West Palm Beach Concrete Block Homes: Flat Terrain Grows Mold

How West Palm Beach's Flat Terrain Feeds Mold Through Concrete Block Homes

Your walls feel dry. There is no water coming in. After some big rain, you notice a smell near the floor part of your inside walls, and the smell stays. The problem is not a leak. The wall is pulling water from the ground under it, all by itself.

Why Concrete Block Walls Pull Moisture In From the Ground

Most homes in Miami-Dade, Broward, and Palm Beach counties use concrete block and stucco. In Florida, people call this CBS construction. Many homeowners think the stucco outside keeps water out. But if the soil stays wet for a long time, it does not.

Building Science Corporation's BSI-037 report by Joe Lstiburek talks about a problem. Concrete block can let in water because it is porous. When the outside stucco goes down to the ground, wet dirt can push water up into the empty parts of the block. The water then moves to the paper part of the drywall on the inside. This happens even if there is not a crack or opening. The wall draws the water in by itself.

This is not just a problem with old homes. Any concrete block house can have this issue when the stucco touches the dirt. If there has been a lot of rain for some time, the risk goes up.

Flat Terrain Traps Water Against Your Home for Days

South Florida has a drain system with three levels. Rainwater goes from your street into a small local canal. Then it moves to bigger main canals that are taken care of by the water district. The South Florida Water Management District runs over 2,175 miles of canals and 936 water gates to send water to the coast.

The problem starts during heavy storms, when every drain lets out water all at the same time. The South Broward Drainage District says that when big canals like C-9 and C-11 are full, the whole system will get backed up. Water can stay against the walls of homes for days, not just hours.

Most places in the country have the ground sloping away from buildings, so water runs off with no trouble. But West Palm Beach is different. The land there is flat, and water just sits at this level until the big canals are ready to take more. That is why post-storm mold in Palm Beach County often shows up near the base of the wall and not higher up with bigger floods.

Area B in South Broward Has the Slowest Drainage in the Region

Not all of South Florida gets rid of water at the same speed. SFWMD canal records show there is an area in south-central Broward with poor water flow. This happens because the land is lower than the coastal ridge. That area is called Area B in SFWMD planning records.

Area B goes from Hollywood Boulevard in the north down to the Miami-Dade county line in the south. It stretches from L-33 in the west to Flamingo Road in the east. When there are storms in this area, the ground can stay wet and water can sit next to block walls for days. In other places, the water dries up in just a few hours. This does not happen by chance. The land here is low compared to the system that moves water away.

Snowbird condos and seasonally empty units in this area deal with their own kind of problem. A place that stays closed during a rainy summer lets water in the walls build up for months. No one sees the issue. That pattern is shared more in this article about West Palm Beach condos that deal with mold every year.

What a Mold Test in a Concrete Block Home Needs to Cover

Standard air cassette checks done in the center of a room at chest height usually do not catch early signs of mold inside block walls. Water goes into the stucco and slides down the hollow parts of the blocks, then gathers at the bottom of the wall spaces. Mold will grow at the base of drywall sheets, which is lower than where most people look.

After a storm, you should test a concrete block house by taking surface samples at the bottom of the inside walls. Just taking air samples at chest height may not catch what is really there. For people living in West Palm Beach rentals where the owner does not agree with a mold complaint, results from the bottom of the wall show a clear path for water to come in. This is better proof than results from just air tests.

Why does my West Palm Beach home smell musty after rain when nothing flooded inside?

A musty smell at the bottom of inside walls can be one of the first signs of mold. It is not a sign of flooding. You will likely notice this smell before you see any stains. Look behind baseboards on walls that face outside, especially if they are on the first, ground floor. Mold growth often starts in the first 12 inches from the floor. A surface test in this area will find it early.

Do concrete block homes grow more mold than wood-frame homes after storms?

Yes, and I will tell you why. Wood-frame walls can dry to the outside. The space inside the wall gives water a way out. But hollow blocks do not have the same way for water to leave. Once water gets inside the block, it stays there. The water keeps moving in or waits until the soil around it dries, and in South Florida, this can take weeks.

What is Area B in Broward County and why does it affect mold risk?

Area B is a term that tells where water will go in SFWMD canal records. If you do not know if your home is in it, you can use the SFWMD flood map at sfwmd.gov. Just put in your address and see which drainage district your street is in. Homes in other nearby districts that send water to C-9 or C-11 have the longest wait for water to clear during big storms.

Can a standard air test miss mold in a block wall after a storm?

Yes. Air cassettes take in spores that are in the room air, but this may not show mold that is growing at the bottom of the wall if it is new and still in one spot. If the test shows a high number of spores near the bottom of the wall but normal numbers at chest height, this means the mold just started to grow on the wall and has not moved out into the room air yet. This shows that you found the problem early before it had a chance to spread more.

Check Your Walls Before the Next Storm Season

Concrete block is still used a lot in West Palm Beach. The ground here is also still flat. What can change is when you spot the problem. You can find it early, or you can wait until it gets worse and moves up the wall on its own.

If you live in Palm Beach County and your home smells musty after heavy rain, do not wait to see mold with your eyes. Get in touch with Fast Mold Testing WPB for testing surfaces and the air in your house. This helps with block wall homes before hurricane season comes again.