Why your ball hops or wobbles crossing a seam on your putting green

A seam is two pieces of turf joined edge to edge, with sand meant to run the same depth straight across it so a ball cannot tell where one piece ends and the next begins. A few things break that.

• A gap. The pieces have pulled slightly apart, and a ball catches the edge of the backing.
• A peak. The seam has lifted just enough to sit slightly higher than the turf on either side.
• Uneven sand depth. One side of the joint has more or less sand than the other, changing how the ball releases across it.
• Failed adhesive. The tape and glue under the seam have let go, even if the surface still looks joined.
• A settled base. The ground under the seam has dropped slightly, so the seam itself dips.

Lay a straightedge or a flat board across the seam and look for daylight or a lip under it. If the board rocks or one side sits higher, you have a peak or a settled base rather than a flat gap. Do this in a couple of spots along a longer seam, not just the worst-looking point, since a seam can play fine in one section and be off a few feet away. Then roll a ball slowly straight across the seam from both directions. A consistent hop from either direction usually means sand depth or a physical peak; a hop that only happens one way can point to a gap catching the ball on one edge only. Press down on the seam itself with your palm; give or a hollow feel under it points toward the base rather than the surface.

Where the sand is uneven, it is brushed and redistributed so the depth matches on both sides of the joint, then rolled to set it. Where the seam itself has lifted or the adhesive has let go, the joint is cleaned, re-taped and re-glued along its full length, then groomed so the fiber grain runs the same direction across it. That is a seam repair, from $250 depending on the length of seam involved, and it is usually a single visit.

If the straightedge shows the seam dipping because the ground underneath has settled, re-gluing the same joint does not hold, since the seam will keep dropping with the base under it. That is base work, lifting the seam, packing and re-compacting what is underneath, and re-laying the turf, which our sister company, TIMELESS Grass & Greens, handles rather than us. We will tell you plainly if that is what a seam needs instead of re-gluing something that will only come back.

Any turf lawn can show a visible or open seam, and our page on seams showing in artificial grass covers the general causes and checks for that. A green seam has one more layer to it: it has to play true under a rolling ball, not just look tight, so a seam that is cosmetically fine on a lawn can still be a real problem on a green if the sand depth across it is off even slightly, similar to how a cup can look fine but still sit slightly low, covered on our sunk or uneven cups page.

Call as soon as a seam starts affecting how putts cross it, rather than waiting for it to open further; a small gap or peak is a quicker, cheaper fix than one that has widened over a season of play. A seam caught early, while it is still just a faint hop rather than a full skip, is usually the simpler repair of the two, which is worth checking after any season with heavy rain or a lot of play. Seam repair on a green runs from $250, similar to a lawn seam, though access and the amount of sand work involved can move it. If the straightedge points to a settled base, we will say so plainly rather than re-gluing a joint that will not hold.