# Mold remediation - I think stachybotrys



## MikoDel (Apr 27, 2013)

I have a mold problem in my basement. I'm pretty sure it's black mold. Breathing it in has given me severe hay fever symptoms that last for as long as 3 weeks. Now whenever I go down there I wear a 3M N95 mask. It's not so bad that I can't walk around down there, but definitely if I start moving things and kicking up dust I wear a mask. The mold forms on things like rubber and vinyl, chair legs and probably of course cardboard and fabric. But I have never seen it on cardboard the way I can see it on things that have oil from human contact. On a black rubber cable it looks like a design, like stripes or swirls. For instance on rubber cables for speakers or electric guitars you can see like a black on black pattern. Inside guitar cases, on my guitars and keyboards - Ugghhh! You can bet none of those are down there anymore.

It doesn't grow in huge patches on the walls or anything like that. One wall had a small dark patch but we scrubbed that years ago and it hasn't come back. If something is near the floor mold will grow on it. Up on a shelf is OK, no growth there. When we first moved in (7 yrs ago) I eventually noticed some idiot put the central AC drain down into the gap of the floating slab. So that used to be saturated in there. It never made it to the sump pump, which was at the time non-functional and bone dry. And that AC puts out about 5 gallons of water a day. I fixed that years ago, but we're not done yet.

We have forced air heat (and of course wood heat) and I use a better grade air filter, the red not the purple. I closed up all the returns down there, and we're lucky because it doesn't seem to be affecting us at all upstairs. But I never took a count up here either.

There is also a radon system. The radon installers used foam cylinders (like the split ones you put on cold/hot water pipes) stuffed into the gap of the floating slab and cemented in with a PL Plus-type construction adhesive. But that job is prolly 20 years old and has deteriorated - needs to be sealed again.

I'll tell the specifics, and anyone with experience is welcome to chime in and tell me if we're on the right track in terms of a good remediation strategy.

THE SPACE
*PA climate - hot summers, cold winters. 
*Unfinished, prob. about 1,000 sq. ft.
*No water, ever. Just normal basement cool temp.
*Sump pump used for AC condensation.
*2 small tilt windows, which open and are screened.  
*Floor is concrete, floating slab, which means perimeter does not join the cinderblock walls. About 1.5" gap, which goes down 6"? deep  to... soil?
*Walls are block, painted but paint is old.
*Ceiling is joists, subfloor, air plenums and pipes.

TACTICS TO MAKE IT LIVEABLE AGAIN
*Scrub the walls and floor with 50% alcohol/water solution.
*Paint the walls, first with (?) something like Killz and then again with paint.
*Seal the floor. (Not sure what to use. It's a big floor, I don't wanna go broke.)
*Dust, vacuum and paint everything on the ceiling, like they do in restaurants.
*Fill in the perimeter of the floating slab, probably with concrete and some expansion joints.
*Shop fan on low in front of a window, pulls air in all summer.
*Use a gas stove (have a big VC cast iron waiting to be installed) to heat and dry. It's not down there yet, but the gas line has already been run. Stack still needs to be built. Plan on running that on low - how often and how long, we'll have to see.
*Looking at purchasing a new dehumid, a bigger one meant for this size space
*Cover sump pump
*If I remember the rel. hum. down there is about 60 or 65% with a small dehumid running. I'm told it needs to be 40% (max) to be healthy.

Thanks so much in advance for any suggestions.


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## dougstove (Apr 27, 2013)

Hi;
"*Shop fan on low in front of a window, pulls air in all summer."
I think this may be a bad idea.  I am guessing summer air in Pennsylvania is warm and humid, and your summer basement is going to be cooler than outside.
So you are going to risk creating condensation as the warm wet outside air hits the cool floor and walls.
The growth from the floor up suggests the cold floor is keeping the local humidity high.
I am wondering if the years of incorrect AC draining saturated the slab and it has never dried out?


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## maple1 (Apr 27, 2013)

This sounds to me like a big problem hiding under your slab. If things are really as dry as they are seeming to be, you should not be getting what sounds like wild mold growth at floor level. I don't think any of the things you are looking at will help, but rather mask short term. It might be time to rent a jackhammer & poke a hole through the slab, maybe with the idea of making a new deeper sump pump pit - but you might want to get some pro advise first.


