Building envelope
A building envelope is the part of a lot where a building may go once the required setbacks, the ground set aside for sewage, and any other recorded limits are taken out. The phrase is working vocabulary, not a term defined in the Virginia statutes or county ordinances that set those limits.
The ground a lot has left once every line is drawn in
Picture the whole lot, then shade every strip where a building may not stand. The unshaded part in the middle is the building envelope. It is shorthand, not statute: the county ordinances on this page do not use the phrase, and speak instead of setbacks, reserve areas and designated locations.
The first strip to shade is the setback, which Carroll County's subdivision ordinance measures from a street right-of-way or the boundary of adjacent property.
Counties set different distances and measure them from different lines, so an envelope sketched under one county's rules does not carry across a county line. The distances locality by locality are set out in how close to the property line you can build.
The next strip is the ground an onsite septic system needs. Carroll County's subdivision ordinance requires a drainfield reserve area equal to 50 percent of the required and permitted field, and no structure may be built on it. That reserve is defined on its own under septic reserve area.
- Setbacks from the street or road and from the lot lines, measured the way that locality measures them.
- Sewage ground: the drainfield site and, where required, its reserve area.
- Recorded limits shown on the plat or written into the deed.
When a Carroll plat already marks where the buildings go
On some Carroll County plats the envelope is close to drawn already, because where sewage is not public sewer the ordinance requires each lot's building locations, water source and wastewater disposal facilities to be designated on the plat.
Larger lots are handled differently. Where every lot in a subdivision is greater than five acres, the plat need not show on-site water and sewer or the setback line on each lot, and carries notes instead, one of them saying the lots have not been evaluated for on-site water and sewer.
A lot made by a family subdivision in Carroll County is no exception: the ordinance says all of its other requirements apply to the lot created, so the same building distances shape what is left to build on.
The envelope takes on a sharper edge when a new line is drawn around a house that already stands. Where that line runs decides how close the house sits to its new boundary and whether its septic ground stays inside the house lot, which is part of weighing whether to sell the house with the acreage or separately, or to sell the farm and keep the house. How to find each of these cuts on a real lot, one record at a time, is covered in what a building envelope is on a lot you own.
Wondering how much of a lot is left to build on?
Send the county and the plat book and page, or a photo of the plat, and Lowell will go over what the recorded lines take out and what they leave on that lot. No cost, no obligation.
Got it. Thank you.
We'll be in touch shortly with an honest read.
Questions about this term
Can the room left to build on be smaller than the setbacks alone would leave?
Yes. Setbacks are only one cut. Ground held for sewage, the drainfield and the reserve area Carroll County's subdivision ordinance requires for it, comes out of the room the setbacks leave, and so does any line or restriction recorded on the plat or in the deed.
Where this page's facts come from
Every rule, office and figure above traces to one of these. Rules change; check the office before you act on one.
- Subdivision Ordinance, April 14, 2014 (setbacks, building locations, reserve areas, family subdivisions) Carroll County, Virginia
- Building Inspections (setbacks) Floyd County, Virginia