Does moisture barrier padding work?

A waterproof carpet padding that eliminates worries about spills and pet accidents on my carpet?

I’ll take it.

Or is it too good to be true?

That’s not a simple question to answer, but the purpose of this article. I’ll cover what moisture barrier padding is, does it do what it claims, and more importantly, should you buy it.

What is moisture barrier or waterproof padding?

Let’s start with the basics:

Moisture barrier padding is floor padding that has a layer that prevents liquids (spills, urine, etc) from passing from the floor to the floorboards, and it also prevents vapor from coming up from the base floor (concrete, etc) through the carpet.

The hope of this type of padding is to make moisture less of a headache. Your dog’s pee can be removed by simply blotting it up… you don’t have to worry about ripping up the carpet to clean the subfloor (padding or plywood) to get rid of the smell. OR you don’t have to worry about basement moisture seeping through your floor.

Does it work?

It definitely is waterproof. A salesman can hold up the pad, dump a cup of water on it, and show you how the water sits on top of the pad.

The problem is this doesn’t always solve your problem, and it sometimes makes your flooring problems worse.

That’s what we’ll cover below:
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Why a small crack in a waterproof pad is a big problem

Some people buy moisture barrier padding and are disappointed because it actually made their moisture problem worse.

Picture this:

Your dog pees on the floor. It seeps through the carpet and hits the padding. The moisture barrier holds the urine on top of the padding, except there is a crack in the moisture barrier where urine seeps through.

Now, the liquid is trapped under the padding because the barrier doesn’t allow it to evaporate back up. Pooled water in a dark space is a great habitat for mold growth. Not good.

Okay, so you make sure your moisture barrier doesn’t have any cracks in it. It may not be so easy…

Good installation is critical

“Cracks” in moisture barrier can happen in a few ways:

Sometimes the edge where the wall and the padding meet has a gap, sometimes the moisture barrier is installed with staples (this makes little cuts in the barrier), and sometimes it’s not sealed with the proper tape.

Long story short: correct installation of moisture barrier requires an installer that knows what they’re doing, and I’ve heard many stories where people had waterproof carpet pad installed by someone who clearly didn’t know what they were doing.

So how do you find a carpet installer that knows what they’re doing? I have a page on finding the best independent carpet installers in your area. You can also find pre-qualified installers using our contractor referral service, that does some of the homework for you. Click here to get estimates from 3-4 local carpet installers.

I don’t recommend moisture barrier padding for basement moisture in most cases

You might find a retailer who sells you moisture barrier padding to fix your basement moisture problem. But when you really think about it, moisture barrier padding doesn’t make sense in a basement. Basement moisture comes through the ground, and it’s going to whether or not you have a barrier in place.

In fact, the moisture barrier could make things worse, much worse. The barrier will do its job to repel the moisture, but now the moisture is trapped between the concrete floor and the pad. The stale water acts like a petri dish for mold.

Now, there are exceptions to this. If you have a mild moisture problem, sometimes putting a vapor barrier under your floor can prevent it from warping. So I’m not completely against preventing vapors from seeping up.

However, I still go back to the fact that if you have a vapor/moisture problem, it’s not worth the risk of installing flooring in that room. At least, don’t install flooring that can be damaged by the moisture.

I like moisture barrier for pet accidents

Animal urine is one of the most common moisture problems facing homeowners, and it’s also one that moisture barrier padding can make much less problematic. Typically, urine absorbs through padding and into the floorboard. Eliminating the bacteria and odor from urine that’s penetrated the padding requires pulling up the carpet and pad—not a cheap fix.

This is where moisture barrier padding comes in. If it’s installed correctly, the urine will pool on top of the padding, instead of penetrating it. Then, the fluid can be sucked up without seeping into the floorboard. Keep in mind, if you don’t get all of the urine up, it will be sitting on top of the padding and underneath your carpet, which can lead to a pool of bacteria.

It’s worth investing in professional (see above) help to make sure as much of the urine as possible is removed.

What about newer, breathable moisture barrier pads?

What if you could have carpet padding that acted as a barrier to spills and urine from soaking into the floor below, but was “breathable” in the direction of the subfloor to the carpet? Theoretically, this would eliminate all of the problems of moisture barrier padding (trapping moisture between the subfloor and padding) and would still have the benefit of stopping urine and spills from absorbing through the padding.

Today, this padding is available, or at least it claims to be. I haven’t heard feedback from enough people using it to see the results, but I do like the idea of this type of pad.

That said, I don’t think it changes what I’d use the pad for. I’d still consider moisture barrier for pet problems and spills, but I’d avoid it for basement moisture.

Captain’s tips on what you should do now:

Moisture barrier padding is one of those newer inventions that comes with a lot of marketing hype. Even though it can be a good choice for some, you now know that a waterproof carpet pad isn’t always waterproof.

I don’t think it gets the thumbs down for everyone (looking at you pet owners), but you have to make sure that you have a knowledgeable installer. Also, make sure you’re not in the camp of people where it will make the problem worse.

Here’s what I recommend you do next:

  1. A good carpet installer can make or break a waterproof carpet pad. Clicking here to get estimates from pre-qualified installers in your area from Home Advisor.
  2. Check out our carpet padding page to get an unbiased look at all of your padding options.
  3. If you plan on buying carpet, check out our unbiased carpet buying guide if you haven’t already.

Still have questions on moisture barrier padding? Let me know in the comments below.

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Ivan Garcia
2 months ago

Hello Carpet Captain. Excellent insight. Thank you for your posts.
We’re about to purchase carpet for our basement. We are getting it installed right on the concrete. I was just wondering if you’d be able to send me some reputable carpet underpads that are breathable to prevent mold/mildew/musty smell. We do not have a history with flooding or excess moisture in the basement. I am leaning towards the healthier choices 7/16 memory foam, which claims it is breathable. Just wondering if you are aware of any others. Thank you!

Rick McClellan
9 months ago

I have a second floor home built in 1970’s. Installed new carpet in 2017 with Scotchguard moisture barrier padding. Now after 4 years it this pad has trapped moisture between pad and subfloor causing subfloor to buckle in some areas. Now I probable will have to remove carpet, pad and some subfloor too correct. Anyone else have this problem?

Deborah A Hock
8 months ago
Reply to  Rick McClellan

I had a professional carpet cleaner flood my home, entirely by ‘clwan ng’ 2 rooms.
Had to throw a ay carpets, padding furniture. Subfloor buckling, but t I’ve been trying to dry it out.
I can’t afford a whole new floor(no insurance)

Nancy Spanier
11 months ago

Hi I have a first floor condo on the bay front. The building is stick built on pilings. There is a low air space from the ground to my floor. Ever since they sprayed insulation on the underside of the building I’ve had a musty odor. Will replacing the carpeting with a moisture proof padding be beneficial?

1 year ago

This is an excellent article and, unfortunately, I found it AFTER installing pet stain resistant carpeting along with the SpillSafe, moisture barrier pad. It has all been very horrifying. The carpet cleaning instructions are all based upon seeing the animal pee so that one can quickly blot up the puddle. The reality is that no self-respecting pet will do this in front of their owner. Instead, they do it late at night and you will not see it the next morning because the stain resistant carpet hides stains VERY well. With my older carpet, I could use a UV flashlight and animal stains (urine, vomit)… Read more »

Becky Townzen
1 year ago

I have tore the carpet out ,pet urine and moisture built up over time carpet wouldn’t dry. Padding looks ,spill proof padding. Could i put new carpet over existing pad ? Or do I have to replace all of it ?