Sawtooth (monitor) roofs in Miami-Dade's High-Velocity Hurricane Zone require multi-bay wind pressure analysis per ASCE 7-22 Section 27.3, with each ridge-valley combination creating unique aerodynamic zones. At 180 MPH basic wind speed, clerestory glazing must carry Miami-Dade NOA with large missile impact certification, and engineers must evaluate progressive failure cascade scenarios where a single broken panel shifts internal pressure coefficients from +0.18 to +0.55, potentially overloading adjacent bays in sequence.
Animated cross-section of a 3-bay sawtooth roof showing wind acceleration between ridges, external pressure coefficients on each surface, and internal pressure buildup during clerestory failure.
ASCE 7-22 distinguishes sawtooth roofs from standard gable and hip configurations because each bay generates its own windward, leeward, and interior flow pattern. The code provides specific external pressure coefficients through Figure 27.3-4 for multi-span gable roofs, which engineers adapt for the asymmetric sawtooth profile where one face slopes gradually while the opposing face rises vertically.
For the Main Wind Force Resisting System, ASCE 7-22 assigns different Cp values to each surface of each bay depending on its position in the multi-span array. The windward bay sloped surface carries Cp values between -0.9 and -1.3 depending on the roof angle (typically 15 to 25 degrees for sawtooth profiles). Interior bay sloped surfaces see reduced values of -0.7 to -1.0 as the upstream ridges partially shelter them. The leeward bay sloped surface experiences Cp of -0.5 to -0.7.
The vertical clerestory walls between bays behave as wall elements: the windward clerestory face carries positive pressure (Cp = +0.7 to +0.8), while the leeward clerestory face sees suction (Cp = -0.3 to -0.5). These opposing pressures on a single vertical element create significant net forces that the clerestory framing must resist.
Each roofing panel and clerestory glazing unit is treated as a component and cladding element under ASCE 7-22 Section 30.3. The GCp values from Table 30.3-2A apply, but the zone boundaries must be mapped to each bay individually. This means a 5-bay sawtooth building has 15 distinct zone maps (three zones per bay on the sloped surface, three on the vertical face, and overlap zones at ridge-valley intersections).
Corner zones (Zone 3) on the outermost bays of the building produce the highest component loads. For a sawtooth building in Miami-Dade's HVHZ with 180 MPH wind speed, Zone 3 GCp values can yield net design pressures exceeding -85 psf on the outermost sloped roof panels. Interior bay field zones (Zone 1) typically see -35 to -50 psf, which is still substantial compared to standard flat roof field pressures.
Enclosed building: GCpi = ±0.18. Partially enclosed (single breach): GCpi = +0.55 / -0.55. The 205% increase from +0.18 to +0.55 dramatically changes net roof pressures. FBC 2023 Section 1620.2 requires engineers to evaluate the partially enclosed condition for any building with glazing in the HVHZ.
Each bay of a sawtooth roof encounters a fundamentally different aerodynamic environment. The windward bay faces unobstructed flow, interior bays sit in the turbulent wake of upstream ridges, and the leeward bay experiences mixed effects from all preceding bays. This variance demands individual analysis rather than blanket application of a single Cp value across the entire roof.
The first bay faces the incoming wind directly. The sloped roof surface experiences maximum suction as air accelerates over the leading ridge. The vertical clerestory wall behind Bay 1 receives the highest positive pressure of any clerestory in the array, creating a combined push-pull that maximizes net force on this bay's structure.
Interior bays experience reduced but erratic wind patterns. The upstream ridge creates a separation bubble that reattaches partway along the next sloped surface, producing localized high-suction zones. Wind accelerating through the valley between ridges creates a venturi effect, with velocities 1.2 to 1.5 times the free-stream speed in these acceleration corridors.
Leeward bays operate within the accumulated wake of all upstream ridges, resulting in lower mean pressures but higher turbulence intensity. While average Cp values decrease, the peak fluctuating pressures can still govern design. The final bay's trailing edge creates a unique flow separation pattern that affects both the roof surface and the building's overall drag coefficient.
The most dangerous aspect of sawtooth roof design in hurricane zones is progressive failure. Unlike a simple building where one window breach creates a single internal pressurization event, a sawtooth building with multiple clerestory bays can experience cascading failures where each breach amplifies loads on the next bay. ASCE 7-22 Section 26.12 and FBC 2023 Section 1620.2 require designers to evaluate this scenario.
Each stage compounds the damage, turning a localized breach into a building-wide structural emergency.
A single clerestory glazing panel fails due to missile impact or pressure exceedance. Wind enters the bay at the breached opening, pressurizing the interior. Building classification shifts from enclosed (GCpi = +0.18) to partially enclosed (GCpi = +0.55).
+205% internal pressureThe increased internal pressure pushes outward against roof panels and clerestory glazing in adjacent bays. Net suction on the roof increases from approximately -45 psf to -75 psf in field zones. Glazing in the next bay now faces combined internal push and external suction that may exceed its rated design pressure.
Net uplift: +67%If the adjacent clerestory or roof panel fails, the opening area doubles. The building now has two dominant openings, potentially reclassifying internal pressure conditions further. Wind channels through both breaches, creating cross-ventilation that sustains high internal velocities and pressures even during lulls in the external wind.
Opening area: 2xWith multiple bays breached, purlin connections and rafter seats experience loads far beyond their design capacity. Roof panel uplift propagates from compromised fasteners outward. The entire roof system is at risk of progressive peeling failure, where each panel lost reduces the load path for its neighbors, accelerating the sequence.
System failure risk: CriticalSawtooth roofs demand multiple purlin schedules because wind zone boundaries repeat at each bay. A 5-bay building may require three distinct purlin sizes, with the heaviest sections concentrated at the outermost bay corners and ridge-valley intersections. ASCE 7-22 Table 30.3-2A governs component pressures, and effective wind area determines whether a purlin sees Zone 1, Zone 2, or Zone 3 loading.
| Location | Wind Zone | GCp (Net) | Design Pressure | Purlin Size | Spacing |
|---|---|---|---|---|---|
| Bay 1 Corner (outer) | Zone 3 | -2.98 | -87.2 psf | 12ZS3.25x105 | 3'-0" o.c. |
| Bay 1 Ridge Edge | Zone 2 | -2.35 | -68.8 psf | 10ZS2.75x090 | 3'-6" o.c. |
| Bay 1 Field | Zone 1 | -1.60 | -46.8 psf | 8ZS2.50x075 | 4'-6" o.c. |
| Interior Bay Ridge | Zone 2 | -2.10 | -61.5 psf | 10ZS2.75x090 | 3'-6" o.c. |
| Interior Bay Field | Zone 1 | -1.40 | -41.0 psf | 8ZS2.50x060 | 5'-0" o.c. |
| Leeward Bay Field | Zone 1 | -1.20 | -35.1 psf | 8ZS2.25x060 | 5'-0" o.c. |
Values based on 180 MPH basic wind speed, Exposure C, mean roof height 30 ft, Risk Category II per ASCE 7-22. Actual values require site-specific analysis.
Every clerestory window in a Miami-Dade HVHZ sawtooth building must carry a Notice of Acceptance demonstrating compliance with both design pressure and large missile impact requirements per FBC 2023 Section 1626. The elevated position of clerestory glazing between sawtooth bays makes it particularly vulnerable to wind-borne debris, and its failure initiates the progressive cascade that threatens the entire roof system.
Miami-Dade HVHZ requires large missile testing per TAS 201: a 9-pound 2x4 lumber projectile fired at 50 feet per second. Clerestory glazing typically uses laminated glass with PVB interlayer (minimum 0.060" thickness) or polycarbonate inner lites. The NOA must cover the specific glass configuration, frame type, and maximum panel size installed in the sawtooth wall.
Each clerestory panel faces different wind loads depending on its bay position. Windward bay clerestory glazing sees the highest positive pressure (up to +48 psf at 180 MPH). The NOA's rated design pressure must equal or exceed the calculated pressure for that panel's specific location. A single NOA product may not cover all bay positions if the windward bay pressure exceeds the product's rating.
Clerestory window frames in sawtooth walls must transfer wind loads to the structural column or stud below. Aluminum storefront systems are common, but each frame-to-structure connection must be engineered for the design pressure plus a safety factor. The connection detail must appear on the permit drawings and match the NOA's tested configuration. Deviation from the tested assembly voids the acceptance.
Even when glazing survives impact, water infiltration through clerestory seals can cause extensive interior damage to manufacturing equipment and inventory. FBC 2023 Section 1625.2 requires pressure-equalized drainage in the glazing system. Sawtooth clerestories are especially susceptible because rain driven upward by wind flows directly into the vertical glazing face rather than sheeting off as it does on sloped surfaces.
Despite the engineering complexity, sawtooth roofs remain popular for industrial and creative-use buildings in South Florida. The north-facing clerestory design brings abundant natural daylight without direct solar heat gain, reducing cooling costs in Miami-Dade's hot climate. Understanding which building types commonly adopt this profile helps engineers anticipate the unique loads and occupancy conditions they will encounter.
Factories, food processing plants, and heavy manufacturing operations favor sawtooth roofs for daylight-intensive production lines. Bay widths of 30 to 60 feet accommodate overhead crane systems, and the roof height variation allows natural ventilation stack effects. In Miami-Dade, these buildings typically fall under Risk Category II or III depending on the occupancy count and hazardous material storage.
The Wynwood, Little Haiti, and Allapattah arts districts have seen adaptive reuse of older sawtooth buildings into maker spaces, art studios, and event venues. New construction mimics the sawtooth form for its aesthetic appeal and daylighting qualities. These creative-use buildings often have lower occupancy loads but introduce large open-span requirements and unconventional interior layouts that affect internal pressure distribution.
The vertical walls between sawtooth bays are the structural linchpin of the entire roof system. Each vertical wall must simultaneously resist positive wind pressure on its windward face, negative pressure on its leeward face, support the upper ridge framing of one bay and the eave of the next, and carry gravity loads from clerestory glazing and any mechanical equipment mounted at the ridge line. Failure of this element compromises two adjacent bays simultaneously.
Wind loads on the vertical clerestory wall transfer through a defined load path: glazing to frame, frame to structural stud or column, column to rafter/truss connection at the ridge, and down through the column to the foundation. At each connection point, the engineer must verify that fastener capacity exceeds the demand. For steel-framed sawtooth buildings, moment-resisting connections at the column-to-rafter joint are common because the eccentric loading from the asymmetric roof profile creates significant bending moments.
ASCE 7-22 Section 27.3.2 requires that the MWFRS analysis account for the combined effects of external pressure on the roof slope, external pressure on the vertical wall, and internal pressure acting on all interior surfaces. The critical load combination for the vertical wall typically involves maximum positive external pressure combined with maximum negative internal pressure, per ASCE 7-22 load combinations in Section 2.3.
The sloped roof deck between ridges acts as a diaphragm transferring lateral wind loads to the vertical walls at each end of the bay. However, the sloped orientation reduces the horizontal component of diaphragm shear compared to a flat roof. For a typical 20-degree sawtooth slope, the horizontal diaphragm capacity is reduced to cos(20) = 0.94 of the flat capacity, which is usually acceptable. Steeper slopes require explicit diaphragm analysis.
Metal roof deck panels running perpendicular to the ridges provide diaphragm action. The connection of these panels to purlins and to the ridge and valley framing members is critical. Side-lap fasteners between adjacent panels complete the diaphragm. For Miami-Dade's 180 MPH wind speed, the roof deck diaphragm typically requires #12 self-drilling screws at 12 inches on center at supports and 6 inches at side laps in the outermost bays, per Steel Deck Institute recommendations adapted for HVHZ conditions.
The internal pressure coefficient (GCpi) is the single most consequential variable in sawtooth roof design for hurricane zones. ASCE 7-22 Section 26.12 defines the boundary between enclosed and partially enclosed buildings based on the ratio of openings in the windward wall to openings in all other walls. For sawtooth buildings, each clerestory wall is effectively a separate wall surface, multiplying the number of potential opening locations.
When all clerestory glazing is intact and the building envelope is sealed, the internal pressure coefficient is ±0.18. This is the design target. For a sawtooth building with 180 MPH wind speed at 30 ft mean roof height in Exposure C, the internal pressure contribution is approximately ±10.5 psf. This value adds to (or subtracts from) the external pressure on every surface, creating the net design pressure each element must resist.
If any clerestory glazing fails, the building becomes partially enclosed with GCpi = ±0.55. The internal pressure contribution jumps to approximately ±32.1 psf. The net uplift on roof panels increases from approximately 45 psf to 67 psf in field zones. This 49% increase in net pressure is why FBC 2023 mandates that all sawtooth glazing in the HVHZ be impact-rated: preventing the breach that triggers partially enclosed conditions is the primary design strategy.
Sawtooth roof buildings require more extensive permit documentation than conventional structures due to the multi-bay wind analysis, progressive failure evaluation, and NOA requirements for all clerestory glazing. The Miami-Dade Building Department reviews these submissions under the HVHZ provisions of FBC 2023 Chapter 16 with particular attention to the wind load analysis methodology and the cascade failure scenario.
ASCE 7-22 Section 27.3 treats sawtooth and multi-span gable roofs as a special case. Unlike a single gable roof where the windward and leeward slopes have defined Cp values, each bay of a sawtooth roof creates its own aerodynamic zone. The windward bay experiences higher uplift on its sloped face (Cp up to -1.3) because the vertical clerestory wall behind it blocks flow recovery. Interior bays see reduced but still significant pressures (Cp around -0.7 to -1.0), while the leeward bay experiences different patterns due to wake effects from all preceding ridges. The vertical clerestory walls themselves are treated as wall components with Cp values from +0.8 (windward) to -0.5 (leeward). Engineers must analyze each bay independently and apply the specific coefficients from Figure 27.3-4.
All clerestory glazing in Miami-Dade HVHZ must be impact-rated per FBC 2023 Section 1626 and carry a valid Miami-Dade Notice of Acceptance. The glazing must resist large missile impact testing (9 lb 2x4 at 50 fps) and meet the design pressure for its specific location. Because clerestory windows sit at elevated positions between sawtooth bays, they experience higher component and cladding pressures than standard wall glazing. Each panel must have an NOA that meets or exceeds the calculated design pressure for that specific bay position and wind zone. Laminated glass with 0.060" PVB interlayer is the minimum standard; many engineers specify 0.090" PVB for additional margin.
A clerestory failure triggers a progressive failure cascade. When one panel breaks, the building shifts from enclosed to partially enclosed classification under ASCE 7-22, increasing internal pressure coefficients from +0.18 to +0.55. This 205% increase in internal pressure combines with external suction on adjacent bays, potentially exceeding the design capacity of neighboring roof sections, purlins, and glazing. The cascade effect means one broken clerestory can lead to sequential failures across multiple bays. This is why Miami-Dade requires all glazing to be impact-rated rather than allowing shutters alone on industrial buildings with sawtooth profiles.
Purlin design requires zone-by-zone analysis across each bay. Corner zones (Zone 3) on the outermost bays need the heaviest purlins, often 12-inch Z-sections at 3 ft spacing. Edge zones (Zone 2) along ridges and eaves use mid-weight sections at 3.5 ft spacing. Interior field zones (Zone 1) of middle bays allow standard spacing of 4.5 to 5 ft with lighter sections. A 5-bay sawtooth building typically requires three distinct purlin schedules. Each bay must also account for the purlin-to-column moment connection at the clerestory wall, where both gravity and lateral loads transfer through the same joint. ASCE 7-22 Table 30.3-2A provides the GCp values governing each zone.
Yes, sawtooth roof buildings are fully permitted in Miami-Dade, but they require extensive engineering documentation beyond what conventional roofs demand. The permit package must include bay-by-bay wind analysis, impact-rated glazing NOAs for every clerestory panel, progressive failure calculations for the partially enclosed condition, and detailed connection drawings. Many architects choose sawtooth designs for manufacturing facilities, maker spaces, and art studios where north-facing clerestories provide excellent daylighting without solar heat gain. The added engineering cost (typically $8,000 to $15,000 above a standard flat-roof industrial analysis) is offset by long-term energy savings from reduced artificial lighting needs.
Wind acceleration between ridges occurs because the vertical clerestory walls force airflow upward and over each ridge, creating a venturi-like effect in the valley. Wind speeds in these zones can reach 1.2 to 1.5 times free-stream velocity. ASCE 7-22 accounts for this through multi-span roof provisions in Figure 27.3-4 rather than a direct speed-up factor. For Miami-Dade at 180 MPH, the effective velocity pressure in acceleration zones can reach 75 to 90 psf at typical roof heights. Engineers apply appropriate GCp values from the multi-span figures to each surface of each bay. Wind tunnel testing is recommended for buildings with more than 5 bays or unusual aspect ratios to validate the code-based approach.
Get bay-by-bay pressure analysis, purlin schedules, and connection forces for your multi-ridge roof in Miami-Dade HVHZ. ASCE 7-22 compliant with progressive failure evaluation.
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