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## dougstove (Apr 27, 2013)

I am also wondering about your choice of 50% alcohol as a disinfectant.
Is that based upon a recommendation for mould?


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## midwestcoast (Apr 27, 2013)

I have limited experience, but will chime in with some basics first:
Absolutely keep the basement windows closed whenever it's warmer outside than inside. Probably best to just keep them closed all the time.
Air-seal your rim joist area, windows and any penetrations in basement walls to stop warm, moist air entering. 
Check & clean all your eaves-troughs (gutters) & downspouts. Make sure the water is directed away from the foundation with downspout extensions. 

I would get the bigger (energy star) de-humidifier running first & draining to the sump. Get it as dry as possible down there for a good while before you start cleaning / painting. That will allow all the wood & concrete to dry out before it's sealed. 
I'd depend on the de-humidifier to keep it dry down there & not try to heat it.  It's not insulated. You'd be wasting tons of heat.
Keeping 40% rel. humidity down there long term might be tough, but I agree 60-65% is too high.

What the radon guys put around the slab perimeter sounds like "backer rod", which would be a standard thing, but using construction adhesive as the sealant is improper. You could just replace with a high quality flexible caulk at the seams of the backer rod, slab & wall. If the backer rod itself is falling apart (from contact with the wrong adhesive) & needs to be removed, maybe the flexible spray foam would work there instead? That would seem much easier than concrete with joints.

To "kill" the mold look at commercial products over the alcohol & water.  You are planning to do a lot of work, so why skimp on the mold killing?

Questions: What's the humidity in the rest of the house in different seasons?  With wood heat, central AC and a leaky house I find spring & early fall are the only times I run a de-humidifier in the basement. I keep my central heating humidifier off except in full winter.
Is your sump lid sealed? It should be for the radon system to work.

I'll let others comment on the painting.


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## Dave A. (Apr 27, 2013)

First things first -- get the largest dehumidifier running 24/7 and properly drained (ideally into the DWV system -- or at least outside the space) and get the RH under 40 (as dry as possible). Then kill any mold that remains and work on contributing factors.  And the sump must be covered.  Don't like the idea of draining AC into a damp basement either, better into DWV or outside.


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## Ashful (Apr 27, 2013)

I'm just up the road from you, and we keep two or three dehumidifiers going in our basement. All are on auto drains, since the primary trouble with dehumidifiers, is that few people keep up with emptying them the required 1x - 2x per day, mid-summer. We scrubbed that basement clean when we moved in, and have kept it at 50% RH ever since, and have none of the musty / moldy problems the prior owners had.

Do not dismiss how much electric a dehumidifier can use. Some older ones can cost you an extra $100 per month, in a damp basement in real hot/humid weather. It may be worth spending a few dollars more for one that has a better efficiency rating.

If your basement is at all divided into rooms, you will do better with multiple smaller dehumidifiers, than one large one. That said, do not undersize your needs, or it will be running 24/7 (did that in prior house... dehumidifier lived a relatively short life).

I usually plumb them into an air-conditioning condensate pump, which then pumps the water up to the drain trap installed for the water softener.


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## begreen (Apr 28, 2013)

When you say you see mold on walls is this on finished walls or bare foundation walls? If they are enclosed (studded sheetrock) walls then you may have a much greater problem lurking behind them. It might be worth cutting a few 6x6" inspection holes in the worst areas if sheetrock walls. For sure do not blow summer air throughout the place. Its high humidity will condense on the cooler basement surfaces. I second the thought of running a good humidifier down there, year round.

Instead of alcohol I would use bleach and water mix for killing the mold, but considering you have already developed a sensitivity to it, you might want to have pros do this.


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## Dave A. (Apr 28, 2013)

Some pics might help.


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## TheMightyMoe (Apr 28, 2013)

Dave A. said:


> Some pics might help.


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## dave11 (Apr 28, 2013)

You should re-test for radon if you haven't recently. Though some people call that a scam, it is not. Radon has been proven to be the second biggest cause of lung cancer after smoking. And it's easy to fix.

