FAQs

Q?

What Material? What is stucco made of?

A.

The word stucco has changed its meaning over the years. Basically the common thread in stucco is cement.
Stucco is made of cement.  It is basically thin concrete applied vertically instead of horizontally.  It is a mixture of Portland cement, hydrated lime and sharp crushed and washed sand.  It is mixed together with water to provide a homogenized mixture and applied to stucco lathe.  The mixture has changed over the years to accommodate the style of finish currently popular.

Q?

Does the ‘leaky condo’ problem apply to private detached housing?

A.

Yes we have begun to see this problem surfacing on buildings that have acrylic stucco or heavily painted stucco that have poor or no overhangs and that have exposed balconies or decks.  The same repair procedure is followed with the Water Management System.  We know water wants to get in…..so we use the three D’s….Deflect, Drain and Dry!!!.

Q?

What has caused so many ‘leaky condos’ and buildings?

A.

The single greatest problem is lack of overhangs and face sealed stucco in combination.  If water can get into the envelope faster than it can dry out…then moisture will rise…once it passes 25% you have problems….and once rot starts it will continue in one form or another….even as dry rot…until the problem is corrected.

Q?

Is stucco waterproof?

A.

Stucco is weather-resistant, not waterproof.  What is the difference?  A waterproof stucco system such as EIFS or acrylic finished cement stucco is what is called a face seal.  That means it must be waterproof to shed water at its face….that is where the rain or runoff water first impacts it.  If it is not waterproof at that face then water gets behind the face-seal and is there trapped in the stucco sheet.  Conventional cement stucco becomes a face seal stucco if it is painted with a waterproof coating.  What is the danger of having water trapped in the stucco sheet?  The stucco sheet is just really a fine grained sponge 5/8 to ¾ inch thick.  In the case of waterproof stucco finishes or paints the water finds it way inside and fills up the grains of this stucco and it remains saturated for a long, long time.  This saturation wears away at the tarpaper and gradually breaks it down…the wood wets ….the moisture rises and rot occurs.

Q?

Can we paint stucco? If so, with what? how to clean it or change the colour?

A.

tucco should only be painted as a last resort and very carefully.  For 50 years the common expression has been that you should not paint stucco.  Why?...because paint would not stick to stucco.  The high alkalinity, the powdery finish, the lime wash, the loose rocks made it hard to paint well, or for paint to last. So it was a frustrating process….after going perhaps 30-40-50 years on a stucco finish and doing almost nothing to it…they would paint it…and then in just 5 years or less they would have to re-paint it…again and again….but often times the paint from the first coat would be flaking and peeling and make a re-paint very difficult.
Now, we have a different problem.  The paint is too good.  Today's acrylic paints, the oil based paints, the liquid vinyl paints and the 'elastomerics' can stick to almost anything.  They fill in all the pores and bond completely to the cement stucco finish.  This forms a waterproof or almost waterproof face seal.  Now the stucco can no longer breathe out its moisture from the last rain storm….remember the plastic sealed sponge.  They say they are breathable…and they are but not enough…as one manufacturer told me…remember…a pillow is very porous and breathable…but you can smother someone with a pillow.
So if you paint stucco then you begin to reduce the breathability of the stucco finish and water is more likely to be trapped behind the finish.  The denser the paint…the more plasticity it has….the more it will trap moisture and slow down evaporation.  The water-based acrylic latex paint has higher breathability than the oil based paints or the elastomeric/vinyl paints.  However, even today's acrylic latex paints are of such good quality that they also reduce that vital breathability.  Then, if it is later painted to change the colour or spruce it up…..now you have probably 4 coats….2 coats each time…that combine to further reduce the breathability. 
How do you know if a finish is painted?  Chip a little piece off with a knife or your thumb nail….that will allow you to see if the colour is changed or if the surface is smoother more sealed that the back side of the piece chipped off.  If the finish of the stucco shows an in-fill on the texture…this usually means it is painted.  If the finish does not absorb water then that means that it is probably painted or sealed…which can be just as dangerous.  Spray a bit of water onto the surface and observe if the water is absorbed or if the stucco darkens colour…indicating water in the finish.
How do you clean the stucco if it is dirty and dingy?  Usually stucco gets dusty and dingy looking….it may have moldy sections or black or grey mildew or green algae accumulating under windows or on the north walls….or where water splashes against the stucco….or where shrubs are close to the stucco wall. 
Most of these conditions are organic dirt.  That means that the surface for whatever reason is remaining moist long enough for these organisms to grow.  If it is that kind of staining then it can be cleaned by killing the organism and washing away the residue.  To determine if it is organic dirt…a small amount of household bleach can be brushed onto a section mixed 50/50 with water and left to stand for a few minutes then rinsed with a hose or glass of warm water.  If it organic…you should see a marked improvement on the section bleached….be sure to rinse the area well so the bleach does not damage the stucco.  Probably 90% of dirty stucco is caused by organic staining and marking.
The actual cleaning treatment for the stucco is to use a product called “30 seconds” or Behr mildew cleaner…or a solution of household bleach and tsp and tide laundry detergent…this formulation is a bit trickier.  The 30 seconds….you just spray it on and then 30 seconds later it starts to clean….wait about 5-10 minutes and wash it off with a pistol on your garden hose…hot water is best if you can hook up to the laundry tap.  Just follow the directions on the jug...be careful, it's caustic!

