The answer to 'why is my sod thin grass' is that there are several common causes, including improper soil preparation, inadequate watering, and lack of fertilization. Thin sod can also be a symptom of pest infestations or disease.
To fix thin sod, start by aerating the soil to improve drainage and oxygen flow. Then, apply a slow-release fertilizer to provide the nutrients the grass needs to thrive. Adjust your watering schedule to ensure the sod is getting enough moisture, but not too much. If the problem persists, you may need to consider re-sodding the area or consulting a professional landscaper.