Laying sod onto your lawn is a great way to refresh the look of your grass without tearing up your yard to make room for new grass seed. Laying sod is like laying small throw rugs of grass over the area and then letting them naturally take root. To avoid damaging the new sod, you must be careful about when you walk on it and follow other post-laying specifications.
Technically speaking, you can walk on your new sod as soon as you have laid it in place. In fact, you will need to do so to perform regular maintenance like feeding and watering. However, you want to limit this foot traffic as much as possible, because it can disturb the roots that are trying to settle into your lawn. And don't let more than one person walk on the newly laid sod at one time; limit it to just the caretaker, and only when absolutely necessary.
When to Walk
You can walk, run and play on sod as much as you like two weeks after laying the sod in warmer months. If you decide to sod your lawn when temperatures are lower, wait three weeks. The roots will take hold in the ground faster during warmer weather. Waiting the appropriate number of days ensures that your sod firmly embeds in the ground and won't shift or suffer broken roots due to foot traffic.
If you are watering your sod properly immediately following installation, you won't want to walk on it any more than is necessary for maintenance purposes. If watered properly, your sod will be squishy and you will sink in when you walk on it, so wear shoes that you don't mind getting muddy. When you water the new sod, you need to saturate not only the layer you just installed but the soil underneath, so that the sod roots can still access water as they penetrate the soil. Surface watering will result in shallow roots and wilting grass, so the sod should be consistently moist for the first few weeks after installation.
By the time you can walk freely on your sod, it will probably be time for the first mowing. Once you start mowing, reduce your watering so that the lawn receives about an inch of water every week. Many times, you will find that the grass gets enough water from rainfall, but you may still have to water during times of drought or limited precipitation. Even in the worst drought and highest heat, you should need to water an established sod lawn only twice a week, three times in completely desperate situations.