So I have a customer who had a bunch of red oak trees sawn and dried off of their property. They want all slab doors and drawer fronts. I'm planning on putting battens on the doors but I still worry about expansion and contraction and warping. It's a full overlay kitchen and they want tight gaps. I've told them this is a bad idea but the customer is set with this idea. Any thoughts?

Just don't do the job. There's plenty of work to be had right now.

If you need the job have them sign a warranty waiver. At a minimum stating that no issues related to warping/expansion will be covered. However I'd recommend that they have absolutely no warranty at all. This way they can't play dumb and say they didn't know the problem was related to warping.

Make sure they understand that no quality cabinet shop would ever make slab doors from solid material. There are reasons its not done this way.

Really though, just walk away. It may be the only way to get them to rethink their idea. The customer is not always right.

Tight gap on solid slabs? Bad idea is the least of it. How many call backs are you willing to put up with for " the doors aren't opening without rubbing! The doors look horrible with uneven gaps( in the middle of winter)" Veneered over man-made core would be the only way I would do it.

You can make them in the summer with tight gaps, but they will be much wider in the winter. Battens can cause more problems if you fasten them up solid, or even attempt to glue them on. The battens must have slots for the holes at the widest points and can be tight in the center. I thought slab doors with battens went out in the 80s.

Rich is on the right track. If you build them while you are in the humid cycle, then the gaps will grow. Generally, a call back on the too large gaps does not require any work from your people other than you arriving with a few calculations from the Shrinkulator.

You have consulted the Shrinkulator, right?

If you live in the Midwest, the Oak doors will sit at about 7%-9% in a house with 30% RH. If your lumber is 6% upon arrival at your shop, and close to that when shipped, then a 30" wide flatsawn door will expand to just over 30-1/4". If quartersawn, then it will expand to just over 30-1/8".

Prior to building, I would walk them thru this with a nice simple example, explaining that this is science - neither voodoo or guesswork or opinion. Give them a 12" long pice of Red Oak, and show them how they can blow bubbles in a glass of water.

Then ask them if they will let you do what you would do as a professional, or would they prefer tight gaps, and likely problems, with numerous callbacks, ending up with what you suggest today - allowance for the material's properties.

And the cleats on the back? Again, Rich is right that they must be slotted screw holes, with washers under the screwheads. And the slot sizes? Just a hole in the center of the cleat's length, with the slot length increasing as you move out to the ends. The Shrinkulator will help you determine the slot length.

Customer is trying to convince you to do something they know nothing about, and you know better, or wouldn't pose the question.
Thought-Run, do not walk, away

“Customer Management” is your job. You lead them to a decision favorable to your building style, while getting them to think it is their suggestions. I think it a bad idea to ever use the word “no” in these discussions.

If you don’t want to do customer management, then you need to get a job building boxes. Sales and the nuances it entails, is half your job.

I worked at in a shop back in the 80's and this was a trend, but we always had call back with door margins. I am in Nebraska so hot in the summers and cold in the winters so we couldn't win with door margins. Today we only use MDF but I know your customers want the solid wood. I would only build the cabinets with the dreaded mullion like the factories down the middle and that would solve the margin issue but once again you are custom so that probably doesn't help.

Runn the other way!

Jim K - In lieu of the center vertical rail, one can add a batten to the back of one of the paired set of doors. half on, half off, it will blind the gap and prevent seeing the groceries in there.