Because it’s winter, with low humidity, and you have painted mitered cabinets, which are far worse at showing the seam than stick and cope. Come summer, the other end of the miter will open up when the humidity rises. Because wood moves with humidity changes. Your house is too dry. Get a humidifier added onto your HVAC. You need to be 30-60% at all times.

So what you are saying is that in the summer will go back to normal? Some of the corners now it’s actually a gap.....looks HORRIBLE

No, in summer, if the humidity is too high, the other end of the miter will open up. You have to maintain a relatively steady state for humidity in your home. That’s a requirement. Or you wood does what wood does. It moves. It’s hygroscopic. It swells and shrinks with humidity variations. Your home is too dry, which often happens in winter heating conditions.

Got it. Unfortunately the kitchen vendor never...ever disclosure any possible problem with mitered doors and or guidance us to choose any other type of doors...nothing....after $35K paid just for cabs..... looks like a catastrophe now.........so so frustrated and infuriated.

Celadon thank you anyway for your input :)

It would help to know the material and finish. I don't think I've ever seen this kind of cabinet door before.

Susan, why would a vendor discuss humidity? Your wood floors are also susceptible to issues with humidity. We have an add on to our heating system that automatically regulates humidity to a preset range.

Mm, without adjusting your HVAC system, try boiling water in your kitchen. It will increase humidity in short order.

I run a swiss made humidifier twice a week (10 h or so at a time) during winter, it increases the humidity level quickly.

Hi, Susan,

Sorry for your experience. As another poster noted, wood moves with changes in temperature, and even more so due to changes in relative humidity. 5-piece cabinet doors with floating panels allow for a reasonable range of movement. That said, miters are less forgiving than cope-and-stick construction. You'll find other threads here on houzz noting similar problems.

Controlling the relative humidity in your home within a narrow range year 'round will help to minimize movement.

White Corian doors never crack, no matter the humidity, because Corian doesn't grow on trees.

It’s by Ultracraft Oakland Park doors

I had a customer who left for Florida in the winter and turned the heat off for the winter. So the RH was actually high while she was gone. When she got back the vertical portions of her doors were at least 1/8” taller than the rest of the door. The vertical wood had expanded in length that much over the winter.

I had a bedroom door stick all summer. Right now it has about 3/16” clearance, easy.

@mainenell Good point. my advice is to treat the interior of your home like fine furniture and keep the heat at least 55+ minimum. Once you abandon the home for a few weeks mid winter without heat wood finishes will not be the same.

Why would the relative humidity in a house be higher in the winter? What is the source of the increased moisture?

IMO this problem appears to be caused by the design of the cabinet joints not the environment. Well made door stiles and rails have mortise & tenon joints so they should move as a unit and the only evidence, if any, of movement would occur at the panel joint and disguised by the shadow line.

Good luck getting any consideration from Ultracraft; they will say this is normal wear and tear.

Sorry this happened. The last time I bought factory-made white painted cabinetry, I was asked to sign what the company called a “paint waiver” stating that the company would not warrant the finish against miter cracks. It was a small job and I loved the contractor, so I signed. In hindsight, I probably shouldn’t have. Because two miters opened within three months. My contractor made it right at his expense. Sold the house shortly thereafter. My current kitchen is 80% white painted wood by a highly skilled cabinetmaker, and the miters are flawless two years in.

MizLizzie how lucky you were only 2 miter cracks...we have the entire kitchen and it’s only 3 months old. Builder and manufacture rep. Are saying it’s normal...live with it...get a painter for touch ups. House it’s on heat...65...68 degrees since installation.....we truly believe it’s the quality of joints how it was constructed.

$35k for one wall and an island with cabs. It’s infuriating.

Thank u for your input.

RES2. Exactly.! Since the day it was installed the heat was on between 65...68 degrees. ans YES manufacture rep. Already said..its normal..live with it...get a painter to touch up. 3 months old cabs...ENTIRE kitchen is cracked...$35k paid for one wall of cabs and an island trough the builder...and both are saying...nothing they can do about it...it’s infuriating.

@Res2. The customer turned the heat off in a cold climate. This causes the RH to be higher. That is why camps tend to musty. The over winter humidity is very high.

"we truly believe it’s the quality of joints how it was constructed"

It is but it is also perfectly normal which is the frustrating part. It is wood and what wood does. That is there out.

Buy a hygrometer and see what the humidity level is in the house. They are not expensive. Then buy a humidifier. We have lots of wood in our house because it is a log cabin. We keep two humidifiers running on our main floor all winter.

Miters are inherently weak joints. There are a variety of ways to improve them including machining lap miters, tenons, lock miters, and installation of splines and keys--all of which add material and labor expense--and none of which I'd expect to find in mass-produced cabinetry.

