7. Long-Lived Assets

Property, Plant and Equipment—Property, plant and equipment consisted of the following at September 30:

(in thousands of dollars)	Estimated useful lives	2013			2014
Land and improvements	15 - 40 years	$	11,359		$	15,298
Buildings and improvements	5 - 40 years		61,760			69,018
Equipment and vehicles	3 - 20 years		204,438			222,800
Dies and molds	3 - 20 years		79,248			83,299
Construction in progress	—		11,608			16,402

			368,413			406,817
Less accumulated depreciation			(208,794	)		(224,706	)

Net property, plant and equipment		$	159,619		$	182,111

Depreciation expense was approximately $30.8 million, $32.1 million and $33.8 million in 2012, 2013 and 2014, respectively.

Intangible Assets—With the exception of certain indefinite-lived trade names, Headwaters' identified intangible assets are being amortized over the estimated useful lives shown in the table below. The table also summarizes the gross carrying amounts and related accumulated amortization of all intangible assets as of September 30:

		2013				2014
(in thousands of dollars)	Estimated useful lives	Gross Carrying Amount		Accumulated Amortization		Gross Carrying Amount		Accumulated Amortization
Trade names	Indefinite	$	4,800		—	$	15,300		—
CCP contracts	15 - 20 years		106,400	$	58,699		112,300	$	64,192
Customer relationships	5 - 17 years		83,564		44,129		107,953		50,355
Trade names	5 - 20 years		67,790		30,502		67,220		33,394
Patents and patented technologies	5 - 19 years		55,099		46,954		14,526		11,686
Other	3 - 17 years		3,960		1,532		3,935		1,744

		$	321,613	$	181,816	$	321,234	$	161,371

Total amortization expense related to intangible assets was approximately $20.7 million, $20.2 million and $21.3 million in 2012, 2013 and 2014, respectively. Total estimated annual amortization expense for 2015 through 2019 is shown in the following table.

Year ending September 30:	(in thousands)
2015	$	17,827
2016		17,570
2017		16,692
2018		16,643
2019		15,614

Goodwill—Changes in the carrying amount of goodwill, by segment, are as follows for the two-year period ended September 30, 2014.

(in thousands)	Light building products		Heavy construction materials		Total
Balances as of September 30, 2012	$	672	$	115,999	$	116,671
Goodwill related to 2013 acquisition		20,527		0		20,527

Balances as of September 30, 2013	$	21,199	$	115,999	$	137,198
Goodwill related to 2014 acquisitions		35,488		2,900		38,388

Balances as of September 30, 2014	$	56,687	$	118,899	$	175,586

Impairment Testing—In accordance with the requirements of ASC Topic 350 Intangibles—Goodwill and Other, Headwaters does not amortize goodwill or indefinite-lived intangible assets, all of which relate to acquisitions. However, Headwaters is required to periodically test these assets for impairment, at least annually, or sooner if indicators of possible impairment arise. Headwaters performs its annual impairment testing during the fourth quarter of its fiscal year using a June 30 test date and a one- to three-step process. Headwaters' reporting units for purposes of impairment testing are the same as its operating segments.

Under new accounting rules adopted in 2012, Headwaters evaluates qualitative factors, including macroeconomic conditions, industry and market considerations, overall financial performance and cost factors, to determine whether it is necessary to perform step 1 of the two-step impairment test. This qualitative evaluation is commonly referred to as "step 0." After assessing the appropriate qualitative factors, only if it is determined that it is more likely than not that the fair value of a reporting unit is less than its carrying amount, is it necessary to perform step 1.

Step 1 of the impairment testing consists of determining and comparing the fair value of a reporting unit, calculated primarily using discounted expected future cash flows, to the carrying value of the reporting unit. If step 1 is failed for a reporting unit, indicating a potential impairment, Headwaters is required to complete step 2, which is a more detailed test to calculate the implied fair value of goodwill and indefinite-lived intangible assets, and compare that value to the carrying value. If the carrying value of goodwill and indefinite-lived assets exceeds the implied fair value, an impairment loss is required to be recorded.

For all years presented, Headwaters performed a step 0 qualitative evaluation for both the heavy construction materials and light building products reporting units and concluded that it was more likely than not that the fair values exceeded the carrying amounts of goodwill and indefinite-lived assets. Accordingly, further step 1 and step 2 testing for impairment was not required to be performed.