The two coverage limits
Lot coverage counts everything that covers the ground: the house, garage, porches, decks above a certain height, driveway and patios. Main building footprint counts only the house itself. Each has a percentage limit, and the footprint also has a hard cap in square feet (Arlington County Zoning Ordinance).
| District | Standard lot | Lot coverage | House footprint | Footprint cap | With front porch |
|---|---|---|---|---|---|
| R-5 | 5,000 sq ft | 45% | 34% | 2,380 sq ft | 37%, 2,590 sq ft |
| R-6 | 6,000 sq ft | 40% | 30% | 2,520 sq ft | 33%, 2,772 sq ft |
| R-8 | 8,000 sq ft | 35% | 25% | 2,800 sq ft | 28%, 3,136 sq ft |
| R-10 | 10,000 sq ft | 32% | 25% | 3,500 sq ft | 28%, 3,920 sq ft |
| R-20 | 20,000 sq ft | 25% | 16% | 4,480 sq ft | 19%, 5,320 sq ft |
A qualifying front porch and a rear garage each earn extra coverage, which is why so many new Arlington houses have both. The height limit in these districts is 35 feet.
Worked examples
- A 6,000 sq ft lot in R-6: the house footprint can be 30%, or 1,800 sq ft. With a qualifying front porch, 33%, or 1,980 sq ft. On two floors plus a basement that is roughly 5,400 to 5,900 sq ft of floor area.
- A 7,000 sq ft lot in R-6: 30% is 2,100 sq ft, under the 2,520 sq ft cap.
- A 12,000 sq ft lot in R-10: 25% would be 3,000 sq ft, under the 3,500 sq ft cap.
- A 9,000 sq ft lot in R-6: 30% would be 2,700 sq ft, but the cap stops it at 2,520 sq ft (2,772 with a porch).
Undersized lots get the same footprint as a standard lot in the district, as long as the house still meets the setbacks. So a 5,000 sq ft lot in R-6 can still have the footprint allowed on a 6,000 sq ft lot.
The lot checker reads the zoning and lot size for an Arlington address and does this math for you.
Land disturbance: the 2,500 square foot line
Arlington requires a Land Disturbing Activity (LDA) stormwater permit for any project that disturbs 2,500 square feet of land or more. Between 2,000 and 2,499 square feet you need a surveyor to certify the disturbed area. The county’s rule of thumb is that a new building footprint of about 1,000 square feet or more usually crosses the 2,500 square foot line (Arlington LDA FAQs). In practice, every new house needs one.
Projects over 2,500 square feet also fall under Arlington’s Chesapeake Bay Preservation Ordinance, which requires a tree conservation and planting plan reviewed by the county’s urban forestry staff (Arlington tree FAQs).
What this means when you buy a teardown
- Get the zoning district and the lot size first. They set the largest house you can build.
- Check for easements and a Resource Protection Area near streams, which can shrink the usable area.
- Budget for stormwater measures and tree replanting; they are part of every LDA permit.
- Ask builders who work in Arlington. Our permit records show which builders have built here recently.
