Why Does My Door Stick in Summer?

1. Wood Expansion from Humidity

Wood expands primarily across the grain (perpendicular to the grain direction), not along it. This means that a solid wood door panel or frame will swell more in width than in length. When relative humidity rises above 60-70% during summer months, wood can absorb enough moisture to expand by 1/8 inch or more across its width.

The expansion rate depends on several factors: the wood species (oak and maple expand more than pine or cedar), whether the wood is sealed or painted (unsealed wood absorbs moisture faster), and how long the wood has been exposed to high humidity. Even well-sealed doors can absorb some moisture over time as protective finishes degrade.

2. Temperature Effects

Temperature plays a dual role in summer door sticking. First, higher temperatures increase the moisture-holding capacity of air—warm air can hold significantly more water vapor than cool air, which is why summer humidity feels so oppressive. Second, heat itself can cause minor expansion of both wood and metal components (hinges, strike plates).

The combination of heat and humidity creates the perfect storm for door sticking. A 90-degree day with 80% relative humidity provides ideal conditions for wood to absorb maximum moisture and expand to its seasonal peak.

3. Moisture Absorption Patterns

Not all parts of a door absorb moisture equally. Exposed edges (especially the bottom edge, which may lack paint or sealer) absorb moisture faster than painted or sealed surfaces. This can cause uneven swelling, where one edge of the door expands more than another, creating binding at specific points in the frame.

Similarly, door frames made of wood absorb moisture just like the door itself. If both the door and frame expand simultaneously, the gap between them shrinks, causing friction and sticking. This is why summer sticking often affects the entire door perimeter, not just one edge.

4. Swelling Patterns: Where Doors Stick Most

Summer sticking typically occurs along the sides (latch side and hinge side) and at the top or bottom edges. The latch side is particularly vulnerable because it's the farthest point from the hinges, where even minor expansion creates noticeable binding. You may hear scraping sounds when opening or closing, see paint or finish wear along contact points, or need to push harder than usual to close the door.

Doors that stick at the top corner in summer might indicate normal expansion—but they could also signal foundation settlement that's more noticeable when humidity amplifies the problem. This is a critical distinction we'll explore in the next section.

The short answer: Yes, mild summer door sticking is often normal—but severe, worsening, or multi-door sticking can indicate serious problems. Here's how to assess your situation.

When Summer Sticking Is Expected (and Safe to Ignore)

• Slight increase in resistance: If your door requires a bit more effort to open or close during peak humidity, this is typically normal seasonal expansion.
• Consistent pattern every summer: If your door has stuck mildly every summer for years and returns to normal in winter, this suggests predictable humidity-related behavior, not structural issues.
• Single door affected: If only one door sticks—especially an exterior door exposed to weather—and no other doors show similar symptoms, humidity expansion is the likely culprit.
• No accompanying symptoms: If you don't see wall cracks, floor slopes, window sticking, or other structural warning signs, your summer sticking is probably just wood doing what wood does.

When Summer Sticking Indicates a Problem

However, certain patterns should raise immediate concern. Summer sticking can mask or amplify underlying structural issues—and in these cases, professional evaluation is essential.

• Multiple doors sticking in the same pattern: If several doors throughout your home all stick at the top corner, bottom edge, or same side, this may indicate foundation settlement affecting the entire structure—not just humidity.
• Sudden onset: If your door never stuck before but suddenly started sticking this summer, something has changed. It could be foundation movement, frame settling, or structural shifts that humidity is now revealing.
• Worsening each year: If summer sticking gets progressively worse each season, requiring more force or affecting more doors, this suggests an underlying problem that's getting worse, not just normal expansion.
• Year-round sticking with summer worsening: If your door sticks even in winter but gets dramatically worse in summer, the humidity may be amplifying a structural problem like foundation settlement or frame sagging.
• Accompanied by other symptoms: Wall cracks (especially diagonal cracks above doors/windows), windows that stick or won't lock, sloping floors, or gaps between walls and ceiling are red flags that summer sticking is a symptom of foundation issues.

One of the most important diagnostic questions is: "Does your door stick only in summer, or does it stick year-round?" The answer provides critical clues about whether you're dealing with normal seasonal expansion or a structural problem.

Seasonal (Summer-Only) Sticking

Characteristics: Door operates perfectly in fall, winter, and spring. Sticking begins when humidity rises (typically May-September in most climates) and resolves completely when humidity drops. The pattern repeats predictably every year.

Most Likely Cause: Humidity-driven wood expansion. Both the door and frame absorb moisture from humid summer air, swell, and reduce the clearance gap between them. This is normal wood behavior and usually not a structural concern—unless it's severe or worsening.

