Kitchen upper cabinet lengths

You seem to be asking about heights. Cabinets have height (up and down), width (side to side), and depth (front to back).

For an 8' ceiling I like 39" uppers which allow space for trim at the top.

What combination is your cabinet man suggesting?

I agree with @PPF. What you are asking about is the height (not length) of the cabinets, and what your ”cabinet man” is talking about are called ”stacked upper cabinets”.

Stacked upper cabinets do not make sense for an 8’ ceiling as you thought. It also does not make sense for him to say that a single upper cabinet door that meets an 8’ ceiling will warp. You need to find another cabinet source - this guy has red flags all over him. I’d drop him really fast. You’ve been warned.

Don’t forget that you’ll need a crown for the cabinets that meet the ceiling. With an 8’ ceiling, if you get 39” tall upper cabinets as PPF suggested above, you’ll need a 3” crown. Or, you can get 36” tall upper cabinets with a 6” crown.

Definitely 39" uppers, and make sure you order an extra shelf (3 adjustable shelves) for each.

What are your goals for the new kitchen? What do you like and dislike about your current kitchen? Are you keeping the same layout with new cabinets?

Since you are getting new cabinets, make sure you get all drawers. And no angled upper corner cabinet. In fact, if you want some ideas on how to optimize your layout, post a measured floor plan of your space, showing all walls, windows, and doors.

You do not have enough height to split the doors to fake stacked cabinets. It will look squat and frumpy.

8’ ceilings, cabinets to the ceiling, with molding above.

Edited to add: Kitchen is 7 1/2 years old. Birch doors. Location: Long Island, NY, so variable climate with periods of high humidity. Central AC. No warpage.

Had natural maple cabs to the ceiling in former home, we installed in 1990. Also on LI. Sold 30 years later, 2015. No central AC, window units. No warpage.

My kitchen also has 8 ft. ceilings with cabinets that go to the ceiling, The cabinets are 39” with 3” of stacked crown. The cabinets are now more than 10 years old and there had been no warping what so ever.

Not sure why your cabinet maker would suggest shorter cabinets with an additional cabinet above. In my opinion, stacked cabinets would not look good.

The cabinetmaker is worried about the door warping… the OP states that. It is a legitimate concern, more so in some regions and some woods.

Board warpage is logarithmic. A 30” door has little chance of noticeable warp, but the risk of noticeable warp increases exponentially as cabinets grow taller. To combat that you can make the doors a bit thicker or backcut the panel, you can also make sure the rails and stiles are wide enough to retrofit door straighteners if they do warp.

If the cabinetmaker has had this happen a few times, don’t ignore it, but it should be manageable.

As tall as 48" single doors are done all the time. You just need to control your humidity in the home. 30-50%. Use your AC in summer and use a humidifier in winter.

Hickory is notorious for warping on doors (even 30” doors will wapr occasionally) and you are taking a pretty significant risk doing a 39" Hickory door and an exponentially larger risk doing a 48" Hickory door. Oak moves, but rift-sawn is incredibly stable and quarter-sawn is relatively stable (this is why thicker boards are better because there is more rift on a plain-sawn board when it is thicker).

The details matter... it is impossible to reliably say that any homeowner will be fine with taller doors by controlling humidity. The wood matters, how the wood is milled matters even more, the construction method matters, etc. If a cabinetmaker is worried about his doors warping the next question needs to be why. If the cabinetmaker can explain their concern then they likely know what they are talking about... However, there are also a lot of cabinetmakers who really don't know the first thing about wood.