Crawl space moisture and slab rubber carpet pad

[zakthor]

Sorry if I use the wrong terms here.

Spouse insists we need new carpet to replace the 35 year old stuff in a guest room.

We're going to put in a wool berber that's scratchy but a nice color and durable and cheap ($2/sq ft.)

Read up on carpet pads since all the stuff I've ever seen was disgusting. There's a carpet pad called 'slab rubber' that comes in 21lb. Supposed to be super durable, good for berber, insulates and is comfortable to walk on. Our discount shop never heard of it but I persisted and they found a product called "Aurora" that seems to fit the bill, sold by Leggett and Pratt:

https://lpflooringproducts.com/carpet-pad/plus-series/rubber-plus/aurora

Anyone have any experience with this sort of stuff. When I replace carpet the pad has always crumbled to dust but this stuff is supposed to last through multiple carpets.

Now, the moisture. Room is on the house's ground, has a wood/plywood floor with a 3' crawl space underneath. The crawl space has a thick vinyl tarp over it and a sump pump under that. The tarp isn't taped/sealed to the foundation or support posts, nor where it overlaps.

I've got a sensitive nose. I've never seen any wet in crawl space there but since the guest room smells wet to me I run a dehumidifier there year 'round. Generally it rains a ton here in the fall (like right now with flooding, etc) but the dehumidifier picks up the most water in the late spring. I can't explain why, maybe the trees do something then? In the spring it will pull a gallon/week, rest of the year its a gallon a month or less. Its run through a month of solid rain and not received a gallon.

I've checked crawl space about once a year for past 20 years and it always looks like it was just built, no mold or rot or anything, it all looks like new. Under the tarp is gravel, not concrete or anything. And the ground of crawl space is 5-6 feet below grade. Id expect foundation on uphill side to be wet but the concrete is all always absolutely desicated so I think moisture is just rising from the ground.

So... if I put this rubber carpet pad down... is that going to seal out the moisture? Trap moisture between floor and pad? Will that cause crawl space to rot, etc?

Anyone used that rubber carpet pad before? Should I crawl around with butyl tape and seal that tarpage? Do I need to put a dehumidifier down there? Would suck to empty as it is not very comfortable to visit.

[SCadaddle]

My parents built their family home in 1956. Mid century modern on conventional foundation in very humid Mississippi. As a kid throughout the 70's it was my job every couple of years to pull out all the old visqueen and roll in the new. Overlapped the joints never taped anything and all was fine. The vertical height of the crawl space was only about 2 feet so once I got bigger we quit replacing it. As of just a few years ago it was all fine under the house. Adequate foundation wall vents were probably the trick. As for the carpet pad can't help you there, but the same house that had beautiful hardwood floors had a pad and carpet put down in the 70's to cover it up as well. Apparently my Mom thought the house was too noisy with the wood floors. Never had any moisture issues in the house. You might try a bucket of unscented or lightly scented damp-rid in the room. I'm sold on that stuff for the house I'm in now. It works.

[zakthor]

Originally Posted by SCadaddle

My parents built their family home in 1956. Mid century modern on conventional foundation in very humid Mississippi. As a kid throughout the 70's it was my job every couple of years to pull out all the old visqueen and roll in the new. Overlapped the joints never taped anything and all was fine. The vertical height of the crawl space was only about 2 feet so once I got bigger we quit replacing it. As of just a few years ago it was all fine under the house. Adequate foundation wall vents were probably the trick. As for the carpet pad can't help you there, but the same house that had beautiful hardwood floors had a pad and carpet put down in the 70's to cover it up as well. Apparently my Mom thought the house was too noisy with the wood floors. Never had any moisture issues in the house. You might try a bucket of unscented or lightly scented damp-rid in the room. I'm sold on that stuff for the house I'm in now. It works.

