Segment Data (Details)	1 Months Ended					3 Months Ended			6 Months Ended			9 Months Ended	12 Months Ended
	Feb. 28, 2021 USD ($)	Sep. 30, 2020 USD ($)	Aug. 31, 2020 USD ($)	May 31, 2020 USD ($)	Apr. 30, 2020 USD ($)	May 31, 2020 USD ($)	Nov. 30, 2018 USD ($)	Aug. 31, 2018 USD ($)	Aug. 31, 2020 USD ($)	Feb. 29, 2020 USD ($)	Aug. 31, 2019 USD ($)	Aug. 31, 2019 USD ($)	Aug. 31, 2022 USD ($) segment	Aug. 31, 2021 USD ($)	Aug. 31, 2020 USD ($)	Aug. 31, 2019 USD ($)
Segment data
Revenue													$ 325,660,000	$ 293,336,000	$ 261,162,000
Income before income taxes													58,598,000	58,594,000	45,320,000
Total assets													611,580,000	404,159,000
Interest													425,000	297,000	246,000
Depreciation													3,547,000	3,946,000	4,015,000
Amortization													11,751,000	12,858,000	11,576,000
Loss on upward adjustment of performance based earn out contingent consideration		$ 1,664,000
Loss on impairment of goodwill													$ 0
Number of operating segments | segment													3
Severance costs						$ 183,000
Write-down of certain assets under construction														100,000	405,000
Expenses related to acquisition	$ 128,000												$ 4,000,000	128,000	274,000
Pension related settlement costs															(155,000)
Gain on sale of real estate (Note 19)															2,551,000
Exit costs related to facilities													842,000	977,000	807,000
Pawtucket, RI manufacturing facility
Segment data
Gain on sale of real estate (Note 19)					$ 760,000	760,000								760,000
Exit costs related to facilities						$ 85,000	$ 260,000	$ 1,272,000				$ 0
Granite Falls Location
Segment data
Exit costs related to facilities									$ 0	$ 559,000	$ 526,000			0
Westwood, MA
Segment data
Exit costs related to facilities													232,000
Adhesives, Sealants and Additives
Segment data
Revenue													135,770,000	126,864,000	96,208,000
Income before income taxes													37,657,000	36,520,000	25,953,000
Total assets													153,784,000	161,968,000
Interest													170,000	116,000	98,000
Depreciation													924,000	1,065,000	994,000
Amortization													10,466,000	10,685,000	9,313,000
Exit costs related to facilities													463,000	0
Adhesives, Sealants and Additives | ABchime
Segment data
Loss on upward adjustment of performance based earn out contingent consideration													432,000
Adhesives, Sealants and Additives | Woburn, MA
Segment data
Exit costs related to facilities													463,000
Adhesives, Sealants and Additives | Newark, CA
Segment data
Exit costs related to facilities													147,000
Industrial Tapes
Segment data
Revenue													143,954,000	120,873,000	118,960,000
Income before income taxes													41,387,000	37,407,000	31,237,000
Total assets													87,751,000	72,301,000
Interest													170,000	83,000	111,000
Depreciation													1,568,000	1,718,000	1,746,000
Amortization													1,280,000	1,537,000	1,800,000
Corrosion Protection and Waterproofing
Segment data
Revenue													45,936,000	45,599,000	45,994,000
Income before income taxes													17,415,000	15,913,000	16,638,000
Total assets													33,037,000	31,067,000
Interest													85,000	98,000	37,000
Depreciation													516,000	588,000	615,000
Amortization													5,000	636,000	463,000
Construction Materials | Engineering Studies related to Facility Consolidation and Rationalization Initiative
Segment data
Write-down on certain other structural composites assets																$ 405,000
Gain on refund																$ 170,000
Reportable segments
Segment data
Income before income taxes													96,459,000	89,840,000	73,828,000
Total assets													274,572,000	265,336,000
Corporate and common costs
Segment data
Income before income taxes													(37,861,000)	(31,246,000)	$ (28,508,000)
Total assets													$ 337,008,000	138,823,000
Severance costs				$ 183,000										183,000
Expenses related to acquisition														274,000
Pension related settlement costs														155,000
Corporate and common costs | Pawtucket, RI manufacturing facility
Segment data
Exit costs related to facilities														85,000
Corporate and common costs | Randolph MA
Segment data
Gain on sale of real estate (Note 19)			$ 1,791,000											1,791,000
Corporate and common costs | Engineering Studies related to Facility Consolidation and Rationalization Initiative
Segment data
Business development cost														$ 150,000