Make sure you seal tightly the perimeter of the slab, and make sure the vent functions well.


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## jharkin (Apr 29, 2013)

Joful said:


> Do not dismiss how much electric a dehumidifier can use. Some older ones can cost you an extra $100 per month, in a damp basement in real hot/humid weather. It may be worth spending a few dollars more for one that has a better efficiency rating.


 
+1

My place is quite small,  with 700ft2 of stone wall/concrete slab basement and ~300ft2 of dirt crawl. Our dehumidifier uses up to 10KWh/day in the wet months, or as much as 30-40% of our electric bill!

Generally the largest capacity dehumidifiers have the best efficiency ratings, but sadly most of the newer ones dont last.  We got rid of an ancient sears for a Frigidaire 70 pint digital model with a 1.8 EER. It saved us a few bucks on the monthly bill but died in 2 years.  I got a free replacement on warrany but based on reviews I fear I will do it again in a couple years (register that warranty card!!)


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## begreen (Apr 29, 2013)

I got one a couple years back for our greenhouse and it has done very well. Power usage is not too bad, I keep it set to 70% humidity and it doesn't run continuously. I empty it about twice a week. It's a Frigidaire FDF50S1, 50 pint capacity.


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## TheMightyMoe (Apr 29, 2013)

Dehumidifier + Sump pump = win.


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## maple1 (Apr 29, 2013)

I just re-read things. From that, I think at first your sump was dry, now I think it's just pumping the a/c drainage?

I still have a feeling that there is something wrong under your slab - I'm picturing a soggy mess under there with a ton of water that is for some reason not making it to your sump pit. Maybe improper gravelling? They wouldn't pour the floor without a good layer of gravel underneath that would feed your sump pit - would they?


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## MikoDel (Apr 29, 2013)

Well I made the classic mistake of beginning the reply in the browser and not a text editor, and alI of it got blown away.

Thanks for all your input, first of all. _All you'se guys._

Comments:
- Of course I don't open the windows if I have a dehumid(s) running, no. Last 2 seasons - don't have one. Had 2, both died. Getting new one this year, prob. a DeLonghi DD50P or equiv. size.Yes, getting a capable De-Hum down there is #1 priority. I agree everything we buy nowadays is s__t and it all breaks too soon. My HVAC is probably 15 years past its design life and it goes like a ba___ard. I love old electric motors.
- I have not opened the windows yet this season, and now I'm glad I didn't.
- Pics attached. Not even during that storm did I get one drop of water. Driveway is maybe 30-35% grade. House is above the street. everything flows down. I don't think there's a pool of water under my floor, but I do think you're right that it's saturated.
- Gas VC "Radiance" stove is not only for a dry-out tactic. It's COLD down there in the winter. HVAC sounds like a 777 at idle and it doesn't do much down there anyway. Gotta turn it off to make music. Hot summer nights I guess I won't be recording!
- As you can see, the walls are not covered with mold, but it's bad in a few spots and you can see it on the floor and on stuff. Some of what's on the walls is more old stains than real growth.
- I read that alcohol, for black mold, is more effective than bleach. But before I do the cleanup, I will make sure.
- Sealing with foam - GreatStuff. I actually did a little with that. Certainly easier than concrete and expansion joints. More flexible too. But that gap doesn't fill so easy. That's a lot of foam. Also wondering if concrete in the "float space" will mean cracks in the floor? Still, leaving it open is not an option.
- Gotta cover the pump too. I don't think the pump is the real culprit here. It's the floor and its open perimeter.
- Radon system is working and showing negative pressure. When the gap is filled and sump covered it should be fine. I have a test kit. I'll use it after I seal everything up and see how it is. No use doing it now with all this work ahead of me. Sump pit used to have a plastic seal over it, very chincy. Was all shredded when we moved in. Think the bloody inspector would have said something!
- Friend of mine used a petroleum based Dry-Lok in his place, with a full "military-style" gas mask. Put him in the hospital anyway. Poisoned him thru his skin, and I mean vapors, not contact. Don't use that stuff inside. Selecting the right stuff is important but I guess it won't be petrol based!
- Of course a lot more stuff needs to go. No cardboard, there will be none left. (Reminds me of Moonstruck, "there will be nothing left...) Goes without saying, gotta get all the old dust out.
- Keep in mind a floating slab is NOT a French Drain. I don't believe there is any grade because I don't think there is any BOTTOM. It's just a gap down to the earth. I could be wrong, I never really stuck anything down there and poked around yet. But I'll get to the truth soon enough.
 - Rel. hum. in the house? Well, in the den w/our stove it's low! (Ha!) House was built in the 70's and a lot of air gets in, but we like it that way cause the stove is HOT. Wife is very allergic to EVERYTHING, so she runs the AC lots during the summer. So I imagine hum. is pretty low.


