How to Build Interior French Doors

I have a small balcony area above my family room. The room is an extension, with cathdedral ceiling, on the gable end of a cape. I opened up to the floor what was previously a second floor window on that gable end, and it is now an interior doorway with a railing.

It is 32.25 inches wide and I want to put small french doors instead of a regular door (figure it will look nicer). So, each door will be 16 inches wide.

Im thinking of getting one piece of 1/2 inch plywood and cutting four inch wide strips, then gluing them so I end up with one inch thick, four inch wide strips.

Then I would make the frame out of these one inch thick pieces. I would have glass, about eight inches wide, in the middle of each door.

I kow I could use solid stock but I cant find anythng thicker than 3/4 inch at home depot and dont really want to run all over looking for a lumber yard - and paying much more - for the wood. A piece of plywood will only cost about 20 bucks.

Im going to paint this anyway so Im not concerned about the edges - Ill just sand them well.

Does this make sense? Is it a reasonable way to go?

If so, for an interior door, what do I do where they meet? Do I do anything special or just leave a 1/8 gap so they dont hit.

 

I don't mean to dampen your enthusiasm for your project, but the idea sounds a bit dubious. One problem you may run into is warpage. Another problem might be the hinge screws, which might not hold into the end grain of the plywood. And then there is the question of joinery- how will the rails and stiles (your 4" strips) be held together? IMO, two layers of 1/2" material would be way too thin. You "might" have more success if you tried using 3 layers of 1/2" material, and then used that middle layer as an area for mortise and tenon joinery, where the middle layer would either be the mortise or the tenon.

11 ply birch plywood (3/4" thick) would be a better choice quality wise, but 3 layers of that would make a door that is 2 1/4" thick, which may be a little much.

And the glass probably needs to be tempered because of safety. You don't want some small child putting his head through a piece of non-tempered glass that is close to the floor. If sized properly and glazed (siliconed) in place, the glass will help square the door, but your frame needs to also have some strength of its own so that it doesn't sag.

As far as the gap between the doors, you can either have a gap, and ball catches on top of the door where the doors will close against the door stop, or you can hide that gap by having an astragal on one door which will cover that gap. The door that the astragal is on would need to be opened first before the other door would open.

 

you think the plywood would have a chance of warping. Thats why I thought of plywood - less chance of warping, no?

And a full inch is thin? Isnt a store bought interior door usually just about 1.25 inches thick?

As for joining I figured I could join it like any other door - even though its plywood. But, your idea of three layers seems much stronger,and easier. Especially if ill be gluing pieces together anyway. Why not just use three instead of two. I was actually thinkng of three pieces of 3/8 but thought the 1/2 would be better and that 1 full inch was thick enough.

As for glass, Id probably use plexi. Since this door is a balcony its 8 feet off the ground above my family room. I wouldnt want a piece of plexi falling on anyones head - but Id prefer it to a piece of glass.

So, the hinge problem aside, it sounds like three pieces of 1/2 inch is the way to go. But do you really think it might warp on me? Because Id prefer to use smaller pieces for my middle layer. The reason being that certain areas that arent exposed could be hollow as far as looks are concerned (such as the very top or the heel of teh door) and I can avoid buying a second sheet of plywood if I only need a few strips.

 

Many residential doors are 1 3/8 thick. Commercial doors are often closer to 2".

Yes, plywood will warp. The front and back sides, as well as the plys in the middle of plywood are made of different quality layers, and they shrink and swell at different rates due to humidity and temperature. If you lay a sheet of plywood in the grass, you'll see just how much it will warp! The warping will be lessened since you are dealing with strips, and will also be lessened because you will be putting the layers back-to-back, which, in theory, would mean the warpage of one would negate the warpage of the other. But in practice, your doors will likely warp somewhat. If this is an exterior door, the temperature and humidity differences will be greater from one side of the door to the other. MDF is less prone to warpage- it generally lays perfectly flat, but you would have even more problems with the hinge screws holding in that, and MDF is generally not rated for exterior use.

