Newly laid sedum roof

Just laid my first ever sedum roof with help from OH

Looks fine, but was wondering with it being about 1 degree in central London at the moment at night, if it's a bad idea to water it or not?

It came as fully grown sedum turf tiles, so you can only just see the edges of the tiles.

Will they freeze if I water them? 

I wouldn't water it while the weather is so cold. Sedum can manage some drought anyway.

Thanks Busy! I knew about its drought tolerance, but was worried it may not knit together properly now, when it's roots are still not established in the growing medium, without any watering. Should I wait 'til the temperature hits 10 degrees or so in March then (allegedly!)?

I really meant when the temperature isn't zero or below during the night, water to ice.

thanks