Q?

What are the weaknesses of balconies/decks and what can be done to protect them?

A.

Balconies and decks are usually built without overhead protection….therefore all rain falls directly on the surface.  The balconies especially have a lot of movement and move differently than the wall…this causes vibrations and expansion, and cracks where the stucco meets the wall.  It is common to find any metal cap flashings on top of the wall terminated just against the finished stucco.  This means that the water running along the metal cap runs into the stucco wall.  If it is cement based/conventional stucco, it will be absorbed at that point and over time will cause damage to the wooden substrate.  If it has a wooden cap, or worse a stucco cap, it will break down much more quickly.  If the stucco is acrylic, or painted…then rot can be expected at each location or intersection of the balcony rail, with the wall.  Sloping the cap to the inside with a piece of cedar shim can reduce the water impact.  Today when we replace these caps we install a 3 dimensional boot flashing that is called a saddle joint.  It totally protects these areas.

Q?

Why does stucco crack? What are the worst kinds of cracks, and how should they be treated?

A.

It is natural for wood frame buildings to move, shrink, expand and contract…and these movements will cause cracks.  However if the stucco is cement based finish coat and if the concealed barrier is intact and properly lapped….these cracks are not much of a concern.  If the finish is acrylic or painted, then sealing of these cracks becomes more of a priority.  Especially horizontal cracks are worrisome…because they intercept water running down the wall.  In the case of acrylic or painted stucco…all the water impacting the stucco finish runs down the wall and so can be turned to run in a horizontal crack….especially one that has opened significantly…not hairline.  The other cracks vertical or angular are not as much of a concern.
What causes the cracks….
Vertical cracks are usually caused by fast warming of the wall…..usually found on the east facing wall….especially if the sun can directly hit it in the early morning when the wall is still cool/cold.  Or the west wall where the hot afternoon sun can hit it.  Usually they are spaced around the stud locations…and may even be counted with studs in extreame cases.
Horizontal cracks…..this is usually caused by breaks in the framing…plywood sheets. Or some kind of framing defect or fault…on floor joist that don’t have a compression joint….or have squeezed shut the compression joint over the years.
Angle cracks…..these are usually found off the upper and lower corners of windows and doors…especially sliding doors.  The reason the thermal expansion contraction of the wall.  The wall gets warm….as the sun heats it….a dark colour can even be hot to the touch on  the sunny wall on a summer day….now touch the window…it is never hot…it is always cool….so this provides a black hole in the wall.  It creates uneven movement and the wall twists…torques..at that location….and the crack runs off the corner and out usually  6 inches to 3 feet.
There are also check cracks….these are small cracks that are in the form of a small line or check in the stucco.  This is from the hydration of the lime and cement in the stucco….causing shrinking…they do not expand nor cause any problems.
On stucco that is sealed….you must maintain the face seal….or the water may get in those cracks and build up moisture and cause rot….on conventional stucco they will rarely cause problems and are very unsightly to repair and are usually better left as they are.