Having a hollow door is no picnic. It lets tons of noise inside and outside of the room, leaving you with a nasty headache, and no privacy. Anyone standing near the door can hear what you’re doing inside. I hate that feeling, and I haven’t met anyone who likes it.
So the question is, do YOU have a hollow door that needs to be soundproofed? Well, try knocking on it. If it sounds a hollow, then it is.
And if you answered with a wholehearted “YES SIR!” I will share with you the most effective method out there. And even if you didn’t say “YES SIR!” don’t worry, I’ll STILL still share this method with you. Because I’m just that kinda guy. I’ll also share 7 other methods that you can try if you don’t want to use the best one (because it requires a bit of work and you hate doing. It’s okay, I understand.).
So let’s start with the most effective method and take it from there:
The most effective way to soundproof a hollow door
1. Use the right soundproofing material
Choosing the right material is the first step in soundproofing your hollow door successfully. There are plenty of materials to choose from, which is not a good thing at all. It only means that there are more mistakes you can make.
I prefer to stick with materials that have worked well for me in the past. To soundproof a hollow door from the inside, the two most effective options are Mass Loaded Vinyl and closed cell foam.
Both materials work well for well for absorbing airborne noise (people talking, loud music etc.). The closed cell foam, which is low cost, comes with an adhesive backing that allows you to install it on the door with little effort.
Mass Loaded Vinyl does not come with an adhesive and it’s more expensive than the foam. However, it offers better results, especially for absorbing impact noise (drum bass, vibrating noise from machines like the washer, engines etc.). So if you’re trying to block that sort of noise, Mass Loaded Vinyl is the way to go.
If you’re interested in learning more about MLV, you can also check out my article about it.
2. How to install the soundproofing materials inside the hollow door
Step 1: Take down the door from its hinges
Using a simple hand tool (usually all you need is a screwdriver), remove the door from its hinges and then place it flat on the floor.
Step 2: Upgrade the hinges
The soundproofing material you are going to install on the hollow door will add some extra weight to it. So make sure that the door hinges are strong enough to accommodate the extra weight. If not, you should get stronger ones that can.
Step 3: Remove the wooden panel to open the door
Once you have placed the door on the floor, you need to remove one of the pressed wood panels.
Hollow doors are made of two wood panels and frames. Therefore, you will need to remove one of them to soundproof the door.
Carefully pry off the wood panel. Do not use a lot of force when prying off the panel from the frame because most panels used on hollow doors are lightweight and weak. Using too much force can damage the panel.
Step 4: Place the soundproofing material into the cavity of the door
Once you have dismantled the hollow door, it’s time to install the soundproofing material of your choice into the door cavity. To ensure that the material fits well into the cavity, take measurements of the cavity and then cut the material accordingly.
Sound just like water will always find a way into empty spaces using the tiniest of gaps. So ensure that the material fits snugly into the cavity of the door, so that there are no gaps left uncovered. If there’s more space left, you can add a double layer of the material for better results.
Step 5: Apply green glue
If you choose to use MLV, which isn’t self-adhesive, consider using green glue. Green glue is not your ordinary adhesive because it acts both as a sound insulator and at the same time sticks things pretty fast.
If you decide to use the closed cell foam, it’s also a good idea to apply the green glue over the wooden frame before placing the panel back in its place. It will act as another layer of soundproofing on the door.
Alternatively, you can use a cheaper adhesive like the 3M General Purpose spray. It will stick the material well, but it won’t add any extra soundproofing.
Step 6: Put the panel back on the door frame
After applying the green glue, carefully place the panel you had removed back to its position. Secure the panel firmly onto the door frame to ensure that there are no spaces between the door and the frame. Once you have completed this procedure, you can now get the door back to its hinges.
However, only covering the hollow part of the door does not guarantee soundproofing success. That’s because the main frame of the door (the area that connects the door to the wall) probably has a few gaps that also need to be covered. That’s the last step that will ensure success, so keep reading.
3. Soundproof the main door frame (top and sides)
To completely soundproof your hollow door, you will have to create a seal between the main frame and the hollow door, so that noise can’t pass through that area.
This is very easy to do by covering the door frame with rubber strips. These strips are commonly used on door frames. They come with an adhesive backing, which makes them easy to install.
Cover the top part of the frame with the rubber stripping in such a way that when the door shuts, it creates an impenetrable seal!
