Cracked or Split Garage Door Section

The most common location we find, and one of the more diagnosable.

Hinges join the sections and carry the load between them. Their fasteners pass into the section's stiles and skin, and those holes take a small load reversal every cycle. Once a fastener loosens, or a hole starts to elongate, the joint has play. The section then absorbs a small shock every time the door starts and stops, right at the hinge fixing, and the material around that fixing is where it shows up.

The important part is the order of events. The hinge didn't crack the section by being faulty; the joint developed play, and the play cracked the section. So replacing the hinge alone puts sound hardware onto material that's already split, and the play comes straight back.

How you can tell: A crack running out from a screw or bolt at a hinge, often diagonally. Frequently there's a loose fastener, an oval hole, or a hinge you can rock with a fingertip.

If the door was dented once and the dent creased the section, you've had a permanent fold across the panel ever since. Steel that has been folded past its yield point never gets its stiffness back, so the fold becomes the place the section prefers to bend.

From then on it flexes there on every cycle. Not much — a fraction of an inch — but thousands of times, in a material that was never intended to work that way. The crack is the end of that process rather than a new event, which is why people describe it as appearing overnight on damage that's years old.

We cover the earlier stage of this on our page about dented panels, and the reason it's worth reading is that the whole sequence is preventable at the point the dent happens. Once the crease has cracked, the section is past assessment and into replacement.

How you can tell: The crack lies along an existing fold, usually horizontal, on a section with visible impact history.

Glazed sections crack at the corners of their openings, and it's a straightforward consequence of geometry rather than a defect.

Cutting an opening into a panel removes material and creates four corners, and corners crowd stress. Under any bending, the highest local load in that section is at a window corner. As long as the section stays rigid, that concentration never amounts to anything. Introduce flex — from racking, from a heavy door, from an out-of-square opening — and the corners are where the material runs out of margin first.

These carry a practical sting. Top sections with windows are among the more expensive panels on a door to replace and often have the longest lead times, because glazing configurations vary and the section is built to order. That makes an early call on a glazed section worth more than an early call on a solid one.

How you can tell: A crack running out from a window opening corner, often at roughly forty-five degrees. Sometimes the frame or the glazing bead has also loosened at that corner.

The cause behind most cracks that show up in more than one place at once.

A door that doesn't rise squarely — one cable holding more than the other, a drum out of adjustment, a bent track, a roller binding on one side — twists as it moves. The sections don't stay parallel to each other. Each joint takes a small twist on every cycle, and that load goes into the stiles, the hinges, and the skin between them.

You'll usually feel it before you see it. The door shudders, rattles at one point in the travel, or shakes as it starts. People adapt to that noise over months and stop hearing it, which is why the crack often seems like the first symptom when it's really the last.

This one matters more than a single cracked panel because racking damages everything at once — rollers, track, hinges, cables. The crack is the visible part of a wider bill.

How you can tell: Cracks at similar positions on more than one section, or a single crack on a door that shakes, shudders or runs unevenly. Often the door also looks slightly out of square in the opening.

Less common, and satisfying to diagnose because the cause is right there in the geometry.

A strut makes a section rigid along its length. Where it stops, the section goes back to being flexible. That transition is an abrupt change in stiffness, and abrupt stiffness changes are stress concentrations in the same way corners and holes are. Bending that the braced part of the panel refuses to do all has to happen in the unbraced part, starting right at the end of the brace.

Usually this means the strut is too short for the door, was fitted to solve a local problem rather than sized for the section, or was added by somebody who didn't take it to the end stiles. It's one of the reasons we're firm about struts being specified rather than bought — a brace that stops short can make a section worse than no brace at all.

There's a Valley-specific reason those ends work harder than they do elsewhere. An insulated door flexes with temperature — DASMA calls thermal bowing inherent to bonded-core sections rather than a defect, and says the door bows toward its hotter face, which here means outward on a sunny afternoon. A strut is what resists that flex. The steel either side of where it stops does not, so the transition is a stress riser that gets worked every hot day, not just every cycle. Wide doors and dark doors flex more, which is why this crack turns up on exactly those.

How you can tell: A crack starting at or just past the end of a horizontal brace on the inside face, often running toward the nearest edge.

The best outcome, and common enough here to check for before anything else. A fine network of cracks across a painted face, or a coating lifting at the edges, is a finish failure. The material behind it is intact.

The mechanism is heat and ultraviolet exposure. A door face in Mesa or Chandler swings through a large temperature range every summer day, the substrate expands and contracts, and a coating that has lost flexibility to UV can no longer follow it. So it crazes. On a repainted door it happens sooner, because the previous coat wasn't prepared properly and the new film is only as good as what it's stuck to.

What makes it worth acting on is what it exposes rather than how it looks. Once the coating opens up, bare material is available to sprinkler overspray, and that's where rust starts on a door in a place that gets very little rain.

How you can tell: A network of fine lines rather than a single crack, distributed across a face rather than radiating from a point, and no movement when you press either side.

Doors with an applied face — composite overlay boards, carriage-style trim, or a wood-look layer over a steel core — fail differently from plain steel, and it isn't the failure most articles describe.

Somewhere else the story would be rot. Here it's expansion and adhesive. The overlay and the substrate behind it expand at different rates through a daily swing that can run forty degrees on a west-facing door. The bond and the fasteners take that difference every day. Over years, joints open, edges lift, and boards split along their length or at the fixings.

Once water can get behind an overlay, the failure accelerates, and around here the water source is usually irrigation rather than weather. That's also why the damage often appears low on the door and on the side nearest the lawn.

How you can tell: Splitting along an overlay board rather than through the door skin, joints opening at the ends, edges lifting, or trim that sounds hollow when tapped.

The quiet one, and the reason we ask people to press the panel rather than only look at it.

An insulated section is a bonded assembly: outer skin, foam core, inner skin. Its stiffness comes from those layers acting together. If the bond fails — from heat cycling, from an impact, from water that found its way in — the layers start behaving as separate thin sheets, and thin sheets are enormously less rigid than the sandwich they came from.

The section then flexes far more than it should under normal load, which produces cracks at all the usual stress points: hinges, corners, stile joints. So delamination often shows up as a section that has started cracking in several places for no visible reason.

The tell is sound and feel. A bonded panel is solid under a knuckle. A delaminated one sounds hollow in the affected area and dishes more easily than the sections around it.

How you can tell: A panel that sounds hollow when tapped, flexes noticeably more than its neighbors under hand pressure, or has visible separation at a cut edge.