An engineering-first buyer checklist from Mack Development Group and Mack Engineering, serving Alpharetta, Milton, Cumming, Canton, Johns Creek, and the rest of North Georgia.
Short answer
Before you close on a lot for a new construction Atlanta home, verify seven things: current zoning, septic vs. sewer service, front-side-rear setbacks, creek and adjoining-property buffers, maximum allowable impervious coverage, cost-to-build fit for the home design you actually want, and whether stormwater is managed by a shared community system or entirely on your own site. Getting any one of these wrong can shrink the buildable area, force a redesign, add six figures to your budget, or kill the project. The safest way to answer all seven is to buy through a builder with an in-house licensed civil engineering firm, which is how Mack Development delivers every home.
Why land due diligence beats floor plans
Most buyers picking out land for a custom home fall in love with the view, the trees, or the address, then ask their builder to make the house fit. That order is backwards. Zoning, soils, buffers, and utilities decide what is legal, buildable, and affordable on a given parcel long before an architect draws a foundation line. In North Georgia, a lot that looks identical to the one next door can carry radically different building rights because of a county overlay, a state stream buffer, or a stormwater easement recorded on the deed.
Mack Development is a custom home builder paired with Mack Engineering, a licensed Georgia civil engineering firm. That pairing means every lot we walk gets a full engineering-grade feasibility review before you close. Below are the seven variables we verify on every North Georgia parcel and what each one costs you if it is ignored.
The 7 variables at a glance
| # | Variable | Why it decides the deal |
|---|---|---|
| 1 | Current zoning | Sets the use, minimum lot size, height, and the house you are legally allowed to build. |
| 2 | Septic vs. sewer | Drives whether a soil test, drainfield, and bedroom cap dictate your floor plan. |
| 3 | Setbacks | Front, side, and rear setbacks carve out the true buildable envelope on your lot. |
| 4 | Creeks, wetlands, and neighbor setbacks | State stream buffers and easements from adjoining properties can quietly erase 25–75 percent of a lot. |
| 5 | Maximum impervious coverage | Caps the combined footprint of your house, driveway, patios, and pool before you draw a plan. |
| 6 | Cost-to-build fit | Slope, rock, access, and utility distance can add six figures before framing starts. |
| 7 | Stormwater responsibility | Determines whether the neighborhood pond handles your runoff or you must engineer and build your own detention. |
1. What is your current zoning?
Zoning is the master switch. It tells you whether the parcel is single-family residential, agricultural, mixed-use, or something more restrictive, and it sets the minimum lot size, maximum height, permitted accessory structures, and the type of home you can legally build. In Cherokee, Forsyth, Fulton, Hall, and Dawson counties, similar-looking rural parcels can carry AG, R-40, R-80, or an equestrian overlay, and each carries a very different rulebook.
What to verify before you close:
- Base zoning district and every overlay (rural, watershed protection, historic, scenic corridor, airport).
- Minimum lot size and frontage against the actual survey — grandfathered lots below current minimums may still be legal but limited.
- Permitted uses — confirm the home type you want (single-family, guest house, accessory dwelling unit, workshop, barn) is allowed by right, not by variance.
- Maximum height and story limits especially if you want a walk-out basement plus two stories.
- Recent or pending amendments — counties around Atlanta rewrite ordinances often; a rezoning application on the adjoining parcel can change your setbacks or buffer overnight.
The cost of skipping this step: at best a variance application that adds 3–6 months and legal fees. At worst, a parcel you cannot build your intended home on at all.
2. Is your lot on septic or sewer?
This is the single most common surprise on North Georgia custom home lots. Public sewer availability changes street by street across Alpharetta, Milton, Cumming, Canton, and Johns Creek, and much of the rural inventory in Cherokee, Forsyth, Dawson, and Pickens counties is septic only.
If the lot is on public sewer:
- Confirm capacity is actually available at the main and that a tap fee has been quoted.
- Confirm the distance from your buildable pad to the sewer main — long lateral runs and rock trenching can add tens of thousands of dollars.
- Get the utility easement locations in writing.
