Hollow doors are lighter and cheaper options, so they often find their way to both interior and exterior applications. However, hollow doors lack the material and mass to prevent sound from easily passing through. Having found this out, you are likely wondering how to soundproof a hollow door. In this post, we gather all the tried-and-true methods of achieving this soundproofing to thoroughly answer your question.
Methods for soundproofing a hollow door are never perfect, but all do offer a certain degree of sound deadening. The most popular methods for accomplishing this are:
- Affix a sound barrier to the door
- Foam insulation panels
- Mass-loaded vinyl barrier
- Acoustic panel
- Install curtains
- Weatherstrip the door
- Add a door sweep
- Fill the door with spray foam
Keep reading the rest of this post for details on each of the above techniques. When appropriate, we'll include product recommendations to help make this task an easier one. To conclude, we'll provide an additional reading list.
How To Soundproof A Hollow Door
Hollow doors are susceptible to sound transfer because rather than wood interiors, the door is given structure by a light wood frame and a lattice of cardboard.
This means that the majority of the door's core is all air which means that there are far fewer molecules of material between one side of a hollow-core door as compared to a solid door.
Those fewer molecules do a worse job of deadening sound than relatively molecule-dense walls or solid core doors. Understanding this principle, all the following techniques add density and molecules to one side of the door, around the door, under the door, and/or in front of/behind the door.
Affix A Sound Barrier To The Door
For these strategies, you are tasked with affixing a material directly to the door. This makes soundproofing more permanent and in some ways more effective. However, if you find that you do not like the look or effect of any of these strategies, it is also sometimes difficult to remove them from your hollow-core door.
Generally, you can attach any of these sound barriers with either high-strength glue or screws. Keep in mind that if you use removable fasteners like screws, it is much easier to remove the barrier.
When affixing the barriers, keep in mind the full range of motion of the door. This means you don't want the sound barriers to catch on the door jam, carpeting, or other in-home obstruction. It is much easier and neater to trim these barriers before you attach them to the door than to wait until after they are attached.
Foam Insulation Panels
Foam paneling is most often sold as insulation. However, the dense nature of these products makes them effective sound barriers.
When shopping for this paneling, which is made using a variety of products, be sure to look at the R-value. While the R-value specifically refers to the heat transfer resistance, a higher R-value also means a better sound barrier.
The largest downside of foam panels is that they are not designed to be placed in visible areas so are relatively unattractive. You can choose to spruce these panels up with a wood or even wallpaper veneer.
It is difficult to find foam insulation panels that are larger than, or as large as, the door you wish to cover. This means that you will likely have to cut sections from one or more panels.
To cut foam panels, use a straight edge such as a carpenter's square or long level and place it on the line you wish to cut. Then draw a utility knife along that straight edge. Even if you do not cut all the way through the panel, the panel should easily snap at that line.
Finally, once you have the panels in place, be sure to draw a bead of caulk in all of the on-door gaps. This step is not 100% nessisary but will produce a more soundproof final product.
Mass-Loaded Vinyl Barrier
Mass-loaded vinyl barriers are commonly referred to by their acronym, MLV barrier. These are relatively thin materials that are specifically designed to cut down on sound transfer. They are often installed in floors and walls.
For a hollow-core door, it is probably easiest and most attractive to glue the mass-loaded vinyl to a piece of precut plywood.
Any high-quality spray-on glue should work for this job. Then, once the vinyl is firmly attached and fully trimmed, you can use screws to affix the plywood/vinyl assembly to the door. For best results, consider putting mass-loaded vinyl on both sides of your door.
Acoustic paneling comes in many shapes and sizes depending on the application and your preference. Most often, you will see acoustic paneling used in the cloth erected walls between office cubicles.
The higher-end acoustic paneling is made of foam and often includes a variety of angles to further deflect and deaden sound. For most hollow-core door applications, you will want to opt for the cheaper and less obtrusive acoustic paneling options such as the one linked above.
In contrast to the several door coverings outlined above, curtains and/or blankets are usually installed on the outside of the door frame rather than onto the door itself.
In many ways, this makes the actual installation process much simpler. This is because you are able to affix the curtain into the home studs rather than into a relatively flimsy hollow-core door.
However, the fact that a curtain will hang on one side of the door means that whenever you pass through the opening, you will also have to push aside or walk through the curtain. This runs the risk of becoming very annoying over time. Also, take note to only install the curtain on the side the door opens away from.
When shopping for these curtains, be sure to measure your door opening first. Then, purchase a curtain that is a perfect fit or slightly oversized for the size of your door.
Weatherstrip The Door
Sound does not only pass through the hollow-core door but also around it. This is especially an issue for interior doors which are rarely, if ever, weatherstripped. Often, more sound will pass through the air gaps around a door than through the actual door itself.
Weatherstripping comes in many forms, but all are designed to fill the gap between a door and the top and side of the frame. For the best results, cut the top piece of weatherstripping square to the door frame and then install the side strips with a cut angle to fully fill the corner space.
Generally, the more expensive the weatherstripping, the better and longer-lasting it will be. Therefore, if you are not sure about adding weatherstripping to your hollow-core door, perhaps the cheap stick-on material is right for you.
On the other hand, if you have large gaps around the door and are sure you want more sound proofness, perhaps metal-backed screw-in weatherstripping is best.
Add A Door Sweep
Often, the gap around a door becomes the most prominent under the door. This location calls for a door sweep rather than weatherstripping. Take note that certain types of bulkier door sweeps may get stuck and not work properly on carpeted floors.
Sweeps come in permanent varieties that are generally screwed onto one side of the bottom of the door or temporary varieties that slide onto the door. Shop around to see what type works best for your application.
Fill Door With Spray Foam
Finally, it is possible to fill your door with spray foam. This method is relatively technical but doable by most handy homeowners. A major upside of this method is that, if done properly, the door's appearance and function will not change significantly.
First, take the door off the hinges and take off the door handle and handle hardware. If you leave the handle assembly on, you run the risk of filling it with spray foam and hindering its functionality. Tape and plug this hole with rags to make cleanup easier later.
Now, drill several small holes along the outside of the door. Space them about 24 inches apart. Then insert the spray foam straw into the hole and fill the space as much as possible.
When the spray is about to come out of the hole, remove the can and tape over the hole to prevent the spray from spilling out. Do this for all of the holes you drill.
Once completed, you should have a well-filled door that will be much more resistant to sound transfer than the hollow-core version. After the foam has completely cured, you can remove the tape and handle hole plug.
In most cases, you may still have small marks on the edges of the doors where you drilled the holes. You can try to patch these with a like-colored permenant marker, paint, or stain. Further, you may have to carve out some foam when you reinstall the handle assembly to ensure proper door function.
In this post, we answered the question of how to soundproof a hollow-core door. We provided several different techniques as well as advice and products when appropriate. Good luck!
To learn more about in-home soundproofing, read these other articles: