Rotting Wood, Rampant Mold Threaten Homes

[Guest guest]

Hazards Ahead

Rotting Wood, Rampant Mold Threaten Homes

http://www.washingtonpost.com/wp-

dyn/content/article/2005/09/17/AR2005091701585.html

By Rick Weiss

Washington Post Staff Writer

Sunday, September 18, 2005; Page A12

New Orleans residents who return to their soggy homes and businesses

this week are in for some rude lessons in physics and biology,

experts say.

Lesson one will focus on the surprising amount of damage that

floodwaters can wreak very quickly upon wood-frame buildings. Lesson

two will be an equally difficult tutorial in the astonishing

versatility of mold and other fungi, which are poised to enjoy a

major population explosion in the steamy microbial incubator that

was once the Big Easy.

Wooden structural supports that have become saturated under water

will in many cases be warped and are unlikely to straighten out

again as they dry, making structures unsafe, according to engineers

with flood experience.

Even those structures deemed sound enough to be salvageable will

soon come under a major assault from some of Mother Nature's

smallest invaders: Health-threatening molds and wood-rot fungi that

are very difficult to control and can consume a house from the

bottom up.

Beyond the obvious need to remove carpets and floor pads, owners

will have to tear out sheetrock and other kinds of porous

wallboards, along with any insulation inside walls, which tends not

to dry out if left in place. Wiring will have to be replaced, as

will many gas lines and plumbing components.

" They're pretty much going to have to strip a lot of these houses

down to the studs, " said Jon Heintz of the Applied Technology

Council, a nonprofit engineering organization in Redwood City,

Calif., that will be training many of the inspectors who will soon

be swarming into New Orleans to judge which buildings can be

salvaged.

" It's pretty simple, " said H. Gilbert of Parsons Brinckerhoff,

a Seattle-based global engineering firm. " If the water gets above

the foundation for any period of time . . . it will likely be

cheaper and safer . . . to clear the site and start fresh. "

If there is one silver lining, urban entomologists said, it is that

the flood probably took a huge toll on New Orleans' famously robust

population of termites, which have been chewing up the city's

buildings and trees to the tune of $300 million in damage every year.

Federal officials have said little about their plans for assessing

the structural damage left in Hurricane Katrina's wake. But with

residents of some neighborhoods getting the go-ahead to return to

their homes over the weekend, experts warned of physical and medical

risks that residents will face as they begin to dig out their homes.

For homes with concrete foundations, residents will first have to

see whether those foundations have cracked or shifted. Floodwaters

can easily scour beneath the edges of concrete slabs, causing an

irreversible settling that can leave the wooden structure above

unsound.

And although basements are unusual in southern Louisiana, where

flooding is so common that even the dead are interred above ground,

any structure that does have a well-sealed cellar will have to be

checked to see if it has been displaced.

" Basements that are watertight can pop up out of the ground and

float, like boats, when they're surrounded by water, " Heintz said.

Also at risk of irreversible damage are weight-bearing wooden

elements, such as posts, beams and floor-supporting joists. When

wood fibers absorb water, they expand and weaken. Horizontal pieces

tend to sag under the weight of the house and typically do not

recover upon drying.

Even after the wood seems to have dried, the slow and destructive

process of rot will often continue -- a process by which various

fungi consume cellulose, the major ingredient in wood and its major

source of structural strength. Some fungi, including the one that

causes so-called dry rot, are expert at drawing water from distant

parts of a structure even as they colonize otherwise-dry wooden

beams, gradually weakening those beams even though they are dry.

That is one reason it is so important to remove all materials that

might be holding moisture anywhere in a once-flooded home, including

paper-covered gypsum board and insulation between walls. Any good

source of moisture can nurture microbial growth at a distance.

The fungi that cause wood rot work slowly and generally do not pose

major health hazards. But other fungi can overwhelm a home within

days after floodwaters recede, sickening residents to the point of

their needing hospitalization, experts said. These are molds, common

at low levels in many a U.S. bathroom but able to enjoy massive

blooms in warm and recently saturated Gulf Coast homes.

" There are hundreds of types of mold spores floating around all the

time, just waiting for a wet surface to land on, " said Claudette

Reichel, a housing specialist with the Louisiana State University

Agricultural Center in Baton Rouge.

The best food for molds is paper, Reichel said, which is one reason

they grow so readily on moist, paper-covered sheetrock. Molds also

feed easily on pressed-wood products and particleboard.

Mold spores can trigger asthma and allergic reactions in people who

are sensitive to them. Even people who are typically tolerant of

mold may find themselves becoming ill once they start stirring up

massive doses in the cleanup process, Reichel said. She strongly

encourages people to wear respirators or masks with ratings of at

least " N95, " which means the pore size is small enough to capture

mold spores.

Diluted bleach kills mold, but even dead spores can cause health

problems when inhaled. That means that the risk of serious asthma

attacks -- a syndrome especially common among African Americans --

is likely to linger long after New Orleans's floodwaters have ebbed,

Reichel said. And because bleach does not leave any mold-fighting

residue, surfaces will need to be treated repeatedly over the weeks

ahead as new spores settle and try to colonize damp surfaces.

Wooden structures that survived Katrina may find themselves better

off in one regard: The city's termites have probably suffered a

significant setback.

Termites prefer wet wood to dry but, as air-breathing insects that

generally live underground, they do not do well in floods, said

Gregg , an urban entomologist at the LSU AgCenter.

After Hurricane blew through the Southeast in 1992,

and colleagues measured termite populations in parts of Georgia that

had flooded, and compared their findings to tallies that had been

done before the rains.

" We showed a 77 percent decrease after the hurricane, "

said, " so floods can certainly affect termite numbers. "

There is one caveat, warned: New Orleans is largely

populated with an alien species of termite inadvertently imported

from East Asia several decades ago. These Formosan termites, it

turns out, often build their nests inside walls and in other places

above ground.

The big question now, said, is whether the termites

planned better than humans did by building enough of their nests

above flood level.