The tenants living in this home in Oakland came home to a flooded basement. They notified their landlord, who sent a plumbing crew out within a day to shut off the water and to repair the broken supply line.

The landlord then had the water pumped out of the basement and brought in fans to dry out the space, assuring the tenants that this would, “…prevent a mold problem.” Well, the standing water dried out, but the tenants believed that they could smell mold and they decided to call out Bay Area Mold Pros for an inspection.

I immediately detected a very strong smell of mold growth, and I took several moisture readings with a variety of meters. I found that both the framing atop the foundation, and the drywall covering this framing, were saturated with water. I could see mold growing on both surfaces, and took air samples throughout the basement.

The lab found high levels of mold spores in every major category, including a fairly high level of marker spores, identified by the lab as Stachybotrys.

This case illustrates what can happen when an inadequate remediation occurs. Many homeowners believe that they can perform their own mold remediation by simply drying out an area that had been subjected to a water-intrusion event. But it’s not that simple. Effective remediations include not just a drying-out process, they involve an appropriate cleaning of all affected surfaces, as well as a proper cleaning of the air through the use of both air scrubbers and machines which utilize negative-air pressure to transfer the mold spores to a location outside of the home.

Property owners who try to save the costs of professional remediations are engaging in a “penny-wise and pound-foolish” approach to what can often be a serious problem. It’s much better to handle any potential mold growth problem as quickly and as effectively as possible as soon as the problem is discovered. Half-measures and money-saving schemes will likely results in what happened in this home…a science project!



I was called out to a 1930’s era home in San Francisco this week to perform a mold inspection of a large flat. I could see obvious signs of water damage around almost all of the windows, and when I started using my meters to determine if the plaster next to the windows was wet, the tenant told me, “Don’t worry, those are all new windows.”

As I moved from room to room in the flat, I could see that none of the original solid wood double-hung windows were still present, they had all been replaced by a combination of vinyl retrofit windows and solid wood retrofit windows. These retrofit windows were all installed in the original sold wood window frames, and although all of the new windows appeared to have been properly installed, the plaster adjacent to each of the windows was wet.

What many homeowners (and some contractors) don’t understand is this…when a new window is installed in an original wood window frame, the condition of the window frame itself will largely determine if rain water will eventually make its way into the home. And not just the window frame, but the surrounding wood trim as well. If the wood trim (typically a piece of 1 by 6 redwood on old San Francisco homes), fails, then rain water has a clear path to enter the wall framing. And if water makes its way into wall framing, you’ve got serious problems!

I took several air samples within this flat, and as expected, the mold spore counts were found to be elevated by my lab. There were additional issues within this unit, including water detected behind the tile above the bathtub, and elevated humidity in the basement below the unit. The real challenge for the client in this process is the fact that she is a tenant, and not a homeowner, so she must now rely on the property owner to “do the right thing” by starting to address the myriad construction issues discovered during the inspection.



I received a call from the long-term tenants in this old apartment on the peninsula about possible mold growth, and I saw numerous issues which are very likely producing mold growth. My meters detected moisture behind the original wall tile above the bathtub on all three walls, and also under the counter tile to the right of the kitchen sink (depicted in photo below).

The quarter-round tiles across the front of the sink are actually all missing, and the rusted edge of the original cast iron sink is visible. The substrate under this kitchen counter tile is most likely dimensional 1 by 8 lumber, which was commonly used in this era of construction. This substrate has probably been wet for numerous years, and mold spores are likely growing on this substrate.

The tenants told me that their landlord is not very responsive to their requests for repairs, and this is a common lament from my clients who rent their homes and apartments. One of the reasons to have a mold inspection completed in a rental unit is to establish a “paper trail” that can be shared with a landlord who is reluctant to make necessary repairs. If, upon receiving the mold inspection report the landlord is still not willing to have the mold-causing problems addressed, the tenants can utilize the report in any civil action they might pursue. Reports from independent third-party inspection companies can be very useful evidence in civil actions, and serve to bolster the tenant’s case.

