Concrete is more sensitive to weather than people think. The temperature when you pour, the humidity that day, and what the ground looks like after a week of rain all affect how the slab cures and how long it lasts. Here's what we tell homeowners around Lake Norman and Charlotte who ask when they should book their project.
Spring and fall are the best windows for concrete work in North Carolina. Think April through early June, and mid-September through early November. Daytime temperatures sit between 55 and 80 degrees, overnight lows stay above 40, and the humidity is moderate. Concrete cures at a steady, predictable rate under those conditions, which gives you the strongest finished slab.
Most homeowners book in late winter or early spring for projects they want done before summer. By March our calendar usually fills out into June, so if you're thinking about a driveway, patio, or slab, getting on the schedule early matters.
Summer pours
Summer in the Piedmont is hot, humid, and unpredictable. We pour all summer, but the crew has to work around the heat. Concrete cures faster when it's 90 degrees out, which can lead to surface cracks if it's not finished and protected fast enough.
We start summer pours early to avoid the worst heat of the afternoon, and we use retarders in the mix when needed to slow the set. Wetting the sub-grade and covering the slab with curing blankets after finishing helps keep the slab from drying out too quickly. None of this is a problem for an experienced crew, but it's why summer projects sometimes look different from spring work if the contractor isn't paying attention.
The other summer factor is afternoon thunderstorms. We watch the radar closely and reschedule if heavy rain is moving in within a couple hours of a pour. A hard rain on fresh concrete is a real problem.
Winter pours and rain delays
We can pour concrete in winter, but there are limits. Anything below 40 degrees overnight makes the cure unpredictable, and below freezing the water in the mix can freeze before the cement sets, which destroys the slab. We use insulated blankets, hot water in the mix, and accelerators for cold-weather work, but if we're looking at a stretch of nights below 30, we'll usually push the pour to a warmer week.
Rain is the other variable that moves dates around. We don't pour on saturated ground because the sub-grade has to be firm and properly compacted. After a heavy rain it usually takes a couple of dry days for the soil to dry out enough to prep. NC red clay holds water, so a Tuesday rain can push a Thursday pour to Monday.
Most of the time we can keep projects on schedule by watching the forecast, but every now and then weather wins. We'd rather delay a pour by a few days than pour on conditions that won't give you a slab that lasts.
If you're planning a project for spring or summer, the best time to call is now. We do free on-site estimates and can put you on the schedule before the calendar fills up. Call (704) 313-8403 to set something up.
Related service: Concrete Driveways