Action Required: For mild seasonal sticking, humidity control (dehumidifiers, AC) and maintenance (sealing door edges, waxing contact points) are usually sufficient. Professional evaluation is only needed if the sticking is severe, affects multiple doors, or gets worse each year.

Year-Round Sticking (with Summer Worsening)

Characteristics: Door sticks even in low-humidity winter months but gets dramatically worse in summer. The door never fully returns to normal operation when humidity drops.

Most Likely Cause: Underlying structural issue (foundation settlement, frame sagging, or structural movement) that humidity amplifies. The baseline problem exists year-round, but summer expansion makes it severe enough to be obvious.

Action Required: Professional foundation inspection is essential. Do not attempt DIY fixes (sanding, planing) until you know the root cause. If foundation settlement is the culprit, door modifications will only mask the symptom while structural damage continues to worsen.

Red Flags That Suggest Structural Issues

• Multiple doors affected in the same pattern: If all doors stick at the top corner, this is a classic foundation settlement indicator—not humidity.
• New cracks appearing: Diagonal cracks above door/window frames, stair-step cracks in brick, or widening gaps between walls and ceiling suggest active structural movement.
• Doors getting worse each season: Progressive worsening indicates an underlying problem that's advancing, not just seasonal expansion.
• Exterior doors more affected than interior: Foundation issues often show up first in exterior door frames because they're more rigidly attached to the structure.
• Windows also sticking or difficult to lock: Combined door and window issues strongly suggest frame distortion from foundation movement.

If you've determined your summer sticking is likely humidity-related (not structural), here are proven short-term and long-term solutions to keep your doors operating smoothly. However, if you have any doubt about the root cause, get professional evaluation before making permanent modifications.

Short-Term Fixes (Immediate Relief)

These solutions provide temporary relief during peak humidity without permanently altering your door or frame:

• Run a dehumidifier: Target 30-50% indoor relative humidity. A whole-house dehumidifier or portable units in problem areas can reduce moisture absorption and allow wood to contract naturally. Cost: $200-$1,500 depending on coverage area.
• Use air conditioning: AC systems naturally dehumidify air as they cool. Running your AC during humid periods can prevent or reduce door swelling. Free if you already have AC; otherwise, window units start around $200-$500.
• Apply paraffin wax or soap: Rubbing paraffin wax, bar soap, or candle wax along door edges that bind creates a lubricating layer that reduces friction. This is a temporary fix but can provide immediate relief. Cost: Under $10.
• Adjust strike plate: If the door latch is binding, slightly loosening or repositioning the strike plate can provide clearance. Only do this if you're confident the issue is not structural. Cost: Free (DIY adjustment).
• Improve ventilation: Opening windows, using exhaust fans, and promoting air circulation can help reduce localized humidity spikes that cause swelling. Cost: Free.

Long-Term Solutions (Permanent Fixes)

If summer sticking is consistent and bothersome, these solutions address the root cause:

• Seal or repaint door edges: Applying a high-quality exterior paint, polyurethane sealer, or marine varnish to all door edges (especially the top and bottom) creates a moisture barrier that prevents humidity absorption. This is the most effective long-term solution for wood doors. Cost: $50-$150 for DIY; $200-$400 for professional sealing.
• Plane or sand door edges (ONLY after professional evaluation): Removing a thin layer of wood from the binding edge provides permanent clearance. WARNING: Do not plane/sand if foundation issues are suspected—you'll create gaps when the structure shifts further. Cost: $150-$300 for professional planing.
• Replace with fiberglass or steel door: Composite doors don't absorb moisture like wood and are immune to seasonal swelling. This is the ultimate long-term solution for chronic summer sticking. Cost: $500-$2,000+ depending on door quality and installation.
• Install weatherstripping with compression seal: High-quality weatherstripping can accommodate minor seasonal expansion while maintaining a seal. Cost: $20-$100 for DIY; $150-$300 for professional installation.

When Foundation Repair Is Needed

If professional inspection reveals that your summer sticking is actually caused by foundation settlement or structural movement, the solutions above won't fix the underlying problem. In these cases, foundation repair is necessary:

• Underpinning (piers/pilings): Stabilizes and lifts settled foundation sections to restore structural integrity. This is the most common repair for differential settlement causing top-corner door sticking. Cost: $3,000-$15,000+ depending on severity and home size.
• Slab jacking / mud jacking: For concrete slab foundations, injecting material beneath the slab can lift and level settled sections. Cost: $2,000-$8,000 depending on area.
• Frame replacement or shimming: In some cases, the door frame itself has sagged or shifted beyond adjustment. Replacing or re-leveling the frame may be necessary after foundation repair. Cost: $500-$2,000 per frame.