Category: Walls, Ceilings & Foundation

Short answer: Thin vertical or hairline cracks, especially above door and window corners, are usually cosmetic and come from normal movement. Bob Vila says cracks under 1/8 inch are likely cosmetic, 1/4 inch is worth watching, and cracks 1/4 inch or wider, or groups of cracks, deserve a professional assessment. Horizontal cracks, 45-degree cracks with sticking doors, and cracks that keep coming back are the ones to take seriously.

Quick diagnosis

What you notice	Most likely cause	What to check	Call a pro?
Hairline crack above a door or window corner	Normal movement and drywall stress	Watch it	No
Diagonal crack at about 45 degrees near a door	Uneven settling	Check if doors stick	If it grows
Horizontal crack	Soil pressure or structural load	Measure and photograph	Yes
Stairstep crack in brick or block	Settling of masonry	Check width and growth	Yes
Crack with yellow or brown stain	Moisture behind the wall	Look for a leak	Often
Crack that returns after repair	Ongoing movement	Mark and date it	Yes

Read the crack

• Width: under 1/8 inch is likely cosmetic; 1/4 inch and up deserves a closer look (Bob Vila).
• Direction: vertical cracks are usually the least worrying; diagonal cracks near doors suggest uneven settling; horizontal cracks need an expert.
• Company: cracks together with sticking doors, sloping floors or gaps at trim point to foundation movement.

Monitor before you patch

This Old House recommends marking the ends of a crack with a pencil line and the date so you can see if it grows. Photograph it with a ruler beside it. Check every few weeks through a change of seasons.

Patching cosmetic cracks

Once you know the crack is stable, open it slightly, apply mesh tape and joint compound, sand and paint. If the crack returns quickly, the movement is ongoing and patching will not fix it.

When to call a professional

• The crack is 1/4 inch or wider, or there are several.
• It is horizontal, stairstepped in masonry, or keeps growing.
• Doors and windows stick, or floors slope.
• There are water stains or mold along the crack.

What it usually costs

Cosmetic drywall crack repair is usually a small job (HomeGuide lists ceiling crack repair at about $150 to $400). If a structural cause is found, This Old House reports foundation repair averaging about $5,179, with a typical range of $2,224 to $8,134.

Frequently asked questions

Are wall cracks normal in an old house?

Fine cracks are common in older homes, especially in plaster. Watch for new, wide or growing cracks.

Who do I call for cracks in walls?

For cosmetic cracks, a drywall or painting contractor. For wide, horizontal or growing cracks, a structural engineer gives an independent opinion before you hire a repair company.

Related problems

• Cracks in the ceiling
• Foundation cracks
• Water stain on the ceiling

Sources

• Bob Vila: When should you worry about cracks in your walls?
• This Old House: Foundation settling vs. foundation problems
• This Old House: Foundation cracks, what is normal and when to worry

This guide is general information, not a substitute for an inspection by a licensed professional. See our disclaimer.

Short answer: Not every foundation crack is a problem. Thin vertical cracks are often from concrete shrinkage or normal settling. This Old House calls horizontal cracks the most concerning, because they usually mean soil pressure is pushing on the wall. Cracks wider than about 1/4 inch, cracks that grow, and cracks with sticking doors or sloping floors are signs to call a structural engineer.

Quick diagnosis

What you notice	Most likely cause	What to check	Call a pro?
Thin vertical crack	Concrete shrinkage or settling	Mark and watch; seal if it leaks	Usually not
Diagonal crack, wider at one end	Uneven settling	Check doors and windows	If it grows
Horizontal crack in a block or poured wall	Soil or water pressure	Look for bowing	Yes
Stairstep crack in block	Settling or pressure	Measure width	Yes
Crack wider than 1/4 inch	Structural movement	Photograph with a ruler	Yes
Crack that leaks water	Water entry through a crack	Check grading and gutters	Often

Why horizontal cracks matter

InspectAPedia and This Old House both describe horizontal cracks as a sign of lateral pressure from soil, water or frost against the wall. If the wall is also bowing inward, have an engineer look at it soon.

Monitor a crack

1. Draw a pencil line across each end of the crack and write the date.
2. Photograph it with a ruler or coin for scale.
3. Check monthly. New cracks and growing cracks are not normal, according to This Old House.

Reduce water pressure on the foundation

• Keep gutters clean and downspouts extended away from the house.
• Grade soil so it slopes away from the foundation.
• Seal small, stable cracks to stop water entry.

When to call a professional

• Any horizontal crack, or a wall that bows or leans.
• A crack wider than about 1/4 inch, or one that grows.
• Cracks plus sticking doors, sloping floors or gaps at windows.
• Water keeps coming through the crack.

What it usually costs

This Old House reports foundation repair averaging about $5,179, with a typical range of $2,224 to $8,134. A structural engineer evaluation is separate and usually far less than repair.

Frequently asked questions

Are vertical foundation cracks normal?

Thin vertical cracks are common and often from shrinkage or settling. Watch them for growth and seal them if they leak.

Should I get an engineer or a foundation repair company?

An independent structural engineer can tell you whether repair is needed before a company quotes the work.

Related problems

• Cracks in walls
• Cracks in the ceiling
• Sewer smell in the basement

Sources

• This Old House: Foundation cracks, what is normal and when to worry
• This Old House: Foundation settling vs. foundation problems
• InspectAPedia: Horizontal foundation cracks

This guide is general information, not a substitute for an inspection by a licensed professional. See our disclaimer.