Yeah sorty should have mentioned this is seattle area so pretty dry year round - cept for the rain…

House built in 1965. Ive searched and see no vents to outside. The crawl space under the room is partitioned from the lower furnace room with concrete foundation, theres a 4’ tunnel that connects the crawl space to basement with furnace and water heater. Maybe thats the ventilation that it needs?

[gregpark]

We refer to the rubber pad as waffle pad. It does break down with age. It's better than it was 40 years ago but you pay for it and there are way better pads out there now. A quality pad translates into density not thickness. But that's not your problem nor will a good padding solve it. I'd say ventilate the crawl space better. Double or triple the amount of vents around the house and staple up some 10 mil visqueen to the under side of the floor as a vapor barrier if possible

[drcoastline]

Originally Posted by zakthor

Sorry if I use the wrong terms here.

Spouse insists we need new carpet to replace the 35 year old stuff in a guest room.

We're going to put in a wool berber that's scratchy but a nice color and durable and cheap ($2/sq ft.)

Read up on carpet pads since all the stuff I've ever seen was disgusting. There's a carpet pad called 'slab rubber' that comes in 21lb. Supposed to be super durable, good for berber, insulates and is comfortable to walk on. Our discount shop never heard of it but I persisted and they found a product called "Aurora" that seems to fit the bill, sold by Leggett and Pratt:

https://lpflooringproducts.com/carpet-pad/plus-series/rubber-plus/aurora

Anyone have any experience with this sort of stuff. When I replace carpet the pad has always crumbled to dust but this stuff is supposed to last through multiple carpets.

Now, the moisture. Room is on the house's ground, has a wood/plywood floor with a 3' crawl space underneath. The crawl space has a thick vinyl tarp over it and a sump pump under that. The tarp isn't taped/sealed to the foundation or support posts, nor where it overlaps.

I've got a sensitive nose. I've never seen any wet in crawl space there but since the guest room smells wet to me I run a dehumidifier there year 'round. Generally it rains a ton here in the fall (like right now with flooding, etc) but the dehumidifier picks up the most water in the late spring. I can't explain why, maybe the trees do something then? In the spring it will pull a gallon/week, rest of the year its a gallon a month or less. Its run through a month of solid rain and not received a gallon.

I've checked crawl space about once a year for past 20 years and it always looks like it was just built, no mold or rot or anything, it all looks like new. Under the tarp is gravel, not concrete or anything. And the ground of crawl space is 5-6 feet below grade. Id expect foundation on uphill side to be wet but the concrete is all always absolutely desicated so I think moisture is just rising from the ground.

So... if I put this rubber carpet pad down... is that going to seal out the moisture? Trap moisture between floor and pad? Will that cause crawl space to rot, etc?

Anyone used that rubber carpet pad before? Should I crawl around with butyl tape and seal that tarpage? Do I need to put a dehumidifier down there? Would suck to empty as it is not very comfortable to visit.

The question is is the pad pourous or solid? if it is solid rubber then it will trap more moisture then if it is pourous. The ends I assume will not be selaed so around the perimtter more moisture will escape.

Even if it is pourous it is going to tend to slow what ever moisture is attempting to escape down.

[zakthor]

Originally Posted by drcoastline

The question is is the pad pourous or solid? if it is solid rubber then it will trap more moisture then if it is pourous. The ends I assume will not be selaed so around the perimtter more moisture will escape.

Even if it is pourous it is going to tend to slow what ever moisture is attempting to escape down.

It is not porous in my book. Maybe porous like goretex. Not like a regular foam pad that I can get some air through. Doesn’t accept liquid water, surface is a sheet of rubber but air bubbles inside.

The moisture flow is exactly the reason I’m asking. It’s been successful for 55 years so change might create a problem.

The other consideration, house is heated, crawl space is cold. Moisture has no reason to condense on warm underside of floor. Water Will want to condense on top surface of floor since floor is cold. Maybe no issue?

