Since we don't know your location or climate we can't say whether they will need watering at all. The root run under pavers is often cooler and moister than in the open so you may not need to water at all.

I live in Northern California, climate zone 9.
Looking for fuss free, drought tolerant hardy ground cover.

So the question is really to suggest a plant that doesn't need regular irrigation? It sounded as if you already had the plants but wanted watering advice. Now we know where you are and what you're after I'm sure you'll get some suggestions. I can't help knowledgably because my climate is very different but I'd imagine that creeping thymes, sedums and dianthus would fare well for you.