Doors and windows are weak links in soundproofing projects. I have mentioned this in a few posts on this site.
And out of the two, soundproofing a door is the more difficult and more expensive task.
I’m sure that you have experienced the same.
For a window in the worst case scenario, you always have the option to cover it with drywall. But the door is something you can’t live without.
I have always had a tough time with this. And the worst thing is, that you cannot ignore the door if you are a home theater enthusiast like me.
When I first tried to soundproof my theater room, I didn’t pay that much attention to the door mainly because the solutions available on the internet were confusing and expensive.
But after all that effort I made with treating the walls, ceiling and floor, the door was the one that played spoilsport.
I decided that I had to do something about it and realized that without any serious research, I would be wasting my money.
The expensive ones were definitely not an option for me. I wanted to find the best way to soundproof a door which would not break the bank.
I am going to share with you what I have learned.
There are three main questions that we will be asking here.
- What are the problem areas?
- What are good soundproofing materials for doors?
- Which type of door assembly is the best?
Problem Areas While Soundproofing A Door
Identifying the problem areas is the first approach that you should take for any soundproofing project.
As far as doors are concerned there are many myths which cause people to make wrong decisions. The myths will come up as we discuss the problem areas one by one.
Problem #1 – Hole In The Wall
A sealed room with no doors and windows is fairly soundproof. The moment you install a door, you are creating a hole in the wall.
Any hole in the wall will destroy the soundproofing completely. Covering this hole with something other than wall material to provide a similar effect, is the major challenge.
The door is not even half as good enough as the walls to block sound. The whole problem starts here and though it is obvious, this needs to be kept in mind.
Problem #2 – Door Frames
In the door itself, the frames are a big weak link. As the door frames are shimmed in place, air gaps are created which leak a lot of sound.
There are two options to solve this:
The door frame can be installed before installing the drywall. After this you can add a drywall layer over the frame.
Though this would mean that you have an exposed edge of drywall, it would be highly beneficial in sealing the door frame.
The second option is to just cement the door frame after it has been shimmed. This is the easier option of the two and is the one I chose.
Whatever option you choose, you will need to use acoustic caulk in between the layers of the door frame and the drywall/cement.
Problem #3 – Door Jambs
Door jambs create flanking paths for passage of sound. This can be countered to some extent with a jamb seal kit.
Problem #4 – Gap under the door
No door can be designed without a gap under it. This is required so that it does not scrape the floor when it is moved. For soundproofing, the gap under the door is definitely not acceptable.
The solution is to buy and install an automatic door bottom. An automatic door bottom is designed such that when the door is closed, there is a seal covering the gap.
When the door is moved, the seal gets lifted through a spring mechanism automatically so that it can move easily.
Problem #5 – Options for materials
There are a lot of material choices when it comes to building walls. Inherently these materials have good soundproofing characteristics.
Doors have to be visually appealing to some extent at least. We all live in homes and cannot afford to have a funny looking door that is made of drywall.
The main problem is that the Transmission Loss required for something like home theaters, cannot be achieved even from the heaviest woods. And that is why soundproof doors are very expensive as they are heavy woods that are modified for soundproofing.
Suitable Wood For Soundproof Doors
Having identified the problem areas, the next thing is to look at is – which type of wood would be good. One thing that I was sure about during my research was that the door would have to be really heavy. Mass is good for soundproofing after all.
MDF was the first thing which came to my mind because that was being used for many soundproofing applications. Or perhaps OSB.
When I went deeper into the subject, the findings were quite different. More than the material, to be precise, it was the type of door which was the underlying factor.
Types of Doors
You will need to know about the types of doors and their soundproofing abilities. There are mainly three categories to consider.
Hollow Core Doors
Hollow core doors are light doors and can be installed where noise isolation is not a priority. These are the low-cost ones that we mostly see in apartments and houses.
They are basically honeycomb structures which are enclosed with fiberboard or veneer shell. These are obviously not a good soundproofing option.
Solid Wood Doors
Solid wood doors are made of natural wood elements put together. These are heavy as well as expensive.
They provide good soundproofing and the looks of these doors are excellent.
So, they look good and sound good? But are they the best for soundproofing?
Not really the best.
Solid Core Doors
Solid core doors are as the name suggests, doors that have a solid core made of composite material.
Solid core doors are the best for soundproofing. This is because they are denser and heavier than solid wood doors.
A Flush veneer covered 1 3/4 thick particle core door is a great choice for a soundproof door.
Solid core doors are also available online on Home Depot.
Best Value Soundproof Doors
Now that we know that solid core doors are best for soundproofing, let’s explore what is the most value for money option available in the market.
But first, there is a technical term that needs to be discussed and that is OITC.
STC or Sound transmission class is a term we have come across often in soundproofing. There is another term called OITC or Outdoor/Indoor Transmission class.
Both STC and OITC are terms used to define how effective a material is for blocking sound. The only difference is that OITC caters for lower frequencies while STC does not take into account frequencies below 125 Hz.
