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Does your exterior siding show effects of trapped moisture?

With all the rain outside lately, it might surprise you that as housing experts we’re mostly concerned with water, in all its forms, getting trapped inside your foundation, house and attic.

Last week we talked about the negative effects of trapped moisture under your house – concentrating on the foundation vents and proper formula to figure out how much venting is optimal.

Today, we want to take you on a tour outdoors to the sides of your house to verbally identify potential damage being done by a wet, silent beast and other hidden sources working on your house that need this water to thrive.


Your home’s exterior siding protects your home from the many wraths of nature’s fury, just as your clothes protect you. When properly installed and maintained, most of the siding material types are generally durable and long lasting.

However, worn, cracked siding material, a bad paint job, UV light from the sun, exposed or poor caulking and rusted or ill-installed flashing and moisture build-up can all damage your house.

What do these bad boys of the siding world have in common? They could have been prevented. Good ventilation and timely maintenance are the best offensive weapons.


Here’s what you want to see as indicators that your home is well protected:

  • A great paint job on every surface

  • Good doors, windows and trim

  • Good gutters and downspouts with splash blocks, to convey the water away from the foundation

  • Black plastic ground cloth in the foundation covering all soil

  • A sealed pipe and flapper vented to the outside for the dryer, kitchen range hood and each bathroom fan

  • High and low attic venting at 1 square foot of vent for each 150 square foot of attic floor area

  • Same for foundation vents in the skirting

  • No woodpiles against the house giving shelter to bugs

  • Happy neighbors admiring your well kept home

So, what should you do if you see something that is not on the desired list?

Well, for starters, if you see peeling paint, or curling composition shingle roofing –you may have a moisture-control problem.

Maybe it is finally time to install black 6 mil. plastic under your house, add foundation or roof vents and actually connect all the fans blowing steamy air into the attic to metal piping vented through the roof in proper flapper vents!

If you already have fans and the dryer is vented too, make sure they are not leaking moist air and that each flapper opens and closes properly when the fan is on. Finally, are the little bathers and busy cooks using them and also leave them on for 20 minutes or more after the bath.

Did you know that dryers put out huge volumes of sticky steam full of lint that can stick to and build up on the inside of the vent pipe and flapper to the point where it takes a long time to dry your clothes or clogs the whole system? This is also a fire hazard! An annual cleaning of the dryer vent system is easy to do and also helps prevent rats from making your dryer into their nursery because they can’t get through a flapper that actually closes when the dryer is turned off. What a concept!


Inspect your siding, windows, roof and gutters for signs of leaks.

What if you see rusty siding nails or bleed marks? It may mean someone used the wrong siding nails and can also mean you have a moisture issue behind the siding.

Once you have found and corrected the sources of moisture, countersink the old nails, fill the old holes and re-nail as you go with galvanized nails. Using a stain blocker over the rust marks, before painting, works well to hide and seal- out moisture.


Woodpiles or lumber stacked near the house can create additional problems—extra moisture and bugs. However, it’s an easy fix if the piles are moved as far from the house as you can, 25 feet if possible.

Now look for bugs, fine sawdust or bug holes of any kind. They can indicate infestation and that usually means a consistent source of moisture. Find and stop the source then repair any bug damage. Consulting a certified pest control applicator to prevent future infestations can be a good idea.

Remember, heavily damaged wood may be hidden in a wall or in the floor. So you will need to follow the signs of moisture-related damage—rot, staining, peeling paint, rusty nails, dampness, dry rot and dead or active bugs—until you get to the root of the problem. This is where a professionally trained and certified pest control inspector is the appropriate source of information to identify the pest, the source(s) that provide an environment that allows the bugs to thrive and to make recommendations for treatment after the source is corrected.

Other common maintenance problems to look for include missing or damaged siding or trim. It’s important to repair and replace these materials to avoid moisture intrusion, causing deeper component structural problems and more unnecessary expense.

If you own vintage housing stock, pay close attention to broken or missing window parts. The sash surrounds the glass panes and must be kept well glazed and painted.

The ‘stool sill’ sheds the rain away from the siding and must be smooth, rot-free and well painted. The trim boards around each window make a weatherproof transition from siding to glass. They, too, must be tightly caulked and painted. When these parts fail it can result in leaks, then wall and floor damage.

When you observe, repair or replace window parts, make sure to stab test the wall sheathing just under the window sill, fixing what you find as soon as possible.

Close observation of your home’s exterior components is the key to maintaining a tight, water-proof shelter that always looks great and keeps you warm and dry in winter!

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.

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