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Moisture Barrier and House Wrap, Why do I need One

For many years, new home builders would wrap the wall sheathing of every home with #15 roofing felt before they installed the siding or brick veneer. My dad built this way all his life and never had a problem with water penetrating the wall sheathing and causing damage.

Then, for some reason, there was a change in the thinking and builders discontinued wrapping houses in felt. I know that many new scientific advances made houses more energy efficient efficient over the years and now are much easier to heat and cool. But I never could figure out why the protective felt was omitted. Then I remembered my dad’s words once when I asked him why a previous carpenter had constructed a particular feature on one of our projects.

I remember him saying, “Son, in life, in politics, in building, and in knowing a man’s heart:   follow the money.”

At the time I did not fully understand the impact of those words. In life, why do people do what they do? In many situations its for the money. In politics the same is true and in the case of construction unfortunately it applies as well.

If it requires more material, more labor, more travel time, more attention to detail then it requires more money. More money spent in building a new home means less profit. Follow the money. That is why a great deal of construction is of poor quality. If you cut corners, save time, save materials that means more profit.

A protective moisture barrier allows water vapor to pass from inside your home to the exterior. But it will not allow water to pass from the exterior to the inside. Kinda like a one way valve that serves one purpose when operated in one direction and a totally different purpose when operated in another direction.

If a house has composition hardboard siding (Masonite, Champion, Georgia-Pacific, Louisiana Pacific, Weyerhaeuser, Certainteed, Abitibi, etc.) then it just makes sense to me that there should be a protective membrane behind the siding to prevent water penetration. Unfortunately not all contractors think that way and there are literally MILLIONS of homes with composite siding (Masonite) made of paper, wood, sawdust, glue, with a thin outer membrane covering homes all over the country.

Unfortunately, for any of these products to give a reasonable service life, many particular conditions would have to have been followed:

  1. The framing must stay dry (a rare occurrence in the construction industry)
  2. Moisture protective membrane should be installed (felt or Tyvek)
  3. The siding was properly installed (nails not overdriven or underdriven)
  4. The framing did not shrink (pulling the nail heads through the outer protective membrane which allows water entry)
  5. A high quality caulk was used to seal openings in the siding (not the builder’s grade)
  6. The siding was properly primed (many painting contractors applied paint directly to the factory product without primer)
  7. A high quality paint was used to provide UV and water protection (not usually specified because of additional cost)
  8. The siding was properly painted
  9. Siding was periodically chemically treated and pressure cleaned (to prevent mold and mildew)
  10. Window, door, fixture, and roof flashings were properly installed to prevent water entry

After sheathing, contractors are supposed to install Tyvek (or competitive brand) house wrap, tape the seams, and flash all the wall penetrations to prevent water entry. In our area, an inspection by the local municipality is required before siding can be installed.

Follow the money. If you do things right the first time, you may save a little money; but more than likely will pay even more when the project is corrected.


Here is an example of wall sheathing damage to the interior and the exterior corner of this chimney chase. Note the black stains/rot on the OSB wall sheathing.


With the cornerboard removed, the water damage is obvious.
The damage affects almost 100% of almost all the corners.
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