DIY Doors Soundproofing

Here is my DIY guide to show how I soundproofed my front and rear Latio doors using the construction-grade alumimium-foil backed bitumen and air-con insulation foam sheets.

Materials required: 1 roll (10m x 1m) of aluminum-backed bitumen sheets, 3 sheets of 1/4 inch thick insulation foam sheets (such as Superlon or Armaflex), gloves, measuring tape, pen-knife, scissors and a can of cleaning solvent (such as WD40).

Firstly, use your fingers to prise out the door handle covers and the windows switch panels partially and then force them out with a flat screw driver via the base of the panels. The wire connectors to the panels can then be unplugged :-

In the slot vacated by the windows switch panels, you should see black screws holding the door covers to the metal door frame. Removing these screws would allow the Latio door covers to be pulled off the holding clips around the edges using both hands.

The stripped door has an original translucent plastic sheet covering for waterproofing. You should strip off the translucent plastic sheet to replace with a layer of bitumen sheet later. Otherwise, the plastic sheet may end up as another source of rattling when you pump up your door speakers :-

Keep these plastic sheets around a while longer as they are still useful as templates to cut single big pieces of bitumen sheets and foam sheets to fit the shape of the door frame. There would be small pieces of styrofoam inside the front doors and it is up to you whether you want to tear them out or leave them there.

This is how one of the Latio rear doors looks with the plastic sheets taken off. If the inner panels are dusty or greasy, they should be cleaned first before applying the bitumen. I did not do this for my Latio as it is just slightly over two months old and the doors are relatively dust-free :-

Below are my aluminum-backed bitumen sheets which comes in rolls of 10m x 1m x 1.5mm. These sheets are rather easy to cut with a pen-knife as the aluminum foil can be punctured easily. You should have a can of WD40 and paper towels nearby as occasionally you would need to use WD40 to soften and wipe off the soft tar that sticks to your pen-knife or scissors in order to maintain their sharpness :-

Use a measuring tape to measure the inner door length in order to cut out appropriately-sized pieces from the bitumen sheets. Most of my cut pieces are in long rectangle shaped tiles.

To obtain double-layer thickness fast and save time, use the first cut piece as a shape template to cut out the second piece. Tear off the backing paper of one piece and paste it exactly over the other piece and voila, double-thickness (3mm) bitumen sheets created in double-quick time. If the pieces are too long or big and are thus difficult to slot them into the holes of the doors, you should cut them into half before pasting them in side by side. Once pasted inside, pound or press them down firmly with your hands to remove air gaps and make them stick well.

Just a reminder: There should be one or two holes at the base of the door to allow the drainage of rain water and it may not be necessary to stick the bitumen sheets there. If you choose to stick them there, please make sure that the two holes (or at least one hole) is not blocked or else rain water may pool up inside the doors and you may hear water swooshing around as you drive.

Always remember to wear gloves before inserting your hands into the inner parts of the doors as the edges can be rather sharp. During one of my front doors' soundproofing, I forgot to bring my gloves and at the end of that session, I counted ten bloody cuts and nicks on both hands.
Here are pictures of the double-thickness heat-deflective aluminum-backed bitumen pasted inside my doors, covering almost every reachable metal panel including the side-impact beams and door struts :-

When the insides are nicely pasted up, I would then cover up the door frame with a large piece of aluminum-backed bitumen sheet. This is where the original plastic sheets torn off earlier comes into good use as a door shape template :-

I pasted the large piece of bitumen sheet on the doors and trimmed them a little to allow the door clips, wires and other obstacles to go through the sheet without blocking.

Warning: In some car doors like in the Lancer and the Sunny, there are 2 exposed metal rods actuating the lock and handle of the door. For my previous Lancers, I always trimmed the bitumen and left part of the brown backing paper next to the exposed rods to prevent them from getting stuck by the sticky bitumen.

However, my Latio lock mechanisms are different as it uses wire cables protected by rubber tubings to actuate the door locks. It was okay for me to paste the bitumen over the cables since they were already insulated with a rubber tubing and the wire cables can move safely within the rubber tubes.

