Nailing it Down — Moisture is silent predator attacking Grays Harbor homes

Mold isn’t the only thing that wet homes encourage.

The last two weeks we’ve been discussing what mold is, where to look for it in your home and how to get rid of it once you find it. We’ve even talked about precautions to take to avoid having mold and mildew grow in your house.

Today we’ll talk again about some of those precautions, but we also want to remind you of other reasons why it’s key that you eliminate as much unwanted moisture in your home as possible.

In fact, it’s now been some 14 years that we’ve written this weekly column and the very first column we wrote was on trapped moisture as the “silent predator attacking Grays Harbor homes.”

A lot has changed these last 14 years, but what hasn’t changed a bit is that trapped moisture in homes is still the most damaging issue we see.

And what is the typical cause of trapped moisture? From the foundation to the roof, improper ventilation is usually the problem.


As we said, in addition to surface mold and mildew, much of what you see on homes — peeling paint, curling shingles, rotted skirting and bug damage — can be prevented by using the correct building materials and methods, properly ventilating the house cavities and timely maintenance.

The good news is that vents can always be installed in your roof, foundation, bath and kitchen without much expense.


You may be wondering: “How do I know if my house is adequately ventilated?”

House attics and foundations, in our area, should have one square foot of ventilation for every 150 square foot of area in each of those areas. For example, a 1,200-square-foot house, divided by 150, would need 8 square feet of ventilation in the foundation and the same amount in the roof.

This can be achieved by adding 1- square-foot foundation vents at every corner and evenly spaced around the foundation skirt. For the roof, we recommend ridge and soffit venting. Inside the house you should have a powered fan, in the kitchen and bathrooms, vented to the outside exterior through metal pipes and flapper vents.

By installing these vents you have taken all the preliminary measures needed for a healthy, breathing home.


Today, we would like to focus on just one area—the foundation—as a source of moisture.

Let’s begin by describing what you want to see and smell under your house.

• At least one good access point to get under the house.

• 18 to 24 inches or more space from the ground to the floor joists.

• Clean, dry 6-millimeter black plastic on the ground, Laid tightly, anchored at the edges, cut around each pier block and overlapped at the seams by 12 inches.

• Very few bugs, spiders or cobwebs.

• No wood-type debris and nothing growing.

• All areas of the foundation, especially under the kitchen and bath, should be dry. There should be lots of fresh air streaming through the vents and no odd smells, standing water or signs of animals.

• All non-treated wood components should be dry, rot-free, away from soil and separated from any concrete by a felt- or composition-roofing barrier.

If you see or smell something you shouldn’t, here’s what you should do:

• If you see lots of spider webs, that usually indicates a constant source of moisture. Look for leaking pipes and standing water. If you find a water puddle, you need to play detective. Clear water usually means a fresh, constant source. That means you should check your water supply pipes for leaks. If instead it is rainwater, install splash blocks, pipe it or pump it away from the house. Never allow it to go into the city sewer system, though.

• If it is gray, filmy or soapy water, it means your sink or tub drainpipes are leaking. Operate each fixture, find the problem and repair it. If the air smells or looks like toilet water, stop using the sinks and toilet and call a plumber! That water is hazardous to your health.

• No pipe leaks but standing water? Place a splash block at each down spout to convey the rain gutter water away from the house.

• If there is no plastic ground cover install 6 mil. black plastic tarp stretch tightly, cut around pier blocks and pinned to the ground

• Do the formula for ventilation, adding more vents if needed.

• If you observe any signs left by critters — urine smells, feces, hair, tracks, the critter! — trap or remove the animal and secure openings in and under the skirt.

• Finally, there may be sawdust trails and holes peppering the wood or larger holes, signs of powder-post beetles, ants or termites. You need to get rid of these pests! Depending on the level of damage, a professional pest spray, enough ventilation and removing all sources of moisture will cure the problem. If you wait too long, you may get to replace your foundation, sub-floor and skirting!

If you see considerable indications of damage you may need a professional inspection.

Dave Murnen and Pat Beaty are construction specialists at NeighborWorks® of Grays Harbor County, where Murnen is the executive director. This is a non-profit organization committed to creating safe and affordable housing opportunities for all residents of Grays Harbor County.

Do you have questions about home repair, renting, remodeling or becoming a homeowner? Call us at 533-7828, write us or visit us at 710 E. Market St. in Aberdeen.