Likewise, when scrupulous landlords are maintaining their rental properties, but have tenants who are complaining about issues (such as mold), a report from a certified mold inspection company that the mold spore counts within a rental unit are not “elevated,” this too can be a valuable piece of evidence in a civil case.



This past winter was the second wettest in two decades, and all of this rain resulted in myriad mold problems for Bay Area homeowners. Even though the calls for rain-related problems started “drying up” a couple of months ago, the problems created by all of this rain have persisted.

The owners of this home in San Mateo County noticed that their crawl space was flooded with water following a particularly heavy period of rain, and they contacted their contractor who then installed a sump pump system to deal with the standing water. Once this standing water was addressed, the homeowners thought that they were good to go, but the soil in the crawl space stayed damp for weeks, even though the sump pump was removing the standing water. This dampness can spike the humidity, and this elevated humidity can lead directly to mold spore growth.

The mold depicted in this photo is growing on the back side of a standard sheet of 1/2″ drywall. The stud bay had been filled with R13 batt insulation, but this didn’t prevent the growth of mold on the drywall itself. Once mold has grown into the paper on drywall (on either side), the drywall needs to be removed and discarded.

So this case is another reminder that moisture issues need to be addressed immediately following any water intrusion event, and this includes drying out the area with commercial dehumidifiers and fans. Mold spores will start to germinate within 24 to 48 hours of being exposed to water, so homeowners need to call in the professionals immediately upon discovery of any water issues. Any delays can (very likely will) lead to mold growth, so don’t wait, make that call!



I often receive calls from tenants regarding their concerns about mold within their homes or apartments, even though their landlord has assured them that “…there’s nothing to worry about.” The photo below depicts the siding that was removed from a a San Francisco town home after it was discovered that a plumbing supply line was leaking inside this wall.

The landlord sent out his “mold expert,” who took an air sample in the room affected by this plumbing leak (kitchen), and the expert assured the tenants that there was nothing to be concerned about (even though he hadn’t yet had the air sample analyzed by a lab!)

I started using my moisture meters in an effort to determine the extent of the water intrusion, and I found that the drywall on the inside of the wall depicted in the photo was saturated with water. When I tested the base cabinet, which was a “Lazy Susan” base, the back of the cabinet was also saturated, and I could smell mold within the cabinet. I then tested the wall cabinet, and it too was saturated. I took an air sample within the base cabinet, and the lab determined that the mold spore count was elevated (about four times the number of mold spores as the control sample).

The landlord had already told the tenants that his solution to this issue was going to be to run a dehumidifier within the kitchen, but I explained to the tenants that this mold problem had already moved beyond the stage where the problem could be addressed with a dehumidifier, and that both the cabinets and the drywall would need to be removed, and that a full mold remediation (by a certified professional) was needed for their home.

Many of the landlords and property management companies that I deal with are professional and responsible, and want to take whatever steps are necessary to deal with mold problems correctly. But many of the landlords that I deal with decide on a “…penny-wise and pound-foolish…” approach to these problems, and this is when tenants are wise to bring in their own independent mold inspection company.

I always explain to my clients that as an independent mold inspection and testing company, I have “…no dog in this race.” I do not perform any remediation work, so there is no reason for my reports to exaggerate the extent of any mold problem. When the tenants in this case presented their landlord with the report from Bay Area Mold Pros, he agreed to do the right thing and to proceed with a professional remediation.



Many older homes have a white powder visible on foundation walls and concrete slabs. This powder is actually salt, which makes its way to the surface of the concrete when it becomes saturated with water. This process, known as “efflorescence,” (which means to “flower out” in French) is strong evidence for the homeowners that they have water problems that they probably need to address.

In the below photo, the efflorescence appears along the lower 12″ of the perimeter foundation. This part of the foundation is completely “below grade,” meaning that the level of the soil on the outside of the foundation is higher than section of the foundation wall where the efflorescence is prominent.

