Prep the soil.

Add the in-ground irrigation.

Seed the grass.

A bit extensive but you'll find the answer to your question from turf experts: http://plantscience.psu.edu/research/centers/turf/extension/factsheets/lawn-establishment

PNW,

I would add one more step after irrig install. Water for a week and kil all the weeds that pop up. Then seed and roll and light seed cover with soil. Then don't let the seed dry out completely for 3 weeks.... etc

lehua49 - We started off by killing the weeds before putting down topsoil. The topsoil was guaranteed weed free and it really was, thank goodness. Had it not been, we would have needed to do as you suggested. Thank you.

In case anyone is curious. In an ideal world, we would have dug our ditches for the irrigation lines first, then brought in topsoil, then installed/attached the sprinkler heads. Then planted (we ended up hydroseeding). However, due to certain circumstances, we were only able to follow these steps for the front lawn. In the back lawn it was topsoil first, then irrigation lines. It was a big project, but with the unusually warm weather in WA this September and October, we have really appreciated the irrigation system with our new grass.

PNW,

Happy Mowing. What type of grass grows well in WA.