What is an infill lot?

Updated November 12, 2026

The word comes from planning, where "infill" means filling in the gaps in places that already have streets, utilities and neighbours, rather than extending development outward. For a builder or an investor it describes a kind of site: smaller and more awkward than a greenfield subdivision, but already connected to everything a new home needs.

What counts as an infill lot

There is no single legal definition, and towns that use the term in their regulations define it for their own purposes. In practice, infill sites fall into a few groups:

• Vacant lots in built-up areas. A lot between two houses that was never built on, or whose building was demolished long ago.
• Underbuilt lots. A lot holding much less than its zoning allows, such as a single small house in a district that permits two, three or more units. Replacing or adding to the building is infill too.
• Oversized lots. A large lot in a neighbourhood of smaller ones, which may be able to be divided into more lots that meet the zoning minimums.
• Leftover and odd parcels. Corner remnants, former parking lots, rear land behind existing houses, and similar pieces that development went around.

Why builders want them

• Infrastructure is there. Streets, and often public water and sewer, already reach the lot, which can save much of the cost of servicing raw land.
• Demand is proven. People already live, shop and commute there.
• Smaller projects. One to a handful of units suits small builders and investors who cannot take on a subdivision.
• Policy often favours them. Planners generally prefer new housing where infrastructure exists, and some towns' regulations make room for it.

What makes them harder

• Size and shape. Narrow or irregular lots leave little room once setbacks, parking and driveways are drawn in.
• Nonconformity. Many older lots are smaller than today's minimum lot size or have less frontage than the district now requires. Whether such a lot can be built on depends on the town's rules for pre-existing lots, and sometimes on whether it has been held in common ownership with the lot next door.
• Neighbours. New construction next to existing homes draws more attention, and anything needing a special permit or variance goes through a public hearing.
• Hidden conditions. Old foundations, fill, buried tanks or contamination on lots that once had other uses.

Zoning decides what an infill lot is worth

Two lots of the same size on the same street can be worth very different amounts if one sits in a district that allows a single house and the other in a district that allows three units. For underbuilt lots, the zoning is the whole opportunity: a small house on a lot zoned for multi-family housing can be the site of a two- or three-family building, or of added units, if the lot meets the district's requirements for lot area per unit, parking and setbacks.

That makes the zone code the first thing to check, and the one most often misread. Zone codes are local: in most Connecticut towns an R district's number is its minimum lot size, not a density, and the same code means different things in neighbouring towns. See how to check the zoning of a property and what zoning allows a duplex or triplex in Connecticut.

Infill lots for sale, and how to find them

Few infill lots are advertised as such. Listings for vacant lots in built-up areas do appear, and an agent with MLS access can watch for them, but most infill sites are found before they are for sale, by working out which parcels are underused and writing to the owners.

That is exactly what the public records can show. The assessor's records give each parcel's land use and, in most towns, its zone; the town's regulations say what each zone allows. Joining the two finds parcels that are vacant or hold a single house in a district that permits more. This site does that join for every town it indexes. In Connecticut it currently finds 51,769 such parcels, 4,199 of them vacant lots. Browse them by county and town or search a county or ZIP code; once you have a lot in mind, see how to find its owner.

A checklist for an infill site

1. Confirm the zoning district and what it permits on a lot of this size.
2. Check whether the lot conforms to the current minimum lot size and frontage, and if not, what the town's rules allow on a pre-existing lot.
3. Confirm public water and sewer, or septic feasibility.
4. Look for wetlands, flood zones and any overlay districts.
5. Read the land records for easements, restrictions and the ownership history.
6. Walk the street and look at what the neighbours have built.

Common questions

What is an infill lot?

A vacant or underused parcel inside a neighbourhood that is already developed, usually on an existing street with utilities nearby, as opposed to raw land on the edge of town.

Is a lot with an old house on it an infill lot?

It can be. A small house on a lot whose zoning allows several units is an underused parcel, and redeveloping it at the density the district permits is a common form of infill.

Are infill lots cheaper to build on?

Often, because streets, water and sewer are usually already there, but small or irregular lots, setbacks, parking and neighbours' objections can add cost and time.

General information drawn from public records and how Connecticut towns publish them, not legal advice. A town's zoning office, and an attorney for anything you are buying, are the authorities on a specific property.