In older homes, there was rarely any waterproofing applied to these foundation walls prior to the “back-filling” of the soil against the foundation wall. Additionally, there were rarely any drain lines (French drains) or gravel placed against the foundation prior to the back-filling. This lack of drainage, combined with a lack of waterproofing, often leads to the water intrusion issues that result in efflorescence.

This efflorescence itself is rarely a problem, but it signals to the homeowner that moisture is likely getting into the crawl space of the home. And this moisture often creates mold problems both within the crawl space, and in the living space directly above.

To deal with this moisture, homeowners are encouraged to speak with both drainage specialists in order to try to prevent the naturally occurring ground water from making its way into the crawl space, and also, vapor barrier specialists, who can install their barriers directly over the exposed soil (or concrete rat-proofing) of a crawl space. These barriers are very effective at reducing both the humidity and water vapor that are common in crawl spaces. And these measures go a long toward dealing with mold growth issues within the home.



Many of my clients arrange an inspection with Bay Area Mold Pros, and then tell me that there was a leak, “…several weeks ago.” Mold spores are a part of our environment, and they are present in almost all of our homes. But these mold spores can’t grow until they are exposed to either water or excess humidity. Once exposed to water, mold spores can begin to germinate within 24 to 48 hours.

And there’s the problem for people who may be prone to procrastination. If there is a water intrusion event in your home (plumbing leak, roof leak, ground water leak), you must deal with it immediately! That’s why remediation companies usually have phone lines that are answered 24 / 7. Their crews will not only try to respond within hours, they will generally have their machines (fans, dehumidifiers, negative air pressure machines) set up and working within hours of arriving.

The photo below depicts the condition of the wall drywall in the basement of an old San Francisco apartment building. A plumbing leak occurred in one of the commercial street-level office spaces and the water made its way into the below-grade basement that became flooded. The water was allowed to evaporate, which took several days. But by the time the water had evaporated from the concrete slab, the wall drywall had been saturated for several days.

Mold spores are looking for organic matter to grow on, and they absolutely love the paper face of drywall. The air samples taken next to the drywall in the photo were found by the lab to contain not only the standard species, but a fair amount of the dreaded Stachybotrys, which is referred to in many internet articles as “toxic black mold.”

The lesson here…if you have a water intrusion…don’t wait! You need to dry out the area immediately, and you may need professional assistance. Don’t procrastinate, unless you don’t mind sharing your home with some moldy roommates!



If you own a home that was built in the 30’s or 40’s in San Francisco, or on the peninsula in San Mateo County, you may still have one of these tiled stall showers. They were generally placed adjacent to a separate cast iron bathtub in these old bathrooms. It is pretty amazing the number of these showers that are still in service, given the eras in which they were constructed.

My grandmother purchased a “brand new” home in the Mission Terrace neighborhood of San Francisco in 1936 for $5,000! That was a considerable amount of money in the depths of the depression, but she managed to pay it off early, and the home remains in our family to this day. The bathroom was finished in “art-deco” tile, and believe it or not, the shower is still being used every day, is still in pretty good shape, and it doesn’t leak!

But our shower is the exception to the rule. The shower depicted in the photo is in a 1940’s era home in San Mateo County, and it is no longer serviceable. During an inspection of this home by my company, Bay Area Mold Pros, my meters detected moisture behind the tile on all three walls, and under the tile in the shower pan. I took air samples both within the shower and in the hallway adjacent to the shower, and both samples came back with elevated mold spore counts.

If your home still has one of these original stall showers, it would probably be wise to have a mold inspector determine what you’re breathing when you’re using the shower. There is really no way to “repair” these old showers, they’re simply too far gone. Most of the pans have failed (they used either a “hot-mop” waterproofing, or a sheet metal pan in this era of construction).

If you determine that your shower is still serviceable, remember to keep it clean, and you may wish to apply some grout sealer. The grout on these old showers is often missing in places, but you can prolong its life with frequent applications of a modern grout sealer.