If the lot is on septic:
- A county-approved Level III soil evaluation must be completed and the drainfield area flagged before you close.
- In Georgia, the drainfield is sized by the number of bedrooms — the soil, slope, and depth to seasonal water table cap how large a home you can build. A four-bedroom plan on a lot only approved for three is a redesign, not a paperwork fix.
- Setbacks matter here too: septic tanks and drainfields carry their own setbacks from property lines, wells, streams, and the house itself, which further reduces your usable pad.
- Reserve area for a replacement drainfield is often required and must be preserved from grading, driveways, and pools.
The cost of skipping this step: sewer surprise fees of $10,000–$60,000, or a septic-driven redesign that eliminates a bedroom, a basement, or the pool you were planning.
3. What are your current setbacks?
Setbacks are the invisible fence around your buildable area. Every zoning district defines a front, side, and rear setback measured from the property line. The area inside those setbacks is your building envelope — the only place your house, attached garage, and covered patios can legally sit.
What to pull and verify:
- Zoning-code setbacks for the specific district on your parcel — not the district next door.
- Corner-lot rules — corner lots typically have two front setbacks, which can consume the pad you were counting on.
- Accessory-structure setbacks for detached garages, guest houses, pools, and outbuildings, which are often different from the primary structure.
- Height-based setback increases — some ordinances require the setback to grow as the building gets taller.
- Recorded plat notes that impose stricter setbacks than the base zoning (extremely common in Milton, Johns Creek, and gated communities).
The cost of skipping this step: a signed contract on a house that will not fit inside the legal envelope, requiring either a variance, a redesign, or a walk-away.
4. Is there a creek on site or funky setbacks from adjoining properties?
This is where lot value quietly evaporates. Georgia enforces a 25-foot state waters buffer measured from the top of the bank of any perennial or intermittent stream, wetland, or lake. Metro-Atlanta jurisdictions layer additional buffers on top: Metropolitan River Protection Act corridors along the Chattahoochee run 2,000 feet, and cities like Johns Creek and Roswell add a 50-foot undisturbed plus a 25-foot impervious setback on many streams. In practice, a 1-acre wooded lot with a small creek can lose 30–60 percent of its buildable area to buffers alone.
Adjoining-property setbacks and easements are the second silent killer:
- Recorded drainage easements from the subdivision development that must be kept clear.
- Utility easements — overhead power, buried gas, water, and sanitary sewer lines all carry setbacks you cannot build within.
- Access easements granting a neighbor the right to cross your lot.
- Septic setbacks from a neighbor’s well — Georgia requires 100 feet from a private well, which can sit on the parcel next door.
- Shared driveways and flag-lot geometry that reduce your usable frontage.
What to verify before you close:
- An up-to-date boundary and topographic survey that shows every stream, wetland, easement, and buffer plotted to scale.
- The state waters and local buffer overlays for your specific city or county.
- A wetlands delineation if any low, wet, or blueline-stream area is visible.
- The recorded plat, title commitment, and all easement documents referenced on it.
The cost of skipping this step: a Notice of Violation and stop-work order from the county or the Georgia Environmental Protection Division, mandatory restoration, and a redesign around a buildable area you did not know was there.
5. Is there a maximum allowable impervious coverage on your lot?
Impervious coverage is the total area of surfaces water cannot soak through: the house footprint, driveway, walkways, patios, pool decking, and detached structures. Almost every North Atlanta jurisdiction caps it — commonly 35 to 45 percent for standard residential districts, and as low as 25 percent inside watershed-protection or stream-buffer overlays.
Why it matters for your custom home:
- It caps the total footprint you can pour before you decide how to split square footage between the house, garage, drive, pool, and outdoor kitchen.
- It often controls whether a circular drive, sport court, or detached guest house is even possible.
- It drives which surfaces must be pervious — permeable pavers, gravel, or turf — which changes the finish budget.
- Exceeding it in construction triggers required removal or a stormwater mitigation package that can cost more than the surface itself.
What to verify before you close:
- The exact impervious cap for the district and any overlay on your parcel.
