Gypsum?

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Mike Wood · Answer

@Ean Savoy If you give it time, it will dry out.  I know mine did.  You will still likely see continue to see the discoloration after its dried.  But like I said, it was open on the inside for months.

If you do remove it, how do you anticipate sealing the house from air drafts?  If you don't have any sheathing, the house will be extremely drafty and likely cause issues with A/C and heating.

The added bonus of the spray foam is excellent energy efficiency. My house was a 900ft2 rental unit (first floor of an up and down duplex), and after the spray foam I put a small wall unit (8000btu if I recall) in a window while I finished construction (central air was not hooked up yet).  I remember using the AC wall unit on a Sunday while working on the house inside.  I turned it off and the next time I returned was Thursday night.  When I opened the door, I was hit with a wave of cold air, and when I stepped inside it was still cold.  That sold me on spray foam.  That would never be possible with batt insulation in Louisiana.

Greg Jeanfreau · Answer

@Ean Savoy

I don't think that there is really any reasonable way to remove it since it is between the brick and the studs. I think your best bet is to use Bora-Care on it and the studs, make sure it is fully dry and then paint it and the studs with an oil based mold inhibiting paint for good measure. I guarantee that 99% of the homes in NOLA that had this sheathing did not remove it before rebuilding. I have yet to hear anyone ask about it. The other route is to have it professionally remediated so that your family will have a mold certificate stating that it has been done professionally. This could come in handy if you have any plans to sell the home in the next few years. Good luck! I'll be in B.R. this weekend to join the fun...Lots to do!

Mike Wood · Answer

@Ean Savoy My original house used the same type of exterior sheathing. Mine was black paper like cover over gypsum. My house is in New Orleans and flood during Katrina. What I did was left if in place, made sure it was well dried (I was not in a rush to cover it, as it too many months to get power restored to the area), and treated it for mold. I then used closed cell spray foam to ensure that it was encapsulated from the interior.

I am not saying this was the best solution, but what I did. I have not had any issues with that property, as I still own it.

I am not saying this was the best solution, but what I did.  I have not had any issues with that property, as I still own it.

Jim Adrian · Answer

@Ean Savoy

You wont be able to remove the board without removing the brick veneer.  I think @Mike Wood has the right idea. For a belts and suspenders approach... I would try to chemically treat the boards and mold.  Let everything dry out really good.  The sprayfoam is mold proof and vapor impermeable, thus sealing it off.  I would spray 2.5" minimum in the stud cavity to meet the 2012 energy code of R-13 in walls.  More insulation is better.  Here is a link to BASF that has information on sprayfoam insulation.  Spraytite 178 I have being installed on a commercial project.  You can even fill the rest of the cavity with batt insulation (unfaced) if you wanted to increase the R-value.  Remember your sprayfoam is now your vapor barrier.

Ron Collins · Answer

Great information inside this post. I will be sure to share this with family and friends in the Baton Rouge. Thanks guys.

Ean Savoy · Answer

Cool, thanks guys!

Andy Hudgins · Answer

Make certain that your MM reads at least 14%, less is better. That includes any concrete slab floors also.  Be sure to do air quality tests. If your dehu has a HEPA filter, great. I agree with someone above that the mold paint is only good for the paint salesman. If wood moisture content is right combined with RH near 45-50ish% and existing mold is removed, all good.

Nicholas R. · Answer

i wouldnt. just let it dry. I had shitty old pressboard (even more absorbent than your stuff i think) behind the siding in my house in Covington (flooded back in March, and again this time!)...i didn't think it would, but it dried fine and even the swelling went down.

Ean Savoy · Answer

I plan on removing wet portion of backing boards, spraying Borax treatment on studs and any board still attached, letting central A/C run for a few weeks along with humidifiers to completely dry the studs out. Then once tests with moisture meter are good, I'll seal studs with mold inhibiting paint and spray foam insulation in the walls.

Jim Adrian · Answer

Spray foam is awesome stuff!   The one con is the upfront cost, remember you pay for what you get.  You get a lot of bang for you buck with this. I don't know how thick @Mike Wood put in his unit but he is right.   Air leakage thru walls is now down to zero.   We have seen great results using as little as 2" of spray foam with batt insul within the stud cavity.  I would make it 4" thick which give you R-24 minimum.  Make sure you use closed cell sprayfoam which is better than open cell sprayfoam.   If you have removed all the interior drywall (which it sounds like you are) then use closed cell sprayfoam.  This has a lot of expanding strength when curing. This also provides great sound deadening properties as well.  Same stuff as the "great stuff" foam in a can.

My rental has open cell sprayfoam and the first winter after installing it, I ran the furnace 3 degrees lower than the previous year and we had a colder winter.  That's a lot of energy saved. I had to use a different product due to my retro fit condition.

Gypsum?

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