How to Identify Moisture Problem Spots

Knowing the common moisture sources in a home is the first step to combating household mold. Our checklist will help you investigate.
check backside of carpeting for moisture

check backside of carpeting for moisture

In DIY's Combating Household Mold workshop, you'll find out what mold is and how to prevent it. In this episode we'll show you how to take a moisture audit of your home. Mold can grow anywhere that moisture is a problem, such as this basement wall.

Jim LaRue, a moisture expert, has developed a "Moisture Audit" to systematically find moisture sources that can cause mold problems. Jim's moisture audit came out of the idea of an energy audit that has been done for a number of years to try to figure out what are the ways a home loses or gains heat so that we can more effectively weatherize. "I thought it might be good if we could do a moisture audit. Find out all the ways in which moisture can make it into a house," Jim says.

Checklist of Moisture Trouble Spots

Note: Mold feeds on starches and sugars in gypsum board, wood and wallpaper glues, but it can also grow on cloth, carpet and dust.

Many paints that are used on basement walls will sometimes be a host for molds. If there's no paint on the walls, the mold probably won't grow as quickly. Air drying wet clothes in an already damp basement is another way to add unwanted moisture to a room. Approximately 40 percent of the moisture in a home can come from the basement alone.

Does it smell musty or damp? If so, check the walls for signs of water intrusion and make sure there are no plumbing leaks. Be sure to check the caulking around the tub and shower enclosures. Any breaks can lead to a moisture problem. Check for proper ventilation — proper venting through the roof or soffit is vital for moisture control in any bathroom.

Be sure to check the backside of carpeting, especially in a basement or any area that's exposed to moisture.

"They're a catch basin for water," Jim says. "A lot of water can gather here." Even if your windows have a drain, make sure the drain is clear of any debris and dirt.

Because the foundations of homes are porous, they can absorb water from the outside and bring the moisture into the home. Don't let efflorescence (a powder that crystallizes when exposed to air — looks like salt) fool you into thinking you have mold. This salt-like substance, however, is a sign that there is a moisture problem.

Chimneys (for a furnace or water heater)
This is another high humidity hot spot that can lead to mold problems. If there is even a slight debris buildup or if there's a blockage in the chimney, the gas that's being burned is not getting out, which means that carbon monoxide is getting back into the house. If there's a sudden moisture problem, it's sometimes related to something collapsing inside the chimney that causes a blockage. It's a good idea to take a flashlight and look in the chimney for excess debris. In fact, it's best to have a professional sweep your chimney on a regular basis.

Walls (exterior and foundation, inside and out)
Look for peeling paint, deteriorated siding, rotted window sills, rotted window trim or door trim, brick-stone-mortar damage, rotted sheathing on the roof and rotted framing members. On the foundation walls, look for holes, spalling mortar joints, deteriorating masonry surfaces, peeling paint, collapsing window wells and rotted window or door sills.

Roof Surfaces
Wet or rotting sheathing, rafters, eaves and soffits are what you want to look for on the roof.

Make sure your gutters are always clean and free of debris to eliminate any backups of water that can leak into the house. Tip: Gutter guards are great for keeping debris out of your gutters. Also, make sure the downspouts are clean and clear at all times for proper drainage. Another good idea to check the storm drains to make sure they are working properly.

Mechanical Systems (plumbing, air-conditioning, etc.)

  • Plumbing -- Be sure to look for leaks around your water-service lines (frozen pipes or corrosion), waste stacks and lines, tubs, sinks, toilets, water heaters, clothes washers, garbage disposals and dishwashers. And be sure to check for any broken fixtures or careless connections.

  • Sewer and Storm Water System -- Check for backup from clogged or broken water lines around the house, along with sump-pump failures.

  • Heating/Cooling/Air Conditioning/Venting -- Look for leaking radiators, leaking or corroded pipes, heat ducts (water leaking into them can act as a humidifier driving moisture vapor into the house), open cold air returns that run into the basement (can carry mold spores and moisture from the basement into the living spaces), heat ducts in exterior walls, air-conditioning units (a common home for moisture problems) and all the vents in your home. Note: It's best to have vents in your bathroom and kitchen to release the moisture from showering and cooking respectively.

  • Interior Framing and Surfaces -- Check the ceiling between the interior and the unconditioned attic spaces, recessed light fixtures, around plumbing stacks that go through the roof, doors and hatch openings into the attic, opening between a chimney and the wood framing, balloon construction framing open from the basement all the way to the attic, chases where mechanical lines or ducts run (may be open from the attic to the basement) and all soffits (over kitchen cabinets and other places that may be open to side walls and floors on outside walls).

Soil Around the Home Foundation
As discussed in previous episodes of this DIY workshop, it's vital that the soil around your home slope away from the foundation properly. Jim suggests that you flash the soil, which involves digging down next to the foundation about 16" and out from the foundation three feet. Rubber-flashing material is then placed against the house and the hole is back-filled with soil.

If you decide to take the audit, be sure to document the location(s) where moisture was a problem and the date.

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