It's probably a result of holding water. You'll likely have to mitigate that or it will always be a problem.
Is there a mixing formula or measurement's for this?g-man said:Like ware said, moss develop when the soil remains moist. I would check how is the grading of your lawn in that section. Normally you want the soil to slope away from your foundation.
Then you could treat the moss with Dawn (dish detergent).