Questions about gate posts, slopes and buried lines on an Austin lot
What should be located before any post hole is dug?
Buried lines come first. Water, gas, electric and communication lines run under front yards and along drives all over Travis County, and a post hole is exactly the kind of digging that finds them the hard way. Texas has a free call-before-you-dig line, reached by dialing 811, and the utilities mark their lines with paint and flags in a few working days. Those marks show where a hole can go and where it cannot.
Private lines are a separate matter. Irrigation pipe, a lighting cable run to a lamp post, a wire feeding a mailbox light or a gas line to an outdoor grill are often not on any public map. The crew walks the proposed post locations looking for sprinkler heads, valve boxes and lines of disturbed turf. On older lots in Hyde Park or Clarksville, where the yard has been dug up and patched many times, probing with a thin rod before the auger goes in is routine.
If a marked line sits where a post wants to go, the post moves. Shifting a hinge post a foot is cheap. Repairing a cut line is not, and it can interrupt service to the whole block.
How wide should the opening be?
The opening is the clear distance between the posts, and it is figured from the hardware outward. A leaf has its own width. Hinges take a little room on the hinge side. The latch and keeper take a little on the other. A small margin on top lets the frame swing without touching either post. Add those up and the result is the post spacing.
For a walk gate, the working question is what has to pass through it: a person, a wheelbarrow, a stroller, a lawn mower. For a drive gate, it is the widest vehicle and the swing of its mirrors. A leaf that is a few inches narrower than the vehicle needs forces a tight turn every time, and drivers end up clipping the post.
A dual swing gate across a wide drive splits the load into two leaves, which lowers the weight on each hinge post. It also needs a center stop so the leaves do not swing past each other, and a latch or drop rod that engages the ground. All of that is planned before the posts go in.
How does a sloped drive change the gate?
Slope changes which way the leaf can open and how the bottom rail has to be built. Austin has plenty of hillsides, from the streets climbing toward Mount Bonnell to the terraced lots around Travis Heights. A drive that rises from the street toward the house will drag an inward-swinging gate across the pavement unless the gate swings the other way or the hinges are mounted high enough to lift the leaf as it opens.
There are a few ways crews handle it. The simplest is to reverse the swing. Another is to build a rising hinge, which lifts the leaf a little as it opens. A third is to use a gate that follows the slope, with the bottom rail cut at an angle that matches the grade. Each option has trade-offs in appearance and in how the latch lines up when the leaf is closed.
Ground clearance on a slope is measured at the lowest point of the swing, which is not always the closed position. A leaf that clears the pavement when shut can scrape halfway through its arc.
Do the posts need to be bigger than the fence posts?
Yes, in almost every case. A fence post holds a panel that leans on its neighbors. A gate post holds a swinging leaf that pulls on it with a lever arm every time someone opens it. The hinge post takes the most punishment, since the weight of the leaf hangs from it, and the pull gets worse the wider the gate is.
A heavy leaf built from galvanized steel tubing, with a full run of pickets and a diagonal brace, wants a thick-walled steel post and a wide concrete footing. A lighter aluminum picket gate puts less strain on its post, but the footing still has to resist the twist. A post that was perfectly fine for the fence on either side often gets replaced or doubled up at the gate.
Wooden posts rot at the ground line, especially in the damp ground near the Colorado River and in low spots by Lady Bird Lake. Steel posts set in concrete last longer, provided the top of the footing is crowned so water runs away from the metal.
What if the old fence line is crooked?
Most old fence lines are. Settling, patching, tree roots and decades of different owners all push a fence away from a straight line. The crew has to decide whether the new gate follows the old line or corrects it.
The answer depends on what the gate sits between. A gate that fills a gap in an old picket fence usually follows the fence, so the leaf looks like it belongs. A gate that anchors a new run of fence can set the line, and the old fence gets adjusted to meet it. In either case the gate posts themselves must be plumb, even if the fence beside them leans. A plumb post next to a leaning fence looks odd for a moment, then looks right once the leaf is hung.
On narrow lots in Tarrytown or Clarksville, the line also has to respect the property edge. Setting posts a few inches over a boundary causes neighbor trouble that no hinge can fix, so the survey pins or a recent plat get checked first.
Does a gate need a different footing near a creek or low spot?
Often, yes. Low ground near Bouldin Creek, Barton Springs Pool or the lower slopes around Zilker Park holds water longer than the rest of the neighborhood. Soil that stays damp swells and softens, and a footing in it can settle or shift sideways under load.
Crews respond with wider holes, a layer of compacted gravel at the base so water can drain away, and a collar of concrete poured a little proud of the surrounding ground. Where the soil is truly soft, a deeper post or a drilled and reinforced footing may be needed. A crew that sees water seeping into the hole as it is dug adjusts on the spot rather than hoping the concrete will sort it out.
Can a gate be installed on top of a retaining wall or a slab?
It can, but the post has to be anchored differently. A post cannot be sunk into a poured slab or the top of a wall without a plan. The usual method is a base plate welded to the bottom of the post and bolted down through the slab with anchor bolts set in epoxy. The plate spreads the load, and the bolts resist the pull from the leaf.
The slab has to be thick enough and sound enough to hold the bolts. A cracked or thin slab will not take the load, and a retaining wall built from loose block or stacked stone cannot carry a gate at all. In those cases the post goes into the ground behind or beside the wall and the leaf spans the gap.
What are the first signs something was done wrong?
A gate that was hung well on well-set posts stays quiet. The early warning signs are small: a latch that needs a lift to catch, a faint scuff arc in the pavement, a gap at the top of the leaf that is wider than at the bottom, or a hinge pin that squeaks and then starts to bind. Any of these points to a post that has begun to lean or a frame that has started to rack.
Caught in the first season, the fix is usually a shim, a hinge adjustment or a new brace. Left for a few years, the fix becomes a reset footing.
Most gate trouble in Austin traces back to the two holes dug on the first day. Getting those right, in whatever ground the lot happens to have, does most of the work.