Gregpark: I gave a link to the product. There’s other pads that look like waffles and which are porous. This stuff is quite stiff and heavy but great to stand on. No embossed pattern, it’s sheet rubber on top and bottom. It doesn’t collapse under weight like all the other stuff I’ve seen, has a more linear spring. It is apparently made to go over concrete radiant floors. Is this still effectively waffle pad? They said no extra charge compared to the foam they usually use (we have that foam upstairs in kids rooms and it sucks.) What would you recommend? The people at the carpet store know nothing - are carpet slangerz. Around here competence is rare and expensive.

I don’t think there are any vents today, except the tunnel to the warm furnace room.

I found some websites that advocate crawlspace ‘encapsulation’, I don’t see harm in taping the current seams. Visquene above… man that will suck to do. Is there a special staple that won’t tear through the sheet?

[drcoastline]

Originally Posted by zakthor

It is not porous in my book. Maybe porous like goretex. Not like a regular foam pad that I can get some air through. Doesn’t accept liquid water, surface is a sheet of rubber but air bubbles inside.

The moisture flow is exactly the reason I’m asking. It’s been successful for 55 years so change might create a problem.

The other consideration, house is heated, crawl space is cold. Moisture has no reason to condense on warm underside of floor. Water Will want to condense on top surface of floor since floor is cold. Maybe no issue?

Gregpark: I gave a link to the product. There’s other pads that look like waffles and which are porous. This stuff is quite stiff and heavy but great to stand on. No embossed pattern, it’s sheet rubber on top and bottom. It doesn’t collapse under weight like all the other stuff I’ve seen, has a more linear spring. It is apparently made to go over concrete radiant floors. Is this still effectively waffle pad? They said no extra charge compared to the foam they usually use (we have that foam upstairs in kids rooms and it sucks.) What would you recommend? The people at the carpet store know nothing - are carpet slangerz. Around here competence is rare and expensive.

I don’t think there are any vents today, except the tunnel to the warm furnace room.

I found some websites that advocate crawlspace ‘encapsulation’, I don’t see harm in taping the current seams. Visquene above… man that will suck to do. Is there a special staple that won’t tear through the sheet?

From your description of your crawl space, it sounds like you are doing pretty well down there. I wouldn't upset the apple cart. Maybe ad a fan or some vents for some airflow.

If I recall correctly even the best carpet pad (not the new one your are researching) only has about a ten year life span? Even if it has a longer life span including the new one if it is time to replace the carpet do you really want to keep the old pad with what ever gets spilled, maybe pet stains, dead skin, dirt, etc?

Keep in mind a few things, mold is ever present. Mold needs three things to grow, an organic food source (wood), Moisture and heat, eliminate an one of the three and the mold remains dormant.

[gregpark]

I just checked out the pad in the link. It's good padding and will work fine. For a loop Berber a very firm padding is more correct. A fiber pad is more commonly used for Berber but a dense rubber pad will work.

You always want to block moisture from the moisture source side of a structure. In other words, block it from under the house. You'll not only block moisture from entering the house but protect your framing structure as well. Adding ventilation is usually the best thing you can do. Forget fans, just ventilate for moisture vapor dispersal. If practical, a visqueen barrier stapled to the bottom of the floor joists wouldn't hurt but ventilation is the best thing you can do for yourselves AND your house.

[drcoastline]

Originally Posted by gregpark

I just checked out the pad in the link. It's good padding and will work fine. For a loop Berber a very firm padding is more correct. A fiber pad is more commonly used for Berber but a dense rubber pad will work.

You always want to block moisture from the moisture source side of a structure. In other words, block it from under the house. You'll not only block moisture from entering the house but protect your framing structure as well. Adding ventilation is usually the best thing you can do. Forget fans, just ventilate for moisture vapor dispersal. If practical, a visqueen barrier stapled to the bottom of the floor joists wouldn't hurt but ventilation is the best thing you can do for yourselves AND your house.

I pretty much agree with Greg on this statement. Personally though I have never been a fan of stapling visqueen to the joists. Unless that barrier is complelty sealed no open ends, rips, tears, taped seams moist air will still get in. No air movement and the moist air will tend to condense.

