Green Glue FAQ
Everything customers ask us about constrained layer damping — how Green Glue works, how much to use, and where it belongs in a wall, ceiling, or floor.
1 What is Green Glue and how does it work?
Sound travels as a wave through the air — an airborne vibration. The waves hit a wall or ceiling and that energy becomes structure-borne. Unless the wall or ceiling material is damped, the vibration travels through the building framing and exits somewhere else as sound again.
2 How does constrained layer damping work?
In a constrained layer damping system (CLD), a damping material is sandwiched between two other, usually stiff, materials — for example Green Glue between two layers of drywall. Damping occurs when the viscoelastic centre of the sandwich is sheared.
When the assembly bends, shear forces pull and stretch the damping layer. Under those conditions the polymer converts mechanical energy into a tiny amount of heat. The vibration energy is not isolated — it is dissipated and gone.
3 How is Green Glue applied?
Green Glue comes in 29 oz. tubes and is applied with any quart-size caulk gun. It is fast and easy to apply, and no special skills are required — random squiggles across the back of the second layer, then screw the layer up while the compound is still wet.
4 Can I use Green Glue with only one layer of drywall?
No. Green Glue has to be a constrained layer, meaning it is sandwiched between two rigid, dense layers of building material. There is no limit to how many drywall/Green Glue layers you can use, and performance improves as the number of layers goes up. For floors you can use any common materials — cement board, OSB, plywood.
5 Do I use nails or screws with Green Glue?
Screws, in accordance with local building codes. Screws help compress the Green Glue layer into a thin film.
6 Should I use conventional adhesive along with Green Glue?
No. Rigid, low-damping materials alongside Green Glue between the layers work against the damping mechanism.
7 How thick is the Green Glue layer?
About 0.5 mm once the layers are screwed together.
8 Can Green Glue be used in floors?
Absolutely. In floors Green Glue yields a double benefit — it helps with both impact (footstep) noise and airborne sound, and is very effective at both. It may be used between layers of subfloor, between subfloor and tile backer board, and between thinset mortar and the surfaces below.
9 Can I treat just the ceiling, or should all surfaces be dealt with?
The most logical path for the sound is the direct path — through the floor/ceiling into the room above. But sound also travels through walls and floors as mechanical vibration, then re-radiates upstairs. Sound taking those indirect routes is called flanking noise.
An aquarium is the usual analogy: a hole in any one of the five sides spills water no matter how tight the other four are. For best results, treat all of the surfaces of the room, and pay attention to doors and ductwork as well.
10 Can Green Glue make a high performance wall without decoupling?
Yes, without a doubt. Green Glue has performance advantages in many applications relative to some decoupling schemes.
11 Can Green Glue be used in conjunction with decoupling techniques?
Yes, and better performance can be had. For walls the preferred decoupling methods, best first, are double studs, staggered studs, modern sound isolation clips, then resilient channel. Where low-frequency isolation matters, resilient channel is not recommended.
12 Will Green Glue perform even better between drywall and soundboard?
No. Soundboard is far lighter than drywall and is not preferable in any wall or ceiling assembly.
13 Is Green Glue toxic?
No. Green Glue is water based, non-toxic, non-carcinogenic, and very low in VOC (under 5 grams per litre, compliant in all 50 states). As with any product, read the safety data sheet and use normal precautions. It has a mild latex odour that dissipates completely.
14 Is Green Glue a fire hazard?
No. Green Glue has been fire tested and can be used in fire-rated walls without affecting the rating of the assembly.
15 How much Green Glue do I need?
The recommended application is 2 tubes per 4' x 8' sheet of drywall. Three tubes per sheet improves performance slightly if budget allows. A case covers about 192 square feet at 2 tubes per sheet, or 128 square feet at 3. Do not exceed 3 tubes per sheet — performance declines above that rate.
16 How can I reduce the cost of a Green Glue room?
Green Glue performs at only a slightly lower level at 1.5 or even 1 tube per sheet instead of the recommended 2 — roughly 70% of the raw damping performance is retained at 1 tube per sheet. Spreading a smaller amount over more surface area usually beats treating one wall perfectly.
Ready to buy? Green Glue for walls and Green Glue for ceilings show the compound, sealant, and tools we stock, or look up any term in the acoustic glossary.