Alpharetta Pool Impervious Surface and Lot Coverage Rules

A backyard pool in Alpharetta is rarely just a pool. The water, the coping, the deck, a new patio and the equipment pad all add hard surface to the lot, and the City counts that surface carefully. Once the total crosses certain thresholds, the project picks up stormwater requirements that can add design work, testing and cost. On homes with septic systems, Fulton County and the state's on-site sewage rules also limit where the pool can go. This guide explains what we could verify from the City's own published documents and the Georgia Department of Public Health, and what to confirm with the City before design.

The pool counts as impervious area

The City's Residential Individual Lot Site Plan Requirements checklist asks every applicant to put an impervious area chart on the plans. The chart lists existing impervious area to remain (the house, driveway, walks, patios and any existing pool), existing area to be removed, and proposed area to be added, with "new pool" listed as its own line. It then totals net new impervious area (proposed minus removed), total new or replaced impervious area, and total impervious area on the site at the end (City of Alpharetta, Residential Individual Lot Site Plan Requirements). If you plan pervious pavers for a driveway or pool deck, the checklist says to show them in the chart; they must meet the City's standard detail, notes, soils tests and a BMP covenant.

Stormwater thresholds: 1,000 and 5,000 square feet

Two numbers drive most residential pool reviews (Site Plan Requirements, items 15 and 16; Alpharetta Stormwater Policy Handbook):

• 1,000 to 4,999.9 square feet of new impervious area. Projects in this range must add green infrastructure if they are within specific watersheds or upstream of areas of drainage concern, and infiltration testing is always required. The Handbook's permit guidance cites UDC Article III Section 3.3.1 for this threshold.
• 5,000 square feet or more created or replaced. The project must provide full stormwater management, including runoff reduction, channel protection, detention and downstream analysis, following UDC Article III Section 3.3 and the Stormwater Policy Handbook.

The Handbook adds a detail many homeowners miss: impervious area calculations are cumulative across all projects on a property over a 2-year period. A patio this year and a pool next year can add up. Where a design lands between 4,900 and 4,999.99 square feet, the checklist requires a note that the designer will certify the final impervious area at the end of the project. The Handbook also lists other triggers that call for a permit determination, including disturbing 1/10 acre or more, working within 200 feet of state waters or a floodplain, encroaching on the critical root zone of trees, and any project that needs a building permit for a pool (Stormwater Policy Handbook, Section 20).

Pervious pavers and gravel

Pavers do not automatically count as pervious. Under the Handbook, the City allows properly designed pervious pavers on residential redevelopment projects to count as pervious for stormwater calculations only if soils testing shows an infiltration rate of at least 0.5 inches per hour where the pavers go, a BMP covenant is signed and recorded in Fulton County before close-out, and the owner maintains the system and keeps records. Even then, the Handbook says pervious pavers are included as lot coverage in the zoning lot coverage percentage and do not count as open space. Gravel or crushed stone used for vehicles is considered impervious, and landscape rock may still count as coverage under zoning calculations (Stormwater Policy Handbook, Section 18).

Lot coverage percentage

Zoning lot coverage is a separate test from stormwater. The maximum lot coverage percentage depends on your zoning district in the UDC, and we were not able to verify the current district limits from the ordinance text, so we do not list them here. Check your district's dimensional standards in the Alpharetta Unified Development Code on Municode or ask the Community Development Department at 678-297-6070, which the Handbook lists as the first contact for permit questions.

Setbacks, easements and buffers

The City's pool permitting handout sets the placement rules for residential pools: no pool in a front yard; at least 20 feet from side and rear property lines or the principal building setback, whichever is less; associated structures such as cabanas or equipment shelters at least 10 feet, or the principal building setback, whichever is less; nothing on a drainage or sewer easement without written approval of the easement holder; and at least 5 feet from any designated undisturbed buffer (City of Alpharetta, Swimming Pool Permitting & Inspections).

Clearing and grading for the pool envelope

The handout says pool permit documents must locate and identify all trees over six inches in diameter within the area of disturbance, and warns that severe penalties apply if the critical root zones of specimen trees are disturbed without approval. The City reviews the critical root zones of specimen trees that encroach into your limits of disturbance and of trees 6 inches and over within 30 feet of it (Handbook, Section 20). If you are clearing specimen trees to make room for a pool, use the Alpharetta specimen tree and replacement calculator to check size thresholds, root zones and replacement density before the layout is final. Leveling the yard, terracing or retaining walls also need City review, and the handout says retaining walls 4 feet or taller require a Georgia professional engineer.

Septic systems and pool location

For homes on septic, the City requires pool location plans to be approved in writing by Fulton County Environmental Health before submission to the City (404-332-1801), so the pool does not land on the area reserved for a back-up absorption field. The City does not keep septic records (Pool handout). The state rules in the Georgia DPH Manual for On-Site Sewage Management Systems set separation distances: a septic tank should be at least 10 feet from swimming pools, and no absorption field may be constructed less than 15 feet from a swimming pool foundation. The County Board of Health may allow lesser or require greater distances after a site inspection (Georgia DPH, Rules 511-3-1-.05(2) and .07(3)). The manual also notes that the County may require larger lots when pools or outbuildings are proposed.

Sources: Angi, in-ground pool cost; Angi, French drain cost; Angi, salt pool conversion cost (add-on list); Angi, pool fence cost. Ranges are attributed to the publisher named; they are national or regional estimates compiled by that publisher, not quotes and not prices from any provider on this site. Stormwater design, infiltration testing and detention costs vary by site and are not included.

Local rules and code references

• City of Alpharetta, Residential Individual Lot Site Plan Requirements: impervious area chart, 1,000 and 5,000 sq ft stormwater thresholds, pervious paver documentation, septic field location on plans.
• City of Alpharetta, Stormwater Policy Handbook: Section 18 pervious surfaces and pavers; Section 20 permit triggers, 2-year cumulative impervious calculation; UDC Art. III §3.3.
• City of Alpharetta, Swimming Pool Permitting & Inspections (revised 2026): pool setbacks, easements, buffers, septic approval, specimen trees, retaining walls.
• Georgia DPH, Manual for On-Site Sewage Management Systems: Rule 511-3-1-.05(2) septic tank location; Rule 511-3-1-.07(3) absorption field 15 ft from a swimming pool foundation.
• Alpharetta Unified Development Code (Municode): zoning district lot coverage and Article III §3.3 stormwater.

Code text, policy forms and department procedures change. Confirm current requirements with the jurisdiction, your insurer or the utility before work starts.