Beware of These Home Designs to Find and Stop Mold (Hopefully Before It Starts)

If you are searching for a new home or building one, there are wise and not-so-wise designs on the market regarding the way they prevent or encourage mold in the home.  Knowing about their construction features is key to avoiding getting “snowed” or blinded by smooth realtor or contractor talk or just the curb appeal of the home itself.  You’ve got to find the “secrets” hidden behind the walls and what they will mean for your air quality (or lack of it) if you buy the home!  Here are some key aspects to research and  investigate.

Roofs: An aging roof is one storm away from major water damage. If you live in a very sunny location (like Florida), the sun will bake roof shingles and prematurely weaken them.  In most cases (and the insurance company will tell you the probable limit), a roof in a state like Florida will only last 15 years. (video)

Roofs: Excessive roof penetrations: Skylights, plumbing and attic vents can cause leaks. If you’re building, planning can eliminate excessive penetrations. Air Admittance Valves (also called Studor valves) can go in walls, and attic vents can go through walls, eliminating these from roofs.  Alternatively, you can do a ridge vent on the roof to vent the attic. An Australian roofing repair professional admits that a lot of their business comes from skylights that leak.  He calls skylights a “compromise”, because it’s just a method of getting light from the sky.  It’s better and easier to put in windows in a vertical plane (walls) and make them waterproof.  Skylights are often installed incorrectly with incorrect flashings, and they have to be maintained.  If leaf debris is not cleared away, it blocks the drainage plane of the skylight, causing rot and deterioration.  The best homes have no skylights but well-designed windows.  Also, skylights let in a lot of heat during the summer.  If you want to shut off the heat, you have to block the skylight. This can be done with blinds but defeats the purpose of having a skylight!  If the skylight is providing light to a dark room, you can use a solar panel in place of the skylight to provide electricity to a new electrical light that is installed in the dark room.  (why are skylights are only compromise solutions)   If you have or buy a home with skylights, we suggest you remove and re-roof over them as soon as possible!  

Roof: Flat roofs: Another feature that’s popular with modern-style homes is flat roofs.  Flat roofs and parapet walls do not promote drainage.  (5 Building Designs That Guarantee Mold)

Roofs: No overhangs: Modern homes with no roof overhangs are popular, but these guarantee that water running down the sides will get into windows and doors.  (5 Building Designs That Guarantee Mold)  Roof Portal in Australia calls overhangs or eaves the “back-up plan” that keep water off the windows and doors. Eaves also provide shade from direct sunlight, as well as direct wind into vents to vent the attic. (The danger of house roofs without eaves)  In addition, a leak at the edge of the roof with eaves will only drip into the fascia of the eave, but without eaves, it can run all the way down the wall, rotting the wall and any interior rooms below.  However, if the eaves are constructed incorrectly, resting on the top of the brickwork, then water getting in the eaves can run down into the wall.  It’s better but more costly to rest the eaves on a second ledge constructed below the top of the eaves.  Without eaves, or properly constructed eaves, you really need to make sure the flashings are super-strong and 100%, because there’s no back-up plan.

Walls: Stucco: If you live in a home with a stucco exterior that has been built after the year 2000, it’s best to take a close look at the surface and make sure it’s holding up.  This is the “skin” of your home.  Traditional stucco on homes built before the 1980’s used a “three-coat” system over metal lath, which is a very stable “anchor” for the stucco. It also had weep screens and formed a path for water to drain on the backside if water made it through the 7/8th inch of cement-like material. Contrast: “one-coat” systems used today take less time and less labor.  The builder saves $4-6 per square foot. The surfaces are not monolithic, but “barrier” systems, and the windows, doors and caulk joints will allow water to get inside.  The problem is that stucco does not reveal water problems behind it–until the structure behind it completely rots and crumbles. This is 5-10 years later, long after any builder warranty has expired. If this one-coat stucco method is present, it’s very likely that other builder steps, like window flashing and other waterproofing steps, were skipped.  You should have a competent inspector do a “stucco-specific” moisture assessment, including thermal imaging and invasive probe testing at every window flashing, roof-to-wall junction, door surround, and exterior penetrations.  This kind of inspection out-performs visual inspections alone to uncover damaging rot. ((95% of Modern Stucco Is a Total Scam (Is Rotting Houses Across America))

Showers: If you are buying a home you didn’t build, check out the substrate of your shower walls.  You might be able to do this by opening or making an “access panel” behind the shower control valves in the next room; this will help you later if you need to replace the valves anyway.  If you can see drywall on the back side of the shower wall, beware that you may have a mold disaster waiting to happen!  This video warns that “builder-grade” shower installations often use drywall or cement board without proper waterproofing.  The tilework may look amazing, but if there’s no waterproofing behind it, the water will seep right through the grout and start a mold colony.

Flooring: Waterproof flooring: LVP.  Why is Luxury Vinyl Plank a bad thing?  Waterproof flooring will keep water from drying out if it gets under the flooring.   Concrete slabs are not waterproof–they are actually porous, and LVP installed over a concrete slab that does not have an adequate moisture barrier will encourage mold between the flooring and the slab..  

Insulation: Spray foam: Closed cell spray foam in walls insulates super well, but if moisture is introduced into the same cavity by a roof leak or hard, driving rain, the water has no where to go and it fosters mold growth and rot.  This is exactly what happens around improperly installed or sealed windows and doors, because even if the whole home is not spray foamed, spray foam is commonly used to seal up air crevices around windows and doors, and the foam acts to trap moisture as well.  Conversely, vapor-open insulations in the wall allow water to dry through the wall, and rain screens behind the siding cause water to flow down and out instead of in.

Bathrooms: Unvented bathrooms are a big problem.  You’ve got to have ventilation if there are water appliances in a room (the shower/bath is the biggest culprit, but even a toilet is an open source of water). 

Here’s a list of criteria from building performance expert Corbett Lunsford that  help you identify potential problems in your home or potential home. (House Hunting Tips for Mold-Sensitive People: How to Find a Mold Resistant Home)  

Green flags (good things): 

• working bath fans (they’re supposed to move at least 50 cfm), 

• working kitchen fan that exhausts outdoors, 

• AC is rated at 700+ sf/ton (because this means a computer calculation was involved)

• HVAC air handler and ductwork inside the conditioned space, 

• Room pressures are not causing doors to close when the HVAC is on and doors are cracked open.  

Red flags (Danger!): 

• AC  is rated at 500 sf/ton (this means the unit was sized by “rule of thumb” without calculations)

• There is a “loadless” room (no windows in the middle of a home) that has a supply grill (Loadless rooms do not need HVAC)

• Gas water heater exhaust flue with melted plastic plugs on either side of it (this means exhaust gases are coming out of the flue into the home)

• Unsealed fireplaces

• Ceiling height changes in the upper floor (means that the top plate is moving),

• Weird smells in the attic

• Side attics (enclosed attic space without ventilation or conditioning). 

Finally, you can find virtually any information you would ever think of asking about home features, on this website maintained by two home inspectors: howtolookatahouse.com.  It’s amazing what they have built and the thousands of questions answered.  We want you to be fully informed about whatever home you’re “getting into”!

Photo by Scott Webb on Unsplash