Troubleshooting Swelling of Doors in a Humid Climate

Once the doors are fit to the opening they may perform fine for many years. September 18, 2014

Question (WOODWEB Member) :
A client has a double door as their main entrance door. This is in a condo complex so itís not being exposed to elements other than whatís in the building already, like air conditioning running 24/7. The doors seemed to be made out of poplar. After getting a call about these doors binding we did the usual thing - sanded down the edges until there was a 1/8" gap again, but now a month later the doors are swelling and binding again. At this point they want us to construct new doors. What is the best wood to resist swelling? Bear in mind this is for a paint grade finish so I canít use heavily grained wood. Are there any engineered wood alternatives that resist moisture more than wood itself? Can you buy fiberglass planks to build the doors?

Forum Responses
(Solid Wood Machining Forum)
From Contributor O:
Poplar in the Bahamas? Poplar is a wood that does like to move with seasonal variations in relative humidity. I'm betting that your doors are swelling to reach their EMC. You can use the Shrinkulator to compute what you are experiencing in cross grain wood movement. If the pair of doors has 5" wide stiles, then you have 20" of available cross grain wood to swell or shrink. Long grain does not swell or shrink appreciably with changes in RH. If you purchased wood that was at 6%, and the EMC (equilibrium moisture content) in your area is 10%, then things are going to swell up to a point. The Shrinkulator and a moisture meter will help you know. Engineered wood substitutes and metal and plastic doors are for those that do not know or understand wood and wood doors, and also have little appreciation for the good properties of wood. Instead of sanding, use a good door planer, give yourself a strong 1/8" clearance with a 3 degree bevel. Or make a 1/4" gap and shim out each hinge 1/16" so the gap narrows to 1/8". Then if they rub in the future, remove a shim or two to open it up. Itís guesswork or science. I prefer science, but there is still a bit of guesswork/experience.

From the original questioner:
Thanks so much I will get on those calculations right away as the client has been waiting on my quote for a long time. So youíre saying you donít recommend poplar? What would be your choice of wood? Itsí a pair of doors to cover a 60" span and I think (donít have my notes with me) they are about 90" tall. One of my reasons for using poplar is because it takes paint so well. So does maple, even more so. Do you think that would be better?

From Contributor O:
You can look at charts to find woods that move less, and remember that quartered moves half as much as flat sawn. Poplar is not necessarily a bad wood for interior doors - I use it all the time, though I prefer maple since it is harder (movement is about the same). I suspect that what you are seeing is related to the dryness of the wood vs the EMC in the Bahamas.

You can build up engineered stiles (their word, not mine) of a quartered core with face veneers 1/8" or so thick, that will limit movement - make it equal to full quartersawn material. Further, you can even go and add a cross band of veneer under the face veneers to stop any/all cross grain movement in the stiles. You need to know the basics of balanced panels here - all materials the same thickness and finish, etc.

I'll bet lunch that once the existing doors hit their equilibrium, they will be stable and go for decades with no problems. This is 100% my experience over the years when we see doors swell. This may avoid having to remake the doors. Explain to your client in scientific terms and a bit of humility and then refit them. I am constantly humbled by wood, and relearn things all the time. Usually when I get cocky, something happens that pulls me back to proper humility and respect.

From the original questioner:
I will look into all of that and will try and work extra labor into some kind of overall good pricing that the client will accept and give a go ahead on.