How Do You Decouple Doors and Windows In A Double Wall System?

airgap double wall system drywall soundproof door soundproof window Apr 29, 2024

Many people have asked me how do you finish the gap between two doors or two windows in a double wall system without connecting the two walls. In this article I will explain how I finish the gap so to speak without physically connecting the two walls. 


1) A Quick Review of the Double Wall System

Many of you may be familiar with the hallmark soundproof wall system: two stud walls with a 1" air gap (30mm) with insulation in each wall and two layers of 5/8" drywall on the outside of each wall. This is the best wall system you can achieve short of two masonry walls with an 8" air gap between them. 



2) Communicating Doors 

With two soundproof doors you want each door frame to only connect to one wall. So, in our double wall system we would build one door and door frame for the outside wall and one for the inside wall. This leaves a gap between the two walls. So there inlies the problem, what do we do with the gap? 

First, before even building the frame I put 1/16" thick layer of rubber from the edge of one stud wall to the edge of the other stud wall. See the diagram below for a visual idea of this. 

You can buy the rubber on amazon or find a local retailer. Rubber is a natural sound barrier and does not conduct vibration easily. It has the added benefit of closing the air gap, which will stop odors that could develop in the wall from entering your studio. 

Once you have the rubber installed you can then build your door frames and hang your two doors with seals. Below is an image of the finished frames with the rubber gap visible. 

So now what do we do with the rubber since it doesn't look nice? Well, the next step is to fill the gap between the frames on all three sides with insulation and acoustic fabric. I recommend a mineral wool with 1.6-3 PCF density. This will function in two ways. First it will fill the gap and make it flush with the frame and the fabric will create a nice clean finished look. Second, it will help with isolation because the insulation will absorb the sound and dampen resonances in the door cavity. This works just like the insulation in our double wall system. 

Below is a diagram of the finished door frame with the insulation and fabric installed. To install the insulation you can simply cut it to size and stick it in the gap. Then use construction staples to attach the fabric to each door frame and cover the staples and fabric with a nice finishing piece of trim. Any way works so get creative with the build, but don't attach your two walls with wood. 


3) Soundproof Windows 

The plan with the windows is the same except instead of door frames and door leafs you are dealing with window frames and glass. 

First, add your rubber all the way around the window rough opening on all four sides. See the diagram below for details. 

Next, once you have the window frames in place you can add the insulation and acoustic fabric to fill the gap between the two window frames. Again, below is a diagram showing this in one of my clients plans. 



So as you can see, it's not really hard to ensure your windows and doors are decoupled, but it does take a precise system to do it. As long as you follow this method you will guarantee your windows and doors maintain their optimum isolation. 


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