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## woodgeek (Apr 30, 2013)

Ok, that looks a bit less horrible than I think we had feared. You don't have 1000 sq ft of moldy drywall on the walls and ceiling!

Your logic above all makes great sense, and the floor and walls are reasonably mold resistant (concrete/block and paint).

First, some recs:
1. If you and the mrs are both allergic to the basement, you need to fix this asap. Most of your house air is prob coming in through there 24/7 and it is making you sick now.
2. I would have a humidity sensor down there....get a wireless temp/humidity monitor (<$30) and you can keep an eye on it without going down there. The same unit will monitor relative humidity (RH) upstairs in the summer. A proper AC system should keep you under 50% RH.
3. Get a new dehumidifier, plumb it into the sump pit so it runs whenever needed, and monitor that it is working.
4. I would put a standalone hepa filter down there. They can be pricey (a couple hundred $$) but if you get the RH below 50% (no growth) and a HEPA filter, then the mold (I think is) upstairs will go down, and maybe you can go down there without 'reacting'. After your prob is fixed, you can clean it up, put in new filters and put it upstairs for the mrs allergies.
5. Get the 'mold food' out of there. Most of the mold is on possessions stored down there, not the floor walls. I would move it all into the yard/shed/back porch and clean it out there in the fresh air. Then try to store it somewhere else until the basement is 'fixed'.
6. Then clean your ceiling joists, walls, etc.

So far, sounds like a few hundred $$ and a WE or 2 of work.

Now, for amateur 'building science sherlock'....

I had some similar problems in my 1960 house. we had a bunch of chit in our (new) garage after we moved in, and it all moldered after a few weeks. Grrr. High humidity is all it takes.

I think you basically have an airsealing problem, not a wet basement problem. If your AC system is older, and your house (70s) leaks a lot of air, then in our climate AC can really struggle with dehumidification. It cools the air ok, but the humidity is higher than it should be.

So, I can guess a lot of things....

A. My guess is that you are setting your AC rather low in the summer (maybe <70) to compensate for poor dehumidification. This upstairs, along with block walls and slab make the basement very cool even in the summer. Very common.

B. My next guess is that your sill plate/rim joists are not sealed or gasketed, and that something in your house (bath fans/kitchen fans/AC + leaky ductwork/dryer) is depressurizing your house even in the summer. Again, a very common thing. In this case, much of your upstairs air is passing through the basement first, makes the mrs' allergies worse.

A+B means that most of the makeup air in your house comes in through the sill/rim into your very cold basement. That humid PA air gets cooled to 70°, and gets close to or above 100% humidity and poof..mold sprouts on everything. Without a dehumidifer, this can happen very fast, like less than a week. One humid heat wave, and you have a mold problem. And we have several of those a year.

Of maybe you just have a dryer down there not vented to the outside?

I personally think a dehumidifer + a HEPA filter will arrest the problem and protect you upstairs from mold.

If I'm correct, the solution is to airseal and insulate the sill/rim. I would clean it up myself and then have a spray foam co come in and spray it. You could keep the dehumidifier there for insurance, but the run cost would drop off and the units wont die of exhaustion every two years. The $$ savings summer and winter might pay for the foam in short order.

If you do have an older central AC, when you replace it, you might have your ducts checked out. leaky ducts could be depressurizing your house whenever the system runs, wasting energy and limiting dehumidification. On a new unit, looks for multiple speed compressors, which will dehumidify a lot better. 73° and dry is a lot more comfortable in the summer than 69° and 65% humidity.

