97,306			$ 62,822				97,306		$ 62,822	97,306	$ 62,822
Engineering Studies related to Facility Consolidation and Rationalization Initiative
Segment data
Business development cost	$ 0	$ 0	$ 150					$ 0			$ 150