Cover the gap beneath the door
You will also have to cover the gap that is usually found between the door and the floor. If you ignore this gap, you will still hear the noise and all your efforts will have gone to waste.
Attaching a silicone door sweep is the best way to seal the bottom gap.
If you strengthen the hollow door with MLV or closed cell foam, and seal the gaps between the frame and the door, you’ll a huge reduction in noise. Congrats!
But what if you can’t or don’t want to remove your door from its hinges and stuff things inside the door cavity? Is there anything else you can do? Yes, there are a few methods, and here they are:
7 more methods you can use
1. Hang noise blocking curtains or drapes in front of the hollow door
Apart from using soundproofing materials to cover the cavity of the hollow door, there are other ways you can use to sound deaden the door.
Hanging noise blocking curtains is another effective way you can use to prevent noise from getting into your room. You will need to install a curtain rod over the door frame. Ensure that the rod completely covers the door area from one side to the other.
Then buy a thick curtain that is made of sound dampening material and hang it from the rod all the way down to the bottom part of the door. Make sure that it’s long enough to cover the door.
This is a good option for people who live in rented houses and they cannot alter the actual door in any way. It’s also convenient, since you can remove the curtains or slide them on and off whenever you want to, and use them for noisy window areas as well.
2. Install fiberglass panels on the door
Fiberglass is another material that can be used to soundproof a hollow door.
They are a bit expensive, but they’re worth it. You don’t have to play with the door’s insides, you don’t have to hang anything in front of the door… you just attach them to the door and you’re done. Also, fiberglass works just as well as Mass Loaded Vinyl.
You will need screws or glue to attach them to your door. Since they bare some weight, you need to ensure that they are well secured onto the door otherwise they will fall off when the door opens or shuts.
Remember to upgrade the hinges of your door if necessary to accommodate the extra weight. For the gap under the door, you should still use the door sweep and use the strips for the gaps between the door and the door frame. You should do that in addition to any of these methods.
3. Hang a fiberglass blanket in front of the door
Similar to using noise blocking curtains, you can hang a fiberglass blanket in the back or front of the door.
As I mentioned before, fiberglass works exceptionally well for impact noise, just like Mass Loaded Vinyl. Just make sure that the fiberglass blanket covers the entire door from top to bottom and from one side to another.
4. Install acoustic foam panels
Acoustical foam panels can also help in soundproofing a hollow door. Some music supply stores have these, but I recommend getting them from Amazon, both due to better prices and more options.
You can attach the panels to the back of your door using Command Strips, glue or screws. It is essential to point out that different foam panels feature different noise-dampening levels. Thicker ones will work better for soundproofing a hollow door.
I recommend you check out this article of mine. I reviewed the best foam panels and how to install them properly without causing any damage to the door/wall.
5. Coat the surface of your hollow door with sound-absorbing paint
Sound-absorbing paint is another way you can soundproof your hollow door from the outside.
You can do it with a brush, roller or spray gun.
Don’t forget to select the color similar to the color of the other doors. Unless you want to get whacky with it of course.
To apply the paint, you can do it yourself by following the instructions on the container. It’s no rocket science. The paint will look similar to the ordinary paint but it might appear a little thicker.
The paint can absorb noise by up to 30% in regular households so it can be a great addition to one of the other methods mentioned above. Can it be used alone on a hollow door to produce satisfying sound absorption? I’m not sure.
It depends on how much noise you’re dealing with to begin with. If it’s not too much noise to begin with, it might just be enough. If the noise is significant, I’d definitely invest in one of the first few methods that I mentioned instead.
6. Correct any door cracks
Cracks in a hollow door can render all of your soundproofing efforts useless if they are left unsealed. Caulk any large cracks on the door with wood caulk. Just make sure that it’s the right color.
7. Soundproof the doorway
If your door opens into a wood floor or tile-covered floor, you can put a rug over it to prevent the sound from bouncing off. It will reduce the noise to some degree before it comes to the door.
So which method do I personally recommend? Well, if you don’t mind removing the door panel and inserting MLV or cell foam inside the door, than definitely do that.
If you want something else, the next best method are fiberglass panels. After that, fiberglass blanket. Then noise-blocking curtains.
That’s would be my “from best to last” list if I had to soundproof a hollow door today.
Having said that, definitely seal off the gaps in the door frame and between the door and the floor regardless of the method you choose. Those empty spaces will let the noise in if you let them!
That’s all I have for you today. Feel free to browse the other articles on the website, and I wish you good luck with your soundproofing project.