Description
Why Mass Loaded Vinyl Seams Have to Be Sealed
Mass loaded vinyl stops sound by putting mass in the way. That only works if the barrier is continuous. Sound is air pressure, and air finds any opening: a gap between two sheets behaves like a hole in a wall, and a wall with a hole in it is only as good as the hole. An MLV install that underperforms almost always comes down to unsealed joints, not the material.
Mass loaded vinyl tape closes those joints. Lay the sheets tight, overlap or butt the edges, and tape the full length of the seam so the barrier reads as one sheet.
- Tape these: vertical seams that do not land on a stud, every horizontal seam, overlaps, and any cut you made too short.
- Skip these: vertical seams where both sheets butt together on a stud and are screwed or stapled through. The framing already closes that joint.
- Also use it on: seams between sheets of acoustic underlayment, and the joints in outdoor fence barrier panels.
What MLV Seam Tape Is
Not every tape sticks to MLV. Vinyl is a low-energy surface, and a rubber adhesive or a general-purpose duct tape will lift off it within weeks. This is a foil-backed tape with an aggressive acrylic adhesive, the same class of tape HVAC installers use to seam duct work, and it bonds to the vinyl on contact and keeps its grip.
- Extreme high-tack acrylic adhesive. Instant, durable bond to mass loaded vinyl and to most clean, dry surfaces.
- Aluminum foil backing. Resists UV, moisture, mold and mildew, so the seal holds outdoors and in damp spaces.
- All-weather. Performs from 40°F to 200°F, which covers a hot attic, a garage in winter and a fence line in full sun.
- UL 723 classified for surface burning characteristics. See the complete marking on the product.
- Low VOC content. Can contribute toward the low-emitting materials credit (EQ credit 4.1) under LEED.
- Roll size: 1.89″ wide by 150′ (50 yards) long.
How to Apply It
- Clean and dry. Wipe dust off the vinyl along the seam. The adhesive is aggressive, but it cannot bond to a dusty surface.
- Center the tape on the joint so roughly an inch lands on each sheet, and run it the full length of the seam in one pass where you can.
- Press it down hard. Acrylic adhesive is pressure-sensitive. Rub the whole length with a seam roller or the heel of your hand. That pressure is what sets the bond.
- Overlap the ends of the tape by a couple of inches when one run ends and the next starts.
- Above 40°F. On a cold day, let the material warm before taping or the adhesive will not wet out.
One roll covers 150 linear feet of seam. A single room done in 4′ wide sheets usually has well under 100′ of seams, so one roll does most rooms and two cover a large one. For a fence run, count the vertical joints between panels times the panel height.
Frequently Asked Questions
- Do I have to tape every seam?
- Every seam that is not closed by the framing, yes. Vertical seams that butt together on a stud and are fastened through are already closed. Everything else, tape it. A single open joint is where the sound gets through.
- Will regular duct tape work?
- Not for long. Cloth duct tape uses a rubber adhesive that does not hold on vinyl and lets go in a few weeks, usually inside a finished wall where you cannot fix it. This tape uses an acrylic adhesive made to bond to low-energy surfaces like MLV.
- Can I use it outdoors on a fence barrier?
- Yes. The foil backing resists UV and moisture, and the adhesive is rated from 40°F to 200°F. Use it to close the vertical joints between Fence Blokker panels.
- Does it work on acoustic underlayment?
- Yes. Tape the seams between sheets of underlayment the same way, so the layer is continuous under the floor.
- How many rolls do I need?
- Add up the length of every seam you will tape and divide by 150 feet. Most single rooms need one roll. A whole-house or fence project needs more, so measure first.
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