How to Soundproof a Door

Soundproof a door

Doors are an important part of any wall assembly, exterior or interior. Doors are also typically the acoustically weakest part of a wall partition and the question how to soundproof a door is often asked.

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Ability of building assemblies to block sound is quantified by an STC (Sound Transmission Class) rating. The table below provide STC values of standard interior walls for comparison with doors described later.

Sound attenuation rating for typical interior wall [Reference 1]

Wall Type

Wall Cavity

STC Rating

Wood studs 2" x 4", 16" on centre, 1/2" drywall on both sides

Hollow

34

Wood studs 2" x 4", 16" on centre, 1/2" drywall on both sides

Fiberglass or rock wool insulation

36

Higher STC rating means better sound insulation.

Soundproof a door! Is it possible?

The tables below provide STC values for typical interior and exterior doors, as well as special acoustical doors.

Interior doors​

(tested as inoperable with the perimeter sealed) [2]

Door Type

Core Type

STC Rating

Flush Series

Mineral

35

Molded Panel (Raised)

Particleboard

33

Molded Panel (Raised)

Engineered

31

Flush Series

Particleboard

31

Molded Panel

Hollow

27

Flush Series

Hollow

24

Exterior doors without glass

(tested as operable exterior door units) [3]

Door Type

Core Type

STC Rating

Fiberglass

Foam

22

Utility Steel

Foam

23

HD Wood Edge Steel

Foam

24

Fiberglass

Particleboard

30

Acoustical doors [4]

Acoustical door type

STC Rating

Model 499723 Wood Door

49

Model 479725 Wood Door

47

Model 4696241 Wood Door

46

Acoustical doors, specially designed for maximum sound attenuation are sometimes referred to as soundproof doors. They are significantly more expensive than standard doors. Most effective method to soundproof a door is to use a special acoustical door.

From the listed STC values provided by the door's manufacturers you can see that hollow interior doors are poor, and solid doors are better sound insulators, but neither is as good as a wall. It is therefore advisable to install special acoustical doors in applications where extra sound attenuation is required, for example in your home theatre, or music practice room.

Referring to manufacturer's information [3], you can see that there is a wide range of acoustic performance for exterior doors.  The STC values range from STC 22 for foam core steel door to STC 38 for particle board core fiberglass door. Somewhat counter intuitively, exterior doors with glass perform better than doors without glass.  However, pay attention to the type of the glass insert.  STC 38 is achieved by fiberglass door with  particle board core and 1-inch thick laminated glass insert.  It is important to refer to manufacturer's information for acoustic performance when specifying exterior doors.  Do not buy doors from manufacturer who cannot provide independent acoustic test data for their doors.

It is important to be aware that the STC rating for interior doors is measured in a laboratory for the door slab only, without hinges and without a gap around the door’s perimeter. This setup is unattainable in a typical door installation; therefore the actual performance of an installed door will be always lower than the ratings given in the table. Some exterior doors are tested complete, with frame and seals.  This test data is more representative of actual performance of the doors in the filed.

To maximize an installed door’s sound attenuation, the gap around the perimeter of the door must be sealed as well as possible with weather-stripping or special acoustical seal. The gap at the bottom of the door also must be sealed with a threshold, door sweep or with a mechanically activated drop-down seal. Exterior doors usually are already equipped with weather-stripping.

Quality of door installation is also important. Often doors (particularly interior doors) are installed with a large gap between door jambs and adjacent wall studs. This gap is just concealed by trim frame and must be filled with insulation and sealed with acoustic caulking to block sound leakage.

How to soundproof a door​

People often ask me how to soundproof a door, particularly an existing door. First step is to verify if the door is hollow or solid. One can usually tell by knocking on the door panel and by checking the door’s weight. If the door is hollow, replace it with a solid door. Once this is done, install quality weather-stripping and threshold, or specialized acoustic seal around the perimeter of the door. These improvements may be sufficient in many situations. If you need more comprehensive solution, do not hesitate to contact me. I am planning to write an article in this blog about ways to soundproof a door, but definitely, a cheap method, as described in another article, does not work.

References​

[1] Master Handbook of Acoustics, Everest and Pohlmann, Sixth Edition, McGraw Hill 2015; p. 328

[2] Masonite interior doors

[3] Masonite exterior doors

[4] Overly Acoustical Doors

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About the Author Ivan Koval

The author is the publisher of the Soundproofing.Expert website. He is a soundproofing and building acoustics consultant working in Toronto and GTA, Ontario, Canada. Telephone (416) 471-2130

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