If Crabgrass or other weeds do get in your lawn, spray them with Bayer Lawn weed and crabgrass killer, just be sure its not over 85 degrees or your lawn will burn

Clay soil is definitely a challenge for us in the TriValley area... Clay is Alkaline not Acidic so it's high on the ph scale not low. Rototilling builders sand and gypsum into the soil will help separate the clay particles and soften the soil for better root pentration and adding compost will help get plantings the nutrients they need and lower

the ph so a more broad range of plants can grow 

Great customer and contractor relationships equal great work and service... 

The best way to manage weeds is to PREVENT them... Pre-emergent prevents seeds from germinating

Apply in February (when you plug aerate your lawn), May, and August, then reseed your lawn in November when the chemical is no longer active.