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  • Henry Ashburn

Don't let leaks ruin your sound isolation!

By: Henry Ashburn, MCH Senior Acoustical Consultant

Does your project include doors to noise sensitive spaces?

It is important that care is taken to ensure those door systems perform as intended.


Regardless of whether you have a laboratory-rated STC door assembly, or simply a gasketed door panel made from a kit of parts, proper adjustment of the door and associated gasketing is a crucial step towards maximizing sound isolation potential between adjacent spaces. It ensures that the gaps between the door panel and the door frame and threshold are sealed airtight to prevent leaks, resulting in unwanted sound transmission.  This post serves as a quick summary of installation and/or adjustment tips for doors and door gasketing where sound isolation is important.


Some common problems that affect door gasketing include:

  • Unnecessary gaps in the gasketing, such as at corners or for hardware

  • Auto-door bottoms with improperly set plungers

  • Doors that are not aligned or correctly hung

  • Fixed gaskets that are not the appropriate dimensions


After installation of the door per the manufacturer's instructions, you can use two simple methods to check the existing quality of the gasketing seal.

  • First, a "light test".  Turn off the lights in one room and keep them on in the other.  Look for any light coming through the door edges when the door is latched closed.  A flashlight might also be helpful for this test.

  • Second, a "credit card test".  Try to slide a credit card, business card, or similarly thin object between the gasket and the door panel. If you can easily insert the card, it means that the gasketing is not tight enough. The card should be tough to insert and tough to slide back/forth when a proper seal has been formed.

Examples of poorly adjusted and/or failing gaskets

"Credit card test" on door bottom

Fixed gaskets can make it difficult to achieve a good seal without adjusting the door itself, which is why we often recommend adjustable gaskets for the ability to fine-tune the seal according to the door conditions.


Even better than a door panel with adjustable gaskets is a laboratory rated STC door assembly that is fully factory assembled, hung, and shipped as a complete unit.  This process prevents common installation errors in the field and reduces the number of trades required to install the door.  While these door assemblies may still require adjustment after installation, many of the common installation pitfalls can be largely avoided by selecting manufacturers that offer this type of product.


To illustrate the importance of a thorough inspection of the gasketing, the chart from Cyril Harris, below, shows how much sound transmission can occur through different sized openings. An opening as small as 0.001% of total panel area can reduce sound isolation by up to 10 STC points, so it is important to ensure that your door gasketing well-adjusted and evaluated prior to any field tests, or prior or building occupancy. 



Remember - carefully follow the manufacturer's installation guidelines and inspect your door systems a few times a year to ensure your building is achieving the sound isolation that building users deserve!


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