- The measurement rules — some jurisdictions count roof overhangs and pool water surface, others do not.
- Existing impervious on the parcel if there is a barn, shed, driveway, or slab.
- A preliminary impervious budget against the home design and site amenities you actually want.
The cost of skipping this step: a home design that looks great on paper but will not survive plan review, or amenities cut post-permit to bring the site back into compliance.
6. Is your lot cost-effective to build on for the home design you want?
Two lots can list at the same price and cost hundreds of thousands of dollars apart to build on. In North Georgia the biggest drivers are slope, rock, access, and utility distance.
The site-cost variables we quantify on every Mack Development lot review:
- Slope and grading volume. Steep lots need retaining walls, deeper foundations, and moved dirt. A 15-percent slope across a house footprint can add $80,000–$250,000 in foundation, walls, and grading alone.
- Rock. North Georgia sits on granite. If bedrock is shallow, blasting or hoe-ram for foundations, septic trenches, and utility runs can add $20,000–$150,000.
- Access and driveway length. A 600-foot driveway with a culvert, turnout, and paving is easily a $60,000–$150,000 line item.
- Utility distance. Every 100 feet of trenched water, power, gas, or sewer adds cost. Well and septic in place of public utilities changes both the budget and the design.
- Tree preservation and clearing. Specimen-tree ordinances in Milton, Roswell, and Alpharetta can require tree save, replacement, or bond escrow.
- Design compatibility. A ranch on a slope wastes the lot; a walk-out basement plan on a flat lot buries a floor. The home design has to match the topography.
What to verify before you close:
- A site walk with a licensed civil engineer, not just a real-estate agent.
- A preliminary grading and utility concept overlaid on your intended floor plan.
- A written site-cost range that includes clearing, grading, retaining walls, foundation type, driveway, utility runs, and stormwater.
The cost of skipping this step: buying a $400,000 lot that costs $600,000 to prepare and finishing the project 20–40 percent over budget.
7. Is stormwater shared or managed on your own lot?
Every custom home in Georgia has to account for the stormwater it generates. The critical question is where that responsibility lives.
Two very different scenarios:
- Shared community stormwater. If your lot is part of a subdivision with a permitted regional detention pond, water quality feature, or shared conveyance system, your runoff is already accounted for by the master plan. You typically pay into an HOA or maintenance covenant, and your on-lot obligation is limited to lot grading and staying within the impervious allowance the developer designed to.
- On-lot stormwater. If the parcel is a standalone rural or infill lot, or you exceed the impervious the master plan accounted for, you are responsible for detaining, treating, and safely conveying your own runoff. In practice that means a designed and permitted stormwater management plan, often including a detention pond, dry well, bioretention area, or underground storage system — plus a maintenance agreement recorded against the property.
What to verify before you close:
- The subdivision’s stormwater permit and whether your lot is inside the drainage area the shared system was sized for.
- The HOA or covenant obligations for stormwater maintenance and any fee.
- The impervious your lot was assumed to have — exceeding it can pull you out of the shared system and into on-lot detention.
- For standalone lots, a preliminary stormwater concept from a licensed civil engineer showing where detention will sit and what it will cost.
- Downstream conveyance — where your water goes, and whether you need an off-site drainage easement.
The cost of skipping this step: a $30,000–$120,000 on-lot detention system discovered at permit review, or a stop-work order for discharging concentrated flow onto a neighbor.
Why an integrated builder-engineer answers all seven at once
Each of these seven variables is a different question for a different professional. In the typical custom-home process the buyer chases a real-estate agent, a surveyor, a soils consultant, a civil engineer, a builder, and an architect — separately, sequentially, and with no one accountable for the whole answer. That is how contracts get signed on unbuildable lots.
Mack Development Group is a custom home builder. Its sister company, Mack Engineering LLC, is a licensed Georgia professional engineering firm. Every prospective lot we evaluate for a client runs through one integrated review:
- Zoning, overlays, and setbacks confirmed against the parcel — not the block.
