I've done this.

Fair warning: it's not easy, it's still pretty expensive even when you do all the work yourself, and it takes at least 4000% longer than you're probably prepared for if you've never rehabbed a lawn before.

If you want a visible transformation before the end of this summer, you would need to completely re-sod.

OR... you can rehab the lawn. There is literally no such thing as a lawn that can't be nursed back to health, if there's even a little bit of actual living grass mixed in with the weed field. It's just a matter of exactly how long it will take (spoiler alert: it's a looong time). And as I said before, it's still pretty expensive, and it's a lot of work. Like, A WHOLE LOT of work. You will definitely be wanting to set it on fire at some point (possibly at least once a week), but in the end it will be soooo worth it.

Okay, so here's what you've got to do:

1. DO NOT SPRAY THE WEEDS. Yeah, I know there's probably millions of them. I know they're an eyesore. I know you're just itching to get rid of them and start fresh or whatever, but that's not how this is gonna work. If you use broadleaf weed spray, you would have to wait at least 3 weeks before you can put seed down because it'll prevent germination and kill any grass seedlings. I know it seems counterintuitive, but you've gotta grow new grass right in the middle of the weed festival and hold your horses on the weed spray.

2. Physically remove the largest weeds. I like that spinny plunge-n-twist weeder stick doodad. You can get one at Menard's for like $10.

3. Mow to a normal height.

4. Either power rake, or heavily hand rake the entire lawn using an old-school metal toothed rake.

5. Mow again, but this time go as short as you can get the blade dropped before it starts scraping the soil and leaving bald patches.

6. Aerate.

7. Top dress (add at least 1/4" of fresh topsoil to the entire surface of the lawn). You do not need special soil, plain ordinary cheap-o topsoil is fine.

8. HEAVILY re-seed, and if you want a lawn with a deep emerald color then use at least 50% Kentucky Blue seed. Good grass seed is expensive, but don't fall for the temptation of cheap seed bags because they're mostly filler and weed seed. Schultz is a reliable discount brand. There will be a lot less waste if you re-seed by hand, rather than using a spreader.

9. Add starter fertilizer. Literally any brand of this is fine, just make sure it says "starter" fertilizer, and use whichever spreader setting it says in the instructions on the bag.

10. Lightly rake the whole lawn. You're basically just using the rake to gently mix the new layer of topsoil, the seed, and the fertilizer.

11. Depending on what the birds are like in your area, you may need to cover your new seed with rolls of that green hay-looking stuff so it doesn't all get eaten.

12. During the germination/growth period, water lightly once a day (twice in hot weather) until the new grass is at least 2" tall.

13. Water deeply every four days (or twice a week if you're like me and that's easier to keep track of). Once the grass is established, it will not need daily watering. You DO NOT need to water a healthy lawn every day. This actually encourages short roots and a weaker, thinner, more weed-prone lawn. Deep, less frequent watering encourages longer roots and hardier turf. Keep an eye out for signs of scorching during the hottest parts of summer, and shorten the interval between watering accordingly (even during crazy hot periods, I still only water the full lawn every 3-4 days and just use a spot sprinkler every other day on a couple of areas that tend to scorch).

14. DO NOT MOW until the new grass is at least 3" tall. This is seriously the hardest part, because you haven't sprayed for weeds yet (since it would kill the new grass seedlings) and you've still got alllll those weeds growing, so it's gonna get long and really, really horrible-looking before it gets better. BUT IT WILL GET BETTER. If you give the seedlings time to establish strong roots, you will eventually get a hardy lawn that will help crowd out weeds.

15. Once your new grass is at least 3" tall, you can finally mow. Set your mower blade to the tallest setting (this is usually 3"). Don't mow the grass short because this encourages a thin and weedy lawn. Mow regularly (twice a week during the active growing season) and you won't need to bag or rake the clippings. Leave them to break down and condition the soil. Don't wait too long between mowings or the clippings will be long and they'll smother the grass.

16. Fertilize again. This time you can use either starter fertilizer or the generic 10-10-10 stuff.

17. After you've been able to mow three times (keeping the blade setting at 3"), NOW you can finally spray the entire lawn with a broadleaf weed spray (like Ortho, although my personal preference is this stuff called "Weed Out With Q" even though it's more expensive). You'll need to do this every ten days, until three weeks before you repeat the entire re-seeding process in the fall.

18. Yeah, you heard me... you gotta do this whole shebang all over again in the fall. Probably also again next spring, and maybe even AGAIN next fall, depending on how bad it really is right now. Are you excited yet?

19. You do not need to power rake or aerate again this fall, so you can skip those steps. You will need to power rake again every spring, and depending on what your soil is like you'll only need to aerate every 2 or 3 years (once a year at most, even if you've got heavy clay soil).

20. After your new lawn is fully established, overseed at least once a year (I usually do it twice, in spring and fall). Follow a regular 5-stage fertilizer schedule, and apply broadleaf weed spray every 4-6 weeks (but remember to wait until 3 weeks after you spray when overseeding, and wait at least 3 weeks after overseeding before you spray again).

So yeah. Like I said, it's a ton of work and it's not a speedy process, but when it's finally done you'll have a lawn that's as close to perfect as any surface made of a million living things can possibly get. It'll be thicker, hardier, and have better color than a sod lawn. And you'll be way more likely to take diligent care of it forever, since you basically broke your back to create it.

Of course, if you want to invest the money, you can hire out any or all of the steps in this process (just be very wary of the seed mix used by anyone you hire). I did all of it myself, except for the aerating. Once it was established, I hired out the fertilizing and weed spraying, and I usually hire out power raking every spring because that chore sucks. I did it manually during the seeding process, but I whined about it the whole time.

Best of luck with everything! Progress pics would be fantastic. I didn't take any when I went through this whole thing (I needed two full growing seasons of this nonsense to get my lawn in tip-top shape) and if I had a time machine I'd go back and kick myself for doing all that work and then being too lazy to take a few snapshots of the progress.

Sometimes and existing lawn is NOT worth renovating/ rejuvenating. This is because the grass may be an old, out of date variety. New varieties of all the major grass types on the market as so much better than they were 20-30 years ago.