I need to buffer a line 1 meter, however when running the buffer tool in QGIS with the end cap style as "flat" I get the result shown below.

What causes this, and how can I fix it?

Buffer with cracks

  • 2
    This stems from bends in your line. Try buffering a line with a 45° bend, and you'll see it more clearly.
    – Erik
    Commented Jun 25, 2020 at 10:20
  • 2
    more likely to be the join style than the end cap
    – Ian Turton
    Commented Jun 25, 2020 at 10:43
  • Is this a collection of lines or a unique polyline? It seems to be a collection of lines, so it has several end caps, and is fragmented. Try to join into a polyline Commented Jun 25, 2020 at 12:41

1 Answer 1


As commented, it seems to be a collection of line and not a polyline. I tried to explain in the image below. The first one has a collection of polylines. You can see that when it is a polyline, the buffer stay connected. And when is another line it has a endpoint/cap.

The second sample is when the buffer is checked the dissolve. It looks like your case.

The third sample is a buffer of a unique polyline.

enter image description here

To tranform the multiline layer to a single poly line you can do it manually with the merge tool in the Advance Digitalization toolbar, or with the function dissolve (vetor > geoprocessing > dissolve).

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