Even though my stock Latio door covers already have about 1/2 inch thick fibrous insulation material, I wanted to add an additional 1/4 inch layer of foam sheets (Superlon) to increase the thickness of this noise barrier. Once again, use the original plastic sheet as a shape template to cut the foam sheets and cut holes for the screws, wires, connectors and door handle. This picture showed the foam sheet planted on the door.

In reality, I had trouble closing back the door covers as the foam sheets were too thick in certain places and I had to take them out to trim them a bit with my scissors. I trimmed them several times until the door covers closed back nicely with click sounds from the plastic door clips without them popping out again :-

Below is a picture of the door cover put back successfully. I then plug back the wire connectors to the windows switch panels and push them and the silvery door handle cover pieces back into their slots until they are clicked shut tightly:-

My doors now feel more 'continental' when closing, slightly heavier and much less tin-can sounding when I do a finger-knock test. Best of all, this door SP complements my floorpan and boot soundproofing very well by cutting off even more road and wind noise.

The roll of aluminum-backed bitumen (10sqm) when used in double-thickness double-layered for 4 doors like what I did would yield a bit extra remainders which I can later use to dampen my boot lid, bonet lid (may be possible as it is heat-deflecting) or for my roof insulation.

I hope this little guide is a useful start for you to DIY soundproof your own ride.

Latio Floorpan and Boot Soundproofing

After doing back-breaking DIY soundproofing of the floorpan on my 2 previous cars, I decided to engage experts from the car audio industry to do it for my latest ride this time.

I completed my Latio floorpan (labour $160) and boot (labour $40) soundproofing at Sin Kit Audiophile (Toa Payoh Industrial Estate) in June 2005 using my own supplied materials such as the 20m x 1m roll of vinyl-backed bitumen sheets and closed-cell insulation foam sheets (such as Armaflex, Aeroflex, Insuflex, Superlon etc.).

The road noise from the Aspec DB tyres at highway speed is now much more muffled and the ride is more refined. At lower speeds, running over humps and rough roads almost produced no noise in the cabin other than feelable bumps from the suspensions. I would say there is a reduction in road noise of at least 50%, not bad from a car already designed to be quiet from ground up.

Here is a picture of my floorpan before the soundproofing. As you can see, there are already small patches of factory-installed bitumen sheets sprayed painted to my vehicle colour on the floor board:-

My floorpan with 4 layers of 1.5mm bitumen sheets pasted on to dampen vibrations and lower the road noise resonance frequency:-

The stock Latio soundproofing comes with these 5cm thick styrofoam plates. It was quite a suprise to see these styrofoam but we decided to put them back after pasting the bitumen layers on the bare metal below:-

More pics of the 4-layers bitumen sheets applied on bare metal on the floorpan and under the rear bench:-

The workers next laid 1/4 inch thick Armaflex insulation foam sheets on the styrofoam and bitumen sheets. The Armaflex sheets serves as an additional sound absorbing layer:-

The insulation foam sheets laid on top of the bitumen :

Next: The boot soundproofing. The sidewall carpets, boot floor cover and spare tyre taken out to reveal naked panels with small patches of factory-installed bitumen pieces:-

The spare tyre well, boot sidewalls and rear wheel arches were generously pasted with an estimated 3 to 4 layers of 1.5mm bitumen dampening sheets. That used up my entire roll of 20 sqm bitumen sheets:-

A layer of insulation foam sheet is then overlaid on the bitumen to act as a noise absorber:-

Overall, I would say the skills level of Darren's workers is good and they are meticulous. It was certainly very hard work as it took 2 to 3 workers almost 7 hours to complete all these.

As with any soundproofing project at ICE shops, before you start, make sure you come to an agreement with the boss on the numbers of layers you expect to have applied and then hang around to ensure it is done as agreed. I have forummers who told me they were cheated on the work done (not at Sin Kit) previously as they "trusted" the boss. They had only one thin layer of bitumen pasted when they finished, with the remaining bitumen thrown or returned back.

Next project: DIY door and roof soundproofing using a new type of aluminium-foil backed bitumen sheets (called Solar Shield, very similar to Accumat Hyperflex but many times cheaper) and Armaflex or Superlon insulation foam.