How to Calculate Dead Load for a Type B Deck Roof in Florida
Add up the weight of every permanent layer: the Type B deck itself (1.6 psf at 22 gauge, 2.0 at 20, 2.6 at 18, 3.0 at 16), insulation, cover board, membrane, ballast, ceilings, sprinklers and hung equipment. The engineer of record then applies the Florida Building Code load combinations. Send us the gauge they choose and we will quote it.
The calculation
Roof dead load (psf) = deck weight + insulation + cover board + membrane + ballast or fill + ceiling + mechanical, electrical and sprinkler allowance. Use manufacturer weights for each product. For point loads such as rooftop units, design the supports separately rather than spreading them into the uniform load.
Two uses for dead load in Florida
- Gravity: dead load adds to live load and must fit within the deck's allowable downward load for the span.
- Uplift: dead load helps resist wind uplift, but the code combinations count only part of it, so do not overstate it.
- Lightweight insulating fill adds weight that changes both checks.
- Record the assumed dead load on the drawings so roof changes can be checked later.
Where the deck weight comes from
The weights in the table are the design weights from our Nov 2024 catalog for 1.5" Type B, 50 ksi. Send your roof section and we will quote the deck to match.
1.5" Type B design weight (catalog)
| Gauge | Design thickness (in) | Weight (psf) |
|---|---|---|
| 22 | 0.0295 | 1.6 |
| 20 | 0.0358 | 2.0 |
| 18 | 0.0474 | 2.6 |
| 16 | 0.0598 | 3.0 |
Related Questions
Do the Type B load tables already include the deck's own weight?
The catalog's tabulated loads are uniformly distributed superimposed loads, meaning loads applied on top of the deck. Treat the deck weight and everything above it per your engineer's method, and check that the total fits the table for your span. The engineer of record confirms how self-weight is handled.
Does heavier deck help with wind uplift?
A few extra pounds per square foot of steel slightly increases dead load, but the bigger gain is strength: heavier gauges have higher upward load capacity and better fastener pullout. Uplift is mainly resisted by the deck, its fasteners and the roof assembly attachment, not by weight alone.