Adding a few more vents won't hurt but could help.

We own a wooden boat so your issues is constant with us. In order to eliminate mold which feeds on the wood we eliminate as much water as possible. We have an air extarction system set up in the bilge and keep the air moving through the boat constantly. In the summer months high humidity the Air conditioners run 24/7. Airconditioners are dehumidifiers.

[javadog]

Could the moisture that you are smelling be coming through a window, or through siding on the outside walls, or somewhere other than the floor?

[zakthor]

Originally Posted by javadog

Could the moisture that you are smelling be coming through a window, or through siding on the outside walls, or somewhere other than the floor?

Whoa thats a great point.

I don't think there is anywhere else for water to enter the room. Row of closed windows and the rest is concrete. Above the ceiling is a deck with surface sealed with vinyl sheet. Everything is very dry. Room has some large closets with good doors and the air in the closets is bone dry. I guess suggests water isn't rising from the crawl space, maybe its outside air condensing on the floor?

The room's door faces the garage entry door and around this time of year the cars are always wet and stay wet. Could be the moisture is humid air from garage.

Could be I collect more water in the warmer spring because that is when the air is most humid outside.

Is tough to judge relative humidity between room and crawl space because there is such a temperature difference and that crawl space smells like concrete. Distorts my sensors.

I think I need data - going to borrow or rent a moisture meter.

[javadog]

Moisture can condense on anything cold and concrete, if it is exposed to the exterior, certainly qualifies. It’s not hard to get condensation inside wall structures. Vapor barriers are funny things, they need to be in different places in the wall, depending on where the higher humidity is and what side of the wall has a lower temperature.

One test we would always do on a concrete slab to check for moisture ingress was to tape a piece of clear plastic down onto the floor and see if moisture accumulated inside it over a period of a few days. Easy to do, you should try that in a couple places. I would suggest one near the outside wall, or close to wherever the moisture sources might be.

When you mention the smell, you described it as moisture and not mildew. Wet concrete gives that odor.

[gregpark]

Ceiling and wall sheet rock is dry, crawl space has a sump pump and smells dank. I'd guess that dankness is permeating your suspended wood subfloor. You won't get mold if the room is kept above 62° but I'm thinking the smell won't be gone until you let the crawl space breath better. You can do a cheap easy test on the concrete beneath the house. Tape down a 2x2 piece of clear plastic and check it the next day to see if it's fogged

^ edit. You beat me to it

[flipper35]

We did thousands of yards of the doubleset for commercial installations and that looks similar but thicker. The doubleset can be glued and the commercial carpet glued on top so I would bet it has good moisture barrier qualities.

For most residential houses if we did higher end carpet we used a pad called (maybe incorrectly) peppermint paddy. It was a pink and white swirl high density foam pad and would last 30+ years. All of them break down eventually and honestly if I were stretching carpet in I would replace the pad anyway.

[fintstone]

Moisture in many homes is largely during seasons where neither the AC nor heat are run as both dry the air. You might get the same results regardless of where you put the dehumidifier. A dehumidifier pulls humidity out of the air which recirculates...so A cheap humidity gauge is helpful to compare rooms.

We have a large dehumidifier in our crawlspace that helps a lot (pumps out lots of water from that area), but plan to add a whole house one like this https://www.santa-fe-products.com/product/santa-fe-ultra70-dehumidifier/
for the living area....as the climate is so mild that my HVAC almost never runs in spring and fall and the humidity is very high then.

[zakthor]

Originally Posted by javadog

Moisture can condense on anything cold and concrete, if it is exposed to the exterior, certainly qualifies. It’s not hard to get condensation inside wall structures. Vapor barriers are funny things, they need to be in different places in the wall, depending on where the higher humidity is and what side of the wall has a lower temperature.

One test we would always do on a concrete slab to check for moisture ingress was to tape a piece of clear plastic down onto the floor and see if moisture accumulated inside it over a period of a few days. Easy to do, you should try that in a couple places. I would suggest one near the outside wall, or close to wherever the moisture sources might be.

