The film is from 1946 in Australia so it doesn't represent current US construction. It shows the construction of a double wythe brick wall which today would be a single wythe attached to a stud or CMU back up wall with brick ties. The damp course they used is not "tar paper" but an asphalt saturated copper-fabric flashing that is compatible with brick mortar.

The space between the brick courses is to allow water to drain downward to grade where it can weep out small holes. Today a layer of through-wall s.s. steel, copper-fabric or self-adhering modified asphalt and sheet polyethylene flashing would be attached to the back-up wall and dropped down a brick and rest on the outer wythe so water in the cavity would be directed to the weep holes in the outer brick. This flashing also prevents moisture from rising in the masonry.

Cinder blocks are made with cement and coal cinders so it is less dense than modern CMU (concrete masonry units). CMUs have a cavity built into them and similar flashing would occur at the ground level. Water that is wicked from the outer surface to the inner surface can be a problem in wet areas so usually an outer layer of brick or tile is added. If the outer finish cannot prevent water from penetrating the wall, there must be some way for the water to drain out by gravity.

Interesting film made in 1946!

The so-called "damp course" inhibits the moisture rising up from the ground through capillary action. In a house with a basement, this "course" goes on top of the footings, on which the blocks or poured wall are then set. Interestingly, this has only become Code in my jurisdiciton in the past few years. (When I have used it in the past, the foundation guys looked at it askance.) The more wythes, the more resistance to water penetration. Public buildings from the 18th Century had walls as much as three wythes thick.

Note, too, the metal flashings under the windows. I bet you can still go around subdivisions and see windows and doors put in with no flashings at all.

So is it standard to use a "damp course" layer in concrete masonry unit homes ? Also in places like miami where it rains alot almost all homes are concrete masonry unit with no brick vanear. All they have is a coat of stucco. Do they put a waterproofing layer behind that like a epoxy or a Tyvek layer?

A stucco finish would be on metal lath over two layers of building paper or two layers of housewrap (one of which would be wrinkled like StuccoWrap) To create a drainage plane with a weep screed at the bottom of the wall or any horizontal interruptions to allow water to escape.

Tyvek is a good wrap but it is not waterproofing; it is a vapor permeable weather and air barrier. Any coating should also be vapor permeable and provide a drainage plane so epoxy would not be appropriate. You might be thinking of a synthetic coating that is intended to look like stucco.

Lstiburek on stucco failures in Florida.

There are tens of thousands of EIFS-clad homes in Florida, the Carolinas and, indeed, across North America that are damaged by rain due to poor EIFS (artificial stucco) installations. Reliance on plastic housewraps and no proper provision for drainage are the major sources of problems.

This post was edited by worthy on Thu, Apr 4, 13 at 22:21

so whats the right way to do it?

For EIFS?

The closest you can get in one line: drainage, suitable weather barriers, careful detailing. See link in previous post, particularly the recommendations.

(Building science, unlike the meaning of the universe, cannot be boiled down to one number, 42.)

so you saying concrete block houses in miami have two layers of housewrap under their stucco?

It all depends when it was built, by whom and whether it's EIFS (synthetic stucco) or traditional stucco. Many Miami concrete block houses go back to the 1950s and earlier.

According to Lstiburek, the traditional method of handling moisture is for the water to be absorbed in a non water sensitive material, then redistributed and released to the interior and exterior in a controlled way. In severe weather conditions, this method fails. Indeed, testing he cites shows that these methods fail in ordinary weather. Plus water enters these homes through doors, windows, appliance vents and service entries.

I am curious why it would be necessary to put house wrap under stucco if its a concrete house? I mean if it was a wooden house of course you would need it to prevent rot but why would a concrete block house need it they cant rot?

Traditional hardcoat stucco over block or brick is direct applied.

EIFS over frame construction is either face sealed or drained. (However, EIFS face sealed always fails.) Appropriate wraps provide a drainage plane.

EIFS over block or brick may or may not be drained. Most installations assume that the brick or block will not be affected by moisture penetration, so there's no drainage plane. However, since moisture will inevitably penetrate the EIFS through cracks in the surface or around fenestrations, the block or brick will get wet. At that point, unless there is a drainage plane, it can only dry to the interior where moisture sensitive materials may be affected.

The Lstiburek study grew out of moisture problems on block homes without stucco of any sort.

My spouse is from Jamaica where homes are built from block with or without hardcoat stucco on the exterior and the interior. Even when Storm Andrew brought ocean fish into her living room, the walls dried without lasting damage.

Wall Section of EIFS over framed wall. Note drainage plane. Source: Building Science Corp.

This post was edited by worthy on Fri, Apr 5, 13 at 17:41

How come with brick houses they uses two courses of brick so the first course can stop the moisture if with concrete block homes they only use one course? How do they stop the moisture?

The hollow blocks act somewhat similar to a double wythe of brick. Aside from coatings to repel water and/or restrict the flow through the wall, they handle moisture by absorbing and releasing it gradually.