There is a category of renovation that most general contractors will politely decline, or take on and struggle with. It is the whole-house project: the one where the kitchen moves to the other side of the house, the stair relocates, two bearing walls come out, a second story goes on, and the back of the house opens to a new covered porch on a lot with a septic field and a drainage swale. Every one of those moves needs an engineer’s answer before a framer can act on it, and a contractor who has to wait on an outside engineer for each one either slows to a crawl or starts guessing.
Mack Engineering was built for that project. We are a civil and structural engineering firm, and our sister company, Mack Development, is a licensed residential contractor. Between the two, we can design the renovation, engineer it, manage it and build it. Or we can design and engineer it and hand your builder a set that is actually buildable. This post walks through how that process works, step by step, and why the two-company structure changes what is possible.
Key takeaways
- Layout changes that move bearing walls, stairs, roofs or floor levels fall outside the IRC’s prescriptive tables and require engineered design under Georgia’s adopted codes.
- A whole-home renovation also triggers site questions: stormwater thresholds as low as 1,000 square feet of new impervious area in Alpharetta and Sandy Springs, septic capacity by bedroom count, setbacks and buffers.
- Mack Engineering designs and engineers the project in Revit, provides construction management for the builder and trades, and through Mack Development can build it turnkey.
- You choose the level of involvement: full design-build, design plus construction management, or design only for your own contractor.
Why most contractors cannot take this on alone
The International Residential Code lets a contractor frame a conventional house from tables. The moment a renovation introduces an element outside those tables, Section R301.1.3 requires that element to be designed in accordance with accepted engineering practice (IRC R301.1.3, summarized by Gold GCP). Georgia adopted the 2024 IRC and IBC with state amendments effective January 1, 2026 (Georgia DCA code adoption memo). On a whole-home renovation, non-prescriptive elements are not the exception; they are the project. Long clear spans over an open plan, transfer beams carrying a relocated second-floor wall, a new stair opening cut through an existing floor, point loads landing on an existing slab, a roof reframed from trusses to a cathedral ceiling: each is a design problem, and together they interact.
A contractor without in-house engineering has three choices. Hire an outside engineer for each condition and absorb the delay. Over-build everything in the hope it works, which is expensive and still may not address load paths to the foundation. Or decline the job. None of those is the homeowner’s fault, but the homeowner pays for all of them.
Step 1: Feasibility before design
We start with what the lot and the code will allow, because the most beautiful plan is worthless if it cannot be permitted. Our feasibility report for a renovation covers zoning setbacks and lot coverage, stream buffers and floodplain, septic location and reserve area, existing utilities, tree-protection rules and the stormwater threshold you will cross. The thresholds are lower than most owners expect: Alpharetta applies its post-construction stormwater standards at 1,000 square feet or more of new impervious surface (Alpharetta UDC Sec. 3.3.1), and Sandy Springs requires a land disturbance permit and stormwater management at the same 1,000-square-foot mark (Sandy Springs Land Disturbance Permits). A new covered porch, a widened driveway and a garage extension can cross that line together. On septic lots, Georgia sizes systems at 150 gallons per day per bedroom (Georgia DPH design flow criteria), so adding a bedroom suite may mean a system evaluation or expansion before anything else.
Step 2: Design and engineering under one roof
With the limits known, our team develops the layout and the structure together rather than in sequence. This is the step where having both a structural engineer and a civil engineer in the same office matters. The structural side produces the framing plans, foundation plans, connection details and calculations described in our post on structural engineering for renovations. The civil side handles stormwater design, grading, erosion control and, where needed, septic design and Level 3 soils. Because the same people are solving both, the new footing does not land in the drainfield reserve and the porch roof does not drain onto the neighbor.
Step 3: Build it in Revit first
We model whole-home renovations in Revit, including existing conditions, demolition, new structure and the major mechanical runs. Our Revit modeling and BIM coordination page explains the workflow; our post on coordinated plans, coordinated costs explains why it matters to your budget. The short version: a beam that conflicts with a duct is a ten-minute fix in the model and a change order in the field. Mack Development’s motto is that every home is built twice, once in Revit and once on site, and its 3D design and virtual walkthroughs let you stand in the new kitchen before a wall comes down.
