What Most Developers Miss When Evaluating Infill Sites
Infill development is supposed to be the answer to a lot of housing supply problems. Underutilized land in established neighborhoods, close to transit, with existing infrastructure — why isn't more affordable housing getting built there?
Part of the answer is that infill sites are harder to develop than they look. Not impossible. Not even usually prohibitive. But harder in ways that are easy to miss if you're evaluating them with the same checklist you'd use for a greenfield site.
This piece is about what those differences actually are — what most developers miss when looking at infill, and what a more complete evaluation looks like.
The visibility problem
Infill sites look simpler than they are because the complications are often underground, in adjacent structures, or buried in regulatory history. A greenfield site in a suburban market has a visible footprint, predictable utilities, and a relatively clean environmental history. An infill site in an urban market may have utility infrastructure that hasn't been mapped accurately in decades, neighbors with structural conditions that affect what you can build, and a regulatory history that requires careful excavation before you understand what's actually on the parcel.
The developers who do infill well are the ones who've learned to look for these complications early — not because they've encountered every possible problem, but because they've developed a systematic approach to finding the surprises before the surprises find them.
Utility and infrastructure gaps
One of the most consistent sources of unexpected cost in infill development is infrastructure. Aging urban utilities often can't support the loads a new residential building requires. A site that appears ready to build may need significant upgrades to water, sewer, gas, and electrical infrastructure — upgrades that can add hundreds of thousands of dollars to development cost and months to the project timeline.
The check is straightforward in theory: contact the relevant utilities early and ask specifically about capacity and required upgrades. In practice, this step gets deferred until design is underway, which is when the upgrades show up as surprises in the cost estimate rather than as known variables in the feasibility model.
Do it first. The answer matters for whether the deal works.
Neighboring structures and shared walls
In dense urban contexts, infill sites often share property lines — sometimes shared walls — with existing structures. This creates complications that don't exist for freestanding sites:
Shared wall conditions. If an adjacent structure has a common wall with the development site, the condition of that wall matters — for structural design, for construction methodology, and potentially for costs that your project has to carry even if they originate with the neighbor's building.
Shoring and excavation. Digging below grade adjacent to existing structures requires shoring that can be significantly more expensive than open excavation. The depth of your underground parking or foundation and the proximity of neighbors will drive this cost. It needs to be visible in early feasibility.
Neighbor notifications and objections. Urban infill is more likely to trigger neighbor opposition than greenfield development, particularly if proposed height or massing feels out of character for the block. This isn't always a fatal risk, but it's a timeline risk — and in some jurisdictions, active neighborhood opposition can meaningfully extend the entitlement process.
The contamination baseline
Infill sites in urban areas have histories. Gas stations, dry cleaners, industrial uses, underground storage tanks — the prior uses of urban parcels and the parcels around them create environmental risk that's absent from most suburban greenfield sites.
A Phase I Environmental Site Assessment is standard due diligence and typically required by lenders. But the Phase I isn't a first-pass tool — by the time you're ordering a Phase I, you should already have a working hypothesis about environmental risk based on what you know about the site's history and context.
Early in the evaluation, ask: what was on this site before? What was on the adjacent sites? Is there a plausible environmental concern that could add cost or delay? The answer doesn't need to be definitive at this stage — it just needs to be honest.
The density paradox in affordable housing infill
Here's a tension specific to affordable housing: infill sites are often smaller than the sites that work best financially for LIHTC. The economics of LIHTC require minimum unit counts — usually at least 60–80 units — that can be difficult to achieve on the irregular, modestly-sized parcels that characterize a lot of urban infill inventory.
The response to this tension takes a few forms. Developers sometimes assemble multiple adjacent parcels — which adds complexity and timeline but can unlock the density needed. Some markets have density bonuses or by-right affordability provisions that allow more units on a given footprint than baseline zoning would permit. And some deals simply accept lower unit counts and find ways to make the math work — usually with more soft debt, not less.
The point is that density assumptions for infill sites need to be grounded in reality: not just what the zoning technically allows, but what's actually achievable given the site's geometry, adjacent conditions, and construction methodology.
Parking and access
Parking minimums have been reduced or eliminated in many urban jurisdictions, particularly near transit. But where they still apply, they create particular challenges for infill — above-ground structured parking is expensive, and underground parking in tight urban contexts with shoring requirements is more expensive still.
Access is the other half of this: a site that's theoretically accessible by car but practically challenging to get in and out of — one-way streets, fire lane requirements, loading zone constraints — can generate design complications that aren't visible from an aerial view.
Both are worth checking early, before design has been completed around assumptions that may not hold.
What a complete infill evaluation looks like
A more complete checklist for infill sites, beyond the standard feasibility screen, includes: utility capacity confirmation from the relevant providers; shared wall and adjacent structure conditions; environmental history — not a full Phase I, but an informed hypothesis; density achievability given site geometry, adjacent conditions, and construction constraints; parking and access realities under local requirements; and neighbor and community context — who will object, and through which processes.
None of these will be fully resolved at the screening stage. But they should all be visible — as known variables or acknowledged uncertainties — before you advance a site to serious underwriting.
The infill sites that work for affordable housing development exist. Finding them consistently requires looking at the right things, in the right order, before the complications find you.
Alpha Deal helps development teams evaluate infill sites against program requirements and site-specific risk factors early in the screening process — so deals that advance have a realistic foundation.