Homeowners sink a lot of money into properly installing a sod lawn. Unfortunately, lawns sometimes appear bumpy even after a new sod installation. A number of factors contribute to uneven sod -- improper site preparation, overly moist conditions on the day of the installation, frost heaves and more can cause bumps to appear in sod. You can level uneven sod in several different ways, depending on how soon you notice the bumps after installation.
Smooth out sod immediately after installation to even it out, removing air pockets and ensuring tight contact with the soil. Fill a lawn roller halfway with water and pace back-and-forth over the sod in neat, controlled lines. Do not apply any extra downward force to the lawn roller, which may overly compress sod.
Lift out panels of newly laid sod to correct any unevenness if the grass has yet to take root in the soil underneath. Remove or add soil as needed to the ground underneath the sod. Replace the sod quickly, tamp the panel back down with your foot and moisten the top 3 to 4 inches of soil.
Aerate the lawn if the sod is firmly established in the soil and bumps appear. Work the sod thoroughly with a power rake after aeration, which will remove accumulated thatch and hopefully loosen any small bumps in the yard. Rake away the thatch and loosened soil afterward.
Add topsoil as desired to fill in any depressions or slight holes. Sprinkle grass seed of the same strain as the sod over the new soil. Rake the area to level out the soil and work in seeds into the ground. Keep the seeds moistened for three to four weeks, until sprouts begin to show.
Maintain a healthy, full lawn to minimize the visual variations caused by uneven sod that cannot be repaired. Apply fertilizer four to five weeks after installation, when the grass is firmly rooted, at a target rate of 1 lb. of nitrogen for every 1,000 square feet of sod. Fertilize the sod regularly, using a schedule appropriate for your region and the type of grass.