ASCE 7-22 Compliant Analysis

Townhome End Units Face 40% Higher Wind Pressures

Per ASCE 7-22, townhome end units in Palm Beach County (150-175 MPH design wind speed) require significantly more structural capacity than interior units. The exposed corner wall creates Zone 5 pressures up to -165 psf while interior units stay in Zone 4 at -95 psf. Missing this difference means undersized shear walls and failed inspections.

Calculate End Unit Loads See Unit Comparison

End Unit vs Interior Unit Wind Loads

Side-by-side comparison per ASCE 7-22 for Palm Beach County 175 MPH wind zone

Higher Requirements

End Unit Townhome

Parameter	Value
Corner Zone Pressure	-165 psf
Shear Wall Required	28 lin ft
Hold-Down Capacity	10,500 lbs
Foundation Depth	24 inches

Standard Requirements

Interior Unit Townhome

Parameter	Value
Field Zone Pressure	-95 psf
Shear Wall Required	16 lin ft
Hold-Down Capacity	6,200 lbs
Foundation Depth	18 inches

Design Parameter	End Unit	Interior Unit
Exposed Exterior Walls	2 walls (front + side)	1 wall (front only)
Party Wall Benefit	1 side only	Both sides
Corner Zones (Zone 5)	2 zones on exposed wall	0 zones (all Zone 4)
Max Negative Pressure	-165 psf	-95 psf
Shear Wall Length (N-S)	28 linear feet	16 linear feet
Shear Wall Length (E-W)	24 linear feet	16 linear feet
Anchor Bolt Spacing	4 ft on center	6 ft on center
Hold-Down Capacity	10,500 lbs min	6,200 lbs min
Footing Depth	24 inches	18 inches
Window DP Rating (exposed)	DP +60/-90	DP +45/-65
Estimated Cost Premium	+$8,000-12,000	Baseline

Understanding Corner Zone Pressures

Why the exposed end wall creates dramatically higher wind loads

WIND

Zone 5

End

Int

End

Zone 5 (Corner)

Zone 4 (End Wall)

Interior (Protected)

ASCE 7-22 Zone Definitions for Townhomes

Per ASCE 7-22 Figure 30.3-1, corner zones (Zone 5) extend a distance "a" from each building corner. For a typical 22-foot wide, 35-foot tall townhome, this creates corner zones approximately 3.5 feet wide on each side of the exposed corner. Wind separating around these corners creates vortices that generate suction pressures 40-60% higher than field zones.

Interior units benefit from the "shielding effect" of adjacent units. Their exterior wall sees only Zone 4 pressures because there are no exposed corners. The party walls on both sides also provide continuous lateral bracing, reducing the shear wall requirements for each individual unit.

Zone 5 Negative Pressure

-165 psf

Zone 4 Negative Pressure

-95 psf

Pressure Difference

+74%

Zone 5 Width

3.5 ft

End Unit Structural Requirements

What Palm Beach County inspectors expect to see on end unit plans

Increased Shear Wall Length

End units require 40-60% more shear wall capacity than interior units. For a 22-foot wide unit, expect 24-28 linear feet versus 16 feet for interior units. Walls must be continuous from foundation to roof.

28 ft minimum

Deeper Foundations

Higher overturning moments require deeper footings. End units typically need 24-inch minimum depth versus 18 inches for interior units. Grade beams may be required to distribute concentrated corner loads.

24 inch depth

Enhanced Hold-Downs

Shear wall ends require hold-down brackets rated for 10,000+ lbs uplift capacity. Simpson HD10 or equivalent required at each end of designated shear wall segments on the exposed wall side.

10,500 lbs capacity

Anchor Bolt Spacing

Tighter anchor bolt spacing on the exposed wall: 4 feet on center maximum versus 6 feet for interior walls. All anchor bolts must be 5/8" diameter minimum with 7" minimum embedment.

4 ft on center

Higher Window Ratings

Windows on the exposed end wall need DP +60/-90 ratings for Zone 5 areas. This is 40% higher than interior unit windows at DP +45/-65. All windows still require large missile impact protection.

DP +60/-90

Roof-to-Wall Connections

Hurricane straps on the exposed wall must be rated for higher uplift: H10 or equivalent at each rafter/truss. Spacing should not exceed 24 inches on center along the exposed wall.

H10 at 24" OC

Townhome End Unit FAQs

Common questions about end unit wind load requirements in Palm Beach County

Townhome end units have an exposed exterior wall that interior units do not. Per ASCE 7-22, this exposed wall creates corner zones (Zone 5) with pressures 40-60% higher than field zones (Zone 4). End units also lose the lateral bracing benefit of adjacent units on one side, requiring more shear wall capacity. In Palm Beach County with 150-175 MPH design wind speeds, an end unit may need 25-35 linear feet of shear wall versus 15-20 feet for an interior unit.

Party walls (shared walls between townhome units) provide significant structural benefits. They act as continuous shear walls that transfer lateral loads between units, creating a rigid diaphragm effect. Interior units are braced on both sides by adjacent units, reducing their individual shear wall requirements by approximately 30-40%. However, end units only benefit from one party wall and must provide additional shear resistance on their exposed side.

Per ASCE 7-22 Figure 30.3-1, corner zones (Zone 5) extend a distance "a" from building corners, where "a" is the lesser of 10% of the least horizontal dimension or 0.4h (40% of mean roof height). End units have two corner zones on their exposed wall, while interior units have none on their party walls. In Palm Beach County, Zone 5 pressures can reach -165 psf negative pressure versus -95 psf for Zone 4 interior zones.

End unit foundations must resist higher overturning moments due to the exposed wall catching wind. This typically requires: deeper footings (24 inches minimum versus 18 inches for interior), more anchor bolts (spacing of 4 feet versus 6 feet), larger hold-down capacities (10,000+ lbs versus 6,000 lbs), and sometimes grade beams to distribute concentrated loads. The foundation design must account for both wind uplift and lateral sliding forces.

In Palm Beach County (150-175 MPH wind zone), end unit townhomes typically require 40-60% more shear wall length than interior units. For a typical 22-foot wide townhome, an interior unit might need 16 linear feet of shear wall in each direction, while an end unit needs 24-28 linear feet. The exact amount depends on building height, roof geometry, and whether the end unit is at a building corner or mid-row end position.

Yes. Windows and doors on the exposed end wall of an end unit face corner zone pressures (Zone 5) rather than interior zone pressures (Zone 4). In Palm Beach County, this means end unit windows may require DP +60/-90 ratings versus DP +45/-65 for interior units. Doors on end walls, especially within 3-4 feet of corners, need the highest ratings. All openings still require large missile impact protection per Florida Building Code.