How much is the 4th pool worth on a property? How about the 29th bathroom? How about the 20th garage? These are absurd examples of “over improvements” in almost any market (unless your market included royal mansions), and present examples of how over improvements diminish in return as the number/quality of amenities increasingly exceed what is normal for a market area.
How do you value a home with one bedroom where 4 is typical? What about a 600 sq ft ranch in a neighborhood of 5,000 sq ft contemporary homes? What about a home with only a wood stove as a heat source? These are examples of under improvements and during valuation a key factor must be considered - “What portion of the market would be willing to purchase such a home?”
Decades of data, nationwide support the fact that buyers gravitate towards what is typical, and the buyer pool diminishes as you deviate from the mean in any particular amenity. Diminished buyer pools result in diminished demand, and therefore diminished value per unit. This is a principle across many economic fields and applies to real estate as well.
Another way of stating this is that “The more of something you have, the less each individual thing is worth,” and one of the easiest and most consistent ways of seeing this in the market is land.
Notice that as you increase the number of acres, the return divided by the total number of acres decreases. Some properties may have a better location in Armstrong County than others, and others may have sold above/below market value, but as a general rule, the trend is clear. Other amenities will have different shaped graphs - take pools for example. In the lower end of the market, pools offer no contributory value. The buyer pool in this range may not have the resources to maintain a pool, and therefore it is seen as a negative by part of the market, positive by some, and a net neutral overall. However, in the higher end of the market, this amenity can have a return (though nearly never higher than the cost of installation). However, imagine a buyers reaction to a second pool on a half acre lot. This would be seen as a liability that needs to be fixed not as an amenity, and therefore have a negative appeal. The second pool’s value on the graph would drop below zero, and so on.
When building/remodeling a home it is vital to consider, “What is normal for my market/buyer pool?” The wider of a divergence from “normal” will result in decreasing returns and difficult sales in the future.