To understand how to clean up after a flood, we talked to Dr. Joseph Lstiburek, the engineer who founded Building Science Corporation. Dr. Joe spoke at length about flooding retrofits, and we converted that conversation into a "7 Minutes of BS" podcast. The flood retrofit process is visually summarized here in a step-by-step how-to approach to cleaning up after a flood and repairing the walls to withstand future floods.
Animation transcript:
It is pretty much a fact of life that some places are prone to flooding. It is also pretty much a fact of life that floodwater is quite dirty. That dirt, muck, and biological waste are absorbed into your walls and floor coverings, which can pollute the indoor air even after they have dried out.
In a perfect world—like animation land—step 1 of flood cleanup is to get a dumpster. In the real world, you may have to pile it in the front yard.
How to clean up after a flood retrofit walls against future flooding:
- Remove the interior trim and wallboard. Chances are, the sheathing was soaked with dirty water, so that will need to be removed, too.
- With the brick exposed, turn your attention to cleaning up the drainage path for future water events. There are usually large blobs of mortar that not only bridge the gap behind the brick but can also fall down and block the escape route for water.
- Chisel excess mortar away from the framing and suck it out of the cavity with a shop vac.
- Now that there is a clear path for water to drain down, give it a place to drain out. Cut out the mortar joints between every third brick along the bottom course and insert a weep screen that will keep insects out while letting water escape.
- With the base of the wall able to expel water, and the cavity behind it clear for drainage, we are ready to flash the bottom of the wall.
- The best way to protect the wall from future flood damage is with a waterproof membrane. Paint over the bottom plate, up the studs a little bit, and down the front of the slab to form a pan that will direct water out of the weep holes we cut earlier.
- Drainage mesh with a facing or filter fabric is installed against the brick. This allows rainwater to get past the brick to drain out of the cavity.
- From there, closed-cell spray foam can be installed in the cavity. Closed-cell, 2-pound density polyurethane spray foam will not absorb the water from the next flood, so it will not need to be replaced next time. This adds thermal resistance, water resistance, and structural integrity to the wall.
One last step before closing it up is to paint the framing with latex acrylic paint. Cover it with non-paper faced drywall and with any luck, the next flooding repair will be much less invasive.