fixing hollow, too-short door
December 5, 2008 7:41 AM   Subscribe

I need to cheaply sound-insulate a door that has two issues: it's hollow, and it has half-inch gaps at its top and bottom.

For the next half-year I'm living in a bedroom inside an apartment that's been really cheaply renovated. The door to my bedroom is a super-light hollow wood door that doesn't fill the full space of the door frame. This is useless both for sound insulation and for air insulation (I want to keep out incense and cooking smells from the hall, as well as sound).

Installing a new door is not an option. So, I'm thinking I need to do two things: fill up the door with something solid, and make its top and bottom not have the gaps.

-- For filling the door, I'd like to seal the bottom (how should I do that?) and fill it by pouring in from the top, with a funnel, something that is dense and cheap but wouldn't make a horrible mess if it somehow spilled (maybe a bag of birdseed?).

-- For making the door reach its top and bottom, just some foam or cloth padding? But there is wall-to-wall carpet in the room unfortunately -- rough and dense carpet that would catch on something that drags past it -- so my solution will have to slide over that carpet. I would really like to do this without a door-sock or something else I have to bend down and manually move every time I need to open the door. Maybe the bottom could be a rubber flap of some kind?
posted by sparrows to Home & Garden (14 answers total)
You could drill some holes in the top of the door and spray in a bunch of spray-foam insulation, which would probably work better than birdseed.

Then you could shim the top and bottom of the door out with some lathes.
posted by dunkadunc at 7:55 AM on December 5, 2008

The rubber things on the bottom of doors are door sweeps
check this hardware store to get an idea.
posted by bdc34 at 8:01 AM on December 5, 2008

The birdseed might attract critters. The spray foam isn't a bad idea, just be careful it doesn't all end up in one spot. The stuff expands as it dries and might split the wood into a godawful mess. What about some heavy drapery? There are some soundproofing ideas in this thread that might be adaptable to your situation.
posted by jquinby at 8:05 AM on December 5, 2008

Best answer: The fact that your door doesn't completely fill the opening may be a feature, not a problem (at least in some respects). If your apartment has a forced-air heating system (i.e. ducts that blow heated or cooled air into your room), the gaps around the door may be necessary for air to return to the unit, which helps with its efficiency, since it only has to heat or cool air that's already been somewhat conditioned instead of starting from scratch with fresh air. The technical term for what's been done to your door in this case is "undercutting". It's probably not a huge deal, but it might not be a process that you want to defeat.

As far as soundproofing, you'll get the most bang for your buck in sealing the gaps, which allow a lot more sound to pass through than the door itself. I'm not entirely sure about what methods are available for your use, but rubber sweeps at the bottom of doors are a fairly common thing, and I'd think you'd be able to find one fairly easily, or perhaps McGyver one out of a bicycle inner tube or something.

If your door is like most hollow doors, it's not completely hollow. There will be a wood frame, maybe with a couple of intermediate members within it to provide strength, covered over with panels of thin partcle board, MDF, or some other sort of engineered wood panel. Within the empty spaces between the frame members, there's usually a sort of honeycomb structure made of corrugated cardboard or some other lightweight board. Essentially, I don't think you'll be able to fill the door from the top - you'd have to remove one of the face panels and fill each cell of the honeycomb individually. Sealing the bottom of the door wouldn't be a problem - just cut a piece of masonite or something to an appropriate size and nail/glue it on. If you plan to attach a gasket to the bottom of the door, you may need to do this anyway.
posted by LionIndex at 8:05 AM on December 5, 2008

Can you just hang a heavy blanket over the door and be done with it? Because LionIndex is exactly right; the door probably isn't really hollow in the sense that it's an open, fillable vessel, and the gap at the bottom is probably necessary unless you have a radiant (electric/steam/hot water) heating system.
posted by jon1270 at 8:18 AM on December 5, 2008

In terms of cost, effort, and outcome, hanging a heavy blanket is your best bet.
posted by unixrat at 8:21 AM on December 5, 2008

Doorsweep for the bottom gap, weatherstripping for the top gap, heavy blanket hung over the door for added muffling and -- bonus -- style!

Do not fill the door. Birdseed is a horrible idea. In addition to the possibility of attracting rodents, lots of birdseed comes with free grain moth larvae, which will quickly turn your apartment into an infested nightmare. You will never get rid of them if you fill the door up with birdseed. Filling the door could also affect the way it hangs, if you add enough weight to monkey with the hinges.
posted by mudpuppie at 8:26 AM on December 5, 2008

If you go the foam route, make sure you get the low rise foam for insulation around windows, otherwise your door will explode. Or use the regular stuff and make a video of your door exploding.
posted by electroboy at 8:42 AM on December 5, 2008 [1 favorite]

Response by poster: Thank you everyone for the great responses so far!

The other bedroom doors (all doors other than mine) do snugly fit their top and bottom, which is what makes me think mine could be extended safely. I will see if I can talk to the building owner...
posted by sparrows at 8:55 AM on December 5, 2008

Seconding LionIndex in saying that there may be stuff inside the door that would prevent the door being filled from a single point.

You'd probably need to remove a face panel - once you've done that you can just cut a piece of fibreglass insulation or styrofoam to fill the space.
posted by le morte de bea arthur at 8:56 AM on December 5, 2008

The other bedroom doors (all doors other than mine) do snugly fit their top and bottom, which is what makes me think mine could be extended safely.

Oh, it's not really a safety issue. If the other doors are snug, yours may have just been taken from someplace else and put in your door opening. The only issue with defeating the undercutting would be reducing the efficiency of your heating system.

You'd probably need to remove a face panel - once you've done that you can just cut a piece of fibreglass insulation or styrofoam to fill the space.

I think removing a face panel would be very difficult to do without destroying the door. My suggestion of doing that was sort of facetious.
posted by LionIndex at 9:10 AM on December 5, 2008

Cheap hollow doors will often have cardboard (yup, the corrugated stuff) in strips scattered throughout, making expandable foam virtually impossible to distribute.

Add to that, the foam doesn't travel long distances once sprayed -- it likes to grab the nearest surface and hang on.

Nthing the blanket.
posted by liquado at 9:10 AM on December 5, 2008

Here is a really nice DIY door draft stopper, from Similar effect would be achieved by rolling up a thick towel. That takes care of the bottom at least!
posted by sararah at 11:42 AM on December 5, 2008

Feeling crafty? Get a sheet of styrofoam insulation (usually blue or pink) sculpt something out of it and hang it on the inside of your door. You'll have to space things carefully on the hinge side, but this would cover the gaps and deaden sound.

It will also be showing it's age in six months, but that's all you need it for.
posted by Kid Charlemagne at 11:28 PM on December 5, 2008

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