How can I find out if my doors are solid or hollow?
June 29, 2016 5:00 PM   Subscribe

I need to hang up some large mirrors on these doors and the mirror dude said they must be solid doors. How can I find out without taking the doors off the hinges?

The mirrors are approximately 7feet x 23" x 1/4" The doors are about 8ft x 24" (The side where the mirrors are have no handles or hardware).

I asked for the mirrors to be cut this size and picked 1/4" thick because I figured they'd have to be at least that thick for the size, but I dunno for sure.

These are closet doors. But they are large and rather heavy.
posted by manderin to Home & Garden (11 answers total)
Drum on them with your fingernails. If they sound hollow, then they are hollow. You can also push a tac in them. If it goes in pretty easily, it's hollow.
posted by myselfasme at 5:04 PM on June 29, 2016 [5 favorites]

Have you tried knocking on them? Drilling a hole would give an answer also. But you'd have to drill where you intend to hang.
posted by taff at 5:04 PM on June 29, 2016 [1 favorite]

A 7' x 23" x 1/4" mirror is probably too heavy to mount on a hollow-core door. A mirror that large needs safety backing and should be glued to a door that's been removed from its hinges and laid flat.

Also, a 1/4" mirror is overkill. I had a glass shop mount a 7' x 23" x 1/8" frameless mirror to my hollow-core closet door, but I removed the door, brought it to the shop, and reinstalled it after they attached the mirror.
posted by mattdidthat at 5:29 PM on June 29, 2016 [1 favorite]

Sometimes (especially on the hinge edge or across the top) the paint layers are thinner, and you might be able to actually see where the sheets that form the front and back of a hollow door join with the side or top strips.

For what it's worth, pretty much all interior doors are hollow --- closet doors, bedroom and bathroom doors, etc. But yeah: tapping to listen for hollow sounds is easiest.
posted by easily confused at 5:30 PM on June 29, 2016 [2 favorites]

They won't necessarily sound hollow. Better hollow-core doors don't. Hollow-core doors are lighter than solid-core, though, by a considerable margin. Also, if your doors are old (say, pre-WWII) then they'll be solid wood. They will be made of separate pieces of wood joined together, and will have noticeable seams if you look for them. High-end contemporary doors will be solid wood too. In general, solid core and solid wood doors are found on higher-end apartments and houses, ones lived in by upper-middle-class and upper-class people. Everybody else typically gets hollow core doors, because doors are expensive and solid doors are much more expensive than hollow ones.
posted by Anticipation Of A New Lover's Arrival, The at 5:33 PM on June 29, 2016 [5 favorites]

This is not exactly what you asked, but just in case let me save you doing the same dumb thing I did:

Say your door is 2.5 inches thick. So you think you can drill 2.5 inches in, or you can safely use a 2 inch screw, or that your door has 2.5 inches worth of strength to hold your mirror. But WAIT....does your door have panels? Recessed panels? Because if the panels are recessed an inch on each side of the door, then guess what? Even if you're door is solid, it's only 1/2 inch of solidness where the recessed panels are.

Yeah, it's obvious once you accidentally drill all the way through, and maybe I'm an idiot for not having thought of it sooner, but I didn't think of it sooner, and I'm sure I'm not the only dumbass who occasionally misses something like that, so I thought I'd point it out.
posted by If only I had a penguin... at 5:59 PM on June 29, 2016 [8 favorites]

If the door is not painted, one way to find out is to look at the connecting edge between the large front surface of the door and the edge. If the door is hollow cored, then the door will be covered with veneer, so you can see that the grain on one surface doesn't flow naturally to the grain on the adjacent surface.

If the door is solid, then those subtle wood-grain bands of coloration will be connected in a "solid wood" way; you can look for more pronounced bands of color to run across the wood, then feed out the side where you'd expect them to lead.

Your best bet is to find a solid door somewhere - preferably one that isn't painted - and look at it closely to see how the wood grain works. You can also try to find one that isn't hung on a hinge (maybe at an architectural salvage store) and pick it up to see just how heavy it is. You can also hit the center of the door with the palm of your hand to see how it sounds and how it feels. Then, you'll be able to test your own door to see the differences, if there are any.
posted by amtho at 7:16 PM on June 29, 2016 [1 favorite]

I'm skeptical that solid core door is required. Heck they used to make sliding mirrored closet doors that were glued to a lightweight panelling wrapped in very light weight aluminum extrusion. They were really common in cheap mobile homes.

Even hollow core doors have an exterior frame of solid material. If it was me I'd use either mirror clips or a narrow mirror moulding screwed directly into the frame material of the door. I'd double up the strength by also applying mirror adhesive/plastic paying careful attention to bead thicknesses and drying times. The clips prevent the mirror from creeping on the adhesive and the adhesive holds the mirror to the door. Something like these people have done. As long as your bottom clips are attached to solid wood they aren't going to go anywhere.

Bad news though, you'll need to take the doors off and lay them flat while the adhesive cures.
posted by Mitheral at 7:48 PM on June 29, 2016

Remove the doorknob.
posted by rhizome at 8:43 PM on June 29, 2016 [13 favorites]

I put mirrors on my hollow doors using foam mounting tape. They make stuff that is seriously strong. Check the weight ratings on the packages. Example 1 rated for 100 lbs per roll, example 2 rated for 30 lbs per roll.

Mind you, my mirrors aren't as thick as yours.
posted by fimbulvetr at 8:52 AM on June 30, 2016 [1 favorite]

There is also mirror mounting tape, holds 10 lbs per roll.
posted by fimbulvetr at 8:56 AM on June 30, 2016

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