If you cut your strips 3 7/8" wide, you should be able to get 12 strips out of one 48" wide sheet of plywood, with 1/8" of waste each time, accounting for the blade width. If you go with the 3 layer idea, and your doors are 80" tall, you'd need 4 stiles, 80" long which would be made up of 3 pieces each (roughly 80/72/80) and would leave you with 8 scraps 16" long, and 4 scraps 24" long. You're rails would be made up of 3 pieces each (roughly 8/16/8).

So it looks to me like if you don't make any mistakes cutting it up, one 4x8 sheet of goods would just make your doors for you. Plexiglass (acrylic) scratches easily and I wouldn't recommend it, but it's your project!!

 

ok, sounds good so far. Just a few final questions...

I think my rails will be 1/4 inch too small? If my stiles are 3 7/8 and the doors are 16" my rails would be 8 1/4 (actually my opening is 16 1/4 so my doors maybe 8 1/8)

But in any case, I guess I would just leave the small gap on teh less visible side, glue in a thin strip and fill it with puddy (treat it like a repair)... right?

The only reason I was thinking plexi was because this is 8' off the ground. But I guess if its tempered it wont break, and it could never just fall out of the door.

And, as for putting the glass insert in. I couldnt use the middle layer, leave it 1/4 recessed on the inside of the stiles and rails, and insert the glass that way. Id leave the front layer higher all around and then tack a molding on the back of it to hold in place... right?

Now that its pretty much ironed out, does it make sense to do it this way.. how would you do it if you needed these doors?

 

And a final thought. Could this work just as well?

Two layers of 3/4 instead of 3 layers of 1/2

To join , just overlap the seams. For example, layout the bottom layer on the floor with the stiles going top to bottom the full 80 inches and the rail between them. Then on the second layer, the rails will go the full width of the door, 16" and over lap the stiles. The stiles would not go the full 80" in this layer but would but up against the rails. Glue and screws would be used to hold it together.

The advantages I can think of with this are:
less cuts
less material used (more room for a mis-cut)
less time consuming to join

What are the disadvantages?

 

You could always make the stiles 79 1/2" long which would leave scraps 16 1/2" long. You will also have an 1/8-3/16" gap on each side of each door, a total of 3/8-1/2". So it looks to me like your doors could be a little less than 16" wide and you'd be okay. If you picture your opening... 3/16" gap, 15 7/8 door, 3/16" gap, 15 7/8" door, 3/16" gap... would add up to roughly 32 1/4. And your opening had better be plumb, level and square because hopefully your doors will be.

For the glass insert, I wouldn't do anything but leave an opening in the middle for it, and stop it in on both sides. Once the doors are built, your opening will be what- 8x72 or so? I'd just apply a type of panel moulding to one side of the door as a stop... then set the glass against it, glazing it with silicone, then apply another panel moulding to the opposite side. See the following picture link for examples of panel moulding profiles: http://www.boisemoulding.com/media/panelmoulding.jpg

There are many profiles and sizes available depending on where you look. You might need to get a 3/4" panel moulding, then 1/4" glass or acrylic then a 1/2" panel moulding for the opposite side to add up to 1 1/2"... or maybe just one size that would be 5/8". If you are using 1/8" glass or acrylic, then you'd need a panel moulding that was 3/4 on one side, 5/8 on the other... or just one size that would be 11/16. The best part with a panel mould is that it covers the cut edge of the plywood and dresses up the perimeter of the glass. A baseshoe or quarter round would also work, but they don't have the lip that covers the cut edge of the plywood around the perimeter. Hope that makes sense. Panel moulding is the bomb for such a thing.

