What This Video Covers
“How much is my house worth?” has an honest answer and a comfortable one. The comfortable answer is a single number. The honest answer is a range — and then a judgement about where inside that range a specific house belongs. This video shows both halves with real Jacksonville-area neighbourhoods, priced on camera.
The science half: what the data can actually tell you
Real estate is hyperlocal, so the map gets drawn as tightly around the house as possible — and only widened until there is enough data to see a market. Then every closed sale and every attempt to sell goes onto one chart, price against living area. Three lines come off it: a fair market value line through the middle of the sales, and a top of market and bottom of market one standard deviation either side of it.
When a neighbourhood cooperates, this is genuinely powerful. In Waterview Ridge, five homes closed in six months, all of them between 1,136 and 1,451 square feet — a tight, consistent group. The fit came back at R² = 0.87, meaning square footage alone explains about 87% of the price difference between those houses. For a 1,332 square foot home the band ran $266,482 to $285,242, with fair market value at $275,862. That is a total spread of about $19,000 on a $276,000 house. Roughly seven percent. That is the math doing real work.
The art half: three ways the chart stops being trustworthy
Not enough sales. Edgewood had exactly two closed sales in the window. Two points define a straight line perfectly, so the fit reported R² = 1.00 — a perfect score that means nothing at all. The standard deviation came back as literally zero, so the computed band had no width and had to be set by hand. The slope also ran downward: taken at face value the line says bigger houses there sell for less. Three brand-new construction homes that sold for around $250,000 in a small new-build pocket also had to be pulled out of the set, because they were not fair comparisons for a much older house. That single decision moves the answer more than any statistic on the chart.
Sales that do not agree with each other. North Springfield Heights had seven closed sales and a fit of R² = 0.13 — size explains about thirteen percent of price. Everything else is condition, street and finish. A line drawn through data like that is a suggestion, not a valuation.
A house that is bigger than its own comps. In that same neighbourhood the subject was 2,318 square feet while the largest home that actually closed was 1,344. The line still prints a number out at 2,318 — $143,216 — but it is extrapolating well past its own data, and a number produced outside the range of the evidence is an artifact, not a ceiling. That is the point at which a person has to make the call. The honest read was $175,000, with $200,000 reachable only by setting a new high for the area rather than matching one.
Why even the good chart got overruled
Here is the part that matters most, and it happened on the best of the three. Waterview Ridge had the clean fit, the tight band, and the subject sitting right in the middle of its comparable sales — and the number still came down. Fair market value said $275,862. The call was $275,000 on a good day, $250,000 on a bad one, and plan on $250,000.
Two reasons, neither of which appears anywhere on the chart. First, the garage had been converted into living space. That trade adds square footage, which the line rewards — but in a neighbourhood where the competing homes all have garages, the buyer notices the missing garage before they notice the extra room. In this case it did not add value, and it may well have cost some. Second, stair-step cracks showed on nearly every corner of the house. Correcting a corner normally takes two pylons at roughly $5,000 each, and there were about twelve to do — call it $35,000 to $60,000 before anything else gets touched. A chart cannot see either of those things.
What actually decides where you land in the band
Condition. Presentation. Whether the house has the features the neighbourhood expects — a garage in a street of garages, a pool where every comparable sale has one. Whether it is the same kind of house as the ones that sold. And how deep the market is underneath it: in Waterview Ridge homes closed at a median 98.2% of asking price in about 51 days with only 1.2 months of standing inventory, while North Springfield Heights ran 95.7% of asking across 3.9 months of inventory. The same house is worth measurably more in the first one.
So the practical answer to “how much is my house worth” is this: get the band from the sales, then be honest with yourself about condition and about what your neighbourhood expects. Anyone who gives you a single number without walking the house is quoting you the middle of a range and hoping you do not ask.
- How the comp map gets drawn: as tight as possible, widened only until there is enough data to read a market
- What the three lines mean — fair market value, top of market, bottom of market — and how wide the band should be
- Why R² = 1.00 can be worthless and R² = 0.87 can be trusted
- The extrapolation trap: what happens when your house is bigger than every comparable sale
- Why a converted garage can add square footage and still subtract value
- How condition, features and market depth decide where inside the band a house actually lands
