In the next few days, I'm going to have some dirt brought in. I have some low spots that I need to take care of. Some of these spots will need several inches of dirt.

Should I get the Roundup out, and kill the grass that's there now, before I add the dirt, or is it OK to to just cover it up?

Thanks.

are you planting the same type of grass over it? Tilling? If so, no need.
The only reason I can see to kill it first is if you're going with a different type of grass. Even then, give it time for the roundup to dissipate or till before planting.
Roundup doesn't claim any residual, but turf grass is finicky enough to grow without adding shit that will kill it into the mix...

Also, I just read 'days' - don't roundup if you plan to seed immediately/shortly.

No on the tilling, Yes on the same type of grass.

I knew I'd have to wait several days after applying the Roundup, but I'd rather not spend the money if I don't need to. It's a fairly large area. I do have a few patches of Bermuda trying to start, so I'll be giving them a dose.

Be sure and tamp the dirt down with a roller; The kind that you fill up with water to add weight. It will save you the trouble of having to do it twice. Ask how I know.

Jim

I would till or turn the soil around the edges of the areas being covered so the new grass can integrate into the grass it's butting up to.
I had to do this & it softened the edge line look of new vs established lawn.

Got that covered Jimbo. Thanks

Grumpy, I'll be spreading the dirt with a box blade. I can lower the scarifiers and rough up the ground where the new dirt will feather out. Good idea.

 
RoundUp is absorbed by the plant's foliage, and not via the root system. Sunlight helps it get absorbed. It also may take a week or two for the plant to die off. If you do spray it, wait for a period before you fill.