Most Tall Fescue/KBG mixes are in the ratio 90:10 or 80:20 BY WEIGHT. Tall fescue seeds are relatively large, 100-200K seeds per pound, while KBG seeds are much smaller 1-2 million per pound. If you do the math you will see that the ratio of seeds per pound is close to 50:50. KBG takes much longer than TTTF to germinate. TTTF takes about a week, while KBG takes 2-3, and grows very slowly. If you stop watering or taper it off because the TTTF is nice and tall your KBG will suffer and you might lose most or all of it. You certainly can overseed with just straight KBG, I would do about 1 pound per 1000 square feet. I would also select a cultivar that has a high heat tolerance like Solar Eclipse, or one of the Mid-Atlantic types, which are more heat tolerant than many of the standard cultivars.

A few relative questions:

* Where in NC are you located? Western, Piedmont, Central.

* Do you have any shade issues?

* Do you prepare ground for seeding, or do you just put seed down and water?

I'm just north of Charlotte.

About 1/4 of yard gets good shade.

Every fall I core aerate, lime, fertilize, seed, water. Not much else...

I don't water much any other time of year so I bet my KBG is suffering from that.

I completely agree with the comments from tiemco. Also, do you submit soil samples for testing? Just wondering why you apply lime every fall unless soil sample test results indicate a need for lime.

I used Scotts sunny mix last fall which is all KBG.
aERATED FIRST AND KEPT THE SEEDS MOIST.
hAD GREAT RESULTS.
uSED ORGANIC FERTILIZER FOR THE FIRST TIME THIS YEAR. rEALLY LIKE IT!

Where did you buy the Sunny Mix? It seems only Fescue seed is available in the big stores in my area.

Have not had a soil test done. I know I should. I just go by local area recommendations.

"Have not had a soil test done. I know I should. I just go by local area recommendations."

I used to be in this boat, but it is one instance where ignorance isn't bliss. My first soil tests showed pH's of 5.5 for my front yard, and 4.4 for the back with deficiencies of macro and micro nutrients, and I was wondering why my grass struggled, duh. Get a soil test, it's 20 dollars that pays for itself (www.loganlabs.com). Anyone that is trying to grow a great lawn that doesn't get a soil test is fighting an uphill battle.

"Where did you buy the Sunny Mix? It seems only Fescue seed is available in the big stores in my area."

The only reason(s) for buying a big box store mix is because it's a lot easier to just go to the store and buy the bag. The reasons why you shouldn't are many. They usually contain mediocre, older cultivars that don't perform well. They can contain weed seeds. They are often more per pound than better seeds from a reputable seed seller especially if they have a watersmart coating. The mixes are poorly thought out and usually contain grass you don't want or need. I have seen very few good mixes/blends at Home Depot, most are to be avoided. The seeds offered are usually specific to the location of the store, i.e. you won't see Bermuda seed in a Connecticut store. This is probably why you don't see KBG in your area, as it's not generally thought of as a grass that should be grown in NC. As I mentioned earlier, there are those KBG cultivars that are more appropriate for your location.

tiemco - where would you look to find better quality seed? Should I go to local nurseries, or look online? suggestions?

Most of your better seed sellers you can find online. If you live near one then by all means buy from them. Here is a short list of some good ones:
Williams Lawn seed, Pawnee buttes seed, the hogan company, summit seed, j.d Oliver, chas hart seed, seed superstore (great seed selection, very very expensive) .