Vacant Developed Lots (VDL): The Lot-Supply Number Builders Watch

VDL is three letters that show up in land-market reports, builder land meetings and lender questions, usually without anyone defining them. They stand for vacant developed lots, and they measure the thing homebuilding cannot do without: finished ground with nothing on it yet.

Here is what counts, how the supply number is calculated, what it can and cannot tell you, and how to run the same math on one community.

What counts as a vacant developed lot

Two conditions, and a lot has to meet both.

Developed means finished: the street is built, water and sewer are to the lot, drainage is in place, and a builder could pull a permit. The finished-lot guide covers exactly what that involves.

Vacant means no home has been started. Once a foundation is poured or framing begins, the lot leaves the count.

What does not count follows from the definition:

• Paper lots, which exist on a recorded plat but have no improvements
• Blue-top lots, which are graded but have no utilities or paving yet
• Lots under development, where the streets and utilities are still being built
• Lots with a start, including model homes and spec homes, from the day construction begins

One thing people get wrong: VDL is about the ground, not the paperwork. A finished lot is a vacant developed lot whether the developer still owns it, a builder has taken it down or it is optioned to someone. Ownership changes who is holding the supply. It does not change whether the supply exists.

The lot pipeline VDL sits in

Think of lot supply as a pipeline with a tank in the middle. Lots flow in from development as phases are finished. They flow out as builders start homes. VDL is the level in the tank.

That structure is why the number moves the way it does. When starts accelerate and development does not keep pace, the tank drains. When starts slow and phases already under way keep finishing, it fills, and there is not much a developer can do about a phase that is half built when the market turns.

Vacant developed lots are not vacant homes

A different number sits one step further down the pipeline and gets confused with VDL constantly: finished vacant homes, meaning completed houses that have not sold.

The two measure different risks. VDL measures ground a builder could start on. Finished vacant homes measure capital already spent on houses nobody has bought. A market can be short of lots and long on unsold homes at the same time, and when that happens the unsold homes are the more urgent problem, because each one carries a builder's full construction cost rather than just a lot price.

For a lot seller, a rising count of finished vacant homes is an early warning. Builders sitting on unsold houses slow their starts, and slower starts are the first thing that lengthens months of lot supply.

How months of supply is calculated

The count on its own says little. Three thousand vacant developed lots is a shortage in a market starting homes quickly and a glut in a slow one. So the count is divided by the pace at which lots are consumed:

Months of supply = vacant developed lots ÷ monthly housing starts

Monthly starts is usually the trailing twelve months of starts divided by twelve, which smooths out the seasons. As an illustration, a submarket with 3,000 vacant developed lots that started 1,800 homes over the last year is starting 150 a month, so it holds 20 months of supply.

Use starts, not sales or closings. A start is the event that consumes a lot. Sales can run ahead of starts when buyers sign on homes not yet begun, and behind them when builders start spec homes, so a supply figure built on sales measures the wrong flow.

What "balanced" means

This is where the number is most often misused. There is no national months-of-supply number that means healthy.

The logic of equilibrium is lead time. If it takes a market roughly two years to take land from approval to finished lots, it needs about two years of lots on hand to keep starts flowing while the next lots are made. A market that can finish lots faster can run leaner. One with slow entitlements or long utility lead times needs more.

That is why research firms that survey lots set equilibrium market by market. Zonda's Lot Supply Index, for example, expresses supply against each market's own balanced level, with 100 meaning exactly balanced and readings well above or below it marking oversupply or undersupply. Something in the region of two years has long been quoted as balanced for many markets, but treat that as a starting point for a question, not an answer.

Why builders watch it

For a builder, VDL is the runway.

When supply is tight, finished lots command higher prices and move quickly, builders compete for the same phases, and more of them move earlier in the pipeline, buying blue-top or entitled ground and taking on development risk to secure future starts. Option agreements and land banking become more attractive because they lock up supply without owning it.

