Door Construction: Methods and Lumber Choices

A general discussion on how to build interior doors, and what kind of wood to use. May 5, 2014

I normally don't delve into house doors, but a builder client of mine asked me to make up a pair and I really can't say no. Size is 36 wide x 84 tall x 2 1/4 thick. It's frame only with 5" stiles, 5" top rail and 7" bottom rails. He plans on setting in some laminated glass after they're installed and then applying moulding to hold it in. Obviously I'd prefer to use poplar (they're interior paint grade), but at that thickness, is stave core the way to go? Incidentally, if stave core gets the thumbs up here, I'd like to try and make them out of 1 1/2" Timberstrand with 3/8" poplar skins (so if that's a terrible idea let me know).

Forum Responses
(Architectural Woodworking Forum)
From contributor A:
Poplar is not considered a stable wood. It can twist and warp. It also swells more with moisture, due to its weed-like structure. Perhaps that's why it sucks up primer like a sponge. Many people build numerous cabinet doors out of poplar before the whole batch goes sideways. They think because it's okay for a cabinet, it's okay for an interior door. I've seen a whole house of poplar interior doors swell shut one week after they were hung properly, due to humidity. Then it gets dry and they shrink so much they won't latch properly. Poplar is a great wood for mouldings, face frames on small projects, maybe veneers, definitely cabinet structure. Soft maple or a decent pine are better choices for interior doors.

From contributor D:
I've made hundreds of poplar interior doors, and have had no problems, but we give them a little more room than we would for other woods if we are hanging them. I have had only one warp so badly I replaced it - a wet piece of wood in a laminated stile on an exterior door.

I prefer soft maple, as long as it doesn't get fuzzy on us. Be sure your builder customer knows to have a stable environment when the doors arrive, and will paint properly asap. No jet heaters blowing on the doors, please.

No matter what, I'd laminate the stiles out of 3 plies of 4/4. Face and edge each ply, then S2S through the planer, glue up for over thickness - 2-1/2" or so will be good. Once you remove from the clamps, face and edge, then plane to final.

I am no fan of engineered cores (exactly what is engineered?), but I have good lumber sources and I trust them with my livelihood. If you do use a mix of materials, be sure moisture content is exactly the same in everything. I don't think most engineered fans would even recommend Timberstrand.

From contributor M:
I'm with contributor D on this one. Three plies, not two, to keep them balanced, and you're good to go. I too have made many doors out of poplar and have had only one go bad on me, with the lock rail separating from stile due to the stile shrinking due to being too wet. I've wondered if poplar from different parts of the country acts differently from other parts. I've had this conversation with someone in CO and he won't touch it, but it's worked ok for me in MI. Go figure.

From contributor D:
I will be first to admit that poplar has weed tendencies. It grows like a weed, and wider, less dense annual rings makes for less stable and far less weatherproof materials. Know your lumber - no matter the species - and it should go well.

From contributor R:
7" bottom rail is a bit narrow. Then if you thought about Timberstrand, what kind of joinery would you put in it to carry all that glass weight? I vote soft maple and big mortise and tenon. 3/8" poplar skins would be like gluing solid wood to the Timberstrand. The poplar would move, Timberstrand not so much. You would get cracks, or open joints in the face wood.

From contributor J:
I followed advice given here when I did a batch of 15, 2-1/4" interior panel doors a little over a year ago. I made a laminated stile out of 3 pieces of solid wood. I also went with soft maple as I really don't like how soft poplar is - it dents if you look at it the wrong way!

The doors weighed a ton, but they went in and are still looking great even through some trying times during the installation, with humid conditions followed by excessive dryness! Out of the 15 doors I did, one stile twisted on me. There were a lot of issues with site conditions and painting (or failure to paint), but I replaced the stile and the rest have held up well.

