What to do about crabgrass-covered lawn?

Question

I live in the San Francisco area, zip 94708. I put in a new lawn (sod) in mid April. It's now 70-80% crabgrass, probably due to improper watering and mowing. Should I try to kill the weeds now and replace with grass seeds? Is that even possible with the weed's extensive root network? Or, shall I let nature take over and have a crabgrass lawn? At what temperature does it die? There is no frost here. Let me know if there's a third and better option.

Answer 1

Are you sure it is Crabgrass?  Seems odd if you sodded your lawn in April.  The reason being that crabgrass germinates in June (and we see it in July), then produces seed in the fall (Sept/Oct.).  With that being the case, the crabgrass seeds would've invaded your lawn long BEFORE you sodded.  And most sod successfully BURIES most weed seeds to the point that you will never see them.  

I'm just thinking that you may have something else.  I know alot of people think they have crabgrass and they really have BERMUDAGRASS.  Crabgrass root system is really not that extensive.  

Temperature that it dies?  NONE, crabgrass is an annual weed. It starts from seed in the spring/summer and dies following flowering/seeding in the fall.  You have bermuda, huh?  Stringy stuff? Spongey?

My brother lives in Haight Distr.  :)