Setback and Lot Coverage Visualiser
Two numbers decide how much of a lot you can build on, and they are not the same number. Enter your lot dimensions and the setbacks for your zoning district to draw the area that is actually left to build in, see whether your proposed structure fits it, and run both caps on your own figures rather than on an average.
Enter the lot dimensions and the three setbacks to draw the plan. Use the figures from your zoning district or your survey — these shapes are drawn from your own numbers.
How each project type is usually counted
The two caps diverge because they regulate different things. Where the answer depends on the material you choose, it is marked as such.
| Project type | Counts toward coverage | Counts toward impervious | Why |
|---|---|---|---|
| Detached ADU or backyard cottage | Usually yes | Usually yes | A dwelling unit is a roofed structure, so it usually counts toward both numbers. |
| Shed or storage building | Usually yes | Usually yes | Small structures are often exempt from coverage while under a size threshold, and that exemption is local. |
| Deck or patio | Usually yes | Depends on the material | Boards spaced so water passes between them are treated as pervious in some codes and not in others. |
| Swimming pool | Usually yes | Usually yes | The water surface is impervious. Whether the surrounding deck counts depends on the material. |
| Driveway or parking pad | Usually no | Depends on the material | Compacted gravel and permeable pavers are credited as pervious in some codes and not in others. |
| Fence or wall | Usually no | Usually no | Fences normally fall outside both calculations, but they are regulated by height and sight-distance rules instead. |
| Chicken coop or run | Usually yes | Depends on the material | A roofed coop usually counts; an open run on bare ground may not. |
| Tree canopy or planting | Usually no | Usually no | Planting is generally credited as pervious, and some codes require a minimum landscaped area. |
The defaults used above are 35% coverage and 50% impervious surface. Typical caps are shown because many codes set a percentage rather than a fixed area. The cap that applies to your parcel is set by your zoning district, not by these defaults. For the reasoning behind the two numbers, read Lot Coverage and Impervious Surface, or use the permit threshold screener to check whether your project needs a permit at all.
Frequently asked questions
What is the buildable envelope?
It is the area left on your lot after every setback has been applied — front, rear and both sides. Anything you build has to sit inside it unless you obtain a variance. The size of the envelope, not the size of the lot, is what usually decides whether a project fits.
Is lot coverage the same as impervious surface?
No. Lot coverage is a bulk control measuring what buildings and structures occupy or overhang. Impervious surface is a drainage control measuring what water cannot pass through. A driveway usually counts toward impervious surface but not coverage, while an overhanging upper floor can do the reverse. Both have to be checked.
Why is my impervious figure shown as a range?
For some project types the answer turns on the material rather than the category. Spaced deck boards, permeable pavers and compacted gravel are credited as pervious in some codes and not in others. Rather than pick one, the tool shows both ends of the range so you know what to ask about.
My project does not fit the envelope. What are my options?
The usual routes are a smaller footprint, a different siting within the envelope, or a variance. A variance requires a hardship specific to the property rather than one created by the design, so it is worth exhausting the first two before applying.
How accurate is the drawing?
It is a scaled schematic, not a survey. The house is drawn on the front setback line and the proposed structure against the rear, which is the usual arrangement but may not be yours. Easements, trees, drainage and existing structures can all rule out a spot that the envelope permits.
ZoneFig provides general reference information, not legal advice. Yard and zoning rules are adopted locally, so the only binding answer for your address comes from your city, town or county planning and building department. Typical thresholds shown here describe patterns across many jurisdictions and are not the rule at any specific property.