About three months after installing turf along our back patio, a ridge about two inches high showed up running along roughly six feet of the edge closest to the concrete slab — right after a stretch of several 95°F+ days in a row. I noticed it first from the kitchen window as a shadow line that hadn’t been there the week before; walking out and pressing a hand flat on it, the turf gave slightly and sprang right back, feeling no different from the rest of the lawn, which ruled out anything spongy going on with the base underneath. That timing turned out to be the whole clue: this wasn’t a shipping wrinkle, it was heat expansion with nowhere to go.
Ripple From Day One vs. a Ripple That Shows Up Later
These are two different problems, and most guides lump them together. If a wrinkle or fold was there from the day the turf went down — a straight crease left over from being rolled for shipping — direct sun for an hour or two usually relaxes it before you ever pin it down, and that’s a pre-installation problem, not a repair. What I had was different: flat and fine for months, then a ridge that appeared out of nowhere, worse on hot afternoons and slightly less noticeable in the early morning. That pattern points to thermal expansion, not a rolling defect, and it needs a different fix.
Why It Happens: No Room to Expand
I pulled back the ridge to look underneath. The edge nails along that six-foot stretch were spaced about 12 inches apart, and the turf had been butted flush against the concrete with zero gap. Installer guides generally call for edge fastening closer to every 6 inches, not 12 — and that gap matters more right at a hard border than anywhere else in the yard, because a hard edge gives the turf nowhere to bow outward. Synthetic backing does expand measurably in heat, and with the edge pinned too loosely and no room to move into, the material had only one direction left: up. The bump wasn’t damage — it was the turf finding the only slack available to it.
There was a second factor stacked on top of the spacing problem. Checking infill depth along that same six feet with a small ruler pushed to the backing, it measured noticeably shallower than infill just three feet further into the yard — infill is awkward to work right up against a hard edge without spilling it onto the concrete, so I’d clearly gone light there without meaning to. That missing weight was one more thing the loose fastening didn’t have working in its favor.
The Fix That Held
- Pulled back the affected section along the full six feet.
- Trimmed about 1/4 inch off the turf edge closest to the concrete, to open a small expansion gap instead of a flush butt joint.
- Re-anchored that edge with new galvanized turf staples spaced every 6 inches, replacing the wider original spacing.
- Worked a hand stretcher across the section to redistribute tension evenly before re-pinning it — pulling by hand alone left a slight pucker at one corner that the tool got rid of.
- Re-brushed the infill back into the seam line.
I considered skipping the trim and just adding tighter staples to the original flush edge, since tighter fastening alone seemed like it should hold the material down. Testing that shortcut on a scrap offcut still produced a small lift under heat, just smaller and slower to show. Without a gap for the material to expand into, some of that pressure still pushes upward no matter how close together the staples are.
Total cost was about $15 in staples and a stretcher rental for the afternoon. It’s been through one full summer since with no ridge coming back, including a run of days hotter than what caused the original problem.
Preventing It the First Time
Space edge fasteners at 6 inches, not wider, anywhere turf meets a hard border — concrete, pavers, a retaining wall. Leave a small gap, roughly 1/4 inch, between the turf and the hard surface instead of butting them flush; infill and a light trim of the edge blade hide it completely once it’s brushed in. Keeping infill topped up to the depth your product calls for also helps generally, since the extra weight resists the same upward buckling — though in my case the edge fastening was the actual failure point, not thin infill. And don’t assume the first hot stretch after installation is the only test: check hard-border edges again after the season’s first real heat wave, since that’s when a too-loose edge shows itself, not necessarily on day one.
Telling This Apart from a Sinking Base
A ridge along a hard edge is easy to mistake for a sinking base problem — poor compaction or a low spot collecting water underneath — and the two need very different fixes. The flat-hand press I did when I first found mine is the quick way to tell them apart: a heat-expansion ridge springs back evenly and feels the same underfoot as the rest of the lawn, because the base hasn’t moved, only the top layer has nowhere to go. A sinking base feels soft or spongy and won’t fully recover when you step off it. That version means pulling the turf back further, re-compacting base material, and re-screeding it level — a bigger job than the one I actually had. Before fixing mine myself, I called a local install crew for a comparison quote — they quoted around $300 to pull back and re-secure a stretch that size, mostly labor, against the roughly $15 my own fix cost.