Lot Coverage Limits: Alpharetta vs Roswell
How do lot coverage limits rules compare between Alpharetta, GA and Roswell, GA?
Alpharetta and Roswell have similar restriction levels.
Alpharetta, GA
Fulton County
Alpharetta's Unified Development Code (Article II — Use of Land and Structures) sets maximum lot coverage and impervious surface limits by zoning district. In the R-15 single-family residential district, the maximum impervious surface is 35% of the lot. The city also requires soil-infiltration testing for any new project in the Residential Overlay District that adds 1,000 to 5,000 square feet of impervious area.
View full Alpharetta rules →Roswell, GA
Fulton County
Lot coverage limits in Roswell vary by zoning district under UDC Article 3. Typical R-1/R-2 single-family districts cap impervious surface at 35-40%; tighter caps apply in environmentally sensitive areas like the Chattahoochee River Corridor Protection Zone.
View full Roswell rules →Key Facts Comparison
| Fact | Alpharetta | Roswell |
|---|---|---|
| Code Reference | UDC Article II, Sec. 2.3 | - |
| R-15 Max Impervious | 35% of lot | - |
| Overlay Trigger | 1,000-5,000 sq ft new impervious | - |
| Variance Authority | Board of Adjustment | - |
| Code | - | Roswell UDC Article 3 |
| R-1 Cap (typical) | - | 30-35% impervious |
| R-3/R-4 (typical) | - | 40-50% |
| MRPA Zone | - | Tighter within 2,000 ft of Chattahoochee |
| Pervious Pavers | - | Can reduce calculated coverage |
Highlighted rows indicate differences between cities.
Alpharetta FAQ
What's the maximum lot coverage in Alpharetta's R-15 zone?
35% impervious surface, under the Alpharetta Unified Development Code Article II development standards. The Board of Adjustment can grant variances; one approved increase was to 40%.
When does the Residential Overlay District trigger extra requirements?
Projects adding between 1,000 and 5,000 square feet of new impervious area in the Residential Overlay District require soils infiltration testing prior to permit issuance.
Roswell FAQ
How much of my Roswell lot can I cover with buildings and driveway?
30-50% depending on zoning district. R-1 estate lots are tighter (30-35%) and small-lot districts allow more (40-50%). Properties near the Chattahoochee are tighter still under MRPA rules.
Do pervious pavers count against lot coverage?
Properly installed pervious pavers can reduce calculated impervious surface, sometimes by 50% or more depending on the engineering documentation submitted.
Compare other topics
See how Alpharetta and Roswell compare on other ordinance categories.
Want to add a third city?
Use our full comparison tool to compare up to three cities.
Open Comparison Tool