Dealing with Mold.....Irene Flood

[Chefwong]

So I got some backwater overflow from our basement during the recent heavy rain followed by Irene a week later.
Both times, we were ontop of of the water but I suppose some overflow seeped into areas unknown.

Long story short, I noticed some fuzz around the 2 areas of my basement baseboards....
Started ripping out some drywall and I've got mold . Under the stair rises, I can clearly see mold dust on the floor, if not on the framing and risers...


This is not going to be pretty.

So I'm up now planning a plan.

I plan to just start gutting the drywalll at least to see the extent of the damage.

Do you guys say bleach / moldicide the beejezus out of the framing or gut it down to a shell ?
I just need to clear some of the kids stuff out before I start creating more dust / exploration.

 

[Dana]

Get a dehumidifier down there ASAP and get the relative humidity under 60% to limit surface mold from growing while you work. Anything that you can remove before you start gutting will help as will setting up room air filters/cleaners while you work. Bleach will kill the mold, but won't prevent it from returning. Keeping the RH below 60% will.

The sooner you can get on the gutting project the better, even if it's just stripping the lowest 12" of gypsum to allow any enclosed cavities to dry quickly, halting/slowing the spread.

 

[Sponsor]

 

[Chefwong]

Thanks Dana.

What do you think is more dryer - AC or Heat.
I have zoned AC......and will do either.

I've just had the windows open since that day - as it's never really *humid* in the basement this time of year, no was there any ~apparent ~ flooding/overflow beyond the bathroom. BUT, after opening up the walls, there definately was ..

 

[Jadnashua]

Think about renting some dehumidifiers and fans.

The following was exerpted from someone taking a mold remediation class:
1/2 gal. white vinegar
1/2 gal. hydrogen peroxide-common peroxide available from your *********
1 cup boric acid

keep closed tightly mix well - use in a spray bottle on a dry surface. Shake well and spray area well. The vinegar/peroxide kills active live mold and the boric acid keeps them that way. (Note: uncapped peroxide loses it's oxygen molecules to the air when not capped tight and becomes H2O [water], so keep this solution in a bottle that can be capped off tight). Instructor stated that boric acid works on mold bodies like it does on roach bodies - cuts them and they bleed to death because they cannot "coagulate" (snakes and snails and puppydog tails). I guess we all know that there are some very beneficial molds, too. One last note on the above solution. This solution will not "bleach" out the mold stain. After mold is under control, then you can bring out the bleach and whiten the mold stains.

 

[Dana]

Thanks Dana.

What do you think is more dryer - AC or Heat.
I have zoned AC......and will do either.

I've just had the windows open since that day - as it's never really *humid* in the basement this time of year, no was there any ~apparent ~ flooding/overflow beyond the bathroom. BUT, after opening up the walls, there definately was ..

Opening the windows of a basement when the outdoor air dew point is above that of the slab make the problem worse, not better. Treat any bulk-water incursion paths, but keep the basement no damper than 60% RH all year with a dehumidifier rather than AC. An EnergyStar 65-70pint unit delivers 1.8liters/kwh, which is significantly more efficient than their 30-pint cousins. Units with "mechanical" dehumistats are fine, but drift a bit with temp and may need re-adjusting 1-2 times/season. Some of the digital dehumidistat versions seem designed to short-cycle the unit to death, and are more susceptible to damage from power disturbances, etc, but will track RH more closely. In a reasonably tight house a single 65-70 pint dehumidifier is big enough to handle a 1500' basement with an open floor plan. Be prepared to pay $200-250 for the unit, and maybe even $100/year in power to run it (and considerably more if you're trying to keep it under 50% RH.) Smaller units cost ~1.3x as much to remove the same amount of moisture, so the $50 you might save up front is usually eaten up well before the thing croaks.

In D.C. the average outdoor dew points are hardly EVER low enough in summer be useful for drying, and air-infiltration is responsible for a large portion of the latent air conditioning load in most homes. By the time the outdoor air is sufficiently dry to dry a basement it's already the beginning of the heating season there.

 

[Chefwong]

Thanks guys for the support !
All I can say is wow. I decided to rip it cause I knew I had backflow that possibly could seeped into the flooring + OMG......alot of the areas is not that bad. I do plan to gut the flooring and redo to tile. However, the area under the stairs is terrible. The risers will need to come down. It's not that bad except for the landing area and the sheetrock that is wedged between the stair riser and the wall adjacent to it.

I can only fathom homeowners who have slow drips with hidden mold that goes on by for years...


JIM - thanks for the witches brew mix !
Very helpful. Framing for the most part looks clean but I plan to give them a good dousing.

 

[Dana]

BTW: Are the foundation walls finished (with studwalls)? If yes, what is the insulation, stackup and vapor-barrier/retarder look like?

 

[Chefwong]

All look very clean. So far, I've been removing at around 30" High, but I'm thinking I will just score a line at 49 off the floor and just take it off all the sheetrock from there.