^^^ This. None of the cabinet doors in our current kitchen and baths are mitered, nor were they in our prior houses. The problem seems to be a function of the construction.

Explain how cold air holds more moisture than warm air. This is on the surface of planet Earth, right?

The diagrams of mitered corners opening up must be from cabinetmakers who don't know how to construct a paneled door.

If the doors can be heated in a shop and disassembled ... biscuits or dowels might be added. That's not as good as mortise and tenon but it would be better than what you have now.

RES2, relative humidity is a measurement of how much moisture is in the air compared to how much moisture could be held in the air at that temperature.

Also, it would be very rare for a cabinet door to have mortise and tenon construction. Cope and stick is the norm.

The OP needs to install a whole-house humidifier for her home. Not just for the cabinets, but for her and her family’s health. In winter, indoor humidity levels for the average heated home without a humidifier are about 13-15%, which is lower than the Sahara desert humidity levels. I am not making that up.

Without some humidity in the air, nasal and throat passages are dry, leaving them more prone to illnesses, and allergic reactions to dust and other allergens. Skin is also constantly dry and rough.

Indoor humidity in winter in a home should be about 35%. Any higher than that in the winter will cause window condensation which over time can ruin window frames. The 35% humidity level is the sweet spot to have human comfort in heated homes in winter, for floors and cabinets not to separate at joints, and also not cause condensation.

Shove a little color matched putty in there please.

“Shove a little color matched putty in there please.”

Worst advice ever. When the weather changes, that filler get squeezed out in ugly chunks as the wood expands. It takes a normal inconvenience and turns it into ruining the cabinets.

Cope and stick for a mitered joint?

Celadon: A little filler has never "ruined" a cabinet. Those miters may never go back together.

There are ways to build a miter corner so that it doesn't separate under normal conditions.

A standard miter is not a strong joint and without some sort of reinforcement the only thing holding it together is glue on end grain.

No way from pictures to tell exactly how they built the mitered corner, but it's hard to beat a mitered half-lap for a solid corner for example.

We have a whole house humidifier. It wasn't that expensive to purchase and have installed. It is a shame that the contractor and cabinet company didn't talk about humidity causing expansion and contraction. We keep our house at around 38% we have only had condensation on our windows twice when we had extreme cold outside like 12 degrees.

Our custom cabinet builder and I became friends during my build. He said it was a good thing we had a humidifier. He had a job once where he made painted white shaker cabinets; he installed them in their new home in the winter before their HVAC unit was installed. That was a bad choice.... The paint cracked on every single cabinet because of how dry the house was and the wood shrinkage! Because he is a good person he now recommends that the furnace and a whole house humidifier be installed before he sets cabinets. Sorry that these guys aren't budging. I would contact their customer service and threaten them with the poor reviews you will post about how terrible their company is to work with. You should at least get a credit since they may not replace the doors. 35k is a lot of money!

KH Thank you for feeling my pain....yes 35k for a small kitchen..just for cabs...according to builder vendor it’s a mid.range line...I doubt it....

HVAC it was installed and working when all Cabinets came in..

Builder vendor never ever even mentioned about pros and cons of mitered cabs and or either gave guidance to choose any other door style or material to avoid a problem like this or said...u may have open mitered corners and There is a waver for it......NEVER

we expected one or two opening..yes...it’s wood.....but EVERY SINGLE ONE? No....no way....

yes...we will do Something about....as now...both...builder and vendor....just says: sorry we can’t do anything about it’s normal ...... it’s beyond frustrated...

Susan, what is the humidity level reading? My system is Trane, and it shows the humidity below the outdoor temperature. My painted cabinets are 5 months old...1st winter...and while my house sometimes reads 28% humidity (which is when I finally remember to run a humidifier) I don't have 1 cracked cabinet door. I like to bring the humidity to at least 32-34%...but forced air running everyday dries it out quickly in an already dry state. I can't imagine your frustration!

K H, which whole house humidifier did you install? Link?

“HVAC it was installed and working when all Cabinets came in..”

@Susan D. - are you saying you do have a whole-house humidifier or not? It would be an installation that is in addition to the standard HVAC set-up of furnace and air conditioner. If you don’t have a whole-house humidifier, I recommend it as I commented above. Depending on your home, and where you live, it would cost about $700-800 to add it.

A whole house Humidifier is a must in Missouri! We have a General Aire (not sure the model) on our forced air heat pump unit with propane back up. When we built I remember going to the house to paint a door. We had a temporary heating unit and our RH was 12% our subfloor started gaping and the paint dried so fast it cracked. I had to resand and repaint the closet door after I brought in my own personal humidifier. @Shannon_WI is correct ours was around $500 purchased and installed.