- Septic feasibility coordinated with soil evaluators; sewer capacity verified with the utility.
- Boundary, topographic, and site conditions walked and mapped by our civil team.
- Buffers, easements, and wetlands identified before you write the earnest-money check.
- Impervious budget built into the schematic design, not discovered at permit review.
- Site-cost range quantified alongside the home budget so total cost is real, not aspirational.
- Stormwater strategy — shared or on-lot — defined before the driveway is drawn.
Because the engineering is under the same roof as the builder, there is one accountable team from feasibility through certificate of occupancy. That is the difference between a new construction Atlanta home that closes on time, on budget, and on plan — and one that spends a year in redesign.
Before you buy the land, get the engineering review
If you are shopping land for a new construction home anywhere in North Georgia — Alpharetta, Milton, Cumming, Canton, Johns Creek, Woodstock, Ball Ground, Dawsonville, Blue Ridge, and every county between — send us the parcel before you write the offer. Mack Development will walk it, engineer it, and give you an honest, written buildability review covering all seven variables above. If the lot is right, we build it. If it is not, we tell you before you close.
Request a free lot review at .
Frequently asked questions
What should I check before buying land for a custom home near Atlanta?
Verify seven things before closing: current zoning and overlays, septic vs. public sewer availability, front-side-rear setbacks, creek and adjoining-property buffers, maximum allowable impervious coverage, site-development cost against the home design you want, and whether stormwater is managed by a shared community system or on your own lot. Missing any one of these can shrink the buildable area, force a redesign, or add six figures to your budget.
How much of a lot can Georgia state stream buffers actually take away?
Georgia requires a 25-foot undisturbed buffer measured from the top of the bank of any perennial or intermittent stream, wetland, or lake. Metro-Atlanta cities like Johns Creek and Roswell layer additional buffers on top, and Chattahoochee corridor lots fall under the Metropolitan River Protection Act. A small creek on a 1-acre wooded lot can consume 30 to 60 percent of the buildable area once state, local, and impervious setbacks are combined.
Does a septic system limit how many bedrooms my custom home can have?
Yes. In Georgia, drainfield size is determined by the number of bedrooms, soil type, slope, and depth to the seasonal water table. If soil conditions only support a three-bedroom drainfield, a four-bedroom plan is not permittable without redesigning the drainfield area or the house.
What is a typical maximum impervious coverage in Alpharetta, Milton, and North Fulton?
Most standard residential zoning districts in the Alpharetta and Milton area cap impervious coverage between 35 and 45 percent of the lot area. Lots inside watershed-protection overlays or stream buffers can be capped as low as 25 percent. Verify the exact number for the district and overlay on your specific parcel before finalizing a home design.
How much can grading, rock, and driveway costs add to a rural North Georgia lot?
Site development on a sloped or rocky lot commonly ranges $80,000 to $400,000 above a flat, roadside lot. Steep grading and retaining walls typically add $80,000 to $250,000, rock excavation for foundations and utilities adds $20,000 to $150,000, and a long private driveway with culvert and paving adds $60,000 to $150,000.
Who is responsible for stormwater on a custom home lot in Georgia?
It depends on the parcel. If the lot sits inside a subdivision that was permitted with a regional detention pond or shared stormwater system, that shared system typically handles runoff and the lot owner pays an HOA maintenance obligation. Standalone rural or infill lots — and any lot that exceeds the impervious the subdivision was designed for — must detain, treat, and convey runoff on their own, which requires a permitted stormwater management plan and, in most cases, a designed detention feature.
Why hire a builder with an in-house civil engineering firm?
An integrated builder-engineer team can answer zoning, septic, setback, buffer, impervious, site-cost, and stormwater questions on the same lot walk, before you close on the property, and can carry those answers straight into design and permit. In a fragmented process, each specialist looks at only one variable, no one is accountable for the whole answer, and buyers frequently sign contracts on lots their intended home cannot legally or affordably fit on. Mack Development pairs custom home construction with sister firm Mack Engineering LLC, a licensed Georgia civil engineering firm, so every parcel gets one integrated feasibility review.
