Flagpole Foundation Dimensions
Reference dimensions for Ground Set and Shoe Base flagpole foundations.
A flagpole's long-term stability depends on a properly sized foundation. The dimensions below are based on NAAMM's Metal Flagpole Manual recommendations for typical soil conditions and should be verified for your specific site by a structural engineer.
What's covered
Ground Set
Ground Set installations are the most robust and widely used flagpole mounting method. This installation involves burying the flagpole shaft in a concrete foundation, with the depth of the burial equal to 10% of the flagpole's mounting height.
Foundation Dimensions
| Flagpole Mounting Height | A | B | C | D |
|---|---|---|---|---|
| 20'-0" | 2'-0" | 2'-6" | 30" | 24" |
| 25'-0" | 2'-6" | 3'-0" | 36" | 24" |
| 30'-0" | 3'-0" | 3'-6" | 36" | 24" |
| 35'-0" | 3'-6" | 4'-0" | 36" | 30" |
| 40'-0" | 4'-0" | 4'-6" | 45" | 36" |
| 45'-0" | 4'-6" | 5'-0" | 45" | 36" |
| 50'-0" | 5'-0" | 5'-6" | 50" | 42" |
| 60'-0" | 6'-0" | 6'-6" | 60" | 48" |
| 70'-0" | 7'-0" | 7'-6" | 60" | 48" |
| 80'-0" | 8'-0" | 8'-6" | 72" | 48" |
25' Mounting Height Exception
- Single-Piece Construction: Flagpoles offered in 25' mounting heights are manufactured in a single piece with an overall length of 26'-6". Below grade, 2'-6" will be inserted into the ground sleeve.
- Nominal Height: When the truck and finial are attached, the nominal height of the completed flagpole will be 25'.
- Shipping: This industry accepted standard allows shipping in a pup trailer at a significant freight savings. Full 27'-6" shafts are available upon request.
Use the dimensions above as a starting point, and confirm final foundation requirements with a structural engineer based on your local soil conditions.
NAAMM's Metal Flagpole Manual offers basic suggestions on foundation measurements in firm, dry soil only using dry tamped sand and 3000 PSI concrete. Soil conditions vary by site. Exact foundation requirements should be verified by a Structural Engineer with knowledge of soil conditions in your locality.
Shoe Base
Shoe Base installations are typically used when an above ground installation is required. The flagpole bolts to anchor bolts embedded in concrete, with a welded base casting held in place by nuts and washers.
Foundation Dimensions
| Flagpole Butt Dia. | AA Base Square | BB Base Height | CC Bolt Projection | Bolt Dimensions (Dia. x Length x Hook Length) |
Bolt Circle Dia. |
|---|---|---|---|---|---|
| 4" | 7-1/2" | 3" | 2" | 3/4" x 17" x 3" | 6-1/2" - 8" |
| 5" | 7-1/2" | 3" | 2" | 3/4" x 17" x 3" | 7-1/2" - 8" |
| 6" | 9-3/4" | 3-1/2" | 2-3/4" | 1" x 36" x 4" | 9" - 10" |
| 7" | 10-1/2" | 3-11/16" | 2-3/4" | 1" x 36" x 4" | 10" - 11" |
| 8" | 11-1/4" | 3-15/16" | 2-3/4" | 1" x 36" x 4" | 11" - 12" |
| 10" (Up to .250" Wall) | 14" | 4-7/8" | 3-1/4" | 1" x 48" x 4" | 14" - 15" |
| 10" (.312" Wall & Larger) | 14" | 4-7/8" | 3-1/4" | 1-1/4" x 48" x 6" | 14" - 15" |
| 12" | 7-1/2" | 3" | 2" | 1-1/4" x 48" x 6" | 16" - 18" |
Compatible Flagpoles
- Size Range: All 20' to 80' flagpoles with a 4"+ butt diameter can be provided in a shoe base installation option.
- When to Use: Shoe base installations are commonly used on parking decks, plazas, and other surfaces where excavation for a ground sleeve isn't possible.
As with ground set installations, exact bolt sizes and base requirements should be confirmed by a structural engineer for your specific project.
Shoe base dimensions vary based on butt diameter, wall thickness, and project wind load requirements. Always verify final specifications with a structural engineer.
