As long as there is grass pretty much everywhere, your client doesn't need an overhaul. Are you mulch mowing? At what height? How often is it getting watered and how much at a time? Is it KBG or a mix?

Just like the lawn went slowly downhill, if they care for it properly, it will slowly improve.

BTW - pretty much all lawns are "dependent" on fertilizer - whether it is synthetic or organic. Lawns are artificial and do not occur naturally. It isn't like "nature" is grinding up soybean mean and sprinkling it over meticulously manicured monsotrands of KBG. If you want an "independent" landscape, plant some native wildflowers and call it a day.

@Bill

Mulch mowing at 3", as to what species of grass... a good bet is a mix, and its getting watered once a week for 2-3 hours.

Whether the grass gets its nutrients from synthetic or organic sources is moot if the actual soil that the grass is growing in is utter crap.

The regular application of synthetic/organic fertilizers does nothing to improve the quality of the soil if it just soaks into the top .5" of soil beneath the thatch, if anything it promotes shallow root growth in compacted nutrient poor soil, which in turn causes the grass to be less able to rebound from environmental stress.

The OP focused on the poor quality of soil and what I thought might work to remedy the overall quality of the soil as well as the health of the lawn by improving the soil that the lawn is actually growing in. Thereby making the lawn better able to rebound from environmental stress such as, long periods of heavy rain or long periods with no rain.

The soil is extremely compacted, so much so that it takes 2-3 days of heavy rain for the rain to penetrate more than a few inches into the soil.

Though I do appreciate your response to my post, I must say it seems as if you only read the top 1/3 and fired off a response that comes across not a little condescending and somewhat snarky and offered neither a confirmation of what I am thinking of suggesting to the client as a remedy to the problem, or even an alternative approach to improving the soil itself.

Thank you for nothing

My thoughts are that if you have very poor quality soil and nothing is done to improve the quality of the soil, then your looking at lifelong application of chemical fertilizers just to keep the lawn on its last legs indefinitely.

You just described the conditions in Florida perfectly (where I live).

I'm not an expert but.... has the soil been tested? It's important to know "which" fertilizer to put on.

Also, the frequency and time of year is important for fertilizer application. As is, for weeds, a pre-emergent in the spring.

Better to get the soil tested first, then go from there.

Sorry if my post was snarky, but if you already know everything, why are you asking?

Your solution was overseeding multiple times a growing season. That is a bizarre idea. If you do it properly, you should be overseeding at MOST once a year.

As for the soil - unless your client wants to move, they just have to work with what they have. Adding organic matter is a good idea in almost all circumstances. It isn't going to help rocks though. General soil conditions usually extend hundreds of miles in every direction, so everyone in the town is likely dealing with similar circumstances but I bet you can find people with nice lawns. You don't need perfect soil to grow grass - (but it certainly makes it easier!) You could set up a lawn to grow with hydroponics if you were willing to continually care for it.

As for your take on fertilizer - I have no idea why you think fertilizer only gets to the top half inch of soil. Synthetic fertilizer goes everywhere water goes. Organic fertilizer is incorporated via our soil friends. Neither stays put in the top half inch.

For watering, if the soil is so hard that it can't absorb water, then why are you watering for 3 hours? Water for 10 minutes. Wait 10 minutes. Water for 10 minutes. Wait 10 minutes. on and on until you get 1" of water to absorb. If you don't know the run time for that, an empty tuna can is a good measuring stick for 1". If they don't have a sprinkler system, they'll probably need to get a timer for the hose. Nobody wants to be out there all day cutting the sprinkler on and off.

You really need to find out what grass is there or at least what is getting overseeded. You need to match the grass type to the environment. Planting a full sun variety in shade etc is a sure way to fail. Also, since you know the soil is shallow and rocky, it doesn't make much sense to select grasses that do best with deep root growth - eg tall fescues. Their drought tolerance is negated unless they have room to grow. Your client will be better off with a variety that goes dormant without water but recovers fast when conditions improve.

I tend to agree with much of what has already been written here. If it's a typical northern mix, it probably has at least some KBG, which spreads via rhizomes. It does poorly in shade, but if there's enough soil for it to grow and you don't have a shade problem, it should fill in and you shouldn't need to overseed.

If you've got soil that won't support deep roots, tall fescue will use more water than KBG. And if it doesn't get it, it will go dormant and die soon after going dormant. KBG can stay dormant much longer and come back once it gets moisture (and fill in bare spots).

If the soil is compacted, core aeration will help, especially if it is followed by top dressing with compost. Adding other organic matter will also help. But if it's a shallow layer of soil over rock, that's a different story (and one that you're not likely going to be able to do much about).

Since you say that it has been getting worse, that implies that it was doing better, so I assume there's some hope for it.