Est. 2003
The 12 types of home additions explained
Feeling cramped but love your Atlanta neighborhood? You’re not alone. A thoughtfully planned addition can change how you live without relocating. Here are the addition types we build most, what each one does to the house structurally, what it takes to permit, and real costs from 22 years building across metro Atlanta.
Conventional room addition
A conventional addition extends the house at ground level on its own new footing, tied into the existing foundation. It is the most versatile type and the one that costs the most per square foot, because it carries a full sequence: a site plan showing the new footprint to every property line, a footing and foundation inspection, a roof tie-in into the existing framing, and then rough-in and final inspections like any other room. The site plan is usually what slows an application down, not the framing, since it has to show setbacks and, on many lots, how much of the parcel will be covered once the addition is built. Before you price out a conventional addition, it helps to look at whether a home addition is worth it for your house and neighborhood.
Second-story addition
Building up instead of out uses no yard, which is why it is the answer on tight infill lots. It is also the most structurally demanding option on this list, because the existing foundation and ground-floor framing were sized for one story, not two. An engineer has to confirm what is already there can carry the new load before a permit is even drawn, and the existing roof usually comes off entirely rather than being tied into. Expect the ground floor to be shored and partly opened up during construction, which is the tradeoff for adding space with no footprint impact.
Bump-out
A 2 to 8 foot extension, often just enough to fix a cramped kitchen or add a bay to a living room. Because the footing is small and frequently lands on an existing foundation ledge, this is usually the fastest addition to permit and build, and the cheapest way to gain real square footage. The roof tie-in is minor, sometimes just a shed extension off the existing eave, which is why the structural review here is the lightest of any type on this list. If you are planning a bump-out in Forsyth County, our home addition contractor in Cumming, GA can help you work through setbacks, roof tie-ins, and the permit process before drawings get too far along.
Sunroom or screened porch
The most common first addition for a lot of owners, and the one where a single decision changes the entire scope: whether the room is conditioned. A heated and cooled sunroom needs a frost-depth foundation, insulation to code, and an added load on the existing HVAC system, and it counts toward the finished square footage of the house. A three-season room needs none of that, sits on a lighter foundation, and costs meaningfully less to permit and build. Decide this before drawings start. Changing your mind after the fact means a new foundation, new insulation, and a new permit, not a change order.
Garage conversion
The most affordable way to add finished space, because the walls and roof already exist. What it is not is free of structural work: a garage slab was never built to residential floor-insulation standards, so a subfloor and insulation package go in regardless of finish level. It is also worth checking your HOA covenants before you commit. Converting covered parking to living space is exactly the kind of change some communities restrict, and finding that out after signing a contract is the expensive way to learn it. If you want one licensed team handling the plans, permits, and build, our residential general contractor can take a garage conversion from demo through final punch list.
Room over garage
Popular wherever there is no yard left to build into. The garage slab and the walls under a room like this were not engineered to carry one, so this addition always starts with an engineer looking at what is already there, before anything is drawn. That review is what separates a straightforward bonus room from one that needs the garage structure reinforced first, and it is the reason a bid for this type should never be a flat number sight unseen.
ADU or in-law suite
The highest value add on this list, and the most complicated to permit, because a self-contained unit with its own kitchen and bath is not treated like a bedroom addition in most jurisdictions. It can trigger a separate zoning review, a second look at septic capacity on a system that was never sized for a second household, and questions about how utilities are metered. None of that makes it a bad project. It does mean the permitting timeline belongs in the budget conversation on day one, not as a surprise partway through.
Other ways to add space
| Addition type | Cost / sq ft | Timeline | What it changes structurally |
|---|---|---|---|
| Basement finish | $75–$200 | 2–5 mo | Nothing outside the foundation walls already there, lowest cost per sq ft on this list |
| Attic conversion | $150–$300 | 2–5 mo | Needs the existing roof structure and joists checked for a livable floor load |
| Dormer addition | $300–$500 | 3–6 mo | Cuts into the roof structure to add headroom and light, a full framing change |
| Modular addition | $250–$400 | 1–3 mo | Factory-built sections still need a site-built foundation and utility tie-ins |
| Mudroom | $200–$350 | 1–3 mo | Usually the smallest footing on this list, similar review to a bump-out |
Compare the options
| Addition type | Cost / sq ft | Timeline | Yard impact | Complexity |
|---|---|---|---|---|
| Conventional | $300–$500+ | 4–8 mo | High | High |
| Second story | $350–$600+ | 6–12 mo | None | Very high |
| Bump-out | $200–$350 | 2–4 mo | Minimal | Low–mod |
| Sunroom | $250–$450 | 3–6 mo | Moderate | Moderate |
| Garage conversion | $100–$250 | 2–4 mo | None | Low–mod |
| Over garage | $200–$400 | 3–6 mo | None | Mod–high |
| ADU / in-law suite | $400–$700+ | 6–12 mo | High | Very high |
Cost ranges reflect typical Atlanta-area pricing and vary with finishes, complexity, and local market conditions. See home addition cost per square foot and home addition permits in Georgia for what each office actually asks for.
Frequently asked questions
How long does a home addition take?
Simple additions like mudrooms take 1–3 months; major projects like second stories take 6–12 months. Permit processing adds 4–8 weeks.
Do I need to move out during construction?
Most additions let you stay home, though some disruption is inevitable. Second stories and major kitchen work may require temporary arrangements for certain phases.
How much value does an addition add?
Well-planned additions typically recoup 60–80% of cost in increased home value, with bathrooms and master suites performing best.
Which addition type is fastest to permit?
A bump-out or a mudroom, because the footing is small and often lands on an existing foundation ledge, and the roof tie-in is minor. A second story or an ADU sits at the other end, since both bring in a full engineering review before drawings are final.
Does converting my garage affect my HOA or insurance?
Check your covenants before you sign a contract. Some communities restrict converting covered parking to living space, and it is far cheaper to learn that from your HOA documents than from a stop-work notice.
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