Building Diagram Number: Difference between revisions

Revision as of 08:56, 10 December 2024

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Building Diagram Numbers are used to classify a building’s foundation type on Elevation Certificates.

Why do they still matter?

Foundation Typing: Essential for documenting and communicating a building’s structural setup.
Floodplain Management: Helps identify mitigation needs like elevation, venting, or floodproofing.
Policy Documentation: Useful for underwriters and agents when verifying compliance with NFIP requirements.


Number	Foundation Type	Key Features
1A	Slab on Grade	Bottom floor directly on the ground, no additional fill used. Often seen in flat areas.
1B	Slab on Stemwall OR Slab on Fill	Concrete slab poured over a stem wall foundation, often with earthen fill mounded inside the stem wall.
2A	Basement	The bottom floor is below ground level (grade) on all sides. The basement level measures more than five feet to the floor above it.
2B	Basement with sub-grade egress	The bottom floor is below ground level on all sides, and the area of egress is also below grade on all sides. This also applies to buildings with negative flow.
3	Split-level Slab	The building layout has an intermediate level between an upper and lower floor. The lowest floor sits at or above ground level.
4	Split-level Basement	The building layout has an intermediate level between an upper and lower floor. The lowest floor sits below ground level on all sides.
5	Elevated without Enclosure	The area below the elevated floor is open, with no obstruction to the flow of floodwaters. Open lattice and insect screening is permissible. "Pier and beam" foundations.
6	Elevated on Piers, Posts, or Piles with Enclosure	The elevated floor is raised by piers, posts, or piles. An area below the elevated floor is enclosed, either partially (a portion of the building footprint) or fully (encloses the entire building footprint). The enclosure measures more than five feet to the floor above it.
7	Elevated on Solid Perimeter Walls	The elevated floor is raised by solid perimeter, load-bearing walls, which also enclose the area below the elevated floor. The enclosure measures more than five feet to the floor above it. Walk-out basements qualify as this diagram number (see below).
8	Above-grade Crawlspace	The main floor is raised above ground by any method, so long as the crawlspace (enclosure) floor sits at or above the surrounding grade. The crawlspace measures five feet or less to the floor above it.
9	Subgrade Crawlspace	The floor above the crawlspace is raised above ground by any method, but the crawlspace floor sits below the surrounding grade on all sides, like a basement. Subgrade crawlspaces must conform to the 2-foot/5-foot rule (see below).

This page contains information about the NFIP. Find more NFIP Resources.

@@ Line 6: / Line 6: @@
 * '''Floodplain Management''': Helps identify mitigation needs like elevation, venting, or floodproofing.
 * '''Policy Documentation''': Useful for underwriters and agents when verifying compliance with NFIP requirements.
+{| class="wikitable"
-== Diagram 1A: Slab-on-Grade  ==
+|+
+!Number
-* '''Key Features''':
+!Foundation Type
-** Bottom floor directly on the ground, no additional fill used.
+!Key Features
-** Often seen in non-coastal, flat areas.
+!Image
-* '''Example Uses''': Standard residential construction in low-risk areas.
+|-
+|1A
-== Diagram 1B: Slab-on-Stemwall ==
+|Slab on Grade
+|Bottom floor directly on the ground, no additional fill used. Often seen in flat areas.
-* '''Key Features''':
+|
-** Bottom floor elevated with fill but at ground level on one side.
+|-
-** Used to reduce flood exposure.
+|1B
-* '''Example Uses''': Homes in areas with minor flood risks.
+|Slab on Stemwall OR
+Slab on Fill
-== Diagram 2A: Full Basement ==
+|Concrete slab poured over a stem wall foundation, often with earthen fill mounded inside the stem wall.
+|
-* '''Key Features''':
+|-
-** Fully below ground level (subgrade) on all sides.
+|2A
-** High flood exposure due to water intrusion risks.
+|Basement
-* '''Example Uses''': Common in older residential structures in flood zones.
+|The bottom floor is below ground level (grade) on all sides. The basement level measures more than five feet to the floor above it.
+|
-== Diagram 3: Split-Level Slab-on-Grade ==
+|-
+|2B
-* '''Key Features''':
+|Basement with sub-grade egress
-** Multi-level design with no part below grade.
+|The bottom floor is below ground level on all sides, and the area of egress is also below grade on all sides. This also applies to buildings with negative flow.
-** Lower levels directly on the ground.
+|
-* '''Example Uses''': Residential homes with uneven interior levels.
+|-
+|3
-== Diagram 4: Split-Level Basement ==
+|Split-level Slab
+|The building layout has an intermediate level between an upper and lower floor. The lowest floor sits at or above ground level.
-* '''Key Features''':
+|
-** One portion of the structure includes a subgrade basement.
+|-
-** Other levels are at or above ground.
+|4
-* '''Example Uses''': Homes built on sloped lots.
+|Split-level Basement
+|The building layout has an intermediate level between an upper and lower floor. The lowest floor sits below ground level on all sides.
-== Diagram 5: Elevated on Piers or Posts (Open) ==
+|
+|-
-* '''Key Features''':
+|5
-** Elevated structure on piers, posts, or pilings with no enclosed area underneath.
+|Elevated without Enclosure
-** Designed for high flood zones or coastal regions.
+|The area below the elevated floor is open, with no obstruction to the flow of floodwaters. Open lattice and insect screening is permissible. "Pier and beam" foundations.
-* '''Example Uses''': Beach houses or properties in velocity flood zones.
+|
+|-
-== Diagram 6: Elevated on Piers or Posts (Enclosed) ==
+|6
+|Elevated on Piers, Posts, or Piles with Enclosure
-* '''Key Features''':
+|The elevated floor is raised by piers, posts, or piles. An area below the elevated floor is enclosed, either partially (a portion of the building footprint) or fully (encloses the entire building footprint). The enclosure measures more than five feet to the floor above it.
-** Elevated on piers with a partially or fully enclosed area below.
+|
-** Requires proper venting to equalize hydrostatic pressure.
+|-
-* '''Example Uses''': Homes in coastal or flood-prone inland areas.
+|7
+|Elevated on Solid Perimeter Walls
-== Diagram 7: Elevated with Walkout Basement ==
+|The elevated floor is raised by solid perimeter, load-bearing walls, which also enclose the area below the elevated floor. The enclosure measures more than five feet to the floor above it. Walk-out basements qualify as this diagram number (see below).
+|
-* '''Key Features''':
+|-
-** Basement partially below grade on some sides, with direct outdoor access via a fully above-grade wall.
+|8
-** The ground slopes away from the building.
+|Above-grade Crawlspace
-* '''Example Uses''': Structures on hilly terrain.
+|The main floor is raised above ground by any method, so long as the crawlspace (enclosure) floor sits at or above the surrounding grade. The crawlspace measures five feet or less to the floor above it.
+|
-== Diagram 8: Non-Elevated with Attached Garage ==
+|-
+|9
-* '''Key Features''':
+|Subgrade Crawlspace
-** Ground-level structure with a garage attached that could be below the main floor.
+|The floor above the crawlspace is raised above ground by any method, but the crawlspace floor sits below the surrounding grade on all sides, like a basement. Subgrade crawlspaces must conform to the 2-foot/5-foot rule (see below).
-** Susceptible to flooding in garage and adjacent spaces.
+|
-* '''Example Uses''': Suburban homes with drive-under garages.
+|}
+*
 {{nfip}}