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©2017 This excerpt taken from the article of the same name which appeared in ASHRAE Journal, vol. 59, no. 11, November 2017

By Joseph W. Lstiburek, Ph.D., P.Eng., Fellow ASHRAE

About the Author
Joseph W. Lstiburek, Ph.D., P.Eng., is a principal of Building Science Corporation in Westford, Mass. Visit www.buildingscience.com.

Rebuilding Houston

The problem with flood-damaged buildings is that the damage is done by dirty water. Everything imaginable and unimaginable is in flood water. We call it “black water” or Category 3 water. It includes sewage, bacteria, fungi—stuff that will make you really, really sick. It is not a Doobie Brothers song. We are not talking Ol’ Mississippi rollin’ on. If there are catfish, they are not jumpin’. They are pretty much dead.

“Black water” is very different from “clean water” or Category 1 water. Category 1 water is easy to deal with. You get it from broken water supply lines, sink and tub overflows and the like. Just dry the wet spot and be done. Big caveat here: dry it quickly before you are overwhelmed with mold. You have days, not weeks, to get it dry. We all know how to do this.

Between Category 1 water and Category 3 water we have, you guessed it, Category 2 water or “graywater.” Stuff from dishwashers, urine in toilet bowls, sump pump failures. We also know how to do this. The same folks who do the Category 1 stuff know how to do the Category 2 stuff.

Houston after Hurricane Harvey is a “black water” Category 3 extreme event. So what do you do? You raise the flag and roll up your sleeves and get to it.

You throw out all the carpets, fabrics, pretty much all your soft furniture, cardboard boxes and on and on. It is typically not worth the effort to professionally have this type of stuff cleaned, except if it is a family heirloom. Again, we all know how to do this.

Now it gets interesting, especially if you have brick. You cut away and get rid of all the interior gypsum board and cavity insulation and your sheathing, leaving bare stud framing and naked exposed brick. When in doubt, throw it out. Now what?

Wash, rinse and dry. Clean all the surfaces with water and detergent, sanitize them with a bleach solution, rewash them and rinse and then dry. Note that we all know how to do this as has already been mentioned.

So here we are clean and dry and having to put things back together. Being the cynic that I am (comes with age), I bet we will get flooded again. If it was me, I wouldn’t rebuild in the same place without a huge regional investment in civil engineering infrastructure: dams, dikes, spillways, canals, pumps, and then I would build up. I would knock everything down and start with a clean sheet of paper. More about that later. But, alas, that is not the way it is going to go.

How to rehabilitate thousands of houses that are not going to be knocked down? And under the assumption that it is going to happen again?

Here goes. First thing we have to do is clean out the debris at the bottom of the wall cavity. Cut the flashing out. Yes, you read that correctly. Use an air compressor to blow stuff out of the gap. Completely expose the concrete in the seat of the slab edge of the foundation. Drill weep holes through the bottom course of brick. Drill them from the outside. How many? Every other vertical joint in the first course of brick. Big weeps, OK? Line them with commercially available insect guards. Go online. We all know how to do this. Pick a Houston manufacturer if you can. They need the business, especially now.


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