Weeds can take from a few weeks to a month to totally die and repeat after six weeks to clean the lawn’s surface of any weeds. Over-seed any bare areas a month after treatment when the weeds have died to prevent these areas being populated by more weeds.
Do not spray newly seeded lawns with weed killer until the new seed is at least four leaf stages (count the leaves) and you have commenced mowing of the new lawn. Mow in multi directions.
If your lawn had localised dry patches on it before it was renovated, the seed may not germinate and establish in these problematic areas. You can only solve these natural occurring hydrophobic (water repelling) soil conditions by applying a surfactant better known as a Wetting Agent, in a tablet, liquid, or granular formulation. Nothing will grow without water and cure and prevent Dry Patch to enable to seed to germinate and establish.