There are currently great rebates and low interest financing on home energy improvements in PA...google up 'EnergyWorks'. Might be a good time to go the energy audit route, it all expires the end of the year. You can currently get a full audit with blower door and thermal imaging for $150, no commitment.

EDIT: if you are unconvinced....5 gallons/day of AC condensate is a decent amount, but not really evidence that your system is doing a good job of dehumidification, actually evidence that you are pulling in vast amounts of humid air. Confirmed by your dehumidifiers quitting after a short time. Your basement being really cold in the winter is also evidence of a major air leak down there (prob the sill/rim). Check out the sill, a 1/16" gap (total) times the perimeter of your house (maybe 150') makes about a square foot of opening, like having a window open all summer and winter. The wife having tons of 'allergies', and you having symptoms for "3 weeks" after exposure sounds more like you are both getting dosed 24/7 at some level. I had a moldy carpet pad in my house for a while, I know how insidious it is. Running the AC with filter return? If the AC ducts leak to the outside, running the AC depressurizes the house and pulls new moldy air out of the basement at a rate proportional to how fast it filters...so it never catches up to clear the air. Call in the pros with a cheap audit....they will figure it all out for you for $150.


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## vinny11950 (May 1, 2013)

The pictures of your block walls look like you have efflorescence not mold.  If it looks powdery and minerally it might be that instead.  This would also mean that you have moisture pushing/pressuring the foundation walls and could be a major source of moisture down there.  Make sure your outside perimeter is not directing water to the foundation.  Other than that, it looks like my basement, not that bad.  Woodgeek has some good ideas.

I am now learning that putting anything in my basement that might be food for mold is a bad idea.

Also remember, you will never kill mold completely no matter what you read from remediation companies.  Mold is everywhere and will find its way back into the basement.  You just have to control the environment so it does not have a great party space to live in.


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## woodgeek (May 1, 2013)

Remember, this part of the country has seen record heavy rainfall from three tropical storms in the last couple years.  If the OP did not get water in his basement from any of that he should have the driest basement in the state. For those farther north, I will explain that the humidity outside in PA is often high enough for me to get condensation on the outside of my (single pane) windows in the summer, i.e. dew points in the mid-70s °F.  What does that air do in a cold basement?


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## ironpony (May 1, 2013)

I am in the environmental business, licensed in asbestos, lead abatement, radon and certified in mold.
without testing you have no idea what type of mold it is, moisture related generally a penicillin strain.
go online and rent an air sample tester to determine counts and species.
mold needs food and water, can't get rid of the food have to reduce the moisture
radon system if moving air should help dry out subgrade, open sump bad for radon mitigation
agree with above, and based on pics, your basement is very wet and you have serious issues
mold spores are everywhere, you can not get rid of them you can only reduce thier growth rate


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## tekguy (May 1, 2013)

painting over the mold wont kill it (more food for the mold) and killz paint isnt antimold.. bleach molecules are to big to penetrate the surface,
scrubbing it down may actually spread the spores around making it worse
i have had good luck using moldex and a dehumidifier.. easy

http://www.homedepot.com/p/Moldex-Disinfectant-64oz-Concentrate-Cleaner-Makes-16-Gal-5510/100642755


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## BrotherBart (May 1, 2013)

I screwed up and molded up my attic this year with too much humidifier and an air leak I didn't know about. I fogged it with Concrobium and it knocked the stuff out really well. My basement has had the same problem as your for many years and it is heading for a fogging next week.


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## MikoDel (Jun 7, 2013)

People - more helpful info Thanks yet again. An air test is more good advice.

I am choosing a dehumid now. (I've been busy with family, and tree work, and collecting firewood on the weekends.) I'm on a site called air-n-water dot com, and am looking at models by Alen, NewAir, Soleus and Danby. If any of you have a preference, I'd be happy to know why. I hear the Soleus is very quiet. I'm looking in the 50 pint capacity range.

I don't think there is a gap on the sill plate. I have spent a lot of time down there doing electrical, and other things, with my head up in the "rafters". But just the same, you make a great case for insulating where the structure joins the foundation, and I will verify if your suspicion is correct about where the makeup air in the house is coming from. I do have a standalone Alen HEPA in the room where the stove is. It was expensive. It's awesome, though. I never thought of putting another one downstairs. Great idea too.

