STC Ratings for Doors: All To Know

You may not be familiar with STC ratings. They are used to provide information on how soundproof a product is.

STC ratings are often used for acoustic products and the rating can come in handy when a consumer or professional is shopping for doors.

When it comes to doors, the STC rating can be used to determine which door will provide the best soundproofing for a room or building.

This can be very helpful in many situations. But understanding and comparing STC ratings isn’t as straightforward as you might think.

When using an STC rating to choose a door, there are many things to consider. Learn everything about STC ratings to better understand their value when choosing doors for your home or business setting.

STC Ratings – The Basics

STC stands for “sound transmission class.” Products that are designed with acoustics in mind usually have two different STC ratings.

The following information can help you understand the difference between the two ratings and the importance of considering both when choosing a door for acoustic purposes.

To determine these ratings, tests are performed using acoustic putty. Doors may be tested in a lab but they are also often tested in real-world settings to see how well they live up to their ratings.

STC ratings should not be confused with NRC ratings.

The NRC rating tells how much sound is absorbed while the STC rating tells how much sound passes through the material.

Both can be valuable and useful, but they are not interchangeable ratings.

  • Sealed in place rating – When testing for the “sealed in place” rating, acoustic putty will be applied around the door to seal the door and remove cracks or openings around the door’s edge. It’s meant to test the door’s soundproofing in a way that would mimic a door that was completely sealed off in an emergency or other situation.
  • Operable rating – The operable rating test is performed without acoustic putty. It determines the soundproofing ability of the door as if it were in operable condition as it would be used in most situations.

The testing performed in this manner is designed to provide an STC rating that indicates how many decibels of sound a door can reduce when operable or when sealed.

While the sealed situation is uncommon, the rating can be helpful when one is comparing different doors based on soundproofing abilities.

A higher STC rating indicates a higher ability to reduce sound inside a structure.

The Importance of Understanding the STC Rating

Soundproofing is important for many reasons in residential and commercial settings.

Anyone who has lived in an apartment or other multi-unit housing situation can likely understand the need for a door that keeps outside sounds from permeating the inside of the dwelling.

Also consider hotels, many of which use thick doors designed not only to keep guests safe but also to prevent sounds from entering the rooms when others are moving about in the hallways.

Many professionals consider the STC rating when choosing doors for their properties.

The rating reveals the functionality of the door when it comes to keeping a peaceful environment inside the building.

This may be useful in many settings where loud sounds are frequent. Schools, mixed-use buildings, offices, and other facilities can benefit from using doors that block sound.

By understanding how the rating works, those in charge of choosing the right door can find the best option based on the specific conditions inside and outside of the property.

STC ratings can also be used for other building materials like drywall, windows, and flooring materials.

Benefits of Soundproofing and Uses for Doors with High STC Ratings

Soundproofing is not a new concept but the technology used for soundproofing, especially when it comes to doors, has come a long way.

A soundproof facility can protect those within from loud noises and disturbances.

Plus, soundproof doors tend to be thicker and able to hold up longer to any type of physical interference on the other side. This can make a higher-STC door safer.

Soundproofing can be important in many industries and in residential settings where there is a lot of noise like in cities and highly populated areas.

Hospitals, schools, government offices, and other commercial buildings can take advantage of soundproofing to keep the inside of the facility safe from disruptions.

This can help the people inside concentrate and can also go a long way in providing privacy, which is essential in settings that deal with sensitive information.

The STC rating is a good indicator of how much sound will be heard through a door when applied to everyday sounds like speech and common household noises.

The rating is not as reliable when it comes to louder sounds from machinery and heavy-duty equipment simply because the frequency can vary so much.

It’s important to note that frequency is also an important consideration when you’re trying to reduce sounds.

More on Sound Transfer

Understanding how sound transfers can be helpful in understanding how important soundproof doors can be. Sound is measured in decibels which shows how loud a sound is when compared to complete silence.

When sounds transfer, they are lessened as they move from one location to another.

This is called transmission loss and it increases when sounds pass through things like doors and walls. The transmission loss varies depending on the material the sound is passing through.

A door with a high STC rating should cause high transmission loss, which makes the sound quieter to those on the other side of the door. Some materials absorb sounds, also making them quieter.

Sound moves differently through different materials which is why it’s important to choose a door made of the right materials for a particular situation.

Transmission loss relates to the decrease or blocking of sound movement. It’s measured in numbers between 0 and 1.

A transmission loss of 1, which equates to 100%, means that all of the sounds are blocked or absorbed by the material, which in this case would be a door. A transmission loss of 0 means that no sound is blocked.

Types of Doors and Their STC Ratings

When comparing doors with different STC ratings, you may feel overwhelmed with the various options.

