Security Gates

Heavier starts with the frame. A yard gate spans a wider opening than a residential driveway gate, and it takes hits from equipment and wind. The tube wall goes up, and the roller hardware and posts grow with it. On our drawings a panel up to 6 feet gets a 2.5 inch square post, and gate posts step up to 4 inch square as the leaf widens. We set gate posts at least 36 inches into concrete, deeper on a wide leaf or a solid panel, and deeper again where an engineered footing or a permit calls for it. Those depths are our shop practice.

Under UL 325 the site sets the operator class. Class I covers residential use at one to four families. Class II is commercial, or multifamily at five or more units. Class III is industrial with no public access, and Class IV is guarded, restricted access with someone watching the gate. A fenced equipment yard the public never enters is normally Class III. The same yard becomes Class II once customers or tenants drive through it.

UL 325 requires two independent entrapment protection means for each entrapment zone, and the two cannot be the same type. Every external device must be monitored, so a missing or faulted sensor stops normal operation. Reversal has to begin within 2 seconds. At least two warning signs are required, visible from both sides of the gate. A gap of less than 16 inches between a moving gate and a fixed counter opposing edge, up to 6 feet above grade on a slide or swing gate, is an entrapment zone under UL 325, the threshold that triggers protection, as defined in DASMA Technical Data Sheet 350.

UL 325 sets one speed limit, and it comes with a load condition. Slide gate operators for Classes I and II, and vertical lift gate operators, do not exceed 1 foot per second when the operator is pulling 75 pounds or more. DASMA Technical Data Sheet 353 carries that wording. Without that load condition the figure is not the rule and not a travel time for a given opening width.

UL 325 is a voluntary standard. It is written into state law only in Nevada, and elsewhere it takes force through the building codes that reference it, the IBC, IFC and IRC. A vehicular operator is never listed for a pedestrian gate. The standard applies once a manual gate is motorized. An old manual slide gate is outside its scope until an operator goes on; then the whole assembly is measured against it.

ASTM F2200, the standard for automated vehicular gate construction, governs how a powered gate is built. It reaches a gate only once an operator is on it, so the walk and hand operated yard gates here fall outside it until they are motorized. On a horizontal slide gate, every weight bearing exposed roller 8 feet or less above grade has to be guarded or covered, and positive stops are required at both ends of travel. A gate must not fall more than 45 degrees from vertical if it comes away from its supporting hardware. These slide gate provisions cover Classes I through III and do not apply to a Class IV gate.

The last construction rule is the one that catches wide yards. ASTM F2200 requires a slide gate, plus the run of fence it covers when open, to be screened so a 2.25 inch sphere cannot pass, from the bottom of the gate up to the top of the gate or 72 inches above grade, whichever is less. Mesh added later puts sail area on a gate whose rollers were sized for something lighter, so we settle infill spacing on the drawing.

Hot dip galvanizing under ASTM A123 sets how much zinc goes on the steel. Powder over galvanizing is a duplex system. The American Galvanizers Association reports a duplex system lasts roughly 1.5 to 2.3 times the combined life of the two coatings alone. ASTM D7803 is the practice for prepping hot dip galvanized steel before powder, and its thermal step prevents outgassing pinholes. For desert sun, ask for an AAMA 2604 class powder, since the basic 2603 tier chalks and fades faster. Those tiers are written for coatings on aluminum, so 2604 names the class of powder to ask for rather than a rating the steel underneath carries.