|Home Depot Sells Consumer Goods|
The lumber in the above picture may look like an immense accumulation of capital goods, where capital goods are a type of commodity. But, I argue, these commodities should properly be thought of as consumer goods.2.0 A Keynesian Perspective
John Maynard Keynes, in The General Theory of Employment, Interest and Money, was interested in the sources of aggregate demand. Aggregate demand is demand for commodities, and an increase in this demand leads to an increase in waged labor. So, for Keynes, capital goods are goods whose use would be accompanied by labor being paid wages.
Home Depot and Loewes market to the Do-It-Yourselfer. (I assume building contractors buy in bulk, and purchase most of their stuff elsewhere.) The purchaser of products from these commercial enterprises may intend to construct a deck, erect a shed in their backyard, or remodel a kitchen or bathroom. But the work in completing this products will not be paid a wage. That is, as far as aggregate demand in a capitalist economy goes, the lumber pictured acts like a consumer good, not a capital good.3.0 A Classical Perspective
Classical economists, such as Adam Smith, distinguished between "productive" and "unproductive" labor. Unproductive labor is that labor which is paid for out of revenue, not out of a capital fund. Unproductive labor does not earn a profit, even tendentially:
"There is one sort of labour which adds to the value of the subject upon which it is bestowed: there is another which has no such effect. The former, as it produces a value, may be called productive; the latter, unproductive labour. Thus the labour of a manufacturer adds, generally, to the value of the materials which he works upon, that of his own maintenance, and of his master's profit. The labour of a menial servant, on the contrary, adds to the value of nothing. Though the manufacturer has his wages advanced to him by his master, he, in reality, costs him no expence, the value of those wages being generally restored, together with a profit, in the improved value of the subject upon which his labour is bestowed. But the maintenance of a menial servant never is restored. A man grows rich by employing a multitude of manufacturers: he grows poor by maintaining a multitude of menial servants." -- Adam Smith, Wealth of Nations, Book II, Chapter 2.
I think of a typical example of unproductive labor as the work of a carpenter hired by a 18th or 19th century British aristocrat to build him a chest with wood that the aristocrat's estate provides. I guess such an estate would support all sorts of servants in the surrounding community. But profits would not be earned on their wages, either by these servants or by their employers.
So, even if the purchaser of the lumber products under consideration here hired some helpers or, perhaps, compensated some assistants with food or drink, these products would still not be capital goods.4.0 A Neoclassical Perspective
A neoclassical might abstract from all these considerations of institutions, particularly for those that constitute capitalism. And the neoclassical economist might classify as capital those goods that last for many periods, providing a flow of services. (I think you can find this perspective in Leon Walras; he certainly distinguishes between a flow of services and the stock of goods.) At the highest level of abstraction, whether the owner of a capital good is a firm or a household is irrelevant. Furthermore, home improvements will increase the price that a house can fetch if you decide to sell it. If you rent it out, you will acquire what Alfred Marshall described as a quasi-rent from these home improvements.
Note, though, that this perspective abstracts from the distinction between goods, that once produced, are given in quantity at a point in time and, say, an annual cycle of (re)production of commodities needed to sustain a capitalist economy. As can be seen on the first page of the first chapter of David Ricardo's Principles of Political Economy and Taxation, classical economic theory focuses on the latter aspect.