Step 4: Construction management for the builder and the trades
Here is the part of our practice that most engineering firms do not offer. Mack Engineering provides construction management oversight to the builders and trade partners on our projects as a standard part of how we work, not as an add-on. Our construction-management team includes licensed professionals across general construction, structural, mechanical, electrical, plumbing and geotechnical disciplines, and the role is to make sure the engineering intent gets built: the beam bearing is where the drawing says, the footing was poured to the size on the sheet, the roof deck got its clips, the shear wall nailing matches the schedule. That oversight is what allows our builder partners to take on the most complex renovations and custom homes with confidence, because the engineering questions that would otherwise stall them get answered on site, by the people who drew the plans. We offer the same service to outside builders and developers through our construction management for residential builders and developers page, and Mack Development offers owner’s-representative project management for clients who want an advocate between them and their contractor.
Step 5: Build it, turnkey or with your builder
You have two paths from here, and we are genuinely indifferent to which you choose.
Turnkey through Mack Development. Our sister company is a licensed residential contractor in Georgia and North Carolina, follows a published five-step process from design through warranty, and backs its structural work with a ten-year warranty. The Mack Development custom build team works from the same Revit model our engineers produced, so there is no translation between the design and the build. Their client reviews are on their site.
Design and engineering for your builder. If you already have a contractor you trust, we deliver a permit-ready set with stamped structural drawings, civil plans and a coordinated model, and we remain available for construction management or for the field questions that come up when walls open.
Why the two-company structure matters
Mack Engineering and Mack Development share ownership, an office and a model. The story of how the Mack family of brands started explains the reasoning; the practical result is that the engineer who sized the transfer beam can walk the site with the framer who is installing it. It also means we are not dependent on a contractor’s willingness to take on a complex job. If the job is too complex for your contractor, Mack Development’s builder and trade partner program can bring in the trades under our construction management. Our page on what makes Mack Engineering different covers the rest.
No matter how you want to work, the service you need, whether that is a feasibility letter, a stamped framing plan, a coordinated design or a finished renovation with a warranty, is available from the same team.
Frequently asked questions
Mack Engineering is the engineering firm. Construction is performed by our sister company, Mack Development Group, a licensed residential contractor in Georgia and North Carolina. Both operate under common ownership and work from the same plans and model.
No. Design-only and design-plus-construction-management engagements are common. We deliver a permit-ready set your contractor can build from.
It depends on the jurisdiction and the new impervious area. Alpharetta applies stormwater standards at 1,000 square feet of new impervious surface and Sandy Springs requires an LDP at the same threshold; other cities and counties have their own triggers. The feasibility step identifies which apply to your lot.
It depends on the scope, the jurisdiction’s review process and how quickly decisions are made. We give a schedule after the feasibility review rather than quoting a generic number.
Thinking about a renovation your contractor said was too complicated? Contact Mack Engineering or call (770) 715-7295. We will tell you what it takes to design it, engineer it and build it, and which parts you actually need from us.
Related reading
- Structural Engineering for Residential Renovations in Georgia
- Structural vs Civil Engineer Georgia: Which Do You Need?
- Feasibility Studies & Reports Atlanta GA
- Stormwater Design & Hydrology Studies Atlanta
- Septic System Design Georgia: Soil Reports & Site Limits
- Revit Modeling & BIM Coordination Services
- Coordinated Plans, Coordinated Costs
- Construction Management Services
- Construction Management Services for Residential Developers
- How It Started: The Mack Family of Brands
- What Makes Mack Engineering Different
- The Custom Home Building Process (Mack Development)
- Our 5-Step Design-Build Process (Mack Development)
- 3D Home Design in Autodesk Revit (Mack Development)
- Project & Capital Management (Mack Development)
- Home Builders: What Mack Believes a Real Builder Is (Mack Development)
- Client Reviews (Mack Development)
Sources
- IRC R301.1.3 Engineered design, summarized in Gold GCP, Structural Coordination
- Georgia Department of Community Affairs, New Codes and Amendments Effective January 1, 2026 (memo)
- City of Alpharetta Unified Development Code, Sec. 3.3.1 Stormwater management (1,000 sq ft threshold)
- City of Sandy Springs, Land Disturbance Permits (1,000 sq ft threshold)
- Georgia Department of Public Health, On-Site Sewage Design Criteria: Peak Sewage Flow (150 gpd per bedroom)
- Mack Engineering, Construction Management (licensed professionals across construction, structural, MEP and geotechnical disciplines)
- Mack Development Group, Custom Build, Process and 3D Design pages (licensed GA/NC, ten-year structural warranty, built twice in Revit)
This article is general information, not a site-specific engineering opinion. Code requirements and local ordinances change; confirm current requirements with the authority having jurisdiction for your property.