The way we've talked about is probably the way I'd do it if I was making a door out of plywood and trying to do it as cheaply as possible. I'd make sure that when I assembled it, I glued the HECK out of it, and held the layers together here and there with some 1" brad nails- especially where the mortise/tenons overlap and then used lots of clamps to keep it all under pressure for 24 hours. I'd take special care to line up the plywood around the edges of the door when it's assembled too, since those edges will be exposed... and if it was me, I'd probably belt sand the edges once the clamps came off, and then I'd apply some sort of iron-on banding to the edges that would be seen- the left and right sides. Any voids in the plys around the perimeter would need to be filled with wood filler like you said, in order to paint up nice. And then the edges of the door would need to be eased a bit with some sandpaper so that they aren't sharp square ends.

 

It would not be as strong, structurally, it would not be asthetically correct (stiles should run from top to bottom when viewed from both sides of the door), and I'm pretty sure that if you went with the 2 layers, overlapped at the corners, you'd definately need to go with the 11 ply birch veneer which is more expensive than the 1/2" ply. If you have 2 layers, glue is only holding one side of the corner. If you have 3 layers, glue is holding BOTH sides of that middle layer at the corner. Much better IMO, and if given a choice between the two, I'd use the 3 layer method. If I was doing it, I'd probably use solid wood, with real mortise and tenons, but if I was trying to do it inexpensively and still do a good job, I'd opt for the 3 layers. I've made some things with the 2 layer overlapping method you've referred to, but they were overlaid with 1/4" oak plywood on each side for strength.

 

First of all, I dont want to forget to thank you for all of the info - this is great.

I forgot, I have some room to play with on the bottom of an interior door so when I measure everything up I can take some space from there if I need.

But now, just three last things I want to understand.

1) Why would you just leave an opening in the middle for glass and use molding on both sides to hold the glass. Wouldnt it be much more secure if the front side of the door had teh plywood extended - even just 1/4 - to act as the stop on the front? The front is the part that, in my case, is only seen from the family room, and that is 8 feet down. Thats where Id think I want as much strength as possible to hold the glass in.

2) Why would you put iron-on band on the edges instead of just sand and paint? Also, Im assuming this is really glued on - or can be. Is that right?

3) Are my savings significant if i do this with ply instead of solid wood? Another problem I have is finding solid wood. I can do teh work at night butcant getto lumber yard so my place for materials is HD or Lowes and they have nothing heavier than 3/4.

I dont want to make this job take forever either. But, I figure if spend a night cutting, gluing, and clamping that my next time I will be at the same point as if I bought solid wood and mortised it.

4) There are different grades of plywood as far as the final layer and sanding goes. Im painting these doors - but I guess I should I go for the ply that is sanded perfectly smooth (Imnot sure if this is the birch)

5) And last, the hinges. I guess just use nice long screws since Im going into end grain?

 

1). simplicity and good looks. and if the moulding you apply to both sides is glued and nailed, it will be as good as your alternative. Having a moulding to cover the cut edge of the plywood on both sides is also superior design- plywood is not usually a product where you allow cut edges to be your finished edge. It would also help make the door look less like a piece of plywood and more like an expensive custom door.

2). iron-on banding has glue that is activated by heat. It's purpose would be to make the edges of the door better suited for paint by covering up the seams between the 3 layers of ply as well as covering up any voids you might have. If the doors will always be closed, perhaps it's not needed. Banding all 4 edges of each door "could" make the door more stable and less susceptable to humidity changes. If the edges of the door were banded, the door would LOOK like a solid door to anyone who opened it, because they would not be able to see the 3 individual pieces of plywood. Again, if the door will never be opened, that's a non-factor.

3). yes. the clear lumber you would need to make those 2 doors would cost a small fortune. Mortise and tenon joints are also difficult and time consuming to make unless you have the tools and the know-how to make them. Using 3 layers of plywood is a sneaky way to do it that will be much faster.

4). right. You'll probably want either AC or AB plywood, depending on what's available at your store. The "A" means the highest grade, sanded with no imperfections or blanks. Birch will likely be better than standard AC plywood. Compare the amount of plys in the wood- you can count them along the edge of the wood like counting layers. More layers is better, which will make the plywood less likely to warp. Don't cheap out when making your decision. The cheaper the plywood the worse the quality.

