Humidity Effects on wood products

30 MARCH, 2013 BY JIM HILL

There are three key steps in manufacturing 5-piece Cabinet Doors that will determine the sizing accuracy of the finished door. If each of these steps is held within a tight tolerance, the finished product will be accurate to within the desired 1/64 inch, or about 15-thousandths.

The first of the three critical operations is moulder accuracy (sometimes americanized as “molder”). The second critical operation is stile & rail length cutting accuracy and the third is consistency in stock removal during the operation of machining the outside edge. Our standard is to hold each of the three critical operations to a tolerance of 5-thousandths of an inch. This produces a finished cabinet door with a worst-case sizing tolerance of 15-thousandths, or 1/64-inch.

The stile stock moulding operation starts the process of insuring sizing accuracy and, without close attention to this step, consistency in sizing the finished door is almost impossible. When cabinet door stile stock is moulded, the width of this stock is the most critical factor in accurately sizing a 5-piece Kitchen Cabinet Doors. If the moulded width of the stile stock is held within a tolerance of 5-thousandths of an inch, the subsequent operations that affect sizing can be standardized.

At The Door Stop length cutting of stiles and rails is performed on CNC machinery so achieving our 5-thousandths tolerance for this operation is actually easy. Cutting accuracies of better than 5-thousandths are normal. The outside edging operation is more difficult to hold because the edging cutter’s diameter changes from sharpening, so slight variations do occur. Our average edging tolerance does achieve the 5-thousandths inch goal, but the standard deviation shows a range from 2-thousandths to 9-thousandths inches.

Because the moulder accuracy is key to Cabinet Doors and Drawer Fronts sizing, let’s look at some examples of inaccurate moulder adjustment and the effects these errors will have on the finished size of a 5-piece cabinet door. First we will assume the moulder is set up correctly and the stile stock, which is targeted at 2 1/4–inch width, is actually oversized by 5-thousandths (2.255 inches). Assuming the rail length cutting and the edging operations are both perfect, the finished door will be 10-thousandths oversized. Most cabinet makers will be measuring the cabinet doors with a tape-measure, so the 10-thousandths error on this door will be considered perfect and within the acceptable range of even the most demanding cabinet professional.

Now let’s assume the moulding operation is not within a width tolerance of 5-thousandths and is actually over by 15-thousandths of an inch. That will make the stile width 2.265 inches, with the additional 15-thousandths doubled to 30-thousandths by the same error in each of the two stiles. This door will be oversized by 1/32 inch even if the other critical sizing operations are perfect.

This 1/32-inch error, while acceptable by the standards of the industry, is detectable with a tape measure.

The challenge to the manufacturer of Kitchen Cabinet Doors is to size the door as accurately as possible by setting tight measurement quality tolerances on the operations that affect door sizing. Sizing is even more critical when building Replacement Cabinet Doors that will be replacing doors in frame-less cabinets, where tolerance is much tighter. These tight-tolerance applications require very accurate sizing that many door manufacturers find challenging. At The Door Stop, we build every door to the tightest tolerances, not just the doors going into frame-less cabinets.

The variable beyond the control of the manufacturer is the normal swing in relative humidity and the effects humidity changes will have on the moisture content of the wood in the doors. All cabinet doors will react to changes in relative humidity by either absorbing, or giving-off moisture. Unfinished doors will react sooner to humidity changes, but even properly finished doors will eventually reach a balance between the relative humidity and the door’s internal moisture content. These moisture content variations will result in dimensional changes to the stiles and rails of the cabinet door.

These dimensional changes can be greater than the total manufacturing sizing tolerances. The definitive study on humidity and its effects on wood moisture content, and the changes it causes to wood dimensions was conducted by the US Forest Service, a department within the US Department of Agriculture. The Forest Service, published the Wood Handbook: Wood as an Engineering Material in 1999 (and 2010), which outlined the expected moisture-content caused dimensional changes in various woods. The 1999 study focused on wood flooring but applies to all wood products kept inside the house and subjected to normal fluctuations in relative humidity. The 2010 study is extensive and covers almost all commercially used woods.

