Soundproofing french doors tends to be a little more complicated than soundproofing a single door. But it can be done–at least to a certain extent. Here are 6 ideas you can use to quiet things down. (I consider all french doors to be double doors, so that is the type of unit I am referring to in this article.)
Interior French Door Soundproofing
1) Seal All Sound Leaks
Do you know that if total openings (gaps, cracks, no weatherstrip, etc.) in a wall equal 1%, they can allow up to 50% of external noise inside. So sealing them is a little more than a ‘make work’ project.
- Insulate the Frame. Most doors are installed with a gap (usually around 1/2″) between the jamb and wall framing to allow for settling and for making the unit square, level , and plumb during installation. That gap is uninsulated and hidden from view by the door casing. Remove the casing from one side, spray about 1″ low expansion foam against the backside of the remaining casing. After it cures, fill the rest of the gap with Roxul rockwool or fiberglass batt. (Do not pack it tightly.) Re-install the casing and use paintable caulking to seal casing to the wall and door jamb on both sides of the door.
- Weatherstrip the Frame. Attach self-adhesive Keliiyo Door Weather Stripping to the door stop on the sides and top of the frame. (This product is available in 4 colors so you should be able to get a close match to your door finish.) Make sure you wash the stop with 50/50 vinegar/water or rubbing alcohol to ensure good adhesion. (Note: Because I can be really anal, I would not butt join the corners or overlap them. I would cut them at 45 degrees to get a perfect seal. If you overlap them, you will have a narrowing 6″ long gap between the door slab and weatherstrip because of the extra thickness.)
- Fix the Center Gap. Most interior french doors use a ball catch to keep both doors closed. Or one door is equipped with flush bolts, and the operating door has a door handle to latch it closed. In either case, there could be a gap between the slabs. If you have a door stop that overlaps the gap (known as an astragal) apply weather strip to it. If not, you will have to install one. Get a piece of door stop that matches the slab, and install it on the non-operating (or rarely-operating) door in such a way that it overlaps the operating slab. Install weatherstrip that the operating door seals to, and paint or stain to match door finish. (Note: An 18 gauge brad nailer makes installing the stop much easier; otherwise you probably have to pre-drill for finishing nails or screws.)
- Install Door Sweep. Most interior doors have a bottom gap of up to 1 1/2″. Buy 2 Holikme Twin Door Sweep and install them on the bottoms of the door slabs. They come in many colors, are easy to install, work on virtually all surfaces, and can reduce noise levels by 3 -4 decibels. (Doesn’t sound like much but the decibel scale is logarithmic so a 3 decibel reduction cuts the noise by half.) If the Holikme is not sliding smoothly, take it off, spray the underside with dry silicone, let it dry, and re-install it. Will work great.
2) Lubricate the Squeaky Hinges
Squeaky hinges are usually not at the top of the noise annoyance list. But if you are going to soundproof your french door–do it all. Spray them with dry silicone lubricant. (Note: the propellant used in the spray is wet but dissipates, leaving dry silicone adhering to the hinge leaves and pin. In my experience this product does not stain anything.
If lubrication does not quiet them–or they start up again in days or weeks–take a look at your door hinges. If there are gaps where the 2 hinge leaves are held together by the pin, they are wearing down and probably binding. Specially with the crappy steel products we are importing. They need to be replaced. If at all possible, get ball bearing hinges. They will eliminate the wear. Change your hinges one at a time; saves having to hold a heavy door in place with one hand and foot, positioning the hinge leaf with another hand, grabing your drill with the third hand . . . You can see where this is going.
Note: Install at least one 3″ screw in each hinge that passes through the jamb and holds to the framing. These long screws hold the door up, keep the your hinges from tearing out of the jamb, and allow for easy adjustment.
3) Install Soundproof Curtains
Note: When ordering soundproof curtains for french doors, make sure you order them long enough to touch the floor. This eliminates any gaps your weather stripping did not seal.
- Nicetown Soundproof Curtains. Heavy curtains that will reduce and absorb sound. Available in many colors and sizes. Requires curtain rod that extends to the appropriate length and curtain holdbacks. Can be ordered as two-panel or one-panel. (Note: If you have one operating door, and limited space, the one-panel curtain can be opened over the non-operating door.)
- Residential Acoustics AcoustiTrac Curtain. Custom manufactured by Residential Acoustics. Lined with Mass Loaded Vinyl (MLV). Blocks 60% – 80% of outside noise. Magnetic strips on center overlapping panels make for a good seal, and magnetic or Velcro perimeter strips seal the edges to the wall. Includes hanging rod and curtain tie-backs. Installation instructions on website or YouTube. Available in many colors and made to your measurements. More expensive than the Nicetown products, but also more effective.
Note: Although the Nicetown Curtains work quite well, they are pleated. The pleats allow sound to travel up and over the curtain. They are more effective in combination with sealing all of the gaps in the doorway.
4) Install Soundproof Blankets
Generally, this is a temporary solution. Most french doors are a focal point of the house. Hanging a black blanket over it is not very appealing. But if you need something quick and have a moving blanket, you can hang it on removable hooks, or even tack it up with a few nails or screws (not particularly cute, but effective). They are a pain to tie back, or to fight your way through–so you might want to use them when the in-laws visit. For more detailed information on soundproof blankets please see our article Soundproof Blankets for Windows.