5). You'll want to router out mortises 1/8" deep or so for the hinge locations so that the hinges will lay flush with the edge of the door, and then predrill the holes with a bit that is 1 size smaller than the screws. This will help prevent splitting. A longer screw would likely be better, but be sure you predrill the holes as deep as your screw is long.

Glad to help with the advice. Heck, if you lived next door I'd come over and help. I had the afternoon off work today.

 

#3 - I figured the plywood method would actually be slower, but I guess Im underestinating the setup and work for the mortise and tenons. Plus Id probably end up buying a new router bit just for this.

Thanks again for all of the advice!

 

Sure! Hope it works for you. Like I mentioned in my initial reply, my biggest concern would be warpage. With such a thin frame, it will want to twist instead of laying straight and plumb. Your hinge side will stay straight, but my concern is where the doors come together in the middle- that if they warp the left door could warp one direction while the right door warps the opposite direction.

If this would happen, you could always get some sort of floor bolts to keep them in line. The astragal mentioned previously might also help keep the doors in line. That's something you could add later, if need be, by ripping some off of one door, then adding the astragal.

Good luck!

 

post some pictures when your done

take some construction pictures to

 

I will, but how do I post pictures here. Do i need to post somewhere else and link to them?

And one last issue...

Last night I checked that my opening was square. It is. When I framed this out, I put 3/4 pine in the opening to hang the doors on when I got around to it.

And while its square there is a problem. The left side, about two feet from the bottom, has a bulge. It pushes in about 1/4 inch, maybe a little more.

Behind this pine are other pine pieces that I used to fill in a void. Those inner pieces are screwed in, and my outer piece of pine (that Ill hang the door on) are screwed into them. I also have molding nailed into the outer peice of pine from the front of the opening - which in turn has a railing in front of it. So dismantling this really isnt an option.

Not sure if this makes any sense, but bottom line - I have a bulge in the frame. There was some separation between teh two layers of pine when I put this in so i may be able to screw the outer piece of pine tighter and pull it in more and reduce the gap.

But, any thoughts on this situation?

 

Thanks again for all of the information. I cut all my strips one night. Glued all of the stiles (2 of the 3 layers), and all the rails (all 3 layers) the next night.

On the third night, I assembled one door. Ill assemble the second door in a couple of days.

I used a lot of glue. I fully coated both sides with carpenters glue and nailed it with 3/4 brads. Then clamped. I didnt think about it until after I was done, but i nailed it like crazy - especially in teh mortise/tenon. I mean - the thing was RIDDLED with brads. Of course, they are all hidden but I dont know what I was thinking. You cant use too many nails right? I hope not. Its plywood so Im sure it didnt split and weaken.

Anyway, its working out great. Much easier and smoother going than I expected - at least so far. Glad I followed all of the advice. If I did it how I initially planned, I would have wasted a ton of time.

But, just a couple of follow-ups.

1) What thickness glass would you use? 1/8 or 1/4. The glass will be about 8"x74". Seems kind of long for 1/8. Wouldnt it flex a lot at that length with so little width?

2) How many hinges on each side for this kind of door. They arent big but they are kind of solid. All of my interior doors use two hinges, but they are hollow luan. My exteriors use 3 but they are steel.

 

1/8" glass would be a lot cheaper, but you'd have to worry about breaking it during transportation. You'd have less to worry about if you were using 1/4" plate glass because it's more rigid. You'd also have better luck trimming the opening with a 3/4 moulding on one side and a 1/2" moulding on the other side (if you went with 1/4" glass). If you centered the 1/4" glass, you'd probably need a 5/8" moulding which might be hard to find.

You can certainly make your own custom moulding by ripping down some pine (round the front edge and notch it so it covers the edge of the plywood opening), in which case it wouldn't matter what thickness glass you got, as far as the stops are concerned.