Thank you too for your suggestions on anti-mold products, like the fog, and advice about to paint or not to paint. I will consider all of this. A great friend of mine works in the energy business. He manages many crews that do the "blower in the front door" thing every day. He will be instrumental in helping to determine the basement situation, insofar as leaking air, etc.

I am very concerned, as you say, about how much of this stuff is getting upstairs. My wife and daughter aren't complaining of any symptoms this season. Me neither - no sneezing or watery eyes. In one of our upstairs bathrooms, black-appearing mold forms on the showerhead pretty quickly. It's an enclosed shower stall. Not so much in our other bathroom, which has the conventional tub setup. The silicone seal around the tub takes a good long time to turn black. I only have to replace it now after about 5 years.
As far as your concerns about a dryer that's  improperly vented or something like that - no way. The only absolutely stupid thing is, I don't have a dehumid running right now. Other than that, stuff is draining properly, vented properly... oh wait... Not having the sump pump covered is stupid #2. Because like one of you says, what the hell good is a radon system with an open hole?!!
So I have to seal the perimiter space
*********************
None of you object to concrete in the floating slab space? 
*********************
and re-do the sump pump setup.


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## Ashful (Jun 7, 2013)

I can't speak to any of those dehumidifier brands.  I guess I didn't put much thought into it.  I went to Lowes Depot, and bought whatever brand they carried at the time, brought it home, and plugged it in.  I have two Whirlpools (one 50 pint, one 75 pint), and one Frigidaire (75 pint).  I had a run of bad luck with the 50 pint Whirlpools dying, but the latest one has been running 6 - 7 years with no trouble, as have my 75 pinters.

If researching dehumidifiers is what has set you back a month and a half since it was first suggested, I'd recommend you stop researching and start buying.  It's in your dirty and damp basement.  Who cares what brand it is, or how quiet it is?

First order of business when setting it up is figuring out placement and drainage.  Only the most extraordinary individual will keep up with emptying it the 1x or 2x per day (EVERY DAY) that's required.  Set up an auto drain.  If you don't want to drain it into your sump pit, then get an AC condensate pump, and use that to pump the water up to a washer or water softener drain.

After a few weeks with that dehumidifier running, you'll be ready to don the mask and do your foaming / cleaning.  Working to clean the basement before it's thoroughly dried and the mold dead, is a waste of time, IMO.


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## MikoDel (Jun 27, 2013)

No, you are 100% correct and that's what we did. I made the (mistake? wise decision?) of sending my wife a link to this thread, and she bought the dehumid within an hour of reading. It's a 50 pint DeLonghi, and it's been running non-stop down there, draining directly into the sump pump for about 3 weeks now. According to the humid indicator on the device's display, the humidity is now down to 50%, and I have the device set for 30 or 40%, can't remember which. Of course I also have a more accurate way of determining the humidity down there (a wet/dry thermometer) and it also has the advantage of being able to take a reading in a different spot. I may also have to buy a second dehumidifier, as the space is large and I don't want to mess around.

I still have to cap the sump pump, and I plan on doing that this weekend with a garbage can top, cut out where needed and glued to the floor around the pump. Last few weekends have been busy with tree work and I have been too tired to do anything after a full day of that in summer heat. **And also take a radon reading of the air.** I have the kit.

I recently had a conversation with a very knowledgeable guy who recommended a product to seal the floating slab. He said to buy a styrofoam "rope" product at the correct size, insert into the crack in the slab, push down below floor level about an inch, and then use self-leveling caulk to seal. You need an oversize, special gun because the caulk comes in a very large tube.
Funny, he was explaining it to me while we were walking in South Street Phila, and he looked down at the sidewalk and said, there, in that seam, that's what I'm talking about. Could be they use self-leveling fill in sidewalk seams too.
He reminded me to clean the inside top edge of the gap so the caulk gets a good bond. Of all the ideas I've heard, this seems like it can be done the quickest, and will not disrupt the way the foundation is handling it's union with the terrain. I'd hate to fill the floating slab gap with concrete, and then have water pissing into a basement which has been dry since the day we moved in!