Doors come in many styles and are made with varying features and from many different materials. The STC rating may be the leading factor that helps you decide which door to choose.

While aesthetics can be important, when you’re looking for functionality, soundproofing capabilities can be the most important quality.

Consider the following information when choosing a door based on the STC rating.

Understand the fact that an STC rating of 25 would allow loud speech to be heard clearly through the door, whereas an STC rating of 60+ would prevent most common residential and commercial sounds from being heard inside.

STC ratings between 25 and 60+ will act accordingly based on where they are in that range.

Interior/hollow doors – These doors are designed to be used inside a home or office. They offer little to no soundproofing and are usually made of lightweight materials. These will generally have an STC rating of 25 or less.

Solid wood/solid core doors

They are made from thicker and denser materials which allows them to offer better soundproofing than the previous option. Most solid wood doors have an STC rating of anywhere from 30 to 45, depending on the exact construction of the door.

Hollow metal doors

These doors are common in industrial settings and are usually made of galvanized steel. The thickness of the steel will determine the STC rating, but they generally offer a rating from 20 to 35.

MDF doors Constructed with recycled wood

MDF doors can range from 30 to 50 in STC rating. This is due to the fact that they are constructed in many different ways and the manufacturing of the door can increase or decrease the STC rating based on thickness and specific materials used.

Glass doors

A glass door may be constructed with other materials, which can vary the STC rating.

glass door

The thickness of the glass also determines the rating. Glass doors can range from 28 to 60+ in the STC rating range, which makes them versatile and great for many uses.

Steel doors

steel door

Steel doors are used commonly as exterior doors, they are usually made of higher-grade galvanized steel and can have an STC rating from 40 to 50.

Fiberglass doors

Another common material used for exterior doors, fiberglass doors can be lightweight which lends to their lower STC rating of between 20 and 30.

Some fiberglass doors are specifically constructed to offer better soundproofing which means they have a higher STC rating than standard fiberglass doors.

Acoustic doors

These are specifically designed for their soundproofing capabilities. Acoustic doors are made to block and/or absorb sounds.

They are constructed from a variety of materials and they can offer an STC rating of 70 or better which makes them ideal for situations where maximum sound reduction is essential.

Choosing the Best Door Based on STC Ratings

Now that you better understand how STC ratings work, you can use the information to choose the right door for your home or facility.

When choosing a door based on STC rating, you’ll want to look for one that is well-made and designed by a company that is known for quality products.

Read reviews from other consumers to know more about the manufacturer and their products.

High-quality doors with high STC ratings can be pricey and they are an important investment for many reasons. Because you may be spending a lot on your doors, don’t be afraid to ask questions.

Contact the company and let them know more about your situation.

Ask for recommendations based on your needs. A good company stands behind its products and the belief in the quality of its products can tell you a lot.

Also, be sure to inquire about warranties and how it would work if a door did not stand up to the manufacturer’s description.

It’s also helpful to understand that many doors with STC ratings may also have other beneficial features.

They may be fire-proof, resistant to blasts, bullet resistant, or may shield from harmful substances. These types of features are helpful in many situations.

A dual-purpose door that blocks sound and keeps those inside safe would be useful for buildings where security is important.

If these added features are important to you, be sure to ask the manufacturer if they offer dual-purpose doors that would meet your needs.

STC Door Installation

Even if you buy a high-quality door with a high STC rating, you still need to install it correctly. Door jambs, seals, and walls should be considered when you’re installing your door.

If those aren’t adequate or are compromised in some way, the door won’t be able to contain the sound to the level of its STC rating. Walls should be well insulated to help prevent sound transfer.

The door trim should also be properly insulated and installed correctly and securely.

Lastly, check the weather stripping to ensure it seals with the door, and be sure there are no gaps or cracks when the door is closed. For situations where soundproofing is of the utmost importance, it’s beneficial to have a professional install the door.

They can check all the variables to be sure you’re getting the most from your soundproof door. Over time, doors can move slightly, especially when installed in high-traffic areas. This is another situation where professional installation is helpful.

If you notice that your soundproof door is no longer performing as it was after the initial installation, it may simply be because the door has moved.

A professional can check the door and adjust it as needed so that it works properly again.

The STC rating is one of the many things to consider when buying a door. And in many situations, it may be the most important factor.

If you’re looking for a door to prevent sound transfer in a professional or residential setting, a higher STC rating is important.

Doors with high STC ratings work well in multi-unit living conditions, hotels, medical care facilities, schools, and locations where security is important.

Compare doors not only using the STC rating, but also the quality and construction.

Good doors should align with the manufacturer’s description. Understand the range of STC ratings so you’re able to choose a door that will prevent sound transfer.

By preventing unwanted sounds, you can maintain a sound level that is peaceful and functional for your needs.