The 500+ page 2010 study can be viewed or downloaded here (Chapters 4 & 13 deal with Moisture and expansion properties) http://www.fpl.fs.fed.us/products/publications/several_pubs.php?grouping_id=100&header_id=p

I have tried to simplify the findings by focusing on plainsawn (Flat Sawn) Red Oak for this example. But, woods other than Red Oak and differing sawing-grain directions, like quarter-sawn, have different Coefficients for Dimensional Change. Because plainsawn woods are more popular and tend to have a greater dimensional reactions to moisture variations, I have used plainsawn in my example. The bottom-line finding of the USDA research is that a 4% change in the moisture content of the 2 ¼-inch stile of a 5-piece Red Oak cabinet door will be expected to cause a dimensional change of 0.0332 inches, or about 1/32-inch, per stile. That means that a 4% change in moisture content is expected to expand, or shrink the width of a 5-piece Red Oak cabinet door by 1/16-inch, which dwarfs the 1/64-inch worst-case tolerance of the cabinet door as it finishes the manufacturing process.

This 1/16-inch moisture-caused change is 4-times the combined total tolerance of the critical steps in the making of a cabinet door, and certainly needs to be considered when designing cabinets. This is especially true when considering the spacing between butt-doors on cabinets. Without proper spacing, butt-doors may not close properly during high humidity periods.

These humidity-caused sizing swings may seem extreme, but keep in mind that these calculations reflect the humidity of the worst-case the country has to offer; the desert regions of the southwest. In the southwestern deserts relative humidity routinely changes from 5% in the dry month of June, to over 90% when the monsoon storms come in July. This wide humidity swing accounts for the 4%+ change in the moisture content of wood products in the southwest. Cabinet doors installed in other parts of the country will typically be expected to experience about half this dimensional change, or about 1/32-inch.

Design provisions to accommodate dimensional changes in the raised panels of cabinet doors are in place allowing the panels to float within the stiles and rails. The panels used in recessed panel doors are either Medium Density Fiberboard (MDF) or MDF core with wood veneers, which are dimensionally stable and react very little to humidity changes.

Looking at the once popular, and hopefully never to return to popularity, Slab Cabinet Door as an example , you can see the makings of a dimensional train-wreck. With the Slab Door we are not just dealing with the moisture-related dimensional properties of a 2 1/4-inch stile. We are now looking at the dimensional properties of a glued-up slab between 12 and 24 inches wide.

Using the same moisture-content calculations for plainsawn Red Oak from the Forest Service Study, we would expect to see a 12-inch wide slab door react to a 4% moisture content change with a width change of over 3/16-inch and a 24-inch slab changing width by over 5/16-inches.

Clearly width changes of these magnitudes are unacceptable and homeowners requesting slab doors need to be made fully aware of the dimensional instability of this cabinet door design.
Cabinet Doors 101: measure openings, install hinges, hanging and alignment.

Shaker Cabinet Doors Click to visit our Shaker Door Page

Search

CabinetDoors.Com is proud to have an A+ BBB Rating

Your Cart
Cart is empty
Customer Reviews

Your Youtube videos are outstanding. You made measuring and hanging my new doors a snap. Thank you. Jen A.

I ordered new cabinet doors for my upper cabinets in my kitchen. They needed to match the bottom doors. Thanks to your very knowledgeable staff, I got perfect doors--the grain matched, the trim matched, and the hardware is outstanding. I am delighted and would recommend this company without reservation. Thank you for an outstanding product. Madge S.

My order of cabinet doors was delivered today, and I could not be more pleased. They are BEAUTIFUL. Thank you so much for making a great product.Stacy K.

I'm a home re-modeling handyman and I just finished a kitchen remodel using your Shaker Doors. This was my first order from you and the sizes and overall quality are much better than my prior supplier. You helped my make my customer very happy.Mike B.

