Frequently Asked Questions
Typically, doors with higher STC ratings have increased cost, weight and lead time.
STC rated doors are generally supplied with a label that is either Mylar or metal, but the products are not listed like fire doors by agencies such as Underwriters Laboratories or Warnock Hersey. Labels are for manufacturer and rating identification purposes only.
STC ratings would be specific to each manufacturer and design, typical higher range ratings are between 50 and 55.
TC is a single number rating that indicates the sound transmission loss over a defined range of frequencies of a door assembly between adjacent closed rooms. Higher values equate to better sound reduction performance.
Decibels dB, are used to express the intensity of a sound wave. Examples of decibels levels are:
- 100-120 Deafening industrial machinery, jet engines
- 80-100 Very loud cocktail party, boom box
- 60-80 Quiet speech
- 20-40 Faint soft whisper, recording studio
- 0-20 Very faint acoustical laboratories, deep caves
Most manufacturers conduct acoustic tests with grout filled frames to optimize the lab performance. Acoustic performance will be reduced on frames over STC 40 when grout or sound retarding material is eliminated.
STC stands for "Sound Transmission Class", a measure of the extent to which sound is prevented from being transferred from one area to another. The higher the STC value, the less sound transferred from one area to another.
The STC scale is a logarithmic progression, meaning that a jump of 3 points in an STC rating equates to a doubling in a door's ability to prevent sound transmission. Acoustical doors are tested as an assembly comprised of the door, frame, hinges, and sound sealing system. See SDI 128 for more information.
The following chart illustrates the sound retardant performance associated with a range of STC values.
|50-60||Excellent||Loud sounds heard faintly or not at all|
|40-50||Very Good||Loud speech heard faintly, but not understood|
|35-40||Good||Loud speech heard but hardly intelligible|
|30-35||Fair||Loud speech understood fairly well|
|25-30||Poor||Normal speech understood easily and distinctly|
|20-25||Very Poor||Loud speech audible|
OITC stands for Outdoor-Indoor Transmission Class and is a measure of the ability of a building material or product’s ability to retard sound transmission. It is similar to STC, but it is not the same. As the name indicates, OITC is a measure of sound transmission from the external environment into the building envelope. Testing to establish an OITC value utilizes ASTM E-1332 Standard Classification for the Determination of Outdoor–Indoor Transmission Class. This standard uses a range of frequencies lower than the STC testing, to more closely replicate the sounds of rail and vehicular traffic.
No, we recommend that the door selection be made on the basis of the STC value that has been specified. Multiple door core types may be capable of achieving the specified value, and can be documented by Certificates available from the manufacturer.
There are many variables that would determine the proper STC value, including the physical proximity of the office building to the airport. To ensure that the specification is properly developed, an acoustic consultant should be engauged to determine the Outdoor / Indoor Transmission Class (OITC) values.
Openings, specifically hardware, have been tested to comply with FEMA 320 and 361 that have the bottom bolt engaging into the hardware rabbet of the frame. This eliminates the bottom rod engaging into the floor and can be single acting function that would comply with ADA requirements.
Yes, SDI members offer door assemblies certified to FEMA 361. These openings must be tested and installed as a system including the hinge, door, frame, anchors and latching hardware. The architect or specifier should investigate the doors available that would satisfy the requirements for those openings.
Some manufacturers have options for aesthetic finishes on these doors, but due to the severity of the testing requirements, almost all tornado shelter doors are very heavy-duty steel designs.
Hurricane resistance ratings are expressed in pounds-per-square-foot (PSF) values, and unlike fire ratings, there are no standard increments. In addition to the PSF values, they are either listed with or without “missile” impact ratings. In this instance, a missile refers to a 2 x 4 piece of lumber weighing 9 lbs. that is fired at the door at 35 miles-per-hour. A door assembly must withstand 3 impacts in order to have a missile impact listing. A typical door listing would be expressed as;
- Design Pressure Rating +75/-65 PSF
- Large Missile Impact - Yes
This listing indicates that the door assembly is rated for 75 PSF when loaded against the stops of the frame, and 65 PSF when loaded away from the stops of the frame
As a general rule, the closer a building is located to the coastline, the higher wind speeds it is expected to experience. The wind speed and debris impact zones for Florida are defined by a map that is found within the Florida Building Code.
Many SDI manufacturers have single swing doors that are 4’0” x 8'0", and pairs that are 8'0" x 8'0", listed with the Florida Building Commission. Special sizes are also permitted by the code to be analyzed by a Registered Design Professional if they fall outside of existing approvals.
No, they are not the same, but they are both related to the construction of tornado shelters. FEMA 361“Design and Construction Guidance for Community Safe Rooms” is a guidance document, but FEMA does not regulate building construction. ICC 500 “Standard for the Design and Construction of Storm Shelters” is written by the International Code Council® and is referenced in the International Building Code in all Editions since 2009.