From contributor A:
Engineered might refer to you laminating 3 sticks of wood together because you know it's more stable than 1 and definitely 2. If the wood (weed) didn't have 1/4" growth rings you might consider using it au natural. We've made hundreds of interior and exterior doors out of solid cedar, eastern white pine, maple and mahogany. No laminations required. I guess there is very little good wood left.

From contributor D:
I agree. I would bet that nearly every woodworker, over the centuries, in this nearly-the-world's-oldest-profession has said that there is no good wood left. I remember 20' long x 40" wide Honduras boards in the 70's.

I rarely use engineered wood since I can use solids, and prefer working with the wood that way. I avoid laminating when I can, and use a lot of 10/4 Honduras as a result. The marketing term "engineered" bothers me since I have lost work to factory crap that is only value engineered, not engineered in a wood tech manner.

In my opinion, there is nothing more engineered than a proper cope and stick mortise and tenon joint.

From contributor L:
We've always made staved cores but it seems to me that 3/8" faces are way too thick and won't respond to changes in moisture like a veneer would.

From contributor N:
I think you East Coast guys get all the good poplar. Most everything we see here is sapwood with big growth rings. We are leery about using this for anything on doors after a couple bad experiences. I built a painted storefront out of poplar in the early 80s using the good stuff and it is still holding up.

From contributor I:
In my area (Central VT), poplar costs more than ash, and soft maple. For another $0.10 or $0.25 per board foot, I can get hard maple. Add another $1.00 I can get FAS cherry. As a result I never build anything out of poplar. Must be pricy because all the lumber yards stock it. All the carpenters must have heard that it is real cheap and supposed to take paint well.

From contributor J:
Maybe they have a lot of poplar right around you? I'm a couple hours south of you and as of last month 4/4 rough FAS stock runs.... poplar $1.44, soft maple $2.49, hard maple $2.69, cherry $3.00. I still use poplar for trim work, but that's about it.

From contributor I:

Poplar runs about $2.00 a board foot. Soft maple and ash are a little less. A year ago I paid $1.30 for soft/brown maple. These are retail/pick prices. Just ordered 230 board feet of FAS cherry and paid about $3.10 delivered from a major northeastern plywood distributor.

I don't have anything against using poplar for paint grade trim work or where appropriate. I just never get asked to use it, and when I have a choice, I usually pick something else with a similar price tag. I have to check, since I may be able to get it a little cheaper wholesale.

Some of the best quality lumber I get comes when I order wholesale. There is a local retailer that I used to do business with, and it seems as if they would end up with racks full of boards rejected by customers. Over the years this seemed to accumulate to where I would go in and they would never have any fresh inventory.

The last time I was there they were griping about how business was slow. Go figure! There is plenty of good wood out there. You just have to know where to find it.

From contributor J:
I have a couple places I buy from but most if it comes from a large wholesale mill. They have had the best quality over time with other places being hit or miss. They do have a decent stock of basics on the racks so you can drive over and pick. But most of it is warehoused so call ahead and they'll pull a stack out for you. I always prefer to hand pick for interior doors. Of course if I need several hundred bd. ft. I just call and get it delivered.

From Professor Gene Wengert, forum technical advisor:
Be aware that there are two poplars and they are not related and are totally different. Tulip poplar grows in the east and south. Aspen poplar grows in northern U.S., Canada and the Rockies. It does look like this discussion has comments related to both, which is why there is a mix of opinions.

For decades yellow poplar was the preferred core material for doors, tables, etc. It is excellent, when dried to the correct final MC so that in use MC changes are minimal. Obviously, avoid the purple and dark colored heartwood.

From contributor D:
Gene, thanks for the input, but I'm afraid you unintentionally added to the confusion. You first mention 2 species - tulip poplar and aspen poplar, but then mention "yellow poplar" in the next paragraph as a preferred wood. Now, I think yellow poplar is tulip poplar, and not aspen. But I do not want to draw conclusions where they are not warranted. I'm confused.

From Professor Gene Wengert, forum technical advisor:
Tulip poplar = yellow poplar.