Building a home is exciting, but the early “paperwork” steps can feel like a buzzkill. Two of the biggest question marks are surveys and perc testing. They’re not just boxes to check. They’re how you avoid expensive surprises once excavation starts.

Below is a plain-English rundown of what each one is, when you’ll likely need it, and why your builder cares so much. 

Do I need a survey? 

A land survey is a professional measurement and drawing of your property. In most cases, the survey your builder wants is a boundary survey (of the lot lines), and sometimes a topographic survey (of the land, including slopes and elevations). 

When you’ll usually need one 

You don’t always “have to” get a new survey, but in real life, these are the most common moments where it becomes necessary: 

• You’re applying for permits or site plan approval. Many jurisdictions require a site plan that’s drawn to scale and based on an accurate boundary survey. 

• You’re building on a lot where the corners aren’t clearly marked (or fences, tree lines, and “what the neighbor said” are doing all the guessing). 

• There are easements, rights-of-way, or setback concerns. A survey helps confirm where you can and can’t build. 

• You want to avoid encroachments. The New York State Education Department specifically calls for using a licensed surveyor to ensure a house or addition is within property lines before construction.  

• A municipality asks for it during review. For example, the Buffalo notes that, for certain site plan review submissions, they want a survey along with the plans and the site plan. 

“I already have a survey.” Can I use it? 

Maybe. The catch is that older surveys may lack details you need for today’s approvals, or they may not reflect changes such as fences, additions, garages, sheds, or driveway shifts. 

A good rule of thumb: if the survey is old enough that you’re not confident it matches what’s actually on the lot right now, assume it’s a risk. 

What a survey helps your builder do 

Even if nobody “required” a survey, it can still save you money because it helps the team: 

• Place the home correctly on the lot (setbacks, driveway alignment, utilities) 

• Plan grading and drainage in a realistic way 

• Identify easements early, before they force a redesign. 

• Reduce change orders and delays caused by “surprise” constraints. 

And if you’re wondering whether you’re getting a real survey vs. a sketch, New York’s guidance is clear that a survey map should be certified by a licensed land surveyor. 

Quick takeaway on surveys 

If you’re building new, especially on a vacant lot, a current boundary survey is one of the best early investments you can make. It’s not glamorous, but it keeps your build grounded in reality. 

What is percolation testing? 

Percolation testing (usually called a “perc test”) measures how quickly water drains through the soil where a septic system’s absorption area would be. 

If your home connects to a public sewer, you typically won’t need a perc test. If you’ll use a septic system or another onsite wastewater setup, you probably will. 

Why it matters 

The soil’s drainage rate helps determine whether the site can support a conventional septic absorption field, and it directly affects system design. 

Under New York’s residential onsite wastewater rules, percolation testing is used as an indicator of soil permeability and must match the soil conditions observed on site.  

How perc testing usually works (high level) 

The basic idea is simple: 

1. A professional digs one or more test holes in the proposed absorption area. 

1. The holes are wetted and allowed to saturate. 

1. Water level drop is measured at set intervals. 

1. The result is expressed as a rate, often in “minutes per inch.” 

One university extension guide defines the percolation rate as the average time, in minutes, for water to fall 1 inch, measured at intervals after saturation. 

How many tests are required? 

New York’s residential onsite wastewater regulations require at least two percolation tests at the site of each proposed sewage treatment system.  

Local health departments can also accept or require other soil tests in place of perc testing in some situations.  

What else is evaluated besides the perc number 

This is the part people miss: a perc test isn’t the only deciding factor. 

For example, in the Erie County Department of Health guidance for onsite wastewater plan review, they call for a soil profile based on at least one deep test hole (minimum 6 feet) and note that at least two percolation tests must be completed in the proposed disposal area. 

New York’s statewide residential rules also reference the use of test holes to confirm soil and site conditions, including groundwater and limiting layers, and note that systems should be designed for the most restrictive conditions found.  

Translation: it’s not just “does it perc,” it’s also “does the site have enough suitable soil, at safe separations, in the right location.” 

What if the perc test “fails”? 

Fail is a scary word here because it often just means: “A conventional system at this exact spot isn’t a great idea.” 

In that same Erie County Department of Health document, they list multiple system options acceptable in the county and reference how percolation rates influence what’s feasible. 

Depending on your lot and local rules, alternatives include modified trench designs, sand filters, mounds, or other engineered approaches. The important part is testing early enough that you still have options for placement and design. 

Quick takeaway on perc testing 

If you’re not on public sewer, perc testing is one of the biggest “can we build here the way we want to?” checkpoints. It’s not just about approval; it’s about avoiding a design that becomes expensive to engineer later. 

The practical game plan 

If you’re in the planning stage, here’s the cleanest order of operations most builds follow: 

1. Get a current survey (at least boundary, topo if needed for design and grading). 
2. Confirm utilities (sewer vs. septic, water source). 
3. If septic, schedule soil evaluation and perc testing early, before finalizing the home’s placement. 
4. Use the results to lock in the site plan and move into permits and construction docs. 

Building a custom home comes with a lot of moving parts, and surveys and percolation testing are two of those early steps that can feel confusing if you haven’t done this before. Natale Builders guides you through the process from the start, so you know what’s needed for your specific lot, what can be handled upfront, and what to expect next. The goal is simple, no surprises, no last minute scrambling, just a clear path from “we love this land” to “let’s build here.”