Wood Door Thickness and Quality

To make 1-3/8" solid wood interior doors, you usually have to start with 8/4 stock. Here, experienced pros explain their door fabrication processes in detail. February 17, 2006

I recently got quoted a job for a house full of 8 foot tall solid wood interior doors. I recommended 1 3/4" thick doors because I thought they would be more stable as well as aesthetically fitting for a door this large. I lost the job to someone supplying 1 3/8" thick doors. This sounds kind or light for the application to me. What has your experience been? Would anyone else out there build a 36" x 96" solid wood interior door 1 3/8" thick?

Forum Responses
(Architectural Woodworking Forum)
From contributor L:
I would, but I haven't built them 8' tall. The standard is 80" tall 36" wide and 1 5/16" thick. If you use a stable wood, quarter-sawn, you won't have problems with movement. Most interior doors are thinner than exterior. It adds about 25% to your material costs by going 1/2" thicker, and then you need the cutters to produce the thicker doors. They basically underbid you and gave the client what they were looking for.

From contributor S:
Did the 1-3/8" doors sell for less than your doors? Did you meet with the buyer to discuss the reasons your doors are better than anyone else's, (for the money), and did you try to educate your buyer? After the fact it is difficult to go in and bad mouth the other supplier (never good) by saying he quoted doors that are too thin, but you should be able to proactively say that you do not recommend tall doors at that thickness, and that you resist building them.

That said, I have refused to price at 1-3/8" x 8' interior doors. I do quote 1-3/4 x 8' all the time, and that is what we build.

Three reasons:
1. Historically, 8' doors (in fact almost all fine interior doors) have always been 1-3/4. A thicker door feels more substantial and secure.
2. Thicker is better at resisting the impulse to bow or twist or flop around in the jambs. Your liability is lessened, and the project will be more successful, long term.

3. Custom doors are custom doors and should reflect the better side of American craft. Any number of makers from here to China is falling all over themselves trying to make a door that is better only because it is less expensive.

I think it wise to have door sections and some info together to indicate why your product is better, and the reasons you build the way you do. Few builders or owners know what is proper, but they all can easily tell by the price which is less expensive. It becomes our job to point out the differences in a positive way so the buyer knows what he is paying for and why. If you build confidence in the buyer's mind, then you have the work. Your job is to communicate your knowledge to them in a simple and clear way.

From contributor T:
All the responses were correct and proper but this client got what he wanted (a cheap, in-efficient and unstable) solid wood interior door. This is sad but this is what some will do to make a sale. Apparently the guy who sold the job does not feel the way we do about our craft. That said; I would agree that you follow up with your quote and your explanation of your superior product because you just might get a call when those eight footers start to go south in the near future.

From contributor M:
I would like to know how you guys can build 1 3/8" doors less expensive than 1 3/4" doors. They both would have to come out of 8/4 lumber, so the only real savings would be in the panels, right? I have never been able to get 6/4 lumber flat at 1 3/8" thickness.

From contributor S:
Contributor M – you’re right. We use 8/4 Poplar for 1-3/8" doors, even if they are only 6/8 or 7/0 - at least for the stiles if not the whole thing. Life is too short to sweat some details. The material is inexpensive, and the storage space limited and the doors are better.

Since we rarely make any 1-3/8" doors, it is not like we give two prices for a batch at 1-3/4 or 1-3/8. If we did, I'd just make up a dollar difference and go with it. Labor is where it's at for us. A couple of bucks per unit would sway a price shopper, whereas someone a bit more savvy would know to go beyond the dollars and try to see what the difference is. I'm curious as to what the percentage difference was between the original questioner's total and the other guy's.

From the original questioner:
The price difference between 13/8 and 13/4 doors is not much, it is mostly labor for me as well. The price I quoted was about $575 for a standard swing door. I thought that was quite competitive, but the customer however said that the difference was substantial.

From contributor D:
I make my 1 3/8" interior doors out of 6/4 alder and poplar all the time. The stock I get is always right at 1 1/2" or 1 15/32. I pick out only the straightest boards. After running them through the planer 2 times on each side (1/32 each pass) I end up with exactly 1 3/8". Then I run them through the drum sander twice on each side which takes them down another 1/32", but after you spray your finish on them, they measure out to 1 3/8" when you’re down.

I agree. An 8' door should only be made at 1 3/4". A lot of the foreign door companies are using laminated stiles and rails now. They are using either 2 pieces of 3/4" stock laminated together, or they are using particle board with a veneer skin laminated to it. It’s supposed to help eliminate bowing and racking.

From contributor D:
I joint one surface on my 8" jointer, 2 passes at 1/32 each, and then I move it over to my 20" thickness planer and run it through 2 passes at 1/32" each. This only works if you get really good straight stock. If you have a slight cup or twist in your board, 6/4 will not work for a 1 3/8" door.

You would need to get 8/4. The stuff my supplier gets is from Cascade and it is usually beautiful stock, straight and flat. I would also like to mention, that after jointing and planing my wood, I sticker it for about 5 days in my shop to see if it goes south or not before the doors are constructed. After dressing up the wood you open up the pores allowing more moisture to enter or escape in the wood which can have an effect on it.

From contributor M:
We produce all our custom doors regardless of species on engineered core and use this as a selling point. I don't mean thin veneers but rather 3/16 thick faces on a finger jointed and edge glued core. The truth is this method is typically more expensive than using solid till you get to about cherry pricing. The payoff is unmatched stability, especially in the taller doors.