The ability to fire rate STC and blast doors would be specific to each manufacture and it is recommended that you contact a quality manufacturer for their specific listing. Follow this link to a listing of SDI manufacturers to ensure you are supplied a top quality door.
To properly specify the desired blast resistance for a door assembly, the following information needs to be provided:
- Peak blast pressure — such as 5 psi.
- Either the blast duration (e.g., 60 milliseconds) or blast impulse (e.g., 150 psi-msec).
- Direction of blast pressure loading (i.e., either seated or unseated).
- Acceptable level of post blast event damage: typically limited to Response Categories I, II or III. In general terms, these ratings correspond to (I) no permanent damage, (II) permanent damage but the door remains operable, and (III) more severe damage with the door being inoperable after the blast.
There is nothing in the standards that prohibit veneers, but they would have to be documented within the manufacturer’s certification to ensure that they pose no hazard to the building’s occupants.
Yes, the primary focus of the Department of Defense’s Unified Facilities Criteria is to protect against injury from architectural glazing, so many SDI member companies have certifications for doors with glasslights.
The Department of Defense created the referenced document to provide a minimum level of protection from blast forces from acts of terrorism. The door assemblies offered by SDI members are specifically engineered and certified for these applications, with a wide variety of blast resistant capabilities. In order to supply the correct door assemblies, you will need to know the PSI/MSEC value (pounds per square inch / millisecond). This is a value that has been calculated by a blast consultant, and would be expressed as a numerical value, i.e. 50 PSI/MSEC. The higher the value the more blast force the opening is designed to withstand. Matching that value to a manufacturer’s certification will allow you to select the correct door, frame, glazing and hardware configuration.
Note: There are many other blast resistant specifications in addition to UFC 4-010-01. Please also keep in mind that the version of the specification is critical, particularly with the UFC 4-010-01 specification.
They are using the wrong terminology, which is not uncommon. While the most common standard for bullet resistance, UL 752 Standard for Bullet-Resisting Equipment, has multiple levels of resistance, none are considered "bullet-proof".
The table below lists the ratings for bullet resistance.
|Rating||Ammunition||Weight (Grains)||Min fps||Max fps||Number of shots|
|Level 1||9mm Full Copper Jacket with Lead Core||124||1175||1293||3|
|Level 2||.357 Magnum Jacketed Lead Soft Point<||158||1250||1375||3|
|Level 3||.44 Magnum Lead Semi-Wadcutter Gas Checked||240||1350||1485||3|
|Level 4||.30 Caliber Rifle Lead Core Soft Point (.30-06 Caliber)||180||2540||2794||1|
|Level 5||7.62mm Rifle Lead Core Full Metal Copper Jacket Military Ball (.308 Caliber)||150||2750||3025||1|
|Level 6||9mm Full Metal Copper Jacket with Lead Core||124||1400||1540||5|
|Level 7||5.56mm Rifle Full Metal Copper Jacket with Lead Core (.223 Caliber)||55||3080||3383||5|
|Level 8||7.62mm Rifle Lead Core Full Metal Copper Jacket Military Ball (.308 Caliber)||150||2750||3025||5|
|Level 9||.30-06 Caliber Rifle, Steel Core, Lead Point Filler, FMJ (APM2)||166||2715||2987||1|
|Level 10||.50 Caliber Rifle, Lead Core FMCJ Military Ball (M2)||709.5||2810||3091||1|
|Shotgun||12-Gauge Rifle Lead Slug||1.0oz||1585||1744||3|
|Shotgun||12-Gauge 00 Buckshot (12 pellets)||1.5oz||1200||1320||3|
There are not specific doors that are designed for psychiatric hospitals. Doors are built based on life safety, ADA and building code requirements.
However, specific hardware such as anti-ligature hardware, can be used for patient room doors to prevent tampering or use as an anchor point. The door hinges should be continuous or use sloped hospital tip hinges to prevent the patient from using the barrel as an anchor point. View panels in patient room doors that allow staff to check on a patient without entering the room should use laminated glazing.
Behavioral health facilities are subject to heavy use and possibly extensive abuse. Doors make up a significant percentage of the exposed wall surface in corridors and have a strong visual impact on these spaces. Painted steel doors are durable and can be easily touched up or refinished.
Guidance for design of steel stud walls for heavier doors can be obtained through members of the Steel Framing Industry Association or Steel Stud Manufacturers Association. Consider using additional jamb anchors to spread the load more evenly on the wall stud.
See our Forced Entry Resistant Doors and Frames page for information on specifying these products and a list of SDI Certified manufacturers.
Properly functioning steel doors around the perimeter of a school building are one of the least expensive solutions for guarding against unauthorized entry. Routine maintenance is recommended to verify the doors are self-closing, and latch every time they are closed. If the doors are in a state of disrepair that prevents them from properly closing and latching, they should be replaced.
These SDI member companies offer doors and frames with radiation shielding options. They are primarily used in medical facilities where the containment of radiation from X-Ray operations are a primary concern.