Answer: Usually, sod will start to root within a week or so and attaches itself pretty firmly (so it's not liftable) in four to six weeks. Without knowing how you prepared the soil ahead of time or how you initially laid and rolled the sod it is hard to diagnose what the problem is.
Ideally, the soil beneath the sod would have been deeply prepared with amendments and any fertilizers added as per soil test results and watered so that it was damp ahead of time, then the sod laid, rolled to assure good root to soil contact and immediately watered very deeply to about eight inches down. Next, you would water daily but lightly for about a week until it began to root, then back off slightly with the watering as the roots grow deeper. After a few weeks, watering would be about twice a week. Eventually it is tight to the ground and that is when you can walk on it or use it.
Watering can be tricky. You need to keep the roots and top layer of soil moist yet not turn the whole thing into a soggy muddy mess because saturated soil will inhibit rooting. On the other hand, so will dry soil.
It is also possible that you have literally pulled up the sod or hindered rooting by mowing too soon. Mowing new sod can be nerve wracking. It is better to let it grow very tall than mow too early! Mowing too short also slows rooting. Finally, if the grass ends up being very tall before you can mow it, then you have to bring the height down gradually by no more than a third at a time so as not to shock it.
If you are concerned about the quality of the sod, you might contact the supplier. If you have concerns about the soil in your yard, you might consult with your County Extension (566-0673) for information about soil testing as well as any special localized conditions affecting sod establishment.
Good luck with that lawn!
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