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## Ashful (Jun 27, 2013)

Good suggestions, although I'd make two others:

1. You may not want to glue the lid onto the sump pump. Just placing it there should do the same job, and you'll be kicking yourself the first time you want to get in there to check something, if you glue it in place.

2. Check with your local swimming pool suppliers. They should have a rubberized gap filler for pool decks, available in larger containers. A standard caulk tube is 10 oz. The larger one you're discussing is 29 oz. = 52 cu.in. Now figure your gap is likely 2" wide, and you'll be filling "an inch below the floor". So, 2 cubic inches per linear inch... or one large tube of caulk per 2 feet of perimeter! You can buy this caulk in 1 or 5 gallon buckets from a pool supply house.


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## velvetfoot (Jun 27, 2013)

They might have used another PL product that is polyurethane caulk.  I bought some at HD a while ago.  It also comes in self-leveling.  Both made for sealing concrete cracks.

I found my basement was less stinky after insulating the walls with extruded polystyrene foam, and covering with sheetrock; less area to condense.  Still nothing on floor though.

I have an electronic radon detector by Safety Siren (~$120).  You can turn off the fan or do some other mods and and see how that affects the radon level.


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## midwestcoast (Jun 27, 2013)

Joful said:


> ... Now figure your gap is likely 2" wide, and you'll be filling "an inch below the floor". So, 2 cubic inches per linear inch... or one large tube of caulk per 2 feet of perimeter! You can buy this caulk in 1 or 5 gallon buckets from a pool supply house.


 That's why the guy he was talking to suggested stuffing backer rod in first. Way less $ than using all that caulk. Also most caulk won't hold in gaps anywhere near that wide without backer rod.
Sounds like a good plan to me


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## Ashful (Jun 27, 2013)

midwestcoast said:


> That's why the guy he was talking to suggested stuffing backer rod in first. Way less $ than using all that caulk. Also most caulk won't hold in gaps anywhere near that wide without backer rod.
> Sounds like a good plan to me


 

Yeah, but my numbers were WITH the backer rod, assuming he puts it 1" below floor, as suggested. Without the backer rod, and assuming that trench is at least 4" deep, he'd be using two 29 oz. tubes per foot!


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## woodgeek (Jun 27, 2013)

So you think all the water is coming in in vapor form through the gap around the floating slab?  Just don't see it.  I still think its the sill/rim, or maybe coming through the concrete walls/floor in vapor form.


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## midwestcoast (Jun 28, 2013)

Joful said:


> Yeah, but my numbers were WITH the back rod, assuming he put's it 1" below floor, as suggested. Without the backer rod, and assuming that trench is at least 4" deep, he'd be using two 29 oz. tubes per foot!


Thanks, I read it too fast. I wonder why the guy told him an inch down? seems like way more than enough to hold the caulk in place. I'd say he could get it more like a half inch below, just leave the caulk level below the slab, or even just run a bead on either side of the backer rod the seal the edges.  The 2 edges are the only place the caulk is doing anything anyway (assuming the rod is closed cell foam).


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## mywaynow (Jun 28, 2013)

If you get to paint stage, use a test area first to make certain the humidity in the floor/wall is not too much for the adhesion/curing.  I just saw what that looks like and it is not pretty.  Old garage floor that got very wet and was epoxy painted before the levels were good.  Created bubbles and fisheyes in the surface and now must be ground off.

FWIW, I did flood cleanup with 50/50 water and bleach to deal with mold.  It worked great and I was never concerned with the possibility of fire (alcohol).


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## Ashful (Jun 28, 2013)

woodgeek said:


> So you think all the water is coming in in vapor form through the gap around the floating slab? Just don't see it. I still think its the sill/rim, or maybe coming through the concrete walls/floor in vapor form.


 

I agree. As stated earlier, this is almost always an issue of outside air infiltration.  However, I also don't see how sealing the perimeter and sump pit can hurt.

Me? I'd stuff the backer rod in the gap, and skip the caulk. See what kind of difference it makes, and what potential problems it causes, before making it permanent. Backer rod is easily removed, caulk isn't.

If he has (or plans to install) a sub-slab radon system, then the perimeter gap is much less relevant with respect to moisture problems.


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