This was my 4th kitchen re-model with your cabinet doors and, just like before, the doors were perfect. The workmanship is top notch and the sanding was exceptional. My 5th kitchen job is scheduled for August and I'll be ordering from you again. You make a great door.Kent's Kitchens

We ordered replacement doors for our 60-year-old home and were very pleased with the product. The milling was of the highest quality. The joinery was very well done, and the wood selection was obviously done by a professional who cares what the finished product looks like. It is one thing to assemble a project with technical skill, and another thing entirely to accomplish the assembly with an eye toward bringing the best out of the wood being used. Both aspects were accomplished, and at a very high level! The dimensions were absolutely perfect. Each door was correctly dimensioned to within less than 1/16 of an inch. It was very pleasing to see this attention to detail, especially since I took the time to measure my cabinets twice, making sure I had done my part. I had never worked with white birch before, and when I saw the issues with staining the wood (soft grain with blotchy absorption of the stain) I was a bit worried. I had no problems at all because the wood was of a higher quality white birch that had been properly handled at the mill and sanded to a stain-ready finish. A good sanding sealer was applied, and then the stain. The results were EXCELLENT! All-in-all, we received a great product, great advice and excellent customer service from CabinetDoors.com. We would certainly recommend them to anyone looking for cabinet doors. Nice job, everyone! Michael R.

The doors arrived today and fit perfectly. Thank you very much. I will be ordering the remaining 18 doors and 6 drawer fronts in the next couple of months. Walter W.

I remodel kitchens for a living and I can only say...I wish I had found you sooner. These are the overall BEST cabinet Doors I have ever installed. Excellent quality and workmanship. Jake A.

Your cabinet doors are much higher quality than the doors that were installed by our home builder. There is really no comparison, you make a GREAT product. Al N.

The contractor remodeling our kitchen was so impressed with the doors we ordered from your website that he is going to use your doors for all his future jobs. Marcia N.

Your cabinet doors, and the finishing tips in your blog, made my kitchen remodel look GREAT. I recommend your doors to everyone. Kay H.

Hi, I have received my 1 door, and I feel like I received the same quality service and product as if it were 50 doors. I am very pleased with a beautiful door delivered as promised. Thanks, David H.

Although I haven't bought the cabinet doors for my kitchen remodeling project yet, I will be making my purchase from cabinetdoors.com. Your site, and especially your Blog, has more useful information than I've found anywhere else on the internet. The information you provide is exceptional and you have helped to give me the confidence to take-on this project. Nancie D.

We took your advice and ordered the smallest door in our kitchen to see your quality...which is absolutely great...Now we are ordering the rest of the kitchen and bath doors. Don & Barb B.

These cabinet doors are PERFECT! Super high quality and right-on size. Harry D.

So glad we remodeled our kitchen with your doors, instead of doors from the hardware chain. You saved us over 35%. The doors arrived in 12 days, (including 4 Fedex shipping days). The hardware chain quoted 28 days, and your quality is far better than their samples. Mark H.

These doors are EXCELLENT! In quality and workmanship and value. Very glad we found you. James L.

A friend put me onto your website and I can't thank her enough. You make an excellent product and I'm completely happy with everything about my purchase. Paula B.

I am very satisfied with these doors. The quality is GREAT!. Alex D.

Very nice cabinet doors, the color matching and the sizes are right-on. Paul L.

Your customer service is fantastic. Somehow you spotted an error I made on my order (I reversed width and height on one door) and called me to ask if the size was correct. Your attention to detail prevented me from ordering one of my doors wrong. Thank you so much. Bryan E.

Shipping Times

Fedex or UPS Shipping time from our factory to you.

Our production time is 7-10 days. Just add shipping to your state for your expected delivery date.

Delivery times

For shipping times to Mexico and Canada Please call.

My Profile
Wood Selection