You mentioned plexiglass (lexan/acrylic) at one point, so I'm not sure it matters what size you use if you chose that option. I'd steer you away from plexiglass just because it scratches so easily, and it's not much cheaper than glass unless you can find some plastics warehouse that will give you some scraps for free (like I did!).

As far as the hinges go, I'd suggest you use 3 per door. The hinges will help keep the door straight so that it doesn't bow. Doors with 2 hinges aren't high quality doors.

Glad things are going well so far.

 

I just unclamped one door and it is warped, longways, on left and right sides.

Anythng I can do about this? Im sure Ill be able to hang it straight on the hinge end (I just clamped it down to a couple of 2x4s and it pulled straight) but what about the non-hinged end.

Anything I can do about this?

Im thinking I can shave off 1/8" and get a strip of metal that is 80"x1.5"x1/8" and screw this to the edge of the door. That should keep it straight, no? If that would buckle (I cant see how), I could always get an "L" shaped piece (1.5x1.5) that would would wrap the corner (on the inside). It could look decorative I suppose. A guy a few houses down makes metal railings so I could probably get a custom size if I need to go with some sort of metal to keep this straight.

Or can I shave 3/4 off and use a piece of solid wood, 80x1.5x 3/4 and dowel and glue that to the edge. Would that stop the warp?

I havent built the second door yet, but Ill assume it will be the same.

Any thoughts?

 

The solid wood might counteract the warp, but the steel definitely would. One would think that if everything was flat, and was clamped flat while glued, that it would all stay reasonably flat. But that's the problem with plywood, it will warp.

 

I checked the 2x4s that I used on eachside to clamp with and they were straight too. I guess the 1/2 that I used was warped to begin with. Some of the strips definitely were but they were so thin I didnt think much of it. When clamped together they seemed straight.

Anyway, so which would you go with. Steel or wood?

If steel, just a piece of flat steel would do it right? Do you think I need the "L" to wrap the corner? I assume not, but what do you think?

Would you try to hide the steel by recessing it - rabbiting out a groove so that its only visible frm the edge, or from one side? Or just attached it to the end.

Also, any thioughts on how thick I would neeed to go.... 1/8... 1/16?

Oh, and one side question. Once the glue dries, I can put them in the garage in the cold - right? with no problem with the glue.

 

I don't know where you live but I would go check out a Mill-works company in your area and see about getting a pair of doors made from fir 1 3/8" thick and also get them to make a side in jamb. Unless you are retired, it could take you a month and several hundred dollars to do what you are proposing anyway.

 

DoorsNThings,

I never even considered that from the start because of the price.
Actually, Im probably at about the 1/2 way point I would say - maybe 40% done. I just need to assemble the next door and add the stops on teh outside - just a couple of hours there.

Then I am ready to hang - then prime and paint.

All total it pronbably will take me about 15-20 hours I am guessing. and, since i am not retired, it probably WILL take a month of elapsed time. But at least the effort is broken down to an hour or two here and there.

As far as price goes, though, my only layout was for one piece of ply and glue. About a 40$ total. I still need glass though. Not sure what that will run. I did have small mirror doors made for a vanity cabinet when I re-did my bathroom and they cost just $25. so Im guessing about $100 for my glass.

Now, I do need to address the slight warp. Im sure a thin flat piece of steel will do it and Ill have t o make sure it looks nice and neat. I cant image that it will cost that much.

So, there is some effort here but overall I enjoy it and Id probably do it again if I needed another pair of doors.

 

Anyone have any thoughts on how to handle these warped doors. I dont really want to scrap this project now. They are built - just have a warp in them.

Im thinking of ripping off 3/4 inch off the door and putting a piece of 3/4 wide, 1/8 thick metal - screwed to the door along the length of the outside. Then capping it with a piece of rabbitted 3/4 stock - glued to the door. If I only go 3/4 wide, there will be some meat on the outside of teh metal to glue to.

A bit of work but it saves me the problem of trying to perfectly fit the metal , countersinking and covering the screws. If its capped with stock that fits around it I wouldnthave to worry about any of that.

Any thoughts?