Customer Says Doors Stick Now But Not Before: Settlement vs Humidity Translation Decision Tree

Why this matters

"My doors stick now but they didn't last year" is the single most common foundation-repair lead description, and it is also the most over-diagnosed. A sticking door can mean the frame has racked because a slab corner dropped, or it can mean nothing more than a wood door swelling 1/16 in across the stile during a humid spell. Selling piers for a humidity problem destroys trust and warranty margin; missing real settlement lets the structure keep moving until drywall and plumbing follow. The job is to translate a layperson observation into a measured structural verdict before you quote anything.

Symptom presentation

Customers report doors that "drag," won't latch, or swing open on their own. Pull the real detail on the first call:

• Which doors? Exterior steel doors barely move with humidity. If a steel slab door binds, suspect frame movement.
• Where on the door does it rub? Top corner binding points to one diagonal direction; a uniform rub all around points to swelling.
• Seasonality. Sticks in summer/wet, frees in winter/dry = humidity signature. Sticks and never recovers, or worsens each year = settlement signature.
• Other co-symptoms. Cracks above door corners, gaps at baseboard-to-floor, separating crown molding, or windows that also bind raise the settlement probability sharply.

Quick checks

On site, before any survey, run these five-minute reads:

• Hold a 4 ft level vertical against the door jamb on the hinge side. Out of plumb more than 1/4 in over the height means the frame is racked, not the door swollen.
• Lay the level across the threshold and along the head jamb. A sloped threshold or out-of-level head confirms the frame moved with the floor.
• Check the reveal (gap) between door slab and frame on all four sides. A tapered reveal (wide at top, tight at bottom on the latch side) is the classic parallelogram of racking; a uniform reveal that closes evenly is swelling.
• Run a moisture meter on the door stile and rail. Wood above ~14-16 percent MC swells; a steel or fiberglass door that binds cannot be blamed on MC, so binding on a non-wood door is a strong frame-movement signal.
• Look directly above the door corners for stair-step or diagonal drywall cracks fanning toward the upper corner, and check whether nearby windows in the same wall also bind.
• Open and close the door slowly and feel where it first touches; a single hard contact point at one corner is racking, a soft drag along a whole edge is swelling.

Isolation tree

Start at the door, end at the floor.

1. Is the door wood and is stile MC above 15 percent with binding only on the latch edge, no jamb out-of-plumb? -> Humidity swelling. Stop. Recommend dehumidification, plane/seal the edge later. No foundation work.
2. Is the jamb out of plumb more than 1/4 in over 80 in AND the reveal tapered? -> Frame is racked. Proceed to floor survey.
3. Run a floor elevation survey across the room with a rotary laser or water level. Set the high point as zero and read relative elevations on a grid roughly every 6-10 ft.
   • Differential less than ~1 in across the room and no progression history -> likely original construction tolerance, not active settlement. Monitor.
   • Differential 1 to 2 in concentrated toward the binding door -> active or historic settlement consistent with the symptom. Proceed to confirming diagnosis.
   • Differential over 2 in or a sharp local dip -> significant settlement. Move to structural scope.
4. Multiple doors and windows binding in the same quadrant of the home, plus exterior grade falling toward that corner -> systemic settlement, not a single-door issue.

Confirming diagnosis

Racking plus a measured floor slope that points toward the binding opening is the confirmation pair. To separate active from dormant movement:

• Install a crack monitor (graduated or tell-tale gauge) across the largest co-located crack and a floor-elevation benchmark. Read at install, then at 30 and 90 days. Movement over ~1/16 in in 90 days indicates active settlement; flat readings indicate the event is dormant.
• Correlate with moisture history. A documented plumbing leak, a clogged gutter line dumping at that corner, or a recent drought are the usual drivers of active soil movement.
• Re-survey after the next significant wet or dry cycle. Seasonal heave/shrink in expansive clay shows up as floor readings that move with the calendar; static readings rule it in or out.
• Photograph the reveal taper and the level reading against the jamb at the visit. A documented baseline lets the next visit prove progression or stability instead of relying on the customer's memory of how the door felt last season.

Remediation

• Humidity-only verdict: whole-home humidity control and door-edge reconditioning. Document that no structural defect was found and decline foundation scope in writing.
• Dormant settlement, frame racked but stable: cosmetic correction (rehang door, re-shim jamb) plus a written monitoring plan. Do not pier a dormant slab on a single sticking door.
• Active settlement confirmed by survey and monitor: scope underpinning (push or helical piers per the load path) at the affected corner, then re-hang openings after lift. Address the moisture driver (drainage, leak) so the corrected slab is not re-loaded by the same soil behavior.

References

• IRC R403.1 - Footings and minimum supporting-soil requirements for foundation systems.
• ICC-ES AC358 - Acceptance Criteria for Helical Systems and Devices (underpinning capacity basis).
• ASTM D4318 - Standard Test Methods for Liquid Limit, Plastic Limit, and Plasticity Index of Soils (expansive-clay screening).
• FEMA P-2090 - Guidance on assessing and repairing foundation movement in residential structures.