Two or more adjoining lots taken together have an added value known as plottage. The added value is due to the fact that the plot of two lots or more may be used or improved to greater advantage. A building of greater size and capable of producing a larger net rental may be erected on the larger plot. In some localities the suitable improvement may be an apartment house of not less than fifty feet in width, in others it is the loft building, office building, hotel, manufacturing plant, or something else requiring a large amount of ground space. Plottage is therefore of great value in such a locality. At other places, small dwellings are erected, each on one lot; plottage is not quite so important here, but it gives some added value because of the economy of building and marketing a number of adjoining houses at the same time Even in farm land, or acreage, large unbroken tracts are advantageous.

The added value due to plottage is usually figured to be ten per cent of the total value of the separate lots. It may be more than this amount in locations where great and important structures are erected, and less in those places where land is plentiful and large plots easily assembled. In a recent proceeding involving the valuation of the Equitable Building in New York City, it was held that there was an additional value due to plottage, but that it was not as much as twenty-five per cent.