Most interior wall cracks are cosmetic. They’re caused by normal settling, seasonal changes in temperature and humidity, or drywall seams and fasteners shifting over time. To fix them properly, open the crack slightly, cover it with drywall tape, apply thin coats of joint compound, then sand, prime, and paint. Filling a crack without tape usually leads to it coming right back.
A small number of cracks point to something bigger, so the first step is figuring out which kind you have.
Quick Answer: Is Your Wall Crack Serious?
Usually not serious:
- Hairline cracks thinner than a credit card
- Straight cracks along drywall seams
- Small cracks at inside corners
- Cracks that appear and stay the same size for months
Worth a closer look:
- Cracks wider than roughly 1/8 inch
- Cracks that grow over weeks or months, or return right after patching
- Diagonal cracks spreading from multiple door and window corners
- Cracks accompanied by sticking doors, sloping floors, or gaps at ceilings or baseboards
- Cracks with water stains or dampness
- Horizontal cracks in basement walls or walls that bulge
Why Interior Walls Crack
Houses move a little. Wood framing shrinks and swells with humidity. Foundations settle, especially in the first years after construction. Drywall seams can separate if tape wasn’t bedded well, and fasteners can loosen over time. Doorways and window openings concentrate that stress, which is why cracks often start at their corners.
Water is another common cause. A leak inside a wall can soften drywall and cause cracking or bubbling, which is a different problem from settling and needs the leak fixed first.
Common Types of Wall Cracks
Seam Cracks
Long, straight cracks, usually vertical, that follow the line where two drywall sheets meet. Often caused by tape that wasn’t fully embedded or by framing movement.
Corner Cracks
Cracks along inside corners where two walls meet or where a wall meets the ceiling. These corners flex as the house moves. Cracks where the ceiling meets an interior wall can also be caused by seasonal roof framing movement in some homes, which a professional can help identify.
Diagonal Cracks at Doors and Windows
Short diagonal cracks running from the corners of openings are common and often cosmetic. Widening diagonal cracks at several openings, especially with doors that stop closing properly, deserve a professional evaluation.
Plaster Cracks
Older homes with plaster walls develop fine “spiderweb” cracks and longer cracks as the plaster ages or loses its grip on the lath behind it. If a plaster wall feels loose or bulges when you press it, the plaster may be detaching.
How to Monitor a Crack Before Repairing It
If you’re not sure whether a crack is stable, watch it for a few weeks before patching:
- Make a small pencil mark at each end of the crack and write the date next to it.
- Photograph it with a ruler or coin beside it for scale.
- Check again in a few weeks. If the crack has extended past your marks or visibly widened, it’s still moving.
This simple habit is part of learning how to find problems in your home before they become major repairs.
What You Need
- Utility knife
- Drywall tape: self-adhesive mesh or paper tape
- Pre-mixed joint compound (setting-type compound is harder and can resist cracking in some situations)
- 4-inch and 6-inch drywall knives
- Fine sanding sponge
- Primer and paint
- For inside corners: paintable, flexible acrylic caulk or corner tape
- Drop cloth, dust mask, and safety glasses
Step-by-Step: Fixing a Hairline or Seam Crack
Step 1: Open and Clean the Crack
Run a utility knife along the crack to remove loose material and create a slight V-shaped groove. This gives the compound something to grab. Brush out dust.
Step 2: Apply Tape
Center self-adhesive mesh tape over the crack, pressing it flat. If you’re using paper tape, spread a thin bed of joint compound first, press the tape into it, and squeeze out excess compound with your knife. Tape bridges the crack so movement doesn’t break through the new surface.
Step 3: Apply the First Coat
Spread a thin coat of compound over the tape with a 4-inch knife, extending a couple of inches on each side. Keep it thin enough that the tape pattern is still slightly visible. Let it dry fully.
Step 4: Feather Additional Coats
Apply a second and third coat with a wider knife, each extending further out and thinner at the edges. Feathering blends the repair so it isn’t visible as a raised stripe.
Step 5: Sand, Prime, and Paint
Sand lightly, check with a flashlight held flat against the wall, touch up any low spots, then prime and paint.
Fixing Inside Corner Cracks
Inside corners move more than flat walls, so rigid compound can crack again. For small gaps, a bead of flexible, paintable acrylic caulk often works better. Cut the tip small, apply a thin bead, smooth it with a damp finger, and paint once cured. For larger corner cracks, remove loose material and re-tape with paper tape folded into the corner or a flexible corner tape product.
Working on Older Walls
If your home was built before 1978, painted plaster and drywall may contain lead-based paint. The EPA’s lead renovation program explains how sanding and scraping old paint can create harmful dust. Minimize dry sanding, clean up with damp methods, and consider testing or hiring a lead-safe certified contractor, especially if children live in the home.
Common Mistakes to Avoid
- Skipping the tape. Compound alone over a crack often cracks again in the same line.
- Using thick coats. Heavy compound shrinks, cracks, and takes longer to sand.
- Patching a moving crack. If it’s still growing, find out why first.
- Ignoring moisture. A crack near a water stain means you need to find the leak before repairing the wall.
When You Should Call a Professional
A large crack that keeps returning, especially near doors, windows, or structural areas, deserves a closer inspection before you simply patch it. Call a structural engineer or qualified foundation professional if cracks are widening, if you see multiple warning signs together (such as sticking doors, sloping floors, and cracks), or if basement walls show horizontal cracks or bulging. See how to fix a door that won’t close properly to rule out simple door issues first. Building codes and permit requirements vary by location, so check with your local building department before any structural repair.
How to Prevent Cracks From Returning
- Keep indoor humidity reasonably stable through the year.
- Maintain gutters and downspouts so water doesn’t saturate soil around the foundation.
- Fix plumbing leaks quickly.
- Use flexible caulk at corners that crack seasonally.
Frequently Asked Questions
Are cracks in walls normal in a new house?
Minor cracks are common in the first few years as framing dries and the house settles. They’re usually cosmetic, but watch for cracks that keep growing.
What size wall crack is a concern?
Many professionals pay closer attention to cracks wider than roughly 1/8 inch, cracks that grow, and cracks that appear alongside other signs of movement. Size alone doesn’t tell the whole story.
Can I just fill a crack with caulk?
Flexible caulk works well at inside corners and trim joints. On flat walls, taping and joint compound give a more durable, invisible repair.
Why does my wall crack keep coming back?
Usually because it wasn’t taped, the underlying movement is seasonal, or there’s an ongoing issue like moisture or settling. Recurring cracks are worth monitoring.
How is fixing a crack different from patching a hole?
Cracks need tape to bridge movement, while small holes can be filled directly. For holes, see how to repair small holes in drywall.
Final Thoughts
Most wall cracks are the house being a house. Tape them, feather thin coats, and they’ll disappear under paint. The real skill is knowing the few signs that mean something more is going on, and choosing to investigate instead of patching over them. If you’re weighing whether to handle it yourself, read DIY vs. hiring a professional.