In my research for the most economical options for solid core doors, I heard about Jeld Wen. The website has STC and OITC data for all their products.
The acoustical data for interior doors can be found on their website. The data is in a downloadable PDF document.
After you download the PDF, have a look at the data. As can be seen from the data, Tria R series would be best suited. These can be got for a couple of hundred dollars. This is cheap if you compare it to other doors that cost several hundreds or thousands of dollars.
I did, however, find some functional issues with these doors. They do the job but there may be problems with improper finishing. So, avoid purchasing online.
There are other options out there, which do a good job and are not very expensive at the same time.
Which Type Of Door Assembly Is The Best?
As per the Wikipedia page, with an STC of 35, loud speech would still be audible, though not intelligible.
A solid core door may not still provide that much sound isolation as a wall. The STC of these doors would be around 35.
For a home theater or any application which requires a lot more, an STC above 50 is desired. Going back to the Wikipedia page, an STC of 50 would help drown loud music to a great extent.
As per data by Egger Industries, a communicating door is the best assembly for soundproofing. A communicating door assembly would have an STC of above 50.
What is a communicating door assembly?
In simple terms, a set of two doors installed, one on the interior side and another on the exterior side of a wall. There is a small gap in between the walls. The video below explains it all better.
Ideally, the gap between the two doors should be 24 inches. The gap will form a strong insulation layer which will increase the STC dramatically.
An STC of above 50 is a fairly good figure to achieve for doors.
We have seen that communicator door assemblies are best for soundproofing the door area. This may not be practical for everybody.
Solid Core Door + Green Glue + MDF
Some experts suggest that an MDF layer can be added to the solid core door with a damping layer, like Green Glue, in between. This will improve the STC by a few numbers.
MDF + Green Glue + MDF
Another option which is cheaper and less effective is to sandwich two layers of MDF with Green Glue in between.
You do avoid the costs incurred in buying a solid core door and it would give a decent performance for a room that is not a home theater.
For a house where you just want to block traffic noise and noisy neighbors, I found this as a good option.
For panels of 16mm and greater thickness, the STC of MDF is 25. On the other hand, plywood has an STC figure as low as 15-20.
Surprisingly, in the case of any material, the STC does not increase with increase in thickness. This means that there is no benefit of having a thicker layer of MDF beyond 16 mm.
If you really want to make a dent in the sound entering or leaving your room, you will need to get industrial grade soundproof curtains.
Personally, I don’t have a first-hand experience with these curtains but I am aware of some people who have used it and found it beneficial.
This is a solution I feel is worth looking into as it can really avoid the hassle of replacing the door. Moreover, it would also be cost-effective.
If you want to soundproof a room which is not intended to be used as a home theater, soundproof curtains are worth considering.
Truths Related To Soundproofing Doors
Having gone through many articles and forums, there are certain truths related to soundproofing doors which I consider worth sharing.
These will provide a clear insight to anyone who is intending to do the same. Truths automatically quell the myths and that is the main thing intended here.
As brought out repeatedly, doors in most cases are the weakest link in a soundproof room. The problems ranging from gaps to materials provide numerous challenges.
Most door seals primarily designed for weather-stripping perform more or less the same when you use them for sealing the gaps in the doors. The quality of seals does not have much of an impact on soundproofing.
The door jambs create a flanking path and in the door structure itself, they are the weakest links. When you install a custom or DIY door which is dense and good for soundproofing, door jambs would be a challenge that you will have to deal with. The readymade soundproof doors have the jambs problem sorted out but again, they are very expensive.
To achieve a high transmission loss for low as well as high frequencies, a large airspace such as that in a communicating door assembly is required. A single door, no matter how dense or heavy, cannot attain this.
Solid wood doors are beneficial for soundproofing. But, they are not as good as solid core doors. Solid core doors are denser and heavier, which makes them good material for blocking sound.
A few tips to summarize what has been covered here.
- Assess your needs. Are you soundproofing a home theater or do you just want to not hear that dog barking at night.
- Accordingly come up with a plan. Decide whether to go for a communicating door assembly or not. Decide whether to buy a ready-made door, go for a diy project or buy soundproof curtains.
- Then address the problem of gaps in the door frames and seal them as described earlier. Apply acoustic caulk where the frame meets the drywall or cement.
- After putting up the doors, use sealing kits for the door jambs and sides. Ensure that there are no gaps anywhere and that the doors shuts snugly into the frame.
- Install an automatic door bottom and that’s it, we’re done.
Soundproofing a door is no easy task. It would have been simple if soundproof doors were not that expensive.
But, a door is an unavoidable necessity and cannot be done away with. For serious noise isolation, a cheaper solution is unlikely.
So, pay special attention to this and don’t take the issue lightly. Making the right choice will avoid wasteful expenditure. Professional help is not a bad idea even if it costs a bit.
Thanks for reading! Before you go, take a minute out and check out my top recommendations for soundproofing products.