Structural Glazing Calculator
Silicone adhesion from glass weight and wind load.
About this calculator
Structural silicone glazing (SSG) replaces mechanical pressure plates with a bead of structural adhesive bonding glass straight to the frame, and the whole design question comes down to how wide that bead -- the "bite" -- needs to be. This calculator sizes it two different ways depending on SSG Sides. In 2-sided SSG only the top and bottom edges are bonded (the other two are mechanically captured), so the bite only has to resist wind suction, and Dead Weight Bite is always exactly zero -- glass self-weight is carried by the mechanical edges instead, not the silicone. In 4-sided SSG all four edges are bonded, so the two vertical joints also have to carry the glass's own weight in sustained shear, and Dead Weight Bite switches on. That single toggle has an outsized effect at this calculator's defaults: a 1500x2400mm, 10mm-thick panel needs only a 9mm design bite in 2-sided SSG -- here Wind Load Bite (5.4mm) doesn't even clear the 6mm floor, so the floor itself governs, not wind -- but around 74mm in 4-sided SSG, because dead weight -- not wind, and not the floor -- ends up governing once all four edges are bonded.
Which of the three (wind, dead weight, or the floor) actually governs shifts with panel size, load, and SSG Sides: the floor governs roughly a third of the time across the declared input ranges (small or lightly loaded panels), wind governs a similar share (large panels or high wind, especially 2-sided), and dead weight governs the rest (mostly 4-sided SSG on larger panels). Design Bite is always the larger of Wind Load Bite, Dead Weight Bite, and the 6mm floor, carried at a 1.5x safety factor and rounded up to the next whole millimetre -- which is why the smallest Design Bite this calculator will ever recommend is 9mm (ceil(6 x 1.5)), not the pre-safety-factor 6mm floor itself. Every other quantity here -- Joint Thickness, Sealant Volume, Cartridges Per Panel -- flows downstream from that one governing dimension. Panel Weight, by contrast, only tracks glass thickness and panel area: it is completely unaffected by wind pressure, silicone strength, or how many sides are bonded.
Inputs
Results
Design bite (mm)
74
Joint thickness (mm)
37
How to Use This Calculator
- Enter the glass panel width and height.
- Set the design wind suction pressure and structural silicone bite dimension.
- Input structural silicone adhesive strength.
- Review the required silicone bite to resist the design load.
- Verify the calculated bite exceeds the minimum per ASTM C1184 and manufacturer requirements.
How the result changes with Panel height (mm)
| Panel height (mm) | Design bite (mm) | Joint thickness (mm) |
|---|---|---|
| 1,200 | 37 | 19 |
| 1,800 | 56 | 28 |
| 3,600 | 111 | 56 |
| 6,000 | 184 | 92 |
What each input means
- Panel width (mm)
- Glass panel width (daylight opening).
- Panel height (mm)
- Glass panel height (daylight opening).
- Design wind pressure (Pa)
- Design wind suction pressure per ASCE 7 or local code.
- Total glass thickness (mm)
- Total glass build-up thickness (e.g., 6+4 laminated = 10 mm).
- SSG sides (2 or 4)
- 2-sided SSG: two edges bonded, two mechanically captured. 4-sided: all edges bonded.
- Silicone design strength (kPa)
- Allowable tensile stress of structural silicone. Typical: 140 kPa (Dow 995), 210 kPa short-term.
What each result means
- Wind load bite (mm)
- Required silicone bite depth from wind suction alone.
- Dead weight bite (mm)
- Required bite from glass self-weight (4-sided SSG only).
- Design bite (mm)
- Governing bite with 1.5× safety factor, rounded up. This is the bonded contact width.
- Joint thickness (mm)
- Sealant depth (glueline thickness). Typically 50% of bite, min 6 mm.
- Sealant perimeter (m)
- Total bonded perimeter per panel.
- Sealant volume (mL/panel)
- Volume of structural silicone required per panel.
- Cartridges per panel
- Number of 310 mL sealant cartridges per panel.
- Glass panel weight (kg)
- Weight of the glass panel only.
How this is calculated
Worked example, using the default values
- Identify Input Parameters4 parametersPanel width (mm) = 1500, Panel height (mm) = 2400, Design wind pressure (Pa) = 2000, Total glass thickness (mm) = 10 = 6 input(s) provided
- Calculate Design biteDesign bite = ceil(governingBite * 1.5)74 = 74
- Calculate Joint thicknessJoint thickness = max(6, round(designBite * 0.5))37 = 37
- Calculate Wind load biteWind load bite = (windPressure * tributarySpan) / (2 * siliconeStrength * 1000)5.4 = 5.4
- Calculate Dead weight bite49.1 = 49.1
Engine last updated . Checked against 2 independently-derived tests — how we verify calculators. Built by Paul Gunder, a software engineer, not a licensed financial, medical, or legal professional.
Frequently Asked Questions
Why is Dead Weight Bite sometimes zero and sometimes not?
Dead Weight Bite is exactly zero whenever SSG Sides is 2 -- in 2-sided SSG only the top and bottom edges are silicone-bonded, and the two vertical edges that would otherwise carry the glass's self-weight are mechanically captured instead, so the silicone never sees that load. Switch to 4-sided SSG and all four edges are bonded, so the vertical joints do carry dead weight and Dead Weight Bite becomes a real, non-zero number.
Does switching from 2-sided to 4-sided SSG ever make the required bite smaller?
No -- across the full input range, Design Bite at 4-sided SSG is never smaller than Design Bite at 2-sided SSG for the same panel and load. 4-sided SSG adds a Dead Weight Bite requirement on top of the same Wind Load Bite that 2-sided SSG already has to satisfy, so going to 4-sided can only hold the design bite steady or push it wider, never narrower.
Panel Weight and Design Bite both come from the same panel -- why doesn't a stronger wind design ever change the glass weight?
Panel Weight is pure geometry and material: Total Glass Thickness times panel area (Panel Width times Panel Height) times glass density -- the same multiplication regardless of what load case governs the joint. Design Wind Pressure, Silicone Design Strength, and SSG Sides all feed into sizing the SILICONE bead around the glass, not the glass itself, so none of them touch Panel Weight even at the extremes of their ranges. Put another way: two panels of identical size and thickness weigh the same whether one is rated for a gentle 500 Pa suburb and the other for a 9,000 Pa hurricane coastline -- the wind rating changes how much silicone holds the glass in, never how much the glass itself weighs.
How does silicone strength affect the required bite?
Wind Load Bite is inversely proportional to Silicone Design Strength -- a stronger-rated silicone (higher kPa) needs a narrower bite to resist the same wind suction, and a weaker one needs a wider bite. Raising Silicone Design Strength across its full 50-300 kPa declared range never widens Wind Load Bite, only holds it steady or narrows it.
What is the practical minimum bite this calculator will ever recommend?
9 mm. Design Bite takes the governing (larger) of Wind Load Bite and Dead Weight Bite, floored at 6 mm -- but that 6mm floor applies BEFORE the 1.5x safety factor, and Design Bite is ceil(governingBite x 1.5). So even at the smallest possible panel under the lightest possible load in 2-sided SSG (where Dead Weight Bite is zero and Wind Load Bite is negligible), governingBite still floors at 6mm and Design Bite comes out to ceil(6 x 1.5) = 9mm -- 6mm is the floor on the intermediate governing bite, not on the final recommended Design Bite.
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