Need a membrane under it to keep cracking to a minimum or don't need it? 257 sq foot kitchen and laundry room. Advice??

use thin set and you ready to go, no need for a membrane

Home builder did my front entryway tile over concrete and it cracked. The 3rd time they were out to fix it they laid a membrane and it has not cracked in the 13 years since.

Put a membrane over existing crack in slab. You can actually buy a brush on membrane. Always use latex fortified thinset.

In my experience I would always put down some type of membrane,unless layed on a mudbed. If you lay straight to the slab and get any kind of movement or cracking,it's going to show in your grout lines and tile. We lay all of our tile over slipsheet. Go to your local surplus floor store and get the cheapest roll vinyl they have for sale. Lay it to the slab upside down where the felt backing is facing up,with vinyl floorinig adhesive. Lay your tile over that with a good multi purpse thinset and your good to go. Don't forget to prep the slab good to,one of the most important parts.

9 out of 10 houses with tile built in the last 10 years are straight to slab. Other way are better, but if every uprgrade or every new house was done the best way possible no one would afford them.

This. Grout is easy to fix, especially if you've got a good post-tension slab and it isn't moving all over the place.

Yep,they can afford them when they buy them. But in the long run it will cost you in money for repairs. I have done repairs on shower stalls in 500,000 $ homes where the tile was layed right to the sheetrock. Two yr. old home and the walls were falling down in the shower. So I guess they just do this so people can afford them? I don't think so.

Yeah the grout is easy to fix, but if it is already popping out and you regrout it. Won't be long before it does the same thing.