Subscribe or Renew Membership Subscribe Renew

Mold from Flooding

davidk357's picture

I have been helping a relative repair their home after flooding from Hurricane (or Tropical Storm) Sandy.  They had about 2 feet of water in the 1st floor of their house.  We had removed all of the sheetrock, insulation and electrical.  All effeted areas inside have been cleaned with bleach.  This past weekend we have been reframing a protion of the house for new windows. Re removed the exterior siding, cementatious shingles (about 15 years old) on Tar paper over 1/2" CDX plywood.  Much to our suprise the lower part of the plywood was still damp, and in some instances spongy, when we removed the Tar paper there was some areas of dampness between the Tar paper and plywood and there was also mold as well, not horrible, but a fair amount of mold.  We spot checked the rest of the house and decided to remove the 1st row of plywood (4 feet up).  They will be residing the house.  We did find mold on the back of the plywood where is was attached to the studs and also mold on the stud as well.  We will be cleaning the stud surface (where it met the plywood) with bleach, the other 3 sides of the stud have been cleaned and look clean.  Here is my question.  Prior to installing new plywood is it a good idea to paint the studs and the plywood, either front or back of the plywood or both with either a paint or wood perservative.  Would this help prevent mold growth in the future and also help with mold removal in the future if there is (god forbid) another flood. Please let me know what you think.



I don't think paint or (post #207798, reply #1 of 7)

I don't think paint or waterproofing  would do much at all.  Well, unless it specifically states that it kills mold.  Copper salts will kill mold, and I believe they are available as an additive, or a component in paint.  There are also mold destroyin compounds better than bleach for killing mold and spores, such as Dow Fungiblock.

Yeah, I'd be inclined to use (post #207798, reply #2 of 7)

Yeah, I'd be inclined to use some sort of fungicidal paint.  (But carefully read labels -- many fungicides are quite hazardous to the eyes and probably should be avoided unless you take special precautions.)

Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville

Mold (post #207798, reply #3 of 7)

Mold only grows where there is food and water.

Mold grows on wood because it feeds on wood and it gets the water from the wet air inside the frame.

If you paint the wood with varnish or a gloss paint, while the warm wet air inside the wall will still condense on the cold wood mold will not form as it will be deprived of food.

Of course the best way forward is to stop the warm wet air from entering the wall, this can be done by fixing  one inch thick sheets of polystyrene over the room side of the frame and then covering that with a water vapor proof layer of plastic sheet, covered in turn with drywall. The plastic sheet will stop the water vapor entering the wall, the layer of polystyrene will stop the water vapor from condensing on the plastic sheet. Just make sure to seal any cracks or gaps, as the polystyrene will make the inside of the wall even colder, when keeping the heat inside the home.

I don't think plastic (post #207798, reply #4 of 7)

I don't think plastic sheeting or polystyrene is going to stop flood water.  In fact, probably would make things worse.

Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville

You might consider a borate-based wood preservative. (post #207798, reply #5 of 7)

Borate products are relatively low cost and have a low toxicity. 

bleach (post #207798, reply #6 of 7)

bleach does not kill mold.  If it ever gets damp again, you will have more mold.

Keep the wall dry (post #207798, reply #7 of 7)

Really, that's all you need to do. Mold requires 4 things to live - Air, food, warmth, and moisture. Remove any one and mold goes away. Since we build with mold food, and we need air and warmth too, the obvious choice is keeping the structure dry. It really is that simple.

Andy Engel

Never try to teach a pig to sing. It wastes your time and annoys the pig.