In modern construction, you’ll always see a space from grade level to framing. This space varies, but it will minimally be about 8″ at the low point. This space helps to address two problems: pests such as termites, and ground water; both of which are trying to enter your home. In older construction, it is common to find the mud-sill at the same (or sometimes even lower) elevation as grade. This is a potentially serious problem, as both termites and water have direct contact with the framing.

When I first looked at the exterior wall depicted in the above photo, I thought it looked pretty sound. The stucco ended at a weep screed, and there was about 8″ spacing between the weep screed (which represent the bottom of the framing / sheathing) and grade. But then I realized that the foundation vents were within the foundation wall, which is unusual. Foundation vents are normally placed atop the mudsill (or higher), but they are almost always placed in the framed portion of the flooring or cripple wall above the foundation.

As I looked more closely, I saw that what I thought was the concrete foundation was actually several long pieces of galvanized sheet metal. So the builder who had performed the last remodel of this home had stripped the old stucco off, sheathed the framing with 1/2″ CDX plywood, and ran the plywood down to the original mudsill, which was at grade.

This resulted in plywood (and the floor framing behind the plywood) extending to grade. So the builder decided to cover the lowest section of the framing with sheet metal, hoping this would provide a “break” between grade level and the stucco and weep screed. Only time will tell if this decision will accomplish what it’s intended to accomplish. In any case, it’s probably preferable what existed previously, which was likely direct contact between the framing and the adjacent soil.



In 1977 I purchased my first home in San Francisco, a Queen Anne Victorian built one year after the 1906 earthquake and fire had devastated San Francisco. The front stairs for the home were original, and extended from a raised concrete landing to a small enclosed front porch just outside the original front door. Everything on the stairs above the concrete landing was solid wood…the stair stringers, the treads and the risers. And even though they were seventy years old the year I bought the home, they were actually in pretty good shape!

But as the Victorian era was ending in San Francisco, so was the era of building homes with exposed wooden front stairs. Terrazzo stairs became quite common, with both the treads and risers for these stairs being fabricated off-site, and then placed over wood framing or a concrete support. And although the Terrazzo material was solid and not prone to water intrusion, the joints where the treads and risers abutted the vertical framing often leaked after decades of service, with the water generally making its way into the basements of these old homes.

Although less common than Terrazzo, many old homes in San Francisco were built with brick front stair systems. These systems almost always involved a brick cover over a wood-framed or concrete substructure, and just like the Terrazzo stairs, once the bricks start leaking, the sub-structure becomes saturated with water.

The good news was that these systems which were wood-framed were almost always left as open framing, so the framing was allowed to dry out between rain storms. And if the supporting structure was solid concrete, there was no wood framing present to rot, even if the water intrusion was significant. But over the years, as real estate values continued to rise at extraordinary rates, the owners of these old homes in San Francisco started to add living space to these old basements and garages, and the space under these old entry stairs often became closets.

Once the framing under these stair systems was covered with plaster or drywall…the problems began. Because now the water intrusion events resulted in not only the soaking of the supportive framing, but the soaking of the plaster or drywall covers as well. And this of course eventually led to…mold growth.

I had an inspection this week at a 1950’s era home in San Francisco’s Noe Valley, and the front stairs were finished with a brick cover. Once the wood framing under brick stairs gets saturated with water, it’s going to support mold growth, and that’s exactly what happened in this home.

If your front stairs have developed leaks, several things will need to be done to address the problem. First, the leak(s) must be stopped! Until the stairs are properly waterproofed and the leaks have been stopped, there is no point in doing any repair or remediation work, but once the leaks have been halted, it’s time for the next steps.

If the leaks have been occurring for a long time, it’s very possible that any wood framing present has suffered rot, and any rotted framing will need to be removed and replaced. The demolition work should be done by a certified mold remediation company, and once the demo work has been completed, then a thorough cleaning of the surrounding area also needs to be completed. Once the demolition and remediation work has taken place, it’s time to have a licensed general contractor take over and complete the framing (and other) repairs.

As you can see, these stair problems can be a headache and can be very costly. But you ignore these stair leaks at your peril! Because the problem that exists today will only get worse if it’s subjected to additional rain and water intrusions.