Building big doors - how to keep them flat?

[guitarchitect]

So last year I built myself a shop, and got my wife to agree to extend it from 24' to 30' (11' wide... it's not huge) on the basis of providing a storage room at the back for household+kid stuff. Never one to want to give up shop space, I've nearly convinced her that instead of a room we can build a deep storage WALL to hold everything. Which means I can keep the floor area free for shop use. The only catch is that I want to make it dust proof, so I'll need to weatherstrip all the doors.

The one thing I'm struggling with a bit is, how to build a tall but FLAT door. The dust-tightness will rely on the doors being dead flat. I will probably build the unit 7'6" tall, leaving 1' open at the top for long/awkward things. The plywood I've been using for shop stuff from home depot, while hitting the right pricepoint, is warped as all heck. Should I make my life simpler and buy a bunch of pre-made hollow core doors? Or is there a better sheet good that I could be using? I could laminate two sheets of baltic birch together, sure... but that gets pricey. Would rail + stile doors be better? We have some closets in our bedroom from the previous owner, and they're at least 7' tall and the doors are dead flat - they're 1" thick and oak veneered, so I'm not sure if they're particleboard or MDF or plywood.

Hard to settle on a path forward so I'm hoping you guys might have some insight!

 

[duburban]

This is a great question because it touches on a lot of nuance in material selection, acquisition and handling.

My thought is to turn to MDF considering your usage sounds light, no kids hanging on the doors/banging them around... The price is right and even if it has a small curve/belly in it the 5-6 hinges will help keep it in line. If you want to get fancy you could use a burgess bit or something similar to let in some hardwood edging so that it performs higher than regular edge MDF.

I'd say baltic birch but you may have a harder time finding it that size at a good price. If you were to laminate sheets together you'd end up with really thick doors and need a vacuum press to do a bang up job with it.

The hollow core door idea is actually really smart. I was working in an Architecture office that had a wall of hollow core door storage and it made a lot of sense and looked good too.

Paint grade?

 

[Stone Message]

There are a number of ways to construct nice true doors and I am sure you will get lots of advice in that area.

One easy thing to do is to put door stop all around and have a lap rebate where the doors meet in the middle. Then you can have four bolts that keep the doors shut (one at the top and one at the bottom of each).

Then all you have to do is to ensure that your door stop is in a true plane. This may help out with your draft proofing plans too.

Peter

 

[Rob-GB]

The hollow core door idea would be my go to solution with the addition of a draught seal like this one
if you cannot fit it into the frame then it can be used in the reversed position in the door edges. I have used it this way in refurb'ing a house full of oak casement windows and it worked really well. If you have doors meeting each other then just offset the grooves a bit.
Rob.

 

[cubevandude]

I vote on the hollow core doors. 

 

[RKA]

What about barrel bolts at the top and bottom of each door?  Even if the door twists a little, the latches will pull everything tight to your weatherstripping which you may need anyway.

Post some pics when you’re done.  Would love to see how it worked out.  I need to build a dust proof storage cabinet in my basement as well. 

 

[lwoirhaye]

Hollow core doors are a great option if you can find some in the right size. 

If you have to make them yourself, consider a torsion box approach.  That's basically what the hollow core doors with the cardboard inside are, but you'd have a hard time working with cardboard to mimic the same effect so a wood core torsion box will work.  Gluing and nailing will be a lot easier than getting set up to glue them by pressing.

 

[Cheese]

I'd visit the local house salvage center or repurpose center. I was at ours last week and there were more hollow core doors in there than you could shake a stick at. No one is looking for hollow core doors so they were all priced at $10 each. A little sanding and some paint & you're good to go.

 

[Birdhunter]

My cheap trick for building totally flat structures is to buy a hollow flat panel door at Home Depot. I usually get them around $12.00. They are nearly perfectly flat. I lay the door on sawhorses and use it as a glue up surface. I’ve built a king bed laminating two 2 by 6 white oak boards together clamped to the door. When the glue dried, I had a totally flat bed rails. It doesn’t matter if the boards were not straight to begin with. The two boards glued together and clamped to the flat door always yields totally flat glue ups. A roll of waxed paper protects the door from the glue overrun.