Reuse Hollow-core Doors To Make Plywood and More

Reusing isn’t new, but items deliberately made from reclaimed materials have become statement pieces. The “upcycling” movement and rising interest in eco-conscious wares has given value to the valueless. Decrepit and dangerous barns once left to decompose are now painstakingly picked for profit. Even shipping pallets have earned a place as sought-after sources of wood. And then there’s my latest obsession: hollow-core doors.

You know what I’m talking about: Those flat, thin doors in casa de Brady Bunch. Inexpensive, (then) stylish, lightweight, and surprisingly durable, they did the job. Alas, times change and nowadays when someone remodels a home these doors are often the first to get tossed. I would guess tens of thousands go to landfills annually. But wait, they have tons of value! I’ve set out to save as many doors as possible and put them back in service. Here is the abridged version of everything you need to know about reclaiming hollow-core doors.

WHAT ARE THEY?

Hollow-core doors typically consist of two ⅛” plywood-skin sheets (one per side), a 1″-thick solid wood frame (usually pine), and a honeycomb of corrugated cardboard filler to add structure to the centers. They are usually about 1¼” thick in total. The wood frame is about 2″ deep on the top and bottom so there’s real wood to cut into when adjusting a door to a jamb, and about 1½” on the sides, to hold hinges. Additional 2″ “knob blocks,” typically 12″–18″ long, are added to the inside edge of the frame on both sides, so a door knob can be mounted on either side. I have also seen doors with thin strips of wood inside them and recently found a batch with slices of thick cardboard tubing used for interior structure.

FINDING DOORS

Besides keeping your eye open at the curb, almost any unremodeled house built between the 1950s and 1990s is full of them. If a house from that era is being renovated in your area, ask! Most contractors will gladly give you the doors to save the dumping fee. Even better, tell your local contractors you want them and they’ll call you from each new job.

I frequently put out messages in local Facebook groups and other social media sites. I also asked friends and family to spread the word and have never had a problem finding someone with a basement full of doors or a home improvement project they’ve been putting off. One time my friend Peter Kelly of 542 Woodworks had just finished a big renovation job and I scored more than 40 of these doors destined for the landfill in one trip!

DISMANTLE A DOOR

If a hollow-core door is 30″×80″, expect to get two sheets of plywood around 23″×75″, plus some usable pine strips.

The doors are glued together with something like hot glue, so the cardboard parts come off fairly easily but if you’re greedy and try to pull the thin plywood from the wood frame you’ll almost always wreck it. Cut your losses on the wood frame around the edge and cut it off (but don’t worry, we’re still going to use that wood, too).

Start by cutting the long sides off (about 1½” from the edge is usually enough) and put those aside. I typically use a table saw for this, and cut through the whole door in one pass, but a circular saw works too. Now you can see the top, bottom and knob blocks inside.

Cross-cut the top and bottom off (use the circular saw and some masking tape to keep these cuts clean).

Then cut off the knob blocks. The easiest way is to slice the whole door another 2″.

You’ll end up with strips of the plywood on either side of the block you can snap off and save for smaller things.

Sometimes you can get the plywood off the knob blocks and get a wider sheet about 27″×75″ but the risk of wrecking it increases. I often will cut off only one knob block and take my chances with the second.

Once all the solid wood is removed, you can peel the two layers apart. Wear gloves, as the glued corrugated cardboard edges are sharp.

Then I usually use a wooden mallet to bang off the stuck cardboard rather than a scraper, which I find too time consuming.

Another option is to stand the door up tall and use a piece of wood or metal the same width as the interior of the door to push the glued cardboard off both sides at the same time. It’s a little more of a cardio workout but you can do both jobs in one motion.

At this point, if you’ve dismantled one 30″×80″ door, you should have two strips of pine approximately 1″×1½”×80″, two pieces of pine 1″×2″×27″ and two pieces 1″×2″×18″ (one with a hole in it), as well as two 23″×75″ sheets of ⅛” plywood, four plywood strips about 2″×30″, and very little waste besides the cardboard (which can be recycled). Well done!

USE AS-IS

I love having this ⅛” plywood around the shop. It is the perfect material for cutting templates, making shims, making drawer bottoms, and more. Almost any idea I have gets prototyped in door skins first.

It’s also great, free material for laser cutters. I made an entire acoustic guitar from doors on my laser.

DIY PLY

To make thicker plywood from door skins, simply glue layers together to your desired thickness. The only downside is anything thicker than ¼” will require you to sand both sides of the skins to remove any cardboard glue residue from the inside and finish from the outside. This is the worst part of the job, but if you use something coarse like 60 grit sandpaper to start, you can make pretty quick work of it.

Use a generous amount of wood glue and make sure every square inch is covered.

I used spring clamps on the edges (a lot of them) and as much weight as I could find to put in the middle to clamp it up.

I’ve been pleased with the results every time with no voids.

LAMINATIONS

But why not keep gluing? Especially since some of your conquest is cut into smaller pieces, why not create full laminated blocks of wood from the plywood? Alternate directions, create patterns, get creative!

I’ve made a few guitars and other things out of scores of skinny layers of plywood glued up and planed into interesting engineered blanks. When you cut and sand these at angles, all sorts of interesting wavy patterns emerge.

OTHER USES

While the plywood is certainly the point of the exercise, there’s still a lot of good wood in the edges that can be used. The trim and knob blocks are usually Douglas fir or some other pine, but I’ve found most of this wood to be pretty high quality and, as a bonus from being hung in a door for decades, incredibly straight and dry — better than any green pine you’ll get at the big box store.

Sometimes I run it through the table saw to remove the plywood still stuck to it and get nice, raw pieces of wood, but sometimes I leave the plywood on there to create new, unique looks.

Hopefully you will never look at an outdated closet door the same way again — and maybe you’ll find some inspiration to add them to your stockpile. Now that we’ve added these doors to the save list, what’s next?

USE THE HASHTAG #HollowCoreDoorsAreTheNewPallet to find more ideas and to share your creations, and peruse my youtube channel for more information. I have more than a dozen builds featuring these doors as well as an in-depth video about my dismantling technique.