Short answer: Find the cause before you paint. Bob Vila lists roof problems, plumbing leaks, HVAC condensate drains and condensation as the common causes. A stain under a bathroom points to plumbing (often the toilet seal or shower), one near an exterior wall or chimney points to the roof or flashing, and a stain in a line may follow a duct. Fix the leak, let it dry, then use an oil-based stain-blocking primer.

Quick diagnosis

What you notice	Most likely cause	What to check	Call a pro?
Stain under a bathroom or toilet	Toilet seal, shower pan or drain leak	Run the shower and flush; watch the stain	Often
Stain near an outside wall, chimney or vent	Roof or flashing leak	Check after rain; look in the attic	Yes (roof)
Stain in a straight line	Condensation along a duct	Look at ductwork above	Often
Stain under the AC air handler	Clogged condensate drain or full drip pan	Check the drain pan	Often
Stain but no leak, dry	Old leak already fixed, or seasonal condensation	Mark the edge and watch	If it grows

Read the stain

Bob Vila notes that stains spreading in a large circle can indicate a pipe leak, stains near the edges may point to gutters, and straight-line stains can follow ductwork. Mark the edge with a pencil and date it; if it grows, the leak is active.

Check for a plumbing leak

Turn off all water and watch the meter. If it still moves, a leak is likely, according to Bob Vila. For a stain under a bathroom, run the shower and flush the toilet separately and see which one makes the stain darker.

Fix the stain

1. Fix the cause first; painting over an active leak only hides it.
2. Clean with a mild bleach solution, rinse and let it dry completely.
3. Prime with an oil-based stain-blocking primer (water stains bleed through latex).
4. Paint with matching ceiling paint.

When to call a professional

• The drywall sags or feels soft (water may be trapped above).
• You see mold or the stain keeps growing.
• The cause is a roof leak or a hidden pipe.
• Water is near light fixtures or wiring: turn off that circuit.

What it usually costs

HomeGuide (2026) lists fixing a leak and replacing the damaged ceiling drywall at about $500 to $2,500, with ceiling crack repair about $150 to $400.

Frequently asked questions

Why is there a water stain on my ceiling but no leak?

It may be an old leak that was fixed, a seasonal condensation problem, or a slow leak that only shows up during rain or heavy use.

Who do I call for a water stain on the ceiling?

A plumber if it is under a bathroom or kitchen, a roofer if it is under the roof or near a chimney, and an HVAC technician if it is near the air handler or ducts.

Related problems

• Cracks in the ceiling
• Sewer smell in the bathroom
• Water heater leaking
• Toilet keeps running

Sources

• Bob Vila: Water stains on the ceiling, common causes and solutions
• InspectAPedia: Photo guide to the causes of indoor stains
• HomeGuide: Ceiling repair cost (2026)

This guide is general information, not a substitute for an inspection by a licensed professional. See our disclaimer.

Short answer: Thin, straight hairline cracks along drywall seams are common and usually cosmetic, caused by seasonal movement and taping. Be more concerned if the crack is wider than about 1/4 inch, keeps growing, comes with sagging or water stains, or appears with sticking doors and sloping floors.

Quick diagnosis

What you notice	Most likely cause	What to check	Call a pro?
Hairline crack along a seam	Drywall tape or seasonal movement	Watch for growth	No
Crack with brown stain	Water leak above	See water stain guide	Often
Crack with sagging ceiling	Water damage or failed fasteners	Do not stand under it	Yes
Crack wider than 1/4 inch or growing	Structural movement	Mark and date the ends	Yes
Cracks plus sticking doors, sloping floors	Foundation movement	Check doors and floors	Yes

What is usually normal

Houses expand and contract with temperature and humidity. Bob Vila describes hairline cracks, about 1 mm wide, as cosmetic and repairable, and says cracks under 1/8 inch thick are likely cosmetic. Many ceiling cracks are simply the tape joint between drywall sheets.

When to worry

Bob Vila says cracks 1/4 inch or wider, or groups of such cracks, may indicate a structural problem worth a professional assessment, and that cracks that reappear and widen after repair deserve inspection. Yellow or brown staining with a crack points to moisture: find the leak first.

Monitor it

Draw a pencil line across the ends of the crack and write the date, or photograph it with a ruler. Check monthly. Growth means active movement.

When to call a professional

• The ceiling sags, bulges or feels soft.
• The crack is wider than 1/4 inch, growing, or keeps coming back after repair.
• Cracks appear with sticking doors, sloping floors or cracks in the foundation.

What it usually costs

HomeGuide (2026) lists drywall ceiling crack repair at about $150 to $400. Structural evaluations cost more and depend on your area.

Frequently asked questions

Are ceiling cracks normal in a new house?

Small cracks are common as framing dries and settles. Cracks that keep widening, especially in a new home, deserve an inspection.

What does a crack across the whole ceiling mean?

A long straight crack is often a drywall joint. If it is wide, uneven in level or comes with sagging, have it inspected.

Related problems

• Cracks in walls
• Foundation cracks
• Water stain on the ceiling

Sources

• Bob Vila: When should you worry about cracks in your walls?
• This Old House: Foundation settling vs. foundation problems
• HomeGuide: Ceiling repair cost (2026)

This guide is general information, not a substitute for an inspection by a licensed professional. See our disclaimer.