This weekend, I'm planning to gut the flooring. I'm spending my nights removing sheetrock, then spraying down the witches brew after I very slowly mop the dust created during sheetrock removal. All done by scoring with a knife and prybars, which minimizes the dust versus power tools.

I don't think it needs to be gutted. The way the floor is pitched - lowest point pitched towards the stair riser landing in the corner, I suspect all the water seeped there and hung out.
I never saw it cause the landing, etc was enclosed.

The molding on risers is just minimal compared to the sheetwork butted against the wall on which the riser leg is butted against.
So me thinks I'm in the clear and will need to

- Remove all sheetrock at 49" height
- Remove entire stair and rebuild from new wood.

The vapor barriers look clear and clean. I will plan to remove the insulation.

I'm thinking the landing will be rebuilt but both the top and the side of the landing will be built with *ball catches* - panels that are removal in the event I do get water, at least I can remove ane verify is there is any there.

 

[Chefwong]

Jim -

Hows does your DIY homebrew compare to Microban...
Just wondering if you may have any insight

 

[Dana]

Vapor barriers have no place in basement insulation, since they tend to cause more problems than they solve. If the foundation isn't allowed to dry toward the basement it's moisture content rises, and can rot the foundation sill. If there's a studwall holding the insulation, placing a vapor barrier on the interior traps ground moisture putting studs at risk, putting it on the exterior between the studs & concrete allows some wintertime moisture accumulation, and puts the foundation sill at risk. The solution is to use a layer semi-permeable rigid foam between the studs and the concrete, but in D.C. you can probably get away with just using unfaced-batts. With anunfaced-batts-only solution in winter there will be some condensing/frost hours on the above-grade concrete, but below grade not at all. The capillary wicking of the concrete would protect the above-grade portion of the studs somewhat during those colder hours. Making the interior gypsum air-tight is key though, since convection currents from the interior could raise the moisture content to mold-inducing levels in winter, left unchecked.

See: http://www.ornl.gov/sci/ees/etsd/btric/RadiantBarrier/RBFactSheet2010.pdf

Note that the moisture analysis is for a Minneapolis climate, with far more condensing hours in winter than you would experience. Also note the locations of capillary breaks at the footings, slab edges, and foundation sills.

Keeping the basement at 60% RH would be more than enough protection from ground-moisture drives as long as there isn't chronic bulk water leakage.

If it can be accomodated at the stairs/doors, and inch of R5 rigid XPS insulating sheathing below any new sub-floor has comfort, energy, and moisture control benefits.

 

[Chefwong]

Dana -

You seem to know numbers...

Do you think running my minisplit is actually cheaper to run than my portable dehumifier. (i have 2 whirlpool units and have been running these since the OP).
However, I just realized that not only does our minisplit do heat and cool, but there is also a dehumfier setting - and just due to how the inverter technology works. if I recall being Pitched.....the minisplits were fairly inexpensive to run.

Opening the windows of a basement when the outdoor air dew point is above that of the slab make the problem worse, not better. Treat any bulk-water incursion paths, but keep the basement no damper than 60% RH all year with a dehumidifier rather than AC. An EnergyStar 65-70pint unit delivers 1.8liters/kwh, which is significantly more efficient than their 30-pint cousins. Units with "mechanical" dehumistats are fine, but drift a bit with temp and may need re-adjusting 1-2 times/season. Some of the digital dehumidistat versions seem designed to short-cycle the unit to death, and are more susceptible to damage from power disturbances, etc, but will track RH more closely. In a reasonably tight house a single 65-70 pint dehumidifier is big enough to handle a 1500' basement with an open floor plan. Be prepared to pay $200-250 for the unit, and maybe even $100/year in power to run it (and considerably more if you're trying to keep it under 50% RH.) Smaller units cost ~1.3x as much to remove the same amount of moisture, so the $50 you might save up front is usually eaten up well before the thing croaks.

In D.C. the average outdoor dew points are hardly EVER low enough in summer be useful for drying, and air-infiltration is responsible for a large portion of the latent air conditioning load in most homes. By the time the outdoor air is sufficiently dry to dry a basement it's already the beginning of the heating season there.

 

[Dana]

Yes, a mini-split running in dehumidify mode will always be more efficient than running a standalone portable dehumidifer, but it will also cool the room somewhat. That's usually not a problem, since basement humidity tends to track outdoor air humidity, which peaks during the cooling season.

Does your mini-split dehumidify to a programmable relative humidity, or is it just a fixed-rate operating mode?

I usually recommend mini-splits to people who are contemplating installing a whole-house dehumidifier, since a small mini-split isn't much more expensive, about as efficient in dehumidify mode, and it provides a lot more function (it's quieter too!)

Which make/model do you have, and do you have the full manual?

 

[Chefwong]

Silly to undercut sheetrock 3/4" off finished floor.
Tilesetters ended up pouring quite a bit of SLC raising the height of the floor and what I though would be a good undercut already is not flush with the FF.

New Crain Saw just came in for some other things....but I'm thinking it might be nice to still redo and undercut the sheetrock 3/4 from the finished tile floor. I am still presuming no water will ever come in, but this is a basement afterall so......