Keeping an eye on your contractor when you’re having a lawn put in on your new home (or being re-done on your old home) is essential. Carelessness, incompetence, and corporate greed can result in a variety of problems for your yard and home, including (but not limited to) flooding your crawlspace, costing you lots of money on your water bill, or causing chronic fungus or draught issues that will kill (or cripple) your grass. Repairing these things after the fact can cost a few hundred to tens of thousands of dollars depending on the problem.
Watch the Grading
This is the single most important thing to watch for when someone is working in your yard. The dirt absolutely needs to slope away from your house (the longer that slope is the better), so that irrigation, rainfall, and flood waters drain away from your home. If an irrigation line breaks, the mess in your yard will be enough work without also having to bail out your crawl-space (and possibly spend years battling mold, which can make your home un-livable). If you think that your lawn is graded toward the house, insist that your contractor add more soil until the problem is fixed.
Take a Core Sample
In my area, and in much of the US, it’s common practice for developers to buy large plots of land, scrape the fertile topsoil off, and then build houses on the rocky dirt or clay that remains. To get grass to take hold they’ll buy some of that topsoil back and spread it thinly over where the sod will be placed or grass will be seeded. Unfortunately the result is that the roots of this new grass sometimes can’t penetrate past this thin layer into that rocky, hard-packed dirt, which makes your grass unnaturally vulnerable to draught, and prevents it from getting properly established. If you can catch it before the grass is planted, check how deep your topsoil layer is. If it’s 4 or 5 inches deep you should be ok, your grass will be able to establish itself well enough that the roots will break into the harder layer below with time.
If you take a core sample of an existing lawn and see that the roots aren’t penetrating more than an inch or three then your topsoil is too thin and the ground isn’t absorbing water well. It’ll probably require more frequent watering than a normal lawn, and that means that if you want to keep your lawn really green you’ll attract fungus. To address this you can let the grass grow longer (3-5 inches) for a season to give the grass a little more power with which to sink its roots. If that doesn’t work, you might be forced to lay dirt on top and possibly re-seed in order to get the necessary topsoil depth.
Get the Right Kind of Grass
One of the biggest drains to our water resources in the western US is the persistent and ridiculous use of Kentucky blue grass in our lawns. It naturally survives in much wetter climates and naturally isn’t as hardy as most local species. Depending on your local climate you can get native or hybrid species that will naturally grow deeper roots in poorer soil while requiring less water.