When you mention the smell, you described it as moisture and not mildew. Wet concrete gives that odor.

The crawl space smells like a … 3 year old parking garage. There’s concrete smell in the air after I climb in. It’s not moisture smell but like concrete that has eaten all the water and wants more, and it’s caustic to my sinuses. Concrete dust.

The room, when it’s left for a week without dehumidifier… smells wet. Not mold, no dank, just wet air, maybe a bit like wet latex paint. My wife and kids can’t smell it but my father and I can. After dehumidifier runs it smells like nice wood and cheap carpet, and a bit of oil paint on window trim still drying after 25 years.

Good idea about the plastic on concrete!

The rooms windowsills are on the top of the foundation wall, and at ground level. Inside they’re about 3ft above the subfloor. So foundation wall is 6’ of dirt against it. Weird topology outside the dirt slopes steeply down away from the windows, maybe that’s why there isn’t high water pressure forcing water inside. But I’ll do the plastic test and see. It all looks crazy dry. Like I said above the crawl space looks and smells new after 55 years.

I went back down and I’m pretty sure the crawl space is drier than the room above. It’s like being in desiccant. Like cement dust is still active.

I’m going to keep the guest rooms door closed a few days with dehumidifier off and see if it stays dry. Normally it’s always open and folks often leave garage door open.

[drcoastline]

Originally Posted by zakthor

The crawl space smells like a … 3 year old parking garage. There’s concrete smell in the air after I climb in. It’s not moisture smell but like concrete that has eaten all the water and wants more, and it’s caustic to my sinuses. Concrete dust.

The room, when it’s left for a week without dehumidifier… smells wet. Not mold, no dank, just wet air, maybe a bit like wet latex paint. My wife and kids can’t smell it but my father and I can. After dehumidifier runs it smells like nice wood and cheap carpet, and a bit of oil paint on window trim still drying after 25 years.

Good idea about the plastic on concrete!

The rooms windowsills are on the top of the foundation wall, and at ground level. Inside they’re about 3ft above the subfloor. So foundation wall is 6’ of dirt against it. Weird topology outside the dirt slopes steeply down away from the windows, maybe that’s why there isn’t high water pressure forcing water inside. But I’ll do the plastic test and see. It all looks crazy dry. Like I said above the crawl space looks and smells new after 55 years.

I went back down and I’m pretty sure the crawl space is drier than the room above. It’s like being in desiccant. Like cement dust is still active.

I’m going to keep the guest rooms door closed a few days with dehumidifier off and see if it stays dry. Normally it’s always open and folks often leave garage door open.

Is this foundation wall concrete/cinder block? and on the outside dirt is piled up sloping away? If so the moisture may be coming through the wall not from below, especially if the crawl is as dry as you say.

[javadog]

There won’t be enough moisture condensing on the interior walls that it will be noticeable, as the interior conditioned air is just generally too dry.

Now that we’re getting a better picture of how the room is constructed, I am in agreement that you need to check the walls, for sure. If you find moisture coming through the concrete, the solution is to excavate outside and waterproof it properly.

[gregpark]

There's buku water under the house during the rainy season. Why do you think someone installed a sump pump?

[drcoastline]

Originally Posted by javadog

There won’t be enough moisture condensing on the interior walls that it will be noticeable, as the interior conditioned air is just generally too dry.

Now that we’re getting a better picture of how the room is constructed, I am in agreement that you need to check the walls, for sure. If you find moisture coming through the concrete, the solution is to excavate outside and waterproof it properly.

He said when the room is left for a week with out a dehumidifier is when he smells it. If cinderblock that would wick enough moisture through the wall. Once th dehimidifer runs it goes away.

Poured concrete like the slab is less pourous and more dense then a block wall.

zakthor- I don't want you to start getting invasive in your room, but, you may want to cut a ppiece from the wall and see what it looks like and smells.