Can I use carpet underlay as sound dampener in doors? How do I stick it on?

**nobb** · 10-21-2007, 03:48 PM

Hi.

My parents had a new house built and I found 2 rolls of carpet underlay (I think thats what its called...it looks like thick foam) in the basement. This stuff is quite thick and the first thing that came to mind was that I can use it as sound deadener. I flicked my finger at the material...and it seems to be pretty good at absorbing sound. Currently, my two rear doors have been deadened with an asphalt based material that was probably designed for roofs. My trunk and front doors are stock.

So I am thinking about using this carpet underlay material as sound deadener in my front doors and trunk. I was initially planning on buying some real deadener next summer to do my front doors...but I am thinking maybe this underlay stuff will suffice? What do you guys think? Will it work well? This stuff is thicker than sound deadener, but less dense..yet it appears that it would be good at absorbing high frequency sounds. I dont want to waste a weekend applying this stuff only to not notice any difference.

The only problem with this material is that it is not sticky. Is there some sort of permanent glue (that I can get at home depot) that you guys can recommend to bond the foam to my metal doors? I live in Canada where there are both hot (35C) and cold (-45C) climate extremes...so the glue would need to stand up to that.

Opinions welcome.

**stealinfool** · 10-21-2007, 04:22 PM

The main issue with that type of foam is that it is probably open celled, meaning it will absorb moisture. If you have this inside of your doors, which you should if you want to deaden sound properly, moisture from the outside will be soaked up in this foam and start to cause odors... not a good thing.

Using it in the trunk probably won't be an issue as it is enclosed. The floors could probably use some as well and you could use some 3M (or similar) spray adhesive to get the stuff to stick.

**Megalomaniac** · 10-21-2007, 09:01 PM

Originally Posted by stealinfool

The main issue with that type of foam is that it is probably open celled, meaning it will absorb moisture. If you have this inside of your doors, which you should if you want to deaden sound properly, moisture from the outside will be soaked up in this foam and start to cause odors... not a good thing.

Using it in the trunk probably won't be an issue as it is enclosed. The floors could probably use some as well and you could use some 3M (or similar) spray adhesive to get the stuff to stick.

i agree. but just a side note Second Skin Rattle pad is open celled, but its been treated with a chemical to avoid that

even though Overkill(closed cell) might be more suited for this application just thought id throw it out there that some companies will treat that.

**nobb** · 10-21-2007, 09:30 PM

I have thought about the moisture issue. However..in my doors, there is a plastic weatherproofing material which separates the metal door from the plastic interior door panel. In fact, the manufacturer even already has some pieces of foam in this area (I dont know what they are for). I was thinking about using proper sound deadening material to keep the metal door panels from vibrating...then using my carpet padding to block the higher frequencies by gluing them to the plastic door panel. I just need to know what to look for in a glue that will bond the underlay to my door panel.

**Megalomaniac** · 10-21-2007, 09:39 PM

Super 77 i should do the trick. make sure you wipe down panel with a degreecer though first so the glue sticks to panel and not grime and dirt

**nobb** · 10-21-2007, 10:07 PM

So with that glue...can I just spray it onto the pad and just press the pad against the surface I want it bonded to? Will I have to keep constant pressure on the area, or will it just stick like a piece of tape (keep in mind that this foam is fairly thick and resists bending more than a piece of tape).

**JKrepps** · 10-22-2007, 05:04 PM

Most of the spray adhesives will be fine. The ones I have used so far have different suggestions based on the goal (ie..permanent or temporary bonding), and will generally have you spray one (or both) sides to be bonded, allow them to sit for 1-5 minutes (for air/gas to escape), and then press them together (and yes, they hold right away, normally no need to apply constant pressure).

I did this with 2 second skin products (OverKill and OverKill pro) which were .125" and .375" thick respectively, so you should have no problem. All I did was lay the vapor barrier out on the uncut pads, cut the pad to fit, and trimmed all required holes for wiring to pass through. Worked well, though I would still be somewhat hesitant about using an open cell foam, but it will probably be fine of course (;

**greatwhite** · 10-22-2007, 06:28 PM

Personally, I wouldn't use carpet underlay in the doors. It will absorb water.
In the trunk would probably be ok though...............

**crez79** · 10-22-2007, 07:07 PM

I agree with JKrepps as far as application goes. I would think any where inside the car except the doors would be okay to put it. Many automakers use padding under the carpet and in the trunk, and I would think this would be like adding more. I am not sure how effective it would be, probably not as good as proper sound deadner, but it can't hurt.