When supply is loose, the leverage flips. Builders can negotiate on price and pace, slow their takedowns, or walk away from options where the contract allows it. See the takedown schedule, explained for how that pace is written down.

Why developers watch it

For a developer, VDL is the timing signal for the most expensive decision in the business: when to start the next phase of horizontal work.

Deliver finished lots into a tight market and they sell at strong prices. Deliver the same lots into a submarket already holding plenty of finished supply and they sit, carrying interest and taxes while the developer competes on price. The horizontal spend has to be committed long before the lots exist, so the decision is made on a forecast of supply, not a reading of it.

Phase size is the main lever a developer controls. Finishing 40 lots at a time instead of 150 lets supply track starts more closely and keeps less capital sitting in finished lots. The price is more mobilizations and a higher cost per lot, so the right size depends on how confident the developer is in the pace.

Lenders ask the same question for the same reason. An A&D lender underwriting a new phase wants to know how much finished competition the lots will face on delivery.

Where the numbers come from

This is the part that surprises people: no national public dataset counts vacant developed lots.

The Census Bureau publishes permits, starts and completions every month. That gives you the flow out of the tank, not the level in it. Recorded plats tell you how many lots legally exist, not which ones are finished. Public builders report lots owned and controlled, but those totals usually mix every stage from raw land to finished.

Actual VDL counts come from field surveys. Research firms send people to drive subdivisions and record the status of each lot, then sell the results by subscription. Everyone else pieces an estimate together from plats, permits and site visits.

At the community level, none of that is needed. Your own records are the survey, provided they are current.

Running the same math on one community

The formula scales down cleanly. For a single community:

Community months of supply = your finished, unstarted lots ÷ your monthly starts

As an illustration: a phase holds 60 finished lots with no homes started, and builders are starting five homes a month, so the community has 12 months of supply. If the next phase takes 14 months to go from notice-to-proceed to finished lots, it needed to start two months ago. That gap is the whole point of the calculation, and it turns an absorption report into a construction decision.

It is also worth splitting the count by who holds each lot. Finished lots the developer still owns are the developer's carry; lots a builder has taken down but not started are the builder's. The total is the community's runway. The split tells you who is paying for it, and who will slow down first.

That is also why the number belongs next to your lot absorption rate. Absorption tells you how fast lots are being used. Months of supply tells you how long what you have will last. Together they tell you when to spend.

Mistakes that distort the number

• Counting paper or blue-top lots as developed. It inflates supply with lots that are months of work away from a start.
• Dividing by sales instead of starts. It measures demand for homes, not consumption of lots.
• Using one strong month. A single month of starts is noise. Use the trailing year.
• Comparing a community to a metro average. A well-located community can be short of lots in an oversupplied metro, and the reverse.
• Counting started lots as vacant. A slab is not a vacant lot, and missing starts overstates the runway.
• Using a stale count. Supply changes every week a builder is starting homes. An old count is a guess.

Where a map fits

At the community level, VDL is not a survey statistic. It is a filter: finished phase, no home started. That filter is only quick when every lot's phase and status sit in one current record rather than across a plat PDF, a takedown spreadsheet and a builder's start report.

A lot inventory map keeps that record. Each phase is shaded separately, every lot carries its status, and the numbers export when a lender asks. The platform and CRM behind it is where the status changes, once, for everyone. It does not forecast the market. It makes sure your own count is right before you compare it to one.

When homes start on those lots, the same record feeds the interactive site map buyers see on the builder's community page.

The Bottom Line

Vacant developed lots are the runway for future housing starts, and months of supply is how long the runway is. Watch the trend rather than the level, compare a market to its own balanced point rather than a national rule of thumb, and never count a lot as developed until a builder could start on it.

For a developer, the most useful version of the number is the smallest one: your own finished, unstarted lots divided by your own starts, set against the time it takes to finish the next phase. When the runway is shorter than the lead time, the decision has already been made for you.