- US Cargo Control. Manufacture a heavy sound control blanket that measures 80″ wide x 96″ high which should be more than enough to cover the complete opening. It comes with grommets on one 80″ side making it easy easy to hang flat to the wall on removable hooks. You can also hang it from a curtain rod which enables you to move it out of the way. Another option is to cut it in half, sew the cut edges (because nobody needs cotton floating around the room), and use curtain holdbacks to allow easy movement through the door.
5) Install Sound Suppressing Glass
Most interior french doors are made with 1/8″ clear glass inserts–great for looking through, pathetic for noise reduction. If your kid is playing Boom Chuka music at 90 decibels in the next room, you are going to hear it, regardless of what kind of glass is in the door. (Note: My no-fail Boom Chuka solution involves a Louisville Slugger–for the speakers.)
A (Very) Little Bit on Glass STC Ratings
Sound Transmission Class (STC) is a measure of the amount of noise reduction expressed in decibels. It is a logarithmic scale meaning that an increased STC rating of 3 will cut the amount of noise in half.
- Single 1/8″ thick glass STC 27
- Dual 1/8″ glass-3/8″ air-1/8″ glass STC 31
- Laminated 1/4″ thick glass STC 33
The following table from Wikipedia – Sound Transmission Class gives you some idea of what that means in the real world.
Change the Glass
Replacing the glass is really not that difficult–specially with a glass suction cup. Measure the existing glass (generally 20″ x 64″ or 22″ x 64″), and order whatever new product you intend to install. Your new glass will likely be thicker so you will have to either cut down your existing stops or buy new ones. Remove the old glass leaving stop on one side, clean the stop with 50/50 vinegar/water or rubbing alcohol, apply double sided foam tape (to stop noise leaking around the glass get the 1/4″ wide product), and install stop on the other side. (Note: It is not necessary to caulk the glass to the stop if you use foam tape.)
Your new glass will likely be much heavier than the existing. Make sure you replace one screw in each hinge with a 3″ screw that penetrates the jamb and secures into the framing.
Note #1: You will probably have to remove both sets of stops, and cut them down, if you are installing a dual glazed unit.
Note #2: Laminated glass is also much safer. If it is broken, it will come apart in hundreds of small pieces like a windshield. Normal glass tends to break into large, jagged, and sharp pieces.
Note #3: If you buy a suction cup, keep it on the glass or in the case. I have had mine for years. They still work great. Although a few employees have been threatened with physical harm for not following that simple rule.
6) Install a New Soundproof Door System
Unless you are remodeling your house, replacing your french door just for soundproofing can be quite expensive. (Between $500.00 – $4000.00 plus labor.) And you still have all of that glass, and will need to use some of the ‘Gap Sealing’ suggestions above. Most interior french doors I have seen are made of either solid wood, or solid core, slabs. (Hollow core slabs do not stand up very well with the weight of glass in them.)
When ordering your new door system, make sure the slabs are at least 1 3/4″ thick solid core or solid wood for the mass. You will need door size (or preferably rough opening), wall thickness, swing, operating and/or non-operating sides. Installing double doors can be more annoying than hemorrhoids so make sure you have at least a working knowledge of construction before starting this project. There are plenty of YouTube videos online to give you an idea of what you are up against. (I would ignore the one telling you that it can be done in under 10 minutes.)
If level, plumb, and square sound like a foreign language to you, call a contractor. (I suggest a company that does ‘supply and install’ rather than you buy it, get it into the house, and have someone come to put it in.)
Exterior French Door Soundproofing
Exterior french doors (also know as garden doors or terrace doors) are easier to soundproof than interior french doors. They are usually sealed better and the glass is at least dual glazed–or should be. They can be either inswing or outswing. You can use any, or all, of the above suggestions with some of the following tweaks that might apply to your door.
- Weatherstrip. You can use the Keliiyo product after removing the existing weatherstrip. But if the door has a foam compression kerf-mounted weatherstrip, replace it with a comparable item. (Note: Kerf is just a fancy word for a groove in the door stop where the weatherstrip is inserted.) Insert the top piece, then cut the side pieces at 45 degrees to get a good seal.
- Center Gap. Should not exist. Door will come with a fixed mullion that accepts weatherstrip. Or an astragal attached to the non-operating door that accepts weatherstrip. (Note: Astragal is another fancy name for a door stop. Check out Wikipedia for more information.)
- Door Sweep. The Holikme sweep will work well for an inswing door. But for an outswing you will need something like the KS Double Bubble Sweep.
- Curtains and Blankets. Before purchasing, and installing curtains or blankets on an inswing door, make sure you can get them out of the way by mounting them on long curtain rods, or having plenty or room on the sides to use curtain tie backs. Otherwise, getting in and out could be a struggle. Using curtains or blankets on outswing doors is not near the issue even if they do not retract completely.
Another worthless cocktail party fact: If you combine all of the gaps and cracks in the exterior walls of an average North American house, the total is the equivalent of a 5″ x 5″ hole open to the outside. Just a tad cold and expensive when it gets to 30 below zero like it does where I live. And every gap and crack allows noise to enter the house.