The door has developed a habit. In late summer it does not seal properly on the left, and there is a wedge of daylight at the bottom corner. By February it is fine again, and by the following August it is back.
Nothing is wrong with the door. Something is happening to the house, and the garage opening is where you see it first.
What the ground under DFW does
A great deal of North Texas sits on expansive clay. The mineral content of that clay takes up water into its structure and swells, then gives it back and shrinks. The volume change is substantial and it is seasonal.
A wet spring swells the clay and lifts what is on it. A long dry Texas summer, especially one with watering restrictions, shrinks it and lets things settle. Trees make it more dramatic, because a mature tree draws a great deal of water out of the soil within its root zone and dries that area far more than the ground twenty feet away.
So a slab does not simply go up and down. It goes up and down unevenly, and that means it also twists slightly.
Why the garage opening shows it first
Three reasons, and together they make the garage the most sensitive instrument on the house.
It is the biggest hole in the structure. A sixteen-foot opening leaves a long unsupported header and two relatively slender jambs. There is much less structure there to resist racking than in a wall full of studs.
It is usually at the edge of the slab. Edges move more than centres, because that is where the soil dries out first and wets first.
The door is a precision fit in a way nothing else is. A door has to seal against the floor along sixteen feet and against the jambs up both sides, while running in two tracks that have to stay parallel. A window can rack a little and nobody notices. A quarter inch of movement in a garage opening is visible as daylight.
How to tell slab movement from a door problem
This matters, because the symptoms overlap and the remedies are completely different.
It is probably the building if:
- The gap is at the bottom corner and is a wedge, wider at the outside edge, rather than an even gap along the whole bottom.
- It changes with the seasons and comes back, rather than getting steadily worse.
- The tracks are still true, the rollers are all in place, and the door runs smoothly by hand.
- There are other clues in the house: a door inside that sticks in the same months, a hairline crack above a window, a bathroom door that has started to swing shut on its own.
It is probably the door if:
- The gap is even across the bottom, which is usually a worn seal.
- The door hangs visibly crooked and one cable is slack, which is a cable or drum problem.
- It binds at one point in the travel, which is a track, a hinge or a roller.
- It got worse suddenly rather than seasonally.
The seasonal question is the most useful one and it is why we ask people how long it has been doing it and whether it was like this last winter.
What can be adjusted, and what cannot
Some of this is genuinely fixable at the door.
Vertical tracks can be re-plumbed and the brackets reset, within limits, to follow an opening that has moved. The stop moulding on the jambs can be adjusted so the door seals against it again. A threshold seal bonded to the floor can close a gap that the bottom astragal no longer reaches, and on an uneven slab that is often the practical answer.
A deeper bottom seal is available for exactly this and is a reasonable fix for a persistent wedge, as long as everybody understands what it is: a wider consumable compensating for an opening that is no longer square.
What cannot be fixed at the door is a jamb that is genuinely out of plumb, or a header that has dropped, or an opening that is racking a quarter inch every season. Chasing that with track adjustments means adjusting it back the other way in six months.
When to talk to somebody else instead
We are garage door people and this is where our part of the problem ends. Signs that the conversation belongs to a foundation engineer rather than to us:
- Diagonal cracking in the brick or the slab edge near the opening.
- Interior doors sticking in more than one room, on a seasonal cycle.
- Visible separation where the garage slab meets the driveway, growing year on year.
- A gap that has got worse every season rather than returning to where it was.
The last one is the important distinction. Seasonal movement that returns to roughly the same place is what clay does. Movement that ratchets in one direction is something else.
What helps, and it is mostly water
The standard advice for clay soils is consistency: keep the moisture around the slab as even as you can, all year. That means functioning gutters and downspouts that discharge well away from the foundation, sensible watering during a long dry spell rather than none at all, and an awareness of what large trees near the garage are doing to the soil under it.
This is not garage door advice, it is North Texas homeownership advice, and it does more for the garage door than anything we can adjust.
The money question
No prices, but the ranking is short. A threshold seal or a deeper bottom astragal is one of the least expensive items on a door. Re-plumbing tracks and resetting brackets is labour and a modest amount of it. Both are reasonable responses to a seasonal wedge of daylight.
What is not a reasonable response is a new door. A new door fitted to an opening that is out of square will have exactly the same gap, and you will have paid a great deal to reproduce it.
What not to buy
- Do not buy a new door for a seasonal gap. The door is not the thing that changed shape.
- Do not buy repeated track adjustments every season. If it needs doing twice a year, the answer is a seal that accommodates the movement, not a chase.
- Do not buy foam or sealant packed into the gap. It traps water against the slab edge and against the bottom of the door, and it stops you seeing the movement.
- Do not buy foundation work on the strength of a garage door gap alone. That is a large decision and it needs someone who assesses foundations, looking at the whole house.
The short version
The clay swells in spring and shrinks in August, the garage opening is the least rigid part of the house, and the door is the most precise fit in it. A seasonal wedge of daylight is usually the ground, not the door.
Which means a fair number of these visits end with a threshold seal and a recommendation to look at the downspouts. Not a large invoice, and considerably better than selling somebody a door that will not fix it.
Garage Doors Pro Service · (469) 693-9000 · garagedoorsproservice.com
Serving Dallas, Plano, Frisco, McKinney and the DFW metro.
