Gate Drags Only Some Days: Post vs Frame vs Hardware Translation Decision Tree

Why this matters

"The gate drags some days but not others" is a translation problem before it is a repair problem. An intermittent drag almost always means something in the system is moving with conditions, usually moisture or temperature, and the dispatcher who books it as a flat "fix the gate" sends the tech in blind. The pattern of when it drags is the single most valuable diagnostic the customer can give you. Captured correctly at intake, it narrows the cause to post, frame, or hardware before anyone arrives.

Get this wrong and you replace a hinge on a gate whose real problem is a post heaving in wet soil. The hinge swap looks fine on a dry day, the customer calls back after the next rain, and you have eaten a callback on a misdiagnosis.

Symptom presentation

Customers describe this as the gate "scraping," "catching," "sticking at the bottom," or "not latching like it used to." The diagnostic gold is the qualifier: only after rain, only in summer heat, only in the morning, or only in cold snaps. Pull that qualifier at intake. The correlation tells you which subsystem is moving:

• Drags after rain or in wet seasons, fine when dry: post movement (saturated soil) or wood swelling.
• Drags in hot weather, fine when cool: thermal expansion of a metal frame, or wood expansion.
• Drags in cold, latches in warm: contraction opening clearances, or frost-affected post.
• Drags worse over months regardless of weather, no recovery: progressive sag (hardware or frame), not intermittent at all.

Quick checks

On arrival, recreate or read the current state, then collect the static measurements that do not depend on weather:

• Gap survey: Measure the gap at the latch side top and bottom, and at the hinge side top and bottom. A gate that is square reads roughly equal top-to-bottom gaps. A diagonal pinch (tight at bottom-latch, open at top-hinge) is a sag signature.
• Post plumb: Put a level on both the hinge post and the latch post, front face and side face. Note any lean and which direction.
• Hinge play: Grab the gate at the latch edge and lift. More than slight vertical play means worn hinges or stripped fasteners.
• Frame diagonal: Measure the two diagonals of the gate frame. Equal diagonals means the frame is still square; unequal means the frame itself has racked.

Isolation tree

Start from the weather correlation, then confirm with the static checks.

1. Drags only after rain / wet season.
   • Re-check post plumb during or just after a wet period if possible. A hinge post that reads plumb dry but leans wet is moving in saturated soil. Excavate and inspect the footing: undersized, shallow, or no concrete crown to shed water. Cause: post/footing.
   • If the post stays plumb wet but a wood gate's bottom rail swells tight against the latch post, cause: wood moisture movement, not post.
2. Drags only in heat.
   • Steel or aluminum frame, drag appears midday and relaxes by evening: thermal expansion closing the latch-side clearance. Cause: hardware clearance / frame, fixable with a latch adjustment and added clearance.
   • Wood gate, drag in humid heat: wood swelling, same family as the wet-weather case.
3. Drags only in cold.
   • Gate sits low and binds at the bottom in a cold snap but is fine in thaw, and the hinge post tips seasonally: frost heave lifting or tilting the post. Cause: footing not below frost line.
4. Drags worse over time, no weather recovery.
   • This is not intermittent; it is progressive sag. Move to the sag branch: check hinge fasteners (pulled/stripped), hinge wear, and frame diagonal. Diagonal out of square means the frame racked (missing or loose anti-sag brace). Frame square but hardware worn means hinges/fasteners.

Confirming diagnosis

• Post confirmed when plumb changes with moisture or temperature and the footing inspection shows shallow depth, no concrete, or no water-shedding crown. Per ASTM F567, gate and terminal posts must be set deeper and more substantially than line posts and below the local frost line.
• Frame confirmed when the two frame diagonals differ and the gap survey shows a diagonal pinch that persists in all weather, with the posts plumb. The frame has racked.
• Hardware confirmed when posts are plumb, frame diagonals are equal, but the gate has measurable lift play at the latch edge or the latch only catches in certain temperatures because of clearance.

Remediation

• Post / footing: Re-set the hinge post below frost depth in a properly crowned concrete footing sized for a gate post per ASTM F567. Frost-heave cases require reaching below the local frost line; wet-soil lean cases require both depth and a footing that sheds water.
• Frame racked: Re-square the frame and install or tension an anti-sag cable-and-turnbuckle running from the top hinge corner to the bottom latch corner, or add a rigid diagonal brace. Recheck diagonals after tensioning.
• Hardware: Replace worn hinges, move to longer/larger lags into sound material, and re-set latch clearance. For thermal-clearance cases, set the latch with enough gap to accommodate the expansion you measured.
• Always recheck the full gap survey after the fix so you confirm the gate closes square across the weather range, not just on the day you visited.

References

• ASTM F567, Standard Practice for Installation of Chain-Link Fence (gate and terminal post setting depth, footing requirements).
• ASTM F537, Standard Practice for Cleaning and Preparing Steel Fence Members (corrosion and fastener assessment on steel gate frames and hardware).
• American Wood Protection Association (AWPA) Use Category standards (moisture movement and ground-contact behavior of treated wood gate posts).