Before you order glass
Every opening has its own number
Design pressure is a property of each opening, not of the house. Exposure, height above grade and whether a unit sits in a corner zone all change what can legally go in the hole.
Before you order glass
Every opening has its own number
Design pressure is not a property of the house, it is a property of each opening: its exposure, its height above grade and whether it sits in the field of the wall or inside the corner zone. Ordering one rating for a whole house is how units end up under-rated exactly where the wind is worst.
Positive pressure
+30 to +38 psf
Negative, suction
-33 to -42 psf
The least demanding case we see, and the one people wrongly assume applies everywhere.
Positive pressure
+30 to +38 psf
Negative, suction
-41 to -55 psf
Corner zones always carry higher suction. Ordering one rating for a whole house is how units end up under-rated at the corners.
Positive pressure
+42 to +55 psf
Negative, suction
-46 to -62 psf
Exposure category alone can move the required pressure by 30 percent or more.
Positive pressure
+42 to +55 psf
Negative, suction
-58 to -78 psf
The most demanding common case in our service area, and the one that drives the unit schedule.
Positive pressure
+28 to +45 psf
Negative, suction
-31 to -50 psf
The largest opening in most houses and the most frequently left at the original 1980s rating.
Pressure ranges shown are illustrative for a Jacksonville area house in Risk Category II. The real figures come from a calculation for your address, your building height and your exposure category, and they belong on the permit set.
What the paperwork has to say
Florida Product Approval number
A statewide approval listed as FL followed by a number, with a revision letter. It states which product, in which sizes, at which design pressures, and under which installation instructions the approval is valid. The permit set needs the number and the matching installation detail.
Miami-Dade Notice of Acceptance
An alternative approval route, often used for products sold into the High Velocity Hurricane Zone. It is accepted in Duval County and is frequently what a manufacturer supplies for impact-rated units.
Design pressure rating, marked DP
The tested positive and negative pressure the unit can take. It must meet or exceed the calculated pressure for that specific opening, in that zone, on that elevation. A DP50 unit in a location calling for DP62 fails plan review.
Impact test standards
Large-missile and small-missile testing under the recognised standards, with the missile level depending on how high above grade the opening sits. Labels stay on the glass until the final inspection, so do not peel them off.
Installation instructions are part of the approval
Fastener type, spacing, edge distance, buck detail and sealant are all specified in the approval document. Install it differently and the approval no longer applies, whatever the sticker says.
Opening protection is an alternative to impact glass
Approved shutters, panels or fabric systems satisfy the same requirement at a lower material cost, in exchange for someone having to deploy them. Both routes are legitimate; the choice is about how the house is used.
How we run an opening schedule
- 01
Measure every opening individually
In a house over thirty years old, assume some openings are out of square. We record each one rather than ordering off a schedule of four sizes.
- 02
Establish exposure and zone
Terrain category, building height and the corner zone width, which is what separates a Zone 4 unit from a Zone 5 unit.
- 03
Calculate the required pressure
Per opening, positive and negative, using the design wind speed for the site and risk category.
- 04
Select products that meet or exceed it
With the approval number and the matching installation detail attached to each unit on the schedule.
- 05
Detail the buck and the flashing
In a block wall, the buck detail is what carries the fasteners. In a frame wall, it is the flashing sequence that keeps water out.
- 06
Install to the approval, then inspect
Fastener type, spacing and edge distance exactly as the approval requires, with labels left on for the inspector.
What goes wrong
Four mistakes we are called in to fix
- 01
One rating ordered for the whole house
Cheaper to quote, and it leaves the corner units under-rated. Plan review usually catches it, which means a reorder and a twelve week wait.
- 02
Installed differently from the approval
Fastener type, spacing and edge distance are part of the approval document, not suggestions. Install it another way and the approval no longer applies, whatever the sticker says.
- 03
No buck detail in a block wall
In concrete block the buck is what carries the fasteners. A unit screwed into a poorly formed or rotten buck is a unit with no real anchorage, regardless of its rating.
- 04
Flashing sequence reversed
Water management is a lapping order, not a product. Sill pan first, then jamb, then head, each lapping the one below. Reverse any of it and the sealant is doing a job it will eventually fail at.
Opening questions
Questions
What clients ask about windows and doors
Inside the wind-borne debris region, every glazed opening has to be either impact-rated or protected by an approved shutter or panel system. Both satisfy the requirement. Impact glass costs more and never has to be deployed; shutters cost less and someone has to put them up. Which is right depends on how the house is used and who is there in September.
Corner zones carry higher negative pressure than the field of the wall, sometimes by 30 percent or more. Specifying one design pressure for a whole house means the corner units are under-rated, which is both a plan review failure and a real risk. We schedule openings individually.
A statewide approval, listed as FL plus a number and a revision, stating which product in which sizes is approved at which design pressures and under which installation instructions. The permit set carries the number and the matching installation detail. A Miami-Dade Notice of Acceptance is an accepted alternative.
Usually yes, and often you must. Replacing original sash with vinyl is generally refused inside the Riverside and Avondale district. We repair and weatherstrip where the sash is sound, and where replacement is unavoidable we specify a profile and sight line the review board will accept.
It is the largest opening in most houses and the most frequently ignored. A garage door that fails pressurises the house from the inside, which is a common path to losing a roof. If you are replacing openings, price the garage door in the same conversation.
The labels carry the approval and impact certification information the inspector needs to see at final. Peel them off early and you may be proving compliance with paperwork instead of a label, which is slower for everyone.
Related checks
The other three we run before design
Electrical service capacity
A NEC 220.83 demand calculation for the finished plan, before rough-in rather than during it.
HVAC sizing for added area
Sensible and latent load, duct static pressure, and when a separate zone beats extending the system.
Floors and subfloor prep
Slab relative humidity, flatness tolerance and the build-up height that decides every doorway.
Bring us